Search

A novel sample double dilution calibration method (SDDCM) and an automatic flow system with in-syringe reaction and spectrophotometric detection were developed for determining lithium in biological samples. The method is based on the reaction of lithium with Thorin in an alkaline medium and the signal was measured at 480 nm. The reaction was performed simultaneously for both standards and samples in three syringes of the automatic flow system. The method was validated and successfully applied to the determination of lithium in synthetic and pharmaceutical samples, with results consistent with the ICP OES method. The novel calibration method, developed for the determination of lithium in biological samples, uses a sample with two dilution degrees. Using the method, the concentration of the analyte is determined by relating the signal for a less diluted sample to the calibration plot for a more diluted sample and vice versa. The implementation of the calibration method was facilitated by preparing solutions directly in the flow system. The use of two sample dilutions makes it possible to determine the analyte in the sample without preliminary preparation. Moreover, obtaining two results based on signals for a sample diluted to different degrees allows them to be verified for accuracy. The proposed approach was successfully verified by the determination of lithium in certified reference materials of blood serum and urine. Using the developed method lithium was determined within the concentration range of 0.06–1.5 mg L−1, with precision (CV, %) less than 6.7, and accuracy (RE, %) better than 6.9. The detection limit was 0.03 mg L−1. [Display omitted] • Novel SDD calibration method is proposed to determine lithium in biological samples. • Lithium is determined spectrophotometrically based on reaction with Thorin. • Developed calibration enables determination of lithium without sample preparation. • Flow-based system with in-syringe reaction was developed for method implementation. • Developed SDD calibration method was verified using CRMs of serum and urine. [ABSTRACT FROM AUTHOR]

Multi-signal calibrations have been recently exploited in molecular spectrochemical analysis alternatively to traditional calibration methods, improving analytical frequency and accuracy. The application of these strategies is simple and minimizes efficiently matrix effects by analyzing two calibration solutions comprising sample plus standard (S1), and sample plus blank (S2). The plot of the signals obtained with S1 and S2 at multiple settings (e.g. different wavelengths) yield a slope that can be related to the analyte concentration in the sample. Similarly, transient signals could also be related to the analyte concentration exploiting a similar strategy. Thus, in this work, two multi-signal approaches developed in flow-based systems are proposed, based on the responses at multiple wavelengths (online multi-energy calibration, OMEC), and on the dispersion profile of the samples, herein denominated multi-dispersion calibration (MDC). The calibrations were carried out with sample solutions after 2-fold dilution with a standard solution and with water. The feasibility of OMEC and MDC were demonstrated using KMnO 4 solutions (without chemical reactions) under continuous and pulsed flow regimes. The applicability of this strategy was also demonstrated by the spectrophotometric determination of urea in milk and pet potty spray in a multi-pumping flow system, based on the color change of bromothymol blue after catalyzed hydrolysis by urease from jack beans (Canavalia ensiformis). MDC and OMEC were compared with external calibrations (EC) and classical standard addition. The limits of detection for urea were estimated at 13 mg L−1, 16 mg L−1, and 10 mg L−1 using MDC, MEC and EC, respectively. Recoveries from 93 to 101%, and the agreement of sample analyzes with the reference procedure demonstrated the good accuracy achieved by the proposed methods. Therefore, it was demonstrated the feasibility of MDC and OMEC for analytical purposes in a simple and efficient way with the advantages of flow-based manifolds. [Display omitted] • Multi-signal calibrations in flow analysis using the diluted sample with the blank and with a standard solution. • Calibration based on the dispersion profile of the sample zone by overlapping transient signals. • Online multi-energy calibration exploiting the simultaneous acquisition of transient signals at multiple wavelenghts. • Fast and simple procedures with appropriateness to overcome some matrix effects. [ABSTRACT FROM AUTHOR]

Laser ablation inductively coupled plasma - mass spectrometry (LA-ICP-MS) is a frequently used microanalytical technique in elemental analysis of solid samples. In most instances the use of matrix-matched calibration standards is necessary for the accurate determination of elemental concentrations. However, the main drawback of this approach is the limited availability of certified reference materials. Here, we present a novel conceptual framework in LA-ICP-MS quantification without the use of matrix-matched calibration standards but instead employment of an ablation volume-normalization method (via measurement of post-ablation line scan volumes by optical profilometry) in combination with a matrix-adapted fluence (slightly above the ablation threshold). This method was validated by cross-matrix quantification of reference materials typically investigated by LA-ICP-MS, including geological and biological materials. This allows for more accurate and precise multi-element quantification, and enables quantification of previously unquantifiable elements/materials. [Display omitted] • New method for non-matrix matched calibration in LA-ICP-MS is proposed. • Optical profilometry was used to quantify the ablated volume and signal was corrected accordingly. • 10 standards (CRMs and prepared in house) were cross validated for accuracy. • Volume corrected calibration with non-matrix matched standards errors are below 10 %. • The approach will allow to calibrate materials with no appropriate CRM, so far accurate quantification was not possible. [ABSTRACT FROM AUTHOR]

Fluorescence spectroscopy is a powerful tool to determine polycyclic aromatic hydrocarbons (PAHs) owing to the strong endogenous fluorescence of these compounds. However, the presence of unknown interferences and overlapped spectra hinders the accurate determination of PAHs in oilfield produced water. Moreover, surfactants frequently coexist in oilfield produced water and will seriously affect the fluorescence signals of PAHs. Herein, a new methodology applying third-order calibration to process four-way (4D) fluorescence data was proposed to solve these problems and achieve accurate determination of pyrene, fluorene, phenanthrene, and fluoranthene as an example in oilfield produced water. The methodology is based on excitation-emission matrix fluorescence modulated by different concentrations of sodium dodecyl benzene sulfonate (SDBS) in the analyzed samples. The 4D fluorescence data were processed by third-order calibration methods including four-way parallel factor analysis (4-PARAFAC) and alternating weighted residue constraint quadrilinear decomposition (AWRCQLD), and the results were compared with those of second-order calibration methods. It was proved that third-order calibration was capable of accurately identifying and quantifying PAHs together with SDBS in oilfield produced water, which has better quantitative results and figures of merit compared to second-order calibration. This study provided a new approach to generating 4D fluorescence data and opened up an avenue for the accurate determination of PAHs in complex oilfield produced water with surfactants. [Display omitted] • 4D excitation-emission matrix fluorescence data modulated by SDBS was first constructed. • Chemometric multi-way calibration algorithms were used to process the 4D fluorescence data. • The proposed strategy could determine PAHs in oilfield produced water with surfactants. • Third-order calibration has more robust performances than second-order calibration. • SDBS could be successfully predicted as an added bonus in third-order calibration. [ABSTRACT FROM AUTHOR]

In this study, we report the simultaneous determination of bromine and fluorine using Second-Order Calibration High-Resolution Continuum Source Graphite Furnace Molecular Absorption Spectrometry (HR CS MAS). The instrumental data acquired correspond to the time versus wavelength matrix per sample that were analyzed using Parallel Factor Analysis (PARAFAC), along with Unfold and N-way Partial Least Squares combined with a post-calibration step known as Residual Bilinearization (U and N PLS/RBL). Despite the significant difference in sensitivity between bromine and fluorine, all approaches provided reasonably accurate results when predicting both analytes in synthetic mixtures within a controlled environment. The relative prediction error (REP) values for bromine were 29.8 % (PARAFAC), 23.6 % (N-PLS/RBL), and 13.1 % (U-PLS/RBL), while for fluorine, the REP values were 3.4 % (PARAFAC), 3.5 % (N-PLS/RBL), and 3.2 % (U-PLS/RBL). When applying this approach to predict unknown samples, a comparison was made between the estimated nominal concentrations of fluorine and bromine obtained using either a reference method or based on labeled values or spiked mass, and those obtained using the proposed method. It was observed that PARAFAC was unable to predict the samples accurately, whereas the REP values for the prediction of bromine and fluorine using N-PLS/RBL and U-PLS/RBL methods were 19.3 %/19.2 % and 13.6 %/13.1 %, respectively. [Display omitted] • HR-CS MAS second-order data modeling. • Simultaneous determination of bromine and fluorine. • Capacity to predict in presence of Spectral overlaps was achieved by second-order. • U and N PLS regression couple to RBL achieved successfully second-order advantage. [ABSTRACT FROM AUTHOR]

Quantification in 2D LA-ICP-MS mapping generally requires matrix-matched standards to minimize issues related to elemental fractionation. In addition, internal standardization is commonly applied to correct for instrumental drift and fluctuation, whereas also differences in ablated mass can be rectified for samples that cannot be sectioned and subjected to total ablation. However, it is crucial that the internal standard element is homogeneously distributed in the sample and that the laser light absorptivity is uniform over the surface. As in practice these requirements are often not met, this work will focus on correction of ablation rate differences within/between samples and standards by normalizing the element maps using the associated ablation volume per pixel as measured by optical profilometry. Due to the volume correction approach the element concentrations are no longer defined as mass per mass concentrations (in μg g−1) but by mass per volume concentrations (in μg cm−3), which can be interconverted in case matrix densities are known. The findings show that ablation volume-aided calibration yields more accurate element concentrations in 2D LA-ICP-MS maps for a decorative glass with highly varying elemental concentrations (murrina). This research presents a warning that if there are variations in ablation rates between samples and standards within and across matrices, even when their sensitivities are the same, generic LA-ICP-MS calibration protocols may not accurately depict the actual element concentrations. [Display omitted] • We present a method to rectify ablation volume discrepancies in LA-ICP-MS mapping. • Optical profilometry was used to quantify the ablated volume per pixel. • Implementation led to more accurate element concentrations in a murrina. • The validity was confirmed through alternative measurement techniques. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) spectroscopy is a rapid, non-invasive and cost-effective technique, for which sample pre-treatment is often not required. It is applied for both qualitative and quantitative analyses in various application fields. Often, large calibration sets are used, from which informative subsets can be selected without a loss of meaningful information. In this study, a new approach for sample subset selection is proposed and evaluated. The global PLS model, obtained with the original large global calibration set after FCAM-SIG variable selection, is used for the selection of the best fitting subset of calibration samples with optimally predictive ability. This best fitting calibration subset is called the optimally predictive calibration subset (OPCS). After ranking the global calibration samples according to increasing residuals, different enlarging fractions of the ranked calibration set are selected. For each fraction, the optimal predictive ability and the corresponding optimal PLS complexity are determined by cross model validation (CMV). After performing CMV with all fractions, the fraction with the best fitting samples and optimally predictive ability, i.e. the OPCS, is determined. The use of the best fitting samples from the global PLS model results in an OPCS-based model which is similar to the global PLS model and has a similar predictive ability. Because the best fitting samples do not need to be representative for the global calibration set, but only need to support the OPCS-based model, the number of samples in the OPCS model is mostly smaller than that selected by a traditional representative sample subset selection method. The new OPCS approach is tested on three real life NIR data sets with twelve X - y combinations to model. The results show that the number of selected samples obtained by the OPCS approach is statistically significantly lower than (i) that of the most suitable and widely used representative sample selection method of Kennard and Stone, and (ii) that suggested by the guideline that the optimal sample size N for reduced calibration sets should surpass the PLS model complexity A by a factor 12. An additional advantage of the OPCS approach is that no outliers are included in the subset because only the best fitting calibration samples are selected. In the new OPCS approach, two additional innovations are built in: (i) CMV is for the first time applied for sample selection and (ii) in CMV , the " one standard error rule ", adopted from " Repeated Double Cross Validation ", is for the first time used for the determination of the optimal PLS complexity of the OPCS-based models. [Display omitted] • A new approach for calibration subset selection, called optimally predictive calibration subset (OPCS) is proposed. • The best fitting subset with optimal predictivity is selected from of a far extended calibration set. • The selective ability of the OPCS approach is significantly better than that of the Kennard Stone method. • Cross Model Validation (CMV), including the " one standard error rule " is for the first time applied for sample selection. [ABSTRACT FROM AUTHOR]

Understanding the role of non-structural carbohydrates (NSC) in tree-level carbon cycling crucially depends on the availability of NSC data in a sufficient temporal resolution covering extreme conditions and seasonal peaks or declines. Chemical analytical methods should therefore get complemented by less extensive retrieval methods. To this end, we explored the potential of diffuse reflectance spectroscopy for estimating NSC contents at a set of 180 samples taken from leaves, roots, stems and branches of different tree species in different biogeographic regions. Multiple randomized partitioning in calibration and validation data were performed with near-infrared (NIR) and mid-infrared (MIR) as well as combined data. With derivative spectra, NIR markedly outperformed MIR data for NSC estimation; mean RMSE for outer validation samples equalled 2.58 (in % of dry matter) compared to 2.90, r 2 was 0.64 compared to 0.52. We found complementary information related to NSC in both spectral domains, so that a combination with high-level data fusion (model averaging) increased accuracy (RMSE decreased to 2.19, r 2 equalled 0.72). Spectral variable selection with the CARS algorithm further improved results slightly (RMSE = 1.97, r 2  = 0.78). On the level of tissue types, we found a marked differentiation concerning the appropriateness of datasets and approaches. High-level data fusion was successful for leaves, NIR data (together with CARS) provided the best results for wooden tissues. This suggests further studies with a greater number of samples per tissue type but only for selected (main) tree species to finally judge the sensitivities of diffuse reflectance spectroscopy (NIR, MIR) for NSC retrieval., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this work, we evaluated the feasibility of Raman spectroscopy as an in-line raw material characterization tool for industrial process control of the hydrolysis of poultry rest raw material. We established calibrations (N = 59) for fat, protein, ash (proxy for bone) and hydroxyproline (proxy for collagen) in ground poultry rest raw material. Calibrations were established in the laboratory using poultry samples with high compositional variation. Samples were measured using a wide area illumination Raman probe at varying working distance (6 cm, 9 cm, 12 cm) and probe tilt angle (0°, 30°) to mimic expected in-line variations in the measurement situation. These moderate variations did not significantly affect performance for any analytes. The obtained calibrations were tested in-line with continuous measurements of the ground poultry by-product stream at a commercial hydrolysis facility over the course of two days. Measurements were acquired under demanding conditions, e.g. large variations in working distance. Reasonable estimates of compositional trends were obtained. Validation samples (N = 19) were also reasonably well predicted, with RMSEP corr  = [0.14, 1.37, 2.36, 1.51]% for hydroxyproline, protein, fat and ash, respectively. However, there were indications that further calibration development and robustification of pre-processing would be advantageous, particularly with respect to hydroxyproline and protein models. It is the authors' impression that with such efforts, potentially in combination with development of practical measurement setup, the use of Raman spectroscopy as a process control tool for the hydrolysis of poultry rest raw materials is within reach., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Tiril Aurora Lintvedt reports equipment, drugs, or supplies was provided by MarqMetrix Inc., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

In this work, the analytical performance of a third-order/four-way calibration is evaluated to model a highly overlapped system, where two spectral dimensions are extremely similar, and the results are then compared with the results of second-order/three-way calibration. The four-way data were obtained during the photodegradation of fluoroquinolones (ciprofloxacin, norfloxacin and flumequine) in the form of excitation-emission matrices and modeled by unfolded partial least squares coupled to residual trilinearization (U-PLS-RTL). According to the results, the model obtained with the second-order algorithm (unfolded partial least squares coupled to residual bilinearization: U-PLS-RBL) was unsatisfactory due to high spectral overlap. The third-order approach obtained a satisfactory fit and better figures of merit (LOD, REP, RMSEP, and sensitivity, among others) even in the presence of unexpected interferences due to third-order advantages. Finally, the analytical method based on third-order multivariate calibration was applied to quantify these fluoroquinolones in spiked fish-farming water samples. In this case, the third-order advantage allowed us to satisfactorily model the data and to quantify these compounds in this complex matrix, demonstrating the superior analytical performance of the high-order data that were evaluated. Image 1 • A new analytical method based on third-order multivariate calibration was proposed for fluoroquinolone determination. • The third-order advantage allowed to reach better figures of merit and to resolve high overlapped signals. • The proposed method was applied to analysis of fish farming water samples, demonstrating its analytical potential. [ABSTRACT FROM AUTHOR]

A review is presented of recent multi-way calibration protocols involving three-, four- and five-way data. A brief description of the various data structures and processing models is shown, with emphasis on model selection based on the matching between the data structure and the physicochemical model assumptions. Calibration research works are then discussed, classified according to the type of measured instrumental data and model/algorithm selection. Image 1 • Recent multi-way calibration protocols are reviewed. • The relationship between data structures and chemometric models is detailed. • Second-, third- and fourth-order data generation is discussed. • Implications to green analytical chemistry are underlined. [ABSTRACT FROM AUTHOR]

This article describes a new, simplified approach for performing quantitative colorimetric assays on paper-based analytical devices that uses calibrant-loaded paper devices to perform external calibration and standard addition calibration using one calibration point. Calibrant-loaded devices consist of sensing areas pre-loaded with a colored product which is produced from the reaction of a standard solution of the analyte with the appropriate colorimetric reagents. When the sample is added into the calibrant-loaded sensing zone the analytical signal (i.e. color intensity) increases proportionally to the concentration of the analyte in the tested sample. The total measured signal corresponds to the sum of the concentration of the analyte in the sample and the standard solution pre-stored in the device and is used to calculate the concentration of the analyte in the sample based on the principles of linear calibration. The applicability of this approach was benchmarked in three colorimetric assays (i.e., for the determination of iron, nickel, and amino acids) that use different reaction chemistries. This work demonstrates a simplified calibration-free approach for assays performed on paper-based analytical devices that requires minimum experimental and computational effort, it can be used for either external or standard addition calibration and can be used to identify and eliminate the presence of interferences in a sample. Image 1 • A new and simplified approach for quantitative assays on paper devices is described. • Single-point calibration and standard addition on paper devices is demonstrated. • The method can be used to identify the presence of interferences in the sample. • The method produces rapid results with minimum user effort and technical resources. [ABSTRACT FROM AUTHOR]

Ambient ionization in open environment brings a capability of a coupled mass spectrometry to detect target molecules in situ. However, it is limited to qualitative and semi-quantitative analysis. By coupling of an ambient ionization-based Direct Analysis in Real Time (DART) with high-resolution quadrupole time-of-flight mass spectrometry (QTOF/MS), we observe that, in one-chemical system, the target molecule displays a non-linear response in MS signal vs concentration, accompanying with large variation in MS signal, suggesting two obstacles for quantification to be overcome. Surprisingly, in a two-chemical system, we observe an apparent suppression effect. We prove that, due to this observed suppression effect, a fluctuant response in the MS signal of the stable isotope-labeled analogue can immediately reflect the change in the analyte concentration and ionization efficiency. For example, by taking advantage of this effect, even the analyte of different concentrations despairingly displayed similar signals would be accurately calibrated through the suppression of the internal stable isotope standard. This puts an important foundation on accurate and linear quantitation of analytes in complex matrix using DART-MS assay. Moreover, we for the first time demonstrate an application of in situ calibration of DART-MS for direct and accurate quantification of target molecule (creatinine) in highly complex samples (human urine) without any pre-separation. The quantification is also validated using HPLC-UV analysis (n = 38). At last, we show that stable isotope-labeled-creatinine (m / z 117.0850 amu) can be used for simultaneous in situ calibration of some other urinary metabolites with a mass/charge ratio varying from 120.069 amu to 333.125 amu. Image 1 • DART-QTOF/MS method is developed for direct and accurate quantification of chemicals in complex matrix such as urine. • Urine excretion rate index creatinine is used as a representative example of target molecule. • Stable isotope-labeled creatinine ([ D 3-creatinine]) is used for accurate in situ calibration. • Several other urinary metabolites can be simultaneously calibrated only using stable isotope-labeled creatinine. [ABSTRACT FROM AUTHOR]

Abstract This article presents a new method for the simpler and faster determination of tin in beverages using EDXRF. Absorption coefficients for aqueous calibration samples were calculated and shown to be nearly identical to those of the beverage samples, thus permitting the use of aqueous standard solutions for external calibration. Beverage samples could then be measured directly using the external calibration. Determination of tin using this method takes 4 min. The LOD and LOQ were 4 mg L−1 and 15 mg L−1 respectively, and the precision was 3.89%. Different canned beverages (cold coffee, various fruit juices) were measured and the results compared to the concentrations obtained using ICP-OES after digestion. The two methods showed good compatibility, thus establishing the newly developed method as a rapid, simple, and accurate method for the determination of tin in beverages. Graphical abstract fx1 Highlights • Energy dispersive X-ray fluorescence for tin determination in beverages. • Aqueous standards and beverages absorption coefficients are nearly identical. • Beverage samples are measured directly. • Measurements are direct, simple and rapid. [ABSTRACT FROM AUTHOR]

Abstract The use of Raman in Bioprocess development have shown great potential for process understanding and monitoring although there are still some challenges and limitations in performance when conditions such as clone, media or scale are changed during bioprocess development. This study proposes different strategies to balance the different information content of multiple mammalian cell cultivations produced during a bioprocess development program, when several conditions are investigated. The result is a pragmatic approach to PAT monitoring that serves both development and manufacturing stages. Combining risk-assessment techniques with two ways of developing monitoring calibrations (local or general models), we were able to obtain good predictive power from Raman spectroscopy used as PAT tool, when multiple cultivation conditions vary. As an example, the effects of process scale, base powder media and cell-line on Raman spectra are discussed and how using local models specific to some of these cultivation conditions, has a positive impact on calibration performance. It is shown how more accurate calibrations can be obtained using Clone-based local models, which requires less batches than usual approaches (up to 3–9). This study uses thirty-five cultivations of four different types of CHO cell lines, eight different clones, and four different scales – 2 L, 7 L, 15 L and 10,000 L – in two Cultivation Modes – fed-batch and perfusion. The aim is to serve as blueprint to how can PAT approaches be best developed in parallel to bioprocess development. Graphical abstract fx1 Highlights • In mammalian cell cultures, Raman Spect. faces challenges in performance when conditions are changed during development. • To develop calibrations, RA assays and local model strategies shown to increase the predictive power when conditions vary. • Process scale, base powder media and cell-line on Raman spectra are conditions with positive impact on model performance. • Clone-based models produce more accurate calibrations with lower number of batches (up to 3-9), unlike usual approaches. [ABSTRACT FROM AUTHOR]

Abstract The simultaneous quantitative analysis of intracellular metabolic coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) is of interest because they participate in many electron-transfer reactions of metabolism. But, the simultaneous quantitative analysis of FAD and FMN is hard to be achieved by traditional analytical methods. This paper proposes a novel strategy of intrinsic fluorescence coupled with four-way calibration method for simultaneous quantitative analysis of intracellular metabolic coenzymes FAD and FMN. Through mathematical separation, this proposed analytical method efficiently achieved the simultaneous quantitative analysis of metabolic coenzymes FAD and FMN in the cell, despite the fact that uncalibrated spectral interferents coexist in the system. The predicted concentrations of FAD and FMN in the cell are 217.0 ± 6.9 and 155.0 ± 1.7 pmol/106 cells respectively, which were validated by the approved liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. This analytical method with second-order advantage simply requires the cell solution to be diluted by a buffer, it could introduce an interesting analytical strategy for multianalyte direct quantitative analysis in complex biological systems. In addition, we explore the third-order advantage of four-way calibration by a comparative study based on this real fluorescence data. The comparisons indicate that a four-way calibration method can provide higher sensitivity and more resolving power than a three-way calibration method. Graphical abstract fx1 Highlights • A new fluorescence strategy for determining intracellular FAD and FMN is developed. • The proposed analytical method has the second-order advantage. • The third-order advantage is also explored based on this experimental data. [ABSTRACT FROM AUTHOR]

Abstract Fluorescent probes have been valuable tools for bioanalytical multiplex assays. However, as a common phenomenon in multiplex fluorescence assays, spectral overlap usually leads to difficulty in spectral analysis for multiple analytes. Although multiway calibrations have provided mathematic approaches for complex spectral analysis, it remains a grand challenge for these methods in practical applications because of the problems such as prior rank estimation. Herein, we report a novel second-order calibration algorithm of alternating residual trilinearization (ART) for the decomposition of complex spectra generated from multiplex fluorescence assays. By alternating iterative convergence to the spectral profiles of each component in convergence process, ART enables automatic rank estimation for second-order calibration, thus able to avoid the risk of chemical meaningless fitting of component spectra. Combined with fluorescence excitation-emission matrix (EEM) spectroscopy, the performance of ART has been demonstrated by a simulated example and an analytical experiment performed using molecular beacons (MBs) for the simultaneous assay of three breast cancer related DNA targets. The results revealed that the proposed algorithm is capable of automatic estimating the number of underlying components during its convergence process to produce acceptable performance in spectral profile resolution and concentration estimation. Compared with other existing iterative trilinear decomposition strategies such as parallel factor analysis (PARAFAC) requiring a prior rank estimation, the proposed ART therefore provides a robust second-order calibration strategy for complex spectral analysis in multiplex fluorescence assays. Graphical abstract In this study, fluorescence excitation-emission matrix (EEM) spectroscopy combined with a novel chemometric algorithm, alternating residual trilinearization (ART), was used to simultaneous assay of three nucleic acid targets based on molecular beacons (MBs) with desirable performance. fx1 Highlights • A novel alternating residual trilinearization (ART) algorithm. • Automatic rank estimation of ART for second-order calibration of three-way data. • Good performance of ART demonstrated using data generated from multiple DNA detection. [ABSTRACT FROM AUTHOR]

Abstract An automated inline method for the separation of trace element impurities from uranium matrices using a 200 µL column packed with UTEVA resin is presented here utilizing an Elemental Scientific, Inc. prepFAST IC in combination with a Perkin Elmer Avio 500 ICP-OES. This method reduces human exposure to highly concentrated acids and uranium-rich samples by automating the chemistry and introduction to the ICP. Calibration standards were prepared using inline dilutions requiring a single stock standard. The separation of trace elements from uranium matrices requires samples to be prepared in 8 M HNO 3 , which can be detrimental to the ICP, thus a post-column dilution step was employed to dilute the eluent matrix to 4 M HNO 3. The method was optimized for a sample-to-sample time of < 9 min and monitored 21 elements in total. Proof of concept experiments for 1 µg mL−1 trace elements spiked into 0.1 vol%, 0.5 vol%, and 1.0 vol% uranium matrices resulted in < 5% relative difference and < 10% relative standard deviation for triplicate measurements of each uranium matrix analyzed. Inline dilutions (pre-column) of 2 vol% uranium + 20 µg mL−1 trace elements resulted in accurate and precise measurements using dilution factors of 2×, 4×, 5×, and 20×. Method detection limits for the 21 elements (Al, B, Ba, Be, Cd, Ca, Co, Cu, Fe, Li, Pb, Mg, Mn, Ni, K, Sr, Na, V, Zn, Zr, and U) analyzed for ranged from 7 to 326 ng mL−1 for 70 µL volume injections. Graphical abstract fx1 Highlights • Reduction of sample size, solvent volume, waste, and sample-to-sample time. • Inline chromatographic separation method to remove uranium prior to ICP-OES in under 9 min. • 70 µL of uranium sample was loaded onto the UTEVA column with LODs of 7–326 ng mL−1. • Autodilution of samples and standards eliminated the sample preparation step for the ICP-OES analysis. [ABSTRACT FROM AUTHOR]

Linear models for calibration curves are overwhelmingly created based on minimization of least squares error, with their goodness-of-fit (GOF) quantified using the square of the correlation coefficient (R 2 ). Yet, R 2 has well-known disadvantages when used to quantify GOF of calibration curves stemming from its calculation based on the absolute error of the signal (i.e., calculated vs. experimental). These disadvantages are exacerbated when using a geometric series of concentrations for calibration standards (e.g., 1, 2, 5, 10, etc.) and when calibration curves span 2–3 orders of magnitude, which is typical for modern analytical techniques. While there are multiple alternative GOF measures, R 2 overwhelmingly persists in the field of Analytical Chemistry as the most reported measure of GOF. We evaluated R 2 , alternative GOF measures, and multiple quantitative bias parameters, along with residual analysis, for over 60 experimental calibration curves. R 2 did a poor job of consistently and accurately quantifying the GOF over the entire calibration curve. This was especially true for situations where the low concentration calibrators were not accurately described by the calibration equation. While other GOF parameters, including the sum of the absolute percent error, mean absolute percent error, and quality coefficient, did a better job of describing GOF of calibration curves, each had significant theoretical and/or practical disadvantages. Therefore, we introduce a descriptive GOF parameter called Percent Residual Accuracy (%RA or PRA) which equally weights the accuracy of all calibrators into a single value, generally falling between 0% and 100%, with 100% representing a perfect fit and a “good” fit for calibration data producing a %RA of 90–100%. The %RA much more effectively described the GOF for the entire calibration range than R 2 , and it similarly quantified GOF as compared to the other GOF parameters tested. With the performance and practical advantages of %RA, we conclude that it is the most advantageous GOF parameter and that it should be reported as a standard GOF measure for calibration curves. [ABSTRACT FROM AUTHOR]

Hyperspectral imaging has emerged as a promising high-resolution and real-time imaging technology with potential applications in medical diagnostics and surgical guidance. In this study, we developed a high-speed hyperspectral camera by integrating a Fabry-Perot cavity filter on each CMOS pixel. We used it to non-invasively detect three blood components (haemoglobin, platelet, and total bilirubin). Specifically, we acquired transmission images of the subject's fingers, extracted spectral signals at each wavelength, and used dynamic spectroscopy to obtain non-invasive blood absorption spectra. The prediction models were established using the PLSR method and were modelled and validated based on the standard clinical-biochemical test values. The experimental results demonstrated excellent performance. The best predictions were obtained for haemoglobin, with a high related coefficient (R) of 0.85 or more in both the calibration and prediction sets and a mean absolute percentage error (MAPE) of only 5.7%. The results for total bilirubin were also ideal, with R values exceeding 0.8 in both sets and a MAPE of 10.6%. Although the prediction results for platelets were slightly less satisfactory, the error was still less than 15%, indicating that the results were also acceptable. Overall, our study highlights the potential of hyperspectral imaging technology for the development of portable and affordable devices for blood analysis, which can be used in various settings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The accurate identification of β-lactamases produced by Enterobacteriaceae is a major challenge in clinical laboratories in order to optimize antimicrobial treatment and patient care. We describe here a rapid voltammetric-based method to detect and to discriminate β-lactamase activity in Enterobacteriaceae i.e. , penicillinase, cephalosporinase (inducible or overproduced), extended-spectrum beta-lactamase and carbapenemase producers. After a 2-h growth step of the sample under three separate conditions: 1) LB (Luria-Bertani) medium, 2) LB supplemented with 4 μg/mL cefotaxime and 3) LB supplemented with 4 μg/mL cefotaxime and 100 μg/mL potassium clavulanate, the β-lactamase activity was measured by incubating a 0.5 mM nitrocefin solution for 15 min followed by the voltammetric detection of the hydrolyzed nitrocefin with disposable carbon screen-printed sensors. The development and the calibration of the method were carried out by analyzing pure cultures of fifty-seven strains with well characterized β-lactam-resistance phenotypes. Thanks to the combination of the three currents (i 1 , i 2 , i 3 ) recorded for each tested bacteria, the proposed procedure allowed to distinguish the different classes of β-lactamase producers. In the second part of the study, the method was applied to the analysis of one hundred and fifteen samples Enterobacteriaceae -positive blood culture samples of bacteraemic patients. Overall data showed that the voltammetric method offered a sensitivity of 100% and a specificity of 80%. Interestingly, all of sixteen samples infected by a third-generation cephalosporins-resistant bacteria ( i.e. ESBL and overproduced cephalosporinase producers) were detected. This study clearly demonstrated that the voltammetric assay is an efficient alternative technique for the rapid discrimination of β-lactamases-producing Enterobacteriaceae in blood culture. In contrast to the approved routine assays, the electrochemical test did not require isolated colonies to be performed and was thus carried out in less than 3 h which could allow early administration of an appropriate antibiotic therapy. [ABSTRACT FROM AUTHOR]

In this work, we present the validation of the chemical method for total reflection X-ray fluorescence (TXRF) analysis of water, proposed as a standard to the International Standard Organization. The complete experimental procedure to define the linear calibration range, elements sensitivities, limits of detection and quantification, precision and accuracy is presented for a commercial TXRF spectrometer equipped with Mo X-ray tube. Least squares linear regression, including all statistical tests is performed separately for each element of interest to extract sensitivities. Relative sensitivities with respect to Ga, as internal standard, are calculated. Accuracy and precision of the quantification procedure using Ga as internal standard is evaluated with reference water samples. A detailed discussion on the calibration procedure and the limitation of the use of this method for quantitative analysis of water is presented. [ABSTRACT FROM AUTHOR]

High salinity and a relatively high pH are two factors characterizing the marine water environment, which is one of the main final reservoirs receiving pharmaceutical residues. The same factors have an undeniable impact on the extraction efficiency and kinetics of uptakes of polar analytes from water by sorbent-based passive sampling techniques. Recently, we presented a novel passive sampling technique, in which ionic liquids are applied as receiving phases for pharmaceutical monitoring in water (the Passive Sampling with Ionic Liquids technique). In this paper we test the impact of salinity and pH on the PASSIL calibration (sampling rate determination) and the extraction efficiencies of sulfonamides, beta-blockers and nonsteroidal anti-inflammatory drugs selected as model contaminants. Trihexyl(tetradecyl)phosphonium dicyanamide ([P666-14][N(CN) 2 ]) was taken as the stable liquid receiving phase. It selectively extracted neutral and negatively charged analytes from donor solutions of different pH (1, 3, 7 and 9). The presence of salt (7, 20 and 35 PSU) decreased the efficiency (by 5–65%) and R s (by 0.017 L day −1 to 0.574 L day −1 ) of PASSIL for all target compounds. The general conclusion is that salinity and pH have a significant impact on the calibration of passive dosimeters for ionizable compounds, both for the new PASSIL technique and standard POCIS techniques. [ABSTRACT FROM AUTHOR]

Metaldehyde is a potent molluscicide. It is the active ingredient in most slug pellets used for crop protection. This polar compound is considered an emerging pollutant. Due to its environmental mobility, metaldehyde is frequently detected at impacted riverine sites, often at concentrations above the EU Drinking Water Directive limit of 0.1 µg L −1 for an individual pesticide. This presents a problem when such waters are abstracted for use in the production of potable water supplies, as this chemical is difficult to remove using conventional treatment processes. Understanding the sources, transport and fate of this pollutant in river catchments is therefore important. We developed a new variant of the Chemcatcher® passive sampler for monitoring metaldehyde comprising a Horizon Atlantic™ HLB-L disk as the receiving phase overlaid with a polyethersulphone membrane. The sampler uptake rate ( R s ) was measured in semi-static laboratory ( R s = 15.7 mL day −1 ) and in-field (R s = 17.8 mL day −1 ) calibration experiments. Uptake of metaldehyde was linear over a two-week period, with no measurable lag phase. Field trials (five consecutive 14 day periods) using the Chemcatcher® were undertaken in eastern England at three riverine sites (4th September-12th November 2015) known to be impacted by the seasonal agricultural use of metaldehyde. Spot samples of water were collected regularly during the deployments, with concentrations of metaldehyde varying widely (~ 0.03–2.90 µg L −1 ) and often exceeding the regulatory limit. Time weighted average concentrations obtained using the Chemcatcher® increased over the duration of the trial corresponding to increasing stochastic inputs of metaldehyde into the catchment. Monitoring data obtained from these devices gives complementary information to that obtained by the use of infrequent spot sampling procedures. This information can be used to develop risk assessments and catchment management plans and to assess the effectiveness of any mitigation and remediation strategies. [ABSTRACT FROM AUTHOR]

Calibration transfer or standardisation aims at creating a uniform spectral response on different spectroscopic instruments or under varying conditions, without requiring a full recalibration for each situation. In the current study, this strategy is applied to construct at-line multivariate calibration models and consequently employ them in-line in a continuous industrial production line, using the same spectrometer. Firstly, quantitative multivariate models are constructed at-line at laboratory scale for predicting the concentration of two main ingredients in hard surface cleaners. By regressing the Raman spectra of a set of small-scale calibration samples against their reference concentration values, partial least squares (PLS) models are developed to quantify the surfactant levels in the liquid detergent compositions under investigation. After evaluating the models performance with a set of independent validation samples, a univariate slope/bias correction is applied in view of transporting these at-line calibration models to an in-line manufacturing set-up. This standardisation technique allows a fast and easy transfer of the PLS regression models, by simply correcting the model predictions on the in-line set-up, without adjusting anything to the original multivariate calibration models. An extensive statistical analysis is performed in order to assess the predictive quality of the transferred regression models. Before and after transfer, the R 2 and RMSEP of both models is compared for evaluating if their magnitude is similar. T-tests are then performed to investigate whether the slope and intercept of the transferred regression line are not statistically different from 1 and 0, respectively. Furthermore, it is inspected whether no significant bias can be noted. F-tests are executed as well, for assessing the linearity of the transfer regression line and for investigating the statistical coincidence of the transfer and validation regression line. Finally, a paired t -test is performed to compare the original at-line model to the slope/bias corrected in-line model, using interval hypotheses. It is shown that the calibration models of Surfactant 1 and Surfactant 2 yield satisfactory in-line predictions after slope/bias correction. While Surfactant 1 passes seven out of eight statistical tests, the recommended validation parameters are 100% successful for Surfactant 2. It is hence concluded that the proposed strategy for transferring at-line calibration models to an in-line industrial environment via a univariate slope/bias correction of the predicted values offers a successful standardisation approach. [ABSTRACT FROM AUTHOR]

Endpoints of coating processes for colored tablets were determined using in-line Raman spectroscopy. Coatings were performed with six commercially available formulations of pink, yellow, red, beige, green and blue color. The coatings were comprising pigments and/or dyes, some causing fluorescence and interfering the Raman signal. Using non-contact optics, a Raman probe was used as process analytical technology (PAT) tool, and acquired spectra were correlated to the sprayed mass of aqueous coating suspension. Process endpoints were determined using univariate (UV) data analysis and three multivariate analysis methods, namely Projection to Latent Structures (PLS)-regression, Science-Based Calibration (SBC) and Multivariate Curve Resolution (MCR). The methods were compared regarding model performance parameters. The endpoints of all coating experiments could be predicted until a total coating time of 50 min corresponding to coating thicknesses between 21 and 38 µm, depending on the density of the coat formulation. With the exception of SBC, all calibration methods resulted in R 2 values higher than 0.9. Additionally, the methods were evaluated regarding their capability for in-line process monitoring. For each color, at least two methods were feasible to do this. Overall, PLS-regression led to best model performance parameters. [ABSTRACT FROM AUTHOR]

Pasta aside from bread is the most consumed cereal-based product in the world. Its taste and cooking ease makes it the basis of many cuisines. The pasta dough formed by mixing flour and water is extruded through an extrusion die to mould the appropriate pasta form and is dried to obtain a stable product. The concentration of moisture in the pasta dough is a one of key parameters determining the final quality of the product. Monitoring the moisture content of pasta after extrusion is also critically important. It enables a selection of suitable drying conditions that ensure the appropriate parameters of pasta, such as texture, color and taste, are met. A method for the quantitative determination of moisture content in pasta dough and in pasta based on the partial least squares treatment of infrared spectra registered using a single-reflection attenuated total reflectance diamond accessory is described. Results of a similar quality were found using models derived from near infrared spectra obtained in a diffuse reflectance mode and slightly worse based on Raman spectra. Relative standard errors of prediction calculated for moisture quantification by ATR/NIR/Raman techniques amounted to 2.54/3.16/5.56% and 2.15/3.32/5.67%, for calibration and validation sets, respectively. The proposed procedures can be used for fast and efficient pasta moisture quantification and may replace the current, more laborious methods used. [ABSTRACT FROM AUTHOR]

A nitrone formation method using a novel fluorescent reagent 4-hydroxylaminopropyl-7-methoxylcoumarin (HAMC) has been developed and applied for the determination of furfurals in foods using high performance liquid chromatography with fluorescence detection (HPLC-FLD). Furfurals samples were derivatized by HAMC in aqueous condition at room temperature in less than 30 min and were subjected to direct HPLC-FLD analysis without extra purification or extraction. Compared with other conventional methods, nitrone formation method produced single chromatographic peak for each analyte, leading to simpler chromatograms and enhancing the overall sensitivity. Low detection limits at sub-nM level (0.08–0.1 nM) and high repeatabilities (intra-day RSD ≤ 4.2% and inter-day RSD ≤ 6.7%) were achieved. The linear range of the calibration curve was 0.2–4000 nM with good correlation coefficients (R ≥ 0.9989). This method was successfully applied for furfurals determination in food samples, including honey and coffee. The accuracy was satisfactory with recoveries ranging from 89.7% to 106.7% Above all, this pre-column derivatization method is simple, reliable and highly sensitive, providing a promising way for future studies of aldehydes from various sources. [ABSTRACT FROM AUTHOR]

Fourteen samples of tourmaline from the Real Museo Mineralogico of Federico II University (Naples) have been characterized through multi-methodological investigations (EMPA-WDS, SEM-EDS, LA-ICP-MS, and FT-IR spectroscopy). The samples show different size, morphology and color, and are often associated with other minerals. Data on major and minor elements allowed to identify and classify tourmalines as follows: elbaites, tsilaisite, schorl, dravites, uvites and rossmanite. Non-invasive, non-destructive FT-IR and in-situ analyses were carried out on the same samples to validate this chemically-based identification and classification. The results of this research show that a complete characterization of this mineral species, usually time-consuming and expensive, can be successfully achieved through non-destructive FT-IR technique, thus representing a reliable tool for a fast classification extremely useful to plan further analytical strategies, as well as to support gemological appraisals. [ABSTRACT FROM AUTHOR]

When using circular dichroism (CD) spectroscopy for quantitative analysis, the samples to be analyzed must be free of light-absorbing interferences. However, in real-world samples, the presence of background absorbers is practically unavoidable. The difference in the matrices between the real-world samples to be analyzed and the standard samples (on which either univariate or multivariate calibration model was built) would result in systematic errors in the quantification results of CD spectroscopy. In this contribution, a novel calibration strategy for quantitative CD spectroscopic analysis was proposed. The main idea of the proposed calibration strategy is to project the CD spectra of both the standard samples and the real-world sample to be analyzed onto a projection space orthogonal to the space spanned by the background CD spectrum of the real-world sample and then build a multivariate calibration model on the transformed CD spectra of the standard samples. The performance of the proposed calibration strategy was tested and compared with conventional univariate and multivariate calibration methods in the quantification of Pb 2+ in cosmetic samples using CD spectroscopy in combination with a G-quadruplex DNAzyme (e.g. PS2.M). Experiments results revealed that the proposed calibration strategy could mitigate the influence of the difference in the matrices between the standard samples and cosmetic samples and realized quantitative analysis of Pb 2+ in cosmetic samples, with precision and accuracy comparable to atomic absorption spectroscopy. The proposed calibration strategy has the features of simplicity and effectiveness, its combination with CD spectroscopic probes can realize accurate and precise quantification of analytes in complex samples using CD spectroscopy. [ABSTRACT FROM AUTHOR]

In our work, we introduced a novel concept of the lab-in-a-syringe tests. We solved the problem of detection in already published LIS tests by putting all the reaction and detection pads directly into the syringe barrel. We also used more layers to make the results visible for users. Two detection layouts: (i) with using rounded pads-based detection, and (ii) with using rectangular detection pads, were studied. As the proof of concept, we studied the determination of Ni(II) using dimethylglyoxime as the reagent and blocking of the interference of Fe(II). The calibrations for Ni(II) at the optimal conditions has excellent R 2 of 0.998 with production costs of 0.2 USD per one test. [ABSTRACT FROM AUTHOR]

Since linear calibration is mostly preferred for analytical determinations, linearity in the calibration range is an important performance characteristic of any instrumental analytical method. Linearity can be proved by applying several graphical and numerical approaches. The principal graphical criteria are visual inspection of the calibration plot, the residuals plot, and the response factors plot, also called sensitivity or linearity plot. All of them must include confidence limits in order to visualize linearity deviations. In this work, the graphical representation of percent relative errors of back-calculated concentrations against the concentration of the calibration standards is proposed as linearity criterion. This graph considers a confidence interval based on the expected recovery related to the concentration level according to AOAC approach. To illustrate it, four calibration examples covering different analytical techniques and calibration situations have been studied. The proposed %RE graph was useful in all examples, helping to highlight problems related to non-linear behavior such as points with high leverage and deviations from linearity at the extremes of the calibration range. By this way, a numerical decision limit which takes into account the concentration of calibration standards can be easily included as linearity criterion in the form of %RE Th =2·C −0.11 . Accordingly, this %RE parameter is accurate for the decision-making related to linearity assessment according to the fitness-for-purpose approach. [ABSTRACT FROM AUTHOR]

A calibration strategy using porous nylon disks and reference solutions is proposed for the first time for matrix matching and determination of As, Ba, Cd, Cr, Pb, Sr and Zn in polymers by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). Polymer samples commonly used in contact with food were analyzed. The procedure consists on the use of porous nylon disks as support for a dried droplet reference solution. Calibration in the range of 0.50–190 μg g −1 for Ba, Cd, Cr, Pb, Sr and Zn and from 0.30–9.0 μg g −1 for As was used. Laser and ICP-MS instrument conditions were evaluated in order to achieve the best signal-to-background ratio. The radiofrequency power and carrier gas flow rate were fixed at 1300 W and 1.25 L min −1 , respectively. Spot size, repetition rate, scan line speed and laser fluency were set to 100 µm, 20 Hz, 100 µm s −1 and 17.9 J cm −2 , respectively, as the established conditions for analysis of standards and samples. By using these conditions, limits of detection, estimated considering B+3s (where B is the value of the blank and s is the standard deviation of 10 measurements of the blank), ranged from 0.09 μg g −1 ( 208 Pb) to 1.09 ( 53 Cr) and 0.05 μg g −1 ( 208 Pb) to 2.10 ( 53 Cr) for calibration with and without 13 C as internal standard (IS). In spite to the use of nylon for matrix matching of different polymeric matrices, the normalization with 13 C as IS was also evaluated. The precision of the method is relatively good (RSD<20%), and the accuracy of the method, evaluated by analysis of certified reference materials (CRM) and by comparison with results obtained from solution analysis by ICP-MS after sample decomposition by microwave induced combustion (MIC) is relatively good. The suitability of the proposed method resulted in direct and reliable analyses of polymer samples with a simplified or unnecessary sample preparation step. In addition, the calibration with dried droplet reference solutions may be considered a promising procedure in view of its advantages to other forms of calibration, as the use of CRM or the preparation of synthetic standards. The use of porous nylon disks spiked with reference solutions for calibration is the main advantage of the present work. [ABSTRACT FROM AUTHOR]

A Staphylococcus aureus ( S. aureus )-specific lytic bacteriophage P- S. aureus -9, isolated from an environmental water sample, was assembled on magnetic beads for capturing S. aureus from samples through magnetic separation. Horseradish Peroxidase (HRP) labeled immunoglobulin (IgG) antibodies were used to detect the captured S. aureus by reacting with protein A on S. aureus followed by colorimetric signals, which were generated from the catalytic reaction between HRP and the substrate 3,3′,5,5′-Tetramethylbenzidine (TMB). Under optimal conditions, the calibration curve was linear from 1.0×10 4 to 1.0×10 6 CFU mL −1 . The limit of detection (LOD) for the assay was 2.47×10 3 CFU mL −1 and 8.86×10 3 CFU mL −1 of S. aureus in PBS and apple juice, respectively. Moreover, the whole assay revealed outstanding specificity towards S. aureus , without any interference of common pathogenic bacteria, and can be completed within 90 min without any pre-enrichment. As far as known, it was the first time to detect S. aureus based on the double site recognition of bacteriophage and mammal IgG. The novel approach has shown good potentials for a rapid, specific, cheap and simple detection of S. aureus in food samples. [ABSTRACT FROM AUTHOR]

The procedure for transfer of calibration models between different analytical methods is suggested. It is based on the direct standardization (DS) algorithm earlier suggested for data conversion between physically different instruments of the same type. As a result, multivariate regression models obtained e.g. for NIR spectroscopic measurements in one wavelength range can be successfully applied for predictions from the data obtained with another NIR spectrometer in another wavelength range. The performance of the suggested method was tested with two simulated and two real datasets. In the latter case calibration models constructed for energy-dispersive X-ray fluorescence, UV–Vis spectrometry and NIR spectrometry were addressed. The observed performance of the method implies that it can have a broad range of possible applications in analytical chemistry; some of them are suggested in the paper. [ABSTRACT FROM AUTHOR]

While the biological function of the 3α epimer of 25-hydroxyvitamin D 3 (25(OH)D 3 ) remains unknown, its presence needs to be accurately captured and separated from the main 3β epimer, to avoid positive bias in vitamin D status analyses. Several recent LC-MS/MS assays for 25(OH)D 3 successfully separate the 3α and 3β epimers by chromatography. Unfortunately, none of the existing LC-MS/MS assays, which utilize dried blood spots (DBS) as sampling/storage vessels, is able to quantify the individual epimers. DBS are often used for analysis of infant blood, however, and these samples are particularly likely to contain significant levels of interfering 3α epimer. Furthermore, proper calibration of DBS samples is much more difficult to achieve than for liquid serum or plasma samples. We addressed this important issue by creating an artificial vitamin D -free whole blood for calibration and then quantified 3α- and 3β-25(OH)D 3 levels from DBS. After chemical derivatization, the vitamin D epimers were separated on a PFP column and concentrations determined by electrospray ionization LC-MS/MS on a triple quadrupole mass spectrometer. Calibration with artificial whole blood showed improved precision over standard addition (7.6 versus 31.5% RSD for 3β-25(OH)D 3 ). The limits of quantification for 3β-25(OH)D 3 and for 3α-25(OH)D 3 were 1.0 and 0.1 ng/mL, respectively. Excellent intra/interday precisions between 2.1 and 2.2% CV (intra) and 4.4–5.3% CV (inter) were established for 3β-25(OH)D 3 and 3α-25(OH)D 3 . For 3β-25(OH)D 3 , only small concentration-independent bias and deviation of <3.3 ng/mL were seen between serum LC-MS/MS and DBS-LC-MS/MS measurements; analyses of 3α-25(OH)D 3 showed deviations of <0.8 ng/mL in all experiments. [ABSTRACT FROM AUTHOR]

A novel approach to calibration, based on automated dilution of a single standard solution, is combined with monitoring of the sample and reagent mixture under batch conditions, that is at equilibrium in a homogenous solution that has been arrested in a flow cell. This procedure eliminates the schlieren effect and demonstrates that there are no differences between reaction rates in deionized water and sea water. The method, based on flow programming, is applied to the determination of phosphate in sea water and is validated by analysis of certified reference materials. [Display omitted] • Flow programming with a batch mode eliminates the schlieren effect. • A concentrated standard is used to develop a multi point calibration automatically. • Deionized water-based calibration is applicable to brackish and open ocean waters. [ABSTRACT FROM AUTHOR]

In this work, a colorimetric microfluidic paper-based analytical device (μPAD) combined with a smartphone readout was proposed for the determination of serum iron (Fe3+), which is linked to transferrin. Firstly, Fe3+ was selectively isolated and preconcentrated from serum by using anti-transferrin immunomagnetic beads (anti-Tf-MBs). Secondly, Fe3+ is reduced to Fe2+ by a hydroxylamine solution (pH 4.8) and then measured in the μPAD, which contains the colorimetric reagent ferrozine. Finally, the intensity of the purple color formed in the μPAD was measured by a smartphone. The approach exhibited an excellent linear correlation (r = 0.996) and good limit of detection (0.3 μg mL−1). Moreover, a certified reference material (human serum) was analyzed by this approach, showing an excellent accuracy (E r < 4%) and inter-device reproducibility (RSD = 1%, n = 3). Interestingly, the μPAD array-design allowed the simultaneous analysis of different samples, improving the sample throughput (up to 5 samples in 130 min, using 100 μL each), and the integration of calibration and analysis into the same device, simplifying the analysis without losing accuracy or sensitivity, and avoiding inter-device variability, which constituted an added value to this approach. These disposable μPADs meet several requirements of point-of-care testing (POCT) because it is cheap, portable, easy-to-use, sensitive, and specific. Therefore, it may be an interesting way for measuring patients' serum iron levels in situ with reliability, especially, in developing countries, where the prevalence of iron deficiency and iron-deficiency anemia is higher and there are lower health resources than in developed countries. [Display omitted] • A colorimetric μPAD with smartphone reading was developed for serum iron determination. • Anti-transferrin immunomagnetic beads were used for iron isolation and preconcentration. • Calibration and analysis were integrated on board the same μPAD. • The method was validated by analyzing a certified reference material (human serum). • The approach showed excellent accuracy (error <4%) and precision (RSD = 1%). [ABSTRACT FROM AUTHOR]

This article tests the suitability of a new method to monitor the degree of substitution of cellulose acetate films, by employing a compact and inexpensive near-infrared miniaturized spectrometer (908.1-1676.2 nm) that can be easily applied in situ. The present study compares the analytical performance of the proposed method against conventional diagnostic strategies based on benchtop micro-attenuated total reflectance Fourier transform Infrared (μATR -FTIR) measurements in the mid-infrared spectral range. The novel calibration function exploits the shifts in the first overtone of the hydroxyl stretching 2νOH band of probe materials and was created using a set of analytical standards with different degrees of substitution. The robustness of the method was assessed by application on a group of sixteen historical cinematographic films. The accurate condition assessment of these films was performed in situ, in a non-invasive manner. The proposed analytical procedure is quick and easy-to-implement, and therefore it constitutes a rapid method to guide conservation strategies regarding film storage and digitalization in cultural institutions, including museums and cinematheques. Potential applications on three-dimensional objects and industrial processes are possible., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Handheld X-ray fluorescence spectrometers (XRFs) represent a more practical, efficient and economic tool to determine the elemental composition of solid inorganic and organic samples than conventional analytical techniques. The objective of this work was to demonstrate that handheld XRFs could be a precise, accurate and reliable tool to analyze up to 27 different elements. This objective was accomplished through the optimization of an empirical calibration curve that, in addition to include certified reference materials (CRM), it also introduced new approaches, such as the use of solid CRM mixtures and combinations of organic and inorganic matrices. These approaches significantly increased the number of calibration points and eliminated hiatuses in the calibration curve. Several factors were evaluated before construction of the calibration curve: incidence time of the X-ray beam, type of film through which the X-ray beams reach the samples, container type, minimum sample volume and sample moisture content. Results show that single elements can be analyzed with variable exposure times or, alternatively, multielemental analyses can be carried out with a constant exposure time (180 s). Costs can be reduced by using Ziploc ® bags as sample containers, but the number of measurable elements drops from 27 to 21, while the possibility of contamination increases. [ABSTRACT FROM AUTHOR]

Bromine has been recognized as a valuable indicator for paleoclimatic studies. Wavelength dispersive X-ray fluorescence (WDXRF) and total reflection X-ray fluorescence (TXRF) methods were applied to study the bromine distributions in lake sediment cores. Conventional WDXRF technique usually requires relatively large mass of a sediment sample and a set of calibration samples. Some analytical approaches were developed to apply WDXRF to small sediment core samples in the absence of adequate calibration samples with a known Br content. The mass of a sample to be analyzed was reduced up to 200–300 mg and the internal standard method with correction using fundamental parameters was developed for Br quantification. TXRF technique based on the direct analysis of a solid suspension using 20 mg of sediment sample by internal standard method was additionally tested. The accuracy of the WDXRF and TXRF techniques was assessed by the comparative analysis of reference materials of sediments, soil and biological samples. In general, good agreement was achieved between the reference values and the measured values. The detection limits of Br were 1 mg/kg and 0.4 mg/kg for WDXRF and TXRF respectively. The results of the Br determination obtained with different XRF techniques were comparable to each other and used for paleoclimatic reconstructions. [ABSTRACT FROM AUTHOR]

The biopharmaceutical industry extensively employs Chinese hamster ovary (CHO) cell culture for monoclonal antibody production. Amino acids represent an essential source of nutrients in all CHO cell culture media, and their concentration is known to significantly impact cell viability, titre, and monoclonal antibody critical quality attributes. In this study, a robust Fourier transform near-infrared spectroscopy (FT-NIR) based quantification method has been developed for of all 20 amino acids (0-24 mM), as well as concentrations of glucose (0-6.7 mg mL -1 ), lactate (0-2.7 mg mL -1 ), and trastuzumab (0-2.5 mg mL -1 ) in the CHO cell culture. Near infra-red absorbance spectrum in the range of 4000-11,000 cm -1 were acquired, and spectra pre-processing through smoothening and derivatives were employed to enhance key characteristic signals. High-performance liquid chromatography with pre-column derivatization was used as the orthogonal analytical tool for quantification. Principal component analysis and partial least squares regression were employed for region selection and calibration model development, respectively. The results demonstrate that a good calibration statistic with the acceptable coefficient of determinations for both calibration (R c 2  = 0.94-0.99) and prediction (R p  = 0.89-0.99, RMSE = 0.04-1.04), validating the model's ability to predict the concentrations of the respective species. The calibration models were successfully applied for at-line monitoring of two perfusion runs on a 10 L scale. To our knowledge, this is the first application where NIR spectroscopy-based measurement of all 20 amino acids in mammalian cell culture samples has been demonstrated. The proposed tool can play a critical role as biopharma manufacturers implement continuous processing as well as for facilitating process analytical technology-based control of mammalian cell culture processes.2  = 0.83-0.98) could be achieved, along with high RPD values (>3) for all components except alanine (2.4). The external validation study also exhibited a satisfactory outcome (R EV 2  = 0.89-0.99, RMSE = 0.04-1.04), validating the model's ability to predict the concentrations of the respective species. The calibration models were successfully applied for at-line monitoring of two perfusion runs on a 10 L scale. To our knowledge, this is the first application where NIR spectroscopy-based measurement of all 20 amino acids in mammalian cell culture samples has been demonstrated. The proposed tool can play a critical role as biopharma manufacturers implement continuous processing as well as for facilitating process analytical technology-based control of mammalian cell culture processes., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Anurag S Rathore reports financial support was provided by India Ministry of Science & Technology Department of Biotechnology., (Copyright © 2022 Elsevier B.V. All rights reserved.)