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The widespread application of enzymes in industrial chemical synthesis requires efficient process control to maintain high yields and purity. Flow injection analysis-electrospray ionization-mass spectrometry (FIA-ESI-MS) offers a promising solution for real-time monitoring of these enzymatic processes, particularly when handling challenging compounds like sugars and glycans, which are difficult to quickly analyze using liquid chromatography-mass spectrometry due to their physical properties or the requirement for a derivatization step beforehand. This study compares the performance of FIA-MS with traditional hydrophilic interaction liquid chromatography (HILIC)-ultra high-performance liquid chromatography (UHPLC)-mass spectrometry (MS) setups for the monitoring of the enzymatic synthesis of N-acetyllactosamine (LacNAc) using beta-1,4-galactosyltransferase. Our results show that FIA-MS, without prior chromatographic separation or derivatization, can quickly generate accurate mass spectrometric data within minutes, contrasting with the lengthy separations required by LC-MS methods. The rapid data acquisition of FIA-MS enables effective real-time monitoring and adjustment of the enzymatic reactions. Furthermore, by eliminating the derivatization step, this method offers the possibility of being directly coupled to a continuously operated reactor, thus providing a rapid on-line methodology for glycan synthesis as well., (© 2024. The Author(s).)

A sequential injection analysis method for the determination of glutathione (GSH) in pharmaceuticals has been developed. It is based on the reduction of the Cu(II)-neocuproine complex by GSH and the formation of an orange-yellow colored Cu(I)-neocuproine complex with maximum absorbance at 458 nm. Under optimal conditions the method is characterized by a linear calibration range of 6.0 × 10 -7 -8.0 × 10 -5 mol L -1 ( A max = 3270 C GSH - 0.0010; R 2 = 0.9983), limit of detection of 2.0 × 10 -7 mol L -1 , limit of quantification of 6.7 × 10 -7 mol L -1 , repeatability (expressed as relative standard deviation) of 3.8%, and sampling rate of 60 h -1 . The newly developed method has been successfully applied to the determination of GSH in pharmaceutical samples with no statistically significant difference between the results obtained and those produced by the standard Pharmacopoeia method.

This work introduces an innovative gold-leaf flow cell for electrochemical detection in flow injection (FI) analysis. The flow cell incorporates a hammered custom gold leaf electrochemical sensor. Hammered gold leaves consist of pure gold and are readily available in Thailand at affordable prices (approximately $0.085 for a sheet measuring 40 mm × 40 mm). Four sensing devices can be made from a single sheet of this gold leaf, resulting in a production cost of approximately $0.19 per sensor. Each electrochemical sensor has the gold leaf as the working electrode, together with a printed carbon strip, and a printed silver/silver chloride strip as the counter and reference electrodes, respectively. Initial investigations using cyclic voltammetry of a standard 1000 μmol L⁻ 1 iodide solution in 60 mmol L⁻ 1 phosphate buffer (PB) solution at pH 5, demonstrated performance comparable to that of a commercial screen-printed gold electrode. The hammered gold leaf electrode was then installed in a commercial flow cell as part of an FI system. A sample or standard iodide solution (100 μL) is injected into the first carrier stream of phosphate buffer (PB) solution, which then merges to mix with the second stream of the same buffer solution before flowing into the flow cell for amperometric detection of iodide. The optimized operating conditions include a fixed potential of +0.39 V (vs Ag/AgCl), and a total flow rate of 3 mL min⁻ 1 . A linear calibration is obtained in the concentration range of 1 to 1000 μmol L⁻ 1 I - with a typical equation of μA = (0.00299 ± 0.00004) × (μmol L -1 I - ) + (0.021 ± 0.020), and R 2  = 0.9994. Analysis of iodide using this gold leaf-FI system is rapid with sample throughput of 86 samples h⁻ 1 and %RSD of a sample of 100 μmol L⁻ 1 I⁻ of 1.2 (n = 29). The limit of detection, (calculated as 2.78 × SD of regression line/slope), is 27 μmol L⁻ 1 I - . This method was successfully applied to determine iodide in nuclear emergency tablets., 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 © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Efficient evaluation of adsorption kinetics of plant total polyphenols is essential for the design of adsorption separation of bioactive compounds. The conventional method uses manual sampling with poor reproducibility. Here, we developed a new method for on-line determination of total polyphenol content (TPC) in plant extracts by applying the Folin-Ciocalteu method in flow-injection analysis (FIA). The FIA parameters were optimized and a standard curve with excellent linearity was established. Precise determination of TPC with a satisfactory sample throughput of 20 h -1 was achieved for the adsorption kinetic study. The pseudo-second-order kinetic model was found to better describe the kinetic parameters of the batch adsorption/desorption process. The developed method proved to be accurate compared with the conventional method. The FIA method holds significant promise for studying and monitoring adsorption processes, due to its automatic on-line nature, low consumption of reagents and samples, and the ability to generate large quantities of highly accurate adsorption data.

The online photoreaction of the rose bengal photosensitized luminol-copper (II) chemiluminescence (CL) system was used for the determination of β-nicotinamide adenine dinucleotide (NADH) and ethanol (EtOH) in pharmaceutical formulations combined with a flow injection technique. NADH can significantly enhance the CL emission of the reaction. For EtOH, alcohol dehydrogenase in soluble form was utilized in the presence of nicotinamide adenine dinucleotide resulting in NADH production. The limit of detection (3σ blank, 𝑛 = 3) of 4.0 × 10 -8 and 2.17 × 10 -5  M, and linear range 1.3 × 10 -7 to 2.5 × 10 -5  M (R 2  = 0.9998, n = 6) and 0.11-2.17 × 10 -3  M (R 2  = 0.9996, n = 6) were obtained for NADH and EtOH respectively. The injection rate was 100 h -1 with a relative standard deviation (n = 3) of 1.5-4.8% in the range studied for both analytes. The procedure was satisfactorily applied to pharmaceutical formulations with recoveries in the range 91.6 ± 3.0% to 110 ± 2.0% for NADH and 88 ± 3.0% to 95.4 ± 4.0% for EtOH. The results obtained were very consistent and did not differ considerably from the reported approaches at a 95% confidence limit. The possible mechanism of the CL reaction is also explained briefly., (© 2023 John Wiley & Sons Ltd.)

A flow injection (FI) methodology using the acidic potassium permanganate (KMnO 4 )-rhodamine-B (Rh-B) reaction with chemiluminescence (CL) detection was established to determine acetochlor and cartap-HCl pesticides in freshwater samples. Experimental parameters were optimized, and Chelex-100 cationic exchanger mini column and solid-phase extraction (SPE) were used as phase separation techniques. Linear calibration curves were observed for the standard solutions of acetochlor and cartap-HCl over the ranges 0.005-2.0 mg L -1 [y = 1155.8x + 57.551, R 2  = 0.9999 (n = 8)] and 0.005-1.0 mg L -1 [y = 979.76x + 14.491, R 2  = 0.9998 (n = 8)] with LODs and LOQs of 7.5 × 10 -4 and 8.0 × 10 -4  mg L -1 (3σ blank) and 2.5 × 10 -3 and 2.7 × 10 -3  mg L -1 (10σ blank), respectively, with an injection throughput of 140 h -1 . These methods were used to estimate acetochlor and cartap-HCl with or without the SPE procedure, respectively, in spiked freshwater samples. Results obtained were not significantly different at a 95% confidence level to those of other reported methods. Recoveries for acetochlor and cartap-HCl were obtained over the ranges 93-112% (RSD = 1.9-3.6%) and 98-109% (RSD = 1.7-3.8%), respectively. The most probable CL reaction mechanism was explored., (© 2023 John Wiley & Sons Ltd.)

A novel flow injection-chemiluminescence (FI-CL) approach is proposed for the assay of pioglitazone hydrochloride (PG-HCl) based on its enhancing influence on the tris(2,2'-bipyridyl)ruthenium(II)-silver(III) complex (Ru(bipy) 3 2+ -DPA) CL system in sulfuric acid medium. The possible CL reaction mechanism is discussed with CL and ultraviolet (UV) spectra. The optimum experimental conditions were found as: Ru(bipy) 3 2+ , 5.0 × 10 -5  M; sulfuric acid, 1.0 × 10 -3  M; diperiodatoargentate(III) (DPA), 1.0 × 10 -4  M; potassium hydroxide, 1.0 × 10 -3  M; flow rate 4.0 ml min -1 for each flow stream and sample loop volume, 180 μl. The CL intensity of PG-HCl was linear in the range of 1.0 × 10 -3 to 5.0 mg L -1 (R 2  = 0.9998, n = 10) with limit of detection [LOD, signal-to-noise ratio (S/N) = 3] of 2.2 × 10 -4  mg L -1 , limit of quantification (LOQ, S/N = 10) of 6.7 × 10 -4  mg L -1 , relative standard deviation (RSD) of 1.0 to 3.3% and sampling rate of 106 h -1 . The methodology was satisfactorily used to quantify PG-HCl in pharmaceutical tablets with recoveries ranging from 93.17 to 102.77 and RSD from 1.9 to 2.8%., (© 2022 John Wiley & Sons Ltd.)

Background: Scientific, accurate, and rapid detection of the composition and content of tea polyphenols is an important basis for their rational use and giving full play to their physiological effect. The spectrophotometric assays for total polyphenols have poor selectivity. Therefore, there is a need to develop a simple and reliable method for the determination of the total polyphenolic level in tea products., Objective: The aim of this research was to develop a flow injection chemiluminescence (FI-CL) method based on the Ag(III)-luminol system for the total polyphenol content analysis of tea and substitute tea., Method: Through Box-Behnken experimental design, we selected the optimum determination condition. The Ag(III) concentration was 5 × 10-5 mol/L, and the luminol concentration was 3 × 10-7 mol/L (including 0.15 mol/L NaOH). The peristaltic pump is 25 r/min, and the photomultiplier voltage is 600 v. Sample extracts were diluted 100 000 times for the FI-CL assay., Results: Under optimal conditions, CL intensities were proportional to total polyphenol content (in terms of gallic acid concentrations) in the range of 0.1∼100 μg/L. The LOD and LOQ were 0.03 μg/L and 0.1 μg/L. The recovery values were in the range of 86.3-111.0% with a RSD of 1.04∼2.62%. The polyphenolic content of 12 teas and 6 substitute teas was determined, and the results of the developed method and Folin-Ciocalteu method were highly correlated (r = 0.9493 for tea and r = 0.8533 for substitute tea)., Conclusions: The proposed method is better than the Folin-Ciocalteu method in terms of selectivity, sensitivity, and accuracy. It is suitable for the determination of polyphenol content not only in tea, but also in substitute tea., Highlights: We developed a new flow-injection analysis method for polyphenolic content determination based on the Ag(III)-luminol chemiluminescence system. It is simple, rapid, sensitive, and accurate. It is suitable for the determination of polyphenols content not only in tea, but also in substitute tea., (© The Author(s) 2022. Published by Oxford University Press on behalf of AOAC INTERNATIONAL. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

This study developed a simple flow injection (FI) method based on diperiodatonickelate(IV)-sulfuric acid reaction using chemiluminescence (CL) detection for the determination of thiram (THI) fungicide in fresh water using quinine as the sensitizer. The possible mechanism of the CL reaction was described using UV-Vis. absorption and CL spectra. Experimental variables were optimized by applying a univariate approach, and a linear calibration curve was obtained in the range of 1.0 × 10 -3 -2.0 mg L -1 (R 2  = 0.9994, n = 9) with a limit of detection of 5.0 × 10 -4  mg L -1 (S/N = 3) and an injection throughput of 200 h -1 . This approach was successfully applied to determine THI in fresh water by using solid-phase extraction and achieved a good recovery rate of 94%-110% with a relative standard deviation of 1.9%-3.7% (n = 4). The results obtained were compared with the reported FI-CL and high-performance liquid chromatography-ultraviolet methods, and the three methods did not differ significantly at the 95% confidence limit., (© 2022 John Wiley & Sons Ltd.)

Background: Newborn screening (NBS) laboratories in the United Kingdom adhere to common protocols based on single analyte cutoff values (COVs); therefore, interlaboratory harmonization is of paramount importance. Interlaboratory variation for screening analytes in UK NBS laboratories ranges from 17% to 59%. While using common stable isotope internal standards has been shown to significantly reduce interlaboratory variation, instrument set-up, sample extraction, and calibration approach are also key factors., Methods: Dried blood spot (DBS) extraction processes, instrument set-up, mobile-phase composition, sample introduction technique, and calibration approach of flow injection analysis-tandem mass spectrometry (FIA-MS/MS) methods were optimized. Inter- and intralaboratory variation of methionine, leucine, phenylalanine, tyrosine, isovaleryl-carnitine, glutaryl-carnitine, octanoyl-carnitine, and decanoyl-carnitine were determined pre- and postoptimization, using 3 different calibration approaches., Results: Optimal recovery of analytes from DBS was achieved with a 35-min extraction time and 80% methanol (150 μL). Optimized methodology decreased the mean intralaboratory percentage relative SD (%RSD) for the 8 analytes from 20.7% (range 4.1-46.0) to 5.4% (range 3.0-8.5). The alternative calibration approach reduced the mean interlaboratory %RSD for all analytes from 16.8% (range 4.1-25.0) to 7.1% (range 4.1-11.0). Nuclear magnetic resonance analysis of the calibration material highlighted the need for standardization. The purities of isovaleryl-carnitine and glutaryl-carnitine were 85.13% and 69.94% respectively, below the manufacturer's stated values of ≥98%., Conclusions: For NBS programs provided by multiple laboratories using single analyte COVs, harmonization and standardization of results can be achieved by optimizing legacy FIA-MS/MS methods, adopting a common analytical protocol, and using standardized calibration material rather than internal calibration., (© American Association for Clinical Chemistry 2022.)

Total dissolved sulfide (TDS) plays multiple important roles in the aquatic environments. However, the determination of trace levels of TDS in natural waters is challenging because TDS is vulnerable to oxidation and volatilization. In this study, a fully automated flow injection analysis spectrophotometric system, incorporating a hollow fiber membrane contactor (HFMC) and a long path length liquid waveguide capillary cell, was fabricated to facilitate the on-site measurement of trace TDS in natural waters. The HFMC was used for matrix separation and analyte preconcentration. The measurement was based on the reaction of sulfide and N,N-dimethyl-p-phenylenediamine in the presence of FeCl 3 under acidic conditions to yield methylene blue (MB). The proposed method was highly sensitive, with detection and quantification limits of 0.57 and 1.90 nmol L -1 , respectively. The linear working range was from 1.90 to 150 nmol L -1 , with a correlation coefficient of 0.9995. The repeatability, expressed as the relative standard deviation, was less than 0.86% (n = 15) and the recoveries varied from 76.2 ± 0.1% to 103.9 ± 0.6% (n = 3) for spiked samples. This method was applied to conduct a field analysis of TDS in a reservoir, giving results aligned with those obtained using a standard MB method. This work demonstrates that the new method for determining TDS was effective for both laboratory analysis and on-site measurement., 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.)

In this article, nickel(II) oxide (NiO) hollow microspheres (HMSs) were fabricated and used to catalyze chemiluminescence (CL) reaction. The studied CL reaction is the luminol-oxygen reaction that was used as a sensitive analytical tool for measuring tuberculostatic drug isoniazid (IND) in pharmaceutical formulations and water samples. The CL method was established based on the suppression impact of IND on the CL reaction. The NiO HMSs were produced by a simple hydrothermal method and characterized by several spectroscopic techniques. The result of essential parameters on the analytical performance of the CL method, including concentrations of sodium hydroxide (NaOH), luminol, and NiO HMSs were investigated. At the optimum conditions, the calibration curve for IND was linear in the range of 8.00 × 10 -7 to 1.00 × 10 -4  mol L -1 (R 2  = 0.99). A detection limit (3S) of 2.00 × 10 -7  mol L -1 was obtained for this method. The acceptable relative standard deviation (RSD) was obtained for the proposed CL method (2.63%, n = 10) for a 5.00 × 10 -6  mol L -1 IND solution. The mechanism of the CL reaction was also discussed., (© 2022 John Wiley & Sons Ltd.)

A chemiluminescence (CL) method based on rhodamine 6G (R6G)-diperiodatoargentate(III) (silver(III) complex) reaction in acid solution is reported for the determination of lansoprazole (LNP) combined with a flow injection (FI) technique. The most likely mechanism for CL reaction was elucidated considering reported data, spectrophotometric and spectrofluorimetric studies. The weak CL reaction between R6G and silver(III) complex could be magnanimously increased in the presence of LNP with a limit of detection (LOD) of 0.002 mg L -1 (S/N = 3), a linear range of 0.01 to 10 mg L -1 (R 2  = 0.9997, n = 7), a relative standard deviation (RSD) of 1.2 to 3.2% (n = 4) and an injection throughput of 140 h -1 . No interference activity of commonly found excipients in LNP was detected. After LNP extraction from pharmaceutical samples, the recovery rate ranging from 93 to 110% (RSD, 1.4-3.3%, n = 4) was calculated. The results of the proposed flow CL method were assessed with a spectrophotometric approach applying paired Student's t-test and the calculated value (0.178) was lower than the distributed value (2.20) at a 95% confidence limit., (© 2022 John Wiley & Sons Ltd.)

A fully-mechanized bioanalytical system for the photometric light-driven lactate determination is presented. The system is based on highly integrated four diode flow-through cell in which two UV-LEDs are used for the photochemical reduction of Fe(III) in the presence of lactate whereas LED-photodiode system allows the photometric detection of Fe(II)-Ferrozine complex to be registered. The developed multicommutation flow analysis system consisting of bifunctional optoelectronic device (photodegradation of Fe(III)-lactate complex and detection), solenoid micropumps and microvalves, is fully controlled and powered by the Arduino-compatible electronics. In consequence, independent and precise control of crucial parameters of the assay, including irradiation time and current supplying UV-LEDs is possible. Under optimized condition the system is useful for the lactate determination in the sub-milimolar range of concentration (6.0-300.0 μmol/L) with satisfactory sensitivity (597.1 AU·L/μmol) and detection limit (3.4 μmol/L), significant reduction of sample and reagents consumption (1.25 μL or 0.5 μL for 40- and 100-fold dilution of human serum samples, respectively) and high sample flow throughput (24 detections per hour). As the system offers the monitoring of detection process, the kinetic discrimination of effects from potential interferents is possible, improving the assay selectivity. The practical utility of the designed system was confirmed by its used for analysis of human serum standards. The recovery values were in the range of 92.1-104.2%. As the limit of quantitation offered by the system is significantly lower than physiological lactate levels, the serum samples have to be diluted what results in further decrease of both sample volume required for analysis and nonselective effects from matrix., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Lysophosphatidylcholine (LPC) plays pivotal roles in several physiological processes and their disturbances are closely associated with various disorders. In this study, we described the development and validation of a reliable and simple flow injection analysis-tandem mass spectrometry (FIA-MS/MS)-based method using dried blood spots (DBS) for quantification of four individual LPC (C20:0, C22:0, C24:0, and C26:0)., Methods: Lysophosphatidylcholines were extracted from 3.2 mm DBS with 85% methanol containing 60 ng/ml internal standard using a rapid (30 min) and simple procedure. The analytes and the internal standard were directly measured by triple quadrupole tandem mass spectrometry in multiple reactions monitoring mode via positive electrospray ionization., Results: Method validation results showed good linearity ranging from 50 to 2000 ng/ml for each LPC. Intra- and inter-day precision and accuracy were within the acceptable limits at four quality control levels. Recovery was from 70.5% to 107.0%, and all analytes in DBS were stable under assay conditions (24 h at room temperature and 72 h in autosampler). The validated method was successfully applied to assessment of C20:0-C26:0LPCs in 1900 Chinese neonates. C26:0-LPC levels in this study were consistent with previously published values., Conclusion: We propose a simple FIA-MS/MS method for analyzing C20:0-C26:0LPCs in DBS, which can be used for first-tier screening., (© 2021 The Authors. Journal of Clinical Laboratory Analysis published by Wiley Periodicals LLC.)

A miniaturized microsequential injection/lab-on-valve (µSIA-LOV) system was developed and shown to be a useful alternative to perform inhibitory studies on acetylcholinesterase. These studies are essential for the evaluation of the potential therapeutic effect of drugs commonly used in the treatment of Alzheimer's disease. Donepezil, galantamine, and rivastigmine were tested, in addition to compounds based on the xanthone scaffold. Four of these xanthone derivatives were identified as having EC 50 values between 676 and 4466 µmol/l, showing a potential inhibitory effect higher than the clinical agent rivastigmine. The developed automatic system added advantages of reduction of reagents and sample consumption (around 55 µl per analysis), lower cost per analysis, and the generation of less waste (around 1.2 ml per analysis). The µSIA-LOV system is also a robust, rapid, reliable, and simple system to use. Docking studies suggested a possible mode of interaction with the target acetylcholinesterase protein., (© 2021 Deutsche Pharmazeutische Gesellschaft.)

The internal flow and macroscopic spray behaviors of a fuel injection process were studied with schlieren spray techniques and simulations. The injection pressures(Pin)and ambient pressures(Pout)were applied in a wide range. The results showed that increasing the Pin is likely to decrease the flow performance of the nozzle. Furthermore, increasing the Pin can increase the spray tip penetration. However, the effect of Pin on the spray cone angle was not evident. The spray cone angle at an injection pressure of 160MPa was 21.7% greater than at a pressure of 100MPa during the initial spraying stage. Additionally, the discharge coefficient increased under high Pout, and the decrease in Pout can promote the formation of cavitation. Finally, increasing the Pout can decrease the penetration, while the spray angle becomes wider, especially at the initial spray stage, and high Pout will enhance the interaction of the spray and the air, which can enhance the spray quality., Competing Interests: The authors have declared that no competing interests exist.

This paper presents the development and the application of a multisyringe flow injection analysis system for the fluorimetric determination of the major heat-stable known allergen in shrimp, rPen a 1 (tropomyosin). This muscle protein, made up of 284 amino acids, is the main allergen in crustaceans and can be hydrolyzed by microwave in hydrochloric acid medium to produce glutamic acid, the major amino acid in the protein. Glutamic acid can then be quantified specifically by thermal conversion into pyroglutamic acid followed by chemical derivatization of the pyroglutamic acid formed by an analytical protocol based on an OPA-NAC reagent. Pyroglutamic acid can thus be quantified between 1 and 100 µM in less than 15 min with a detection limit of 1.3 µM. The method has been validated by measurements on real samples demonstrating that the response increases with the increase in the tropomyosin content or with the increase in the mass of the shrimp sample.

A fully mechanized multicommutated flow analysis (MCFA) system dedicated to determining horseradish peroxidase (HRP) activity was developed. Detection was conducted using a flow-through optoelectronic detector-constructed of paired LEDs operating according to the paired emitter-detector diode (PEDD) principle. The PEDD-MCFA system is dedicated to monitoring the enzyme-catalyzed oxidation of p-phenylenediamine (pPD) by a hydrogen peroxide. Under optimized conditions, the presented bioanalytical system was characterized by a linear response range (33.47-200 U/L) with a detection limit at 10.54 U/L HRP activity and 1.66 mV·L/U sensitivity, relatively high throughput (12 signals recordings per hour), and acceptable precision (RSD below 6%). Additionally, the utility of the developed PEDD-MCFA system for the determination of HRP inhibitors allowing the detection of selected thiols at micromolar levels, is demonstrated. The practical utility of the flow system was illustrated by the analysis of some dietary supplements containing L-cysteine, N-acetylcysteine, and L-glutathione.

A fully automated sequential injection system was tested in terms of its application in liberation testing, and capabilities and limitations were discussed for clotrimazole liberation from three semisolid formulations. An evaluation based on kinetic profiles obtained in short and longer sampling intervals and steady-state flux values were applied as traditional methods. The obtained clotrimazole liberation profile was faster in the case of Delcore and slower for Clotrimazol AL and Canesten cream commercial formulations. The steady-state flux values for the tested formulations were 52 µg cm -2 h -1 for Canesten, 35 µg cm -2 h -1 for Clotrimazol AL, and 7.2 µg cm -2 h -1 for Delcore measured in 4 min sampling intervals. A simplified approach for the evaluation of the initial rate based on the gradient between the second and third sampling points was used for the first time and was found to correspond well with the results of the conventional methods. A comparison based on the ratio of the steady-state flux and the initial rate values for Canesten and Clotrimazol AL proved the similarity of the obtained results. The proposed alternative was successfully implemented for the comparison of short-term kinetic profiles. Consequently, a faster and simpler approach for dissolution/liberation testing can be used.

In this work, an innovative, flow-through, double-beam, photometric detector with direct injection of the reagents (double-DID) was used for the first time for the determination of iron in pharmaceuticals. For stable measurement of the absorbance, double paired emission-detection LED diodes and a log ratio precision amplifier have been applied. The detector was integrated with the system of solenoid micro-pumps. The micro-pumps helped to reduce the number of reagents used and are responsible for precise solution dispensing and propelling. The flow system is characterized by a high level of automation. The total iron was determined as a Fe(II) with photometric detection using 1,10-phenanthroline as a complexing agent. The optimum conditions of the propose analytical procedure were established and the method was validated. The calibration graph was linear in the range of 1 to 30 mg L -1 . The limit of detection (LOD) was 0.5 mg L -1 . The throughput of the method was 90 samples/hour. The repeatability of the method expressed as the relative standard deviation (R.S.D.) was 2% (n = 10). The method was characterized by very low consumption of reagents and samples (20 μL each) and a small amount of waste produced (about 540 µL per analysis). The proposed flow method was successfully applied for determination of iron in pharmaceutical products. The results were in good agreement with those obtained using the manual UV-Vis spectrophotometry and with values claimed by the manufacturers. The flow system worked very stably and was insensitive to bubbles appearing in the system.

With the utilization of small-scale and highly parallelized cultivation platforms embedded in laboratory robotics, microbial phenotyping and bioprocess development have been substantially accelerated, thus generating a bottleneck in bioanalytical bioprocess sample analytics. While microscale cultivation platforms allow the monitoring of typical process parameters, only limited information about product and by-product formation is provided without comprehensive analytics. The use of liquid chromatography mass spectrometry can provide such a comprehensive and quantitative insight, but is often limited by analysis runtime and throughput. In this study, we developed and evaluated six methods for amino acid quantification based on two strong cation exchanger columns and a dilute and shoot approach in hyphenation with either a triple-quadrupole or a quadrupole time-of-flight mass spectrometer. Isotope dilution mass spectrometry with 13 C 15 N labeled amino acids was used to correct for matrix effects. The versatility of the methods for metabolite profiling studies of microbial cultivation supernatants is confirmed by a detailed method validation study. The methods using chromatography columns showed a linear range of approx. 4 orders of magnitude, sufficient response factors, and low quantification limits (7-443 nM) for single analytes. Overall, relative standard deviation was comparable for all analytes, with < 8% and < 11% for unbuffered and buffered media, respectively. The dilute and shoot methods with an analysis time of 1 min provided similar performance but showed a factor of up to 35 times higher throughput. The performance and applicability of the dilute and shoot method are demonstrated using a library of Corynebacterium glutamicum strains producing L-histidine, obtained from random mutagenesis, which were cultivated in a microscale cultivation platform.

Non-enzymatic electrochemical sensors for the monitoring of reducing sugars in foods has great potential as a rapid in-situ detection method. This development involved the assembly of a nanoporous platinum structure on a screen-printed carbon electrode (SPCE). The modified electrode was then employed as an amperometric sensing element in a flow injection analysis (FIA) manifold. The system was successfully applied to the rapid detection of reducing sugars in potatoes, without the need for sample preparation. Optimal signals were achieved in phosphate buffer (pH 7.4) at a flow rate of 0.5 mL min -1 and an applied potential of 0.6 V. Experimental results demonstrated the sensor's long-term stability and high selectivity for reducing sugars. This method provides high sample throughput due to a rapid response time of less than five seconds. Reducing sugar values determined were in good agreement with those recorded using a commercially available enzymatic assay kit., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

A novel method for the analysis of nalbuphine hydrochloride (NAL) is reported based on its enhancement effect on a diperiodatoargentate(III)-rhodamine-B (Ag(III) complex-Rh-B) chemiluminescence (CL) system in an aqueous sulfuric acid medium using flow-injection analysis (FIA). The optimal conditions of the CL reaction were: sulfuric acid, 10 -2 M; Ag(III) complex, 2.0 × 10 -4 M; Rh-B, 2.0 × 10 -5 M; Brij-35, 0.01%; sample loop volume, 300 μL; and flow rate, 3.0 mL/min/stream. The limit of detection (LOD) and limit of quantification (LOQ) were 0.001 and 0.003 mg/L (S/N = 3 and 10); linear calibration range, 5 × 10 -3 - 5.0 mg/L (R 2 = 0.9999) and injection throughput, 150/h. The relative standard deviation (RSD) was from 0.8 - 3.2% over the range studied. The suggested technique was applied for the determination of NAL in pharmaceutical injections, compared with a reported spectrophotometric method, and obtained results were found to be satisfactory. Based on spectrophotometric studies, the most probable mechanism of the CL reaction has been briefly described and drawn schematically.

In this study, we demonstrated nano-flow injection analysis (nano-FIA) with quadrupole time-of-flight mass spectrometry (Q-TOFMS) for 17 highly polar intermediates produced during glycolysis, the tricarboxylic acid (TCA) cycle, and the pentose phosphate pathway (PPP). We optimized the analytical conditions for nano-flow injection/Q-TOFMS, and set the flow rate and ion source temperature to 1000 nL/min and 150 °C, respectively. Under optimal conditions, a single run was finished within 3 min, and the RSD value of 50 sequential injections was 4.2%. The method also showed quantitativity of four stable-isotope-labeled compounds (r 2  > 0.99), demonstrating its robustness, high repeatability, and specificity. In addition, we compared three sample-preparation methods for rodent blood samples and found that protein precipitation with threefold methanol was the most effective. Finally, we applied the method to plasma samples from the serotonin syndrome (SS) model and control rats, the results of which were evaluated by principal component analysis (PCA). The two groups showed clearly separated PCA score plots, suggesting that the method could successfully catch the differences in metabolic profiles between SS and control rats. The results obtained from our new method were further validated by using the established gas chromatography/tandem mass spectrometry method, which demonstrated that there were good correlations between the two methods (R = 0.902 and 0.958 for lactic acid and malic acid, respectively, each at p < 0.001), thus proving the validity of our method. The method described here enables high-throughput analysis of metabolites and will be of use for the rapid analysis of metabolic profiles. Graphical abstract.

Mass spectrometry based metabolomics is a widely used approach in biomedical research. However, current methods coupling mass spectrometry with chromatography are time-consuming and not suitable for high-throughput analysis of thousands of samples. An alternative approach is flow-injection mass spectrometry (FI-MS) in which samples are directly injected to the ionization source. Here, we show that the sensitivity of Orbitrap FI-MS metabolomics methods is limited by ion competition effect. We describe an approach for overcoming this effect by analyzing the distribution of ion m/z values and computationally determining a series of optimal scan ranges. This enables reproducible detection of ~9,000 and ~10,000 m/z features in metabolomics and lipidomics analysis of serum samples, respectively, with a sample scan time of ~15 s and duty time of ~30 s; a ~50% increase versus current spectral-stitching FI-MS. This approach facilitates high-throughput metabolomics for a variety of applications, including biomarker discovery and functional genomics screens.

A flow injection - mass spectrometry method for rapid glyphosate detection in food commodities was developed and validated. The sample preparation protocol included a simple and rapid extract purification step through polymeric solid phase extraction cartridges followed by addition of isotopically labeled glyphosate to the final test sample. The optimized method was subjected to intra-laboratory validation (spiking range 0.5-100 mg/kg) in chickpeas, grapes and apples, as representatives of three different commodity groups as defined in SANTE/11813/2017 guidelines. Recoveries were in the range 60-111%, repeatability and within laboratory reproducibility were ≤17%.The trueness of the results generated with the developed method was evaluated by analysis of a set of incurred chickpea and wheat samples (glyphosate range 0.5-36 mg/kg) and comparison with the reference method (Quick Polar Pesticides Method), confirming the method fitness-for-purpose of rapid compliance testing., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A preconcentration module operated in flow mode and integrated with a sequential injection system with spectrophotometric detection was developed. Using the system, preconcentration was performed in continuous mode and was based on a membraneless evaporation process under diminished pressure. The parameters of the proposed system were optimized and the system was tested on the example of the spectrophotometric determination of Cr(III). The preconcentration effectiveness was determined using the signal enhancement factor. In the optimized conditions for Cr(III), it was possible to obtain the signal enhancement factors of around 10 (SD: 0.9, n = 4) and determine Cr(III) with precision and intermediate precision of 8.4 and 5.1% (CV), respectively. Depending on the initial sample volume, signal enhancement factor values of about 20 were achieved. Applicability of the developed preconcentration system was verified in combination with the capillary electrophoresis method with spectrophotometric detection on the example of determination of Zn in certified reference materials of drinking water and wastewater. Taking into account the enhancement factor of 10, a detection limit of 0.025 mg L -1 was obtained for Zn determination. Zn was determined with precision less than 6% (CV) and the results were consistent with the certified values.

The intestinal microbiome plays an important role in human health and disease and fecal materials reflect the microbial activity. Thus, analysis of fecal metabolites provides insight in metabolic interactions between gut microbiota and host organism. In this work, we applied flow injection analysis coupled to Fourier transform mass spectrometry (FIA-FTMS) to identify and quantify lipid species in human fecal samples. Fecal homogenates were subjected to lipid extraction and analyzed by FIA-FTMS. The analysis of different subjects revealed a vast heterogeneity of lipid species abundance. The majority of samples displayed prominent signals of triacylglycerol (TG) and diacylglycerol (DG) species that could be verified by MS2 spectra. Therefore, we focused on the quantification of TG and DG. Method validation included limit of quantification, linearity, evaluation of matrix effects, recovery, and reproducibility. The validation experiments demonstrated the suitability of the method, with exception for approximately 10% of samples, where we observed coefficients of variation higher than 15%. Impaired reproducibility was related to sample inhomogeneity and could not be improved by additional sample preparation steps. Additionally, these experiments demonstrated that compared with aqueous samples, samples containing isopropanol showed higher amounts of DG, presumably due to lysis of bacteria and increased TG lipolysis. These effects were sample-specific and substantiate the high heterogeneity of fecal materials as well as the need for further evaluation of pre-analytic conditions. In summary, FIA-FTMS offers a fast and accurate tool to quantify DG and TG species and is suitable to provide insight into the fecal lipidome and its role in health and disease.

An innovative automatic purge-and-trap (P&T) system coupled with fluorimetric sequential injection (SI), for the on-line separation and preconcentration of volatile compounds, is presented. The truth of concept is demonstrated for the ammonium fluorimetric determination in environmental water samples with complex matrices without any pretreatment. The P&T flow system comprises a thermostated purge-vessel where ammonium is converted into gaseous ammonia and a trap-vessel for ammonia collection. This configuration results in matrix removal as well as analyte preconcentration, avoiding membrane-associated problems. All the main parameters affecting the efficiency of a P&T system were studied and optimized. The proposed method is characterized by a working range of 2.7-150.0 μg L -1 of NH 4 + , with a detection and quantification limit of 0.80 and 2.66 μg L -1 , respectively, for a 10-mL sample consumption. The accuracy of the method was assessed by recovery assays in seawater, estuarine, and lake water samples as well as by the analysis of standard reference material.

Titanium dioxide (TiO 2 ) is a unique material for biosensing applications due to its capability of hosting enzymes. For the first time, we show that TiO 2 can accumulate reactive oxygen species (ROS) under daylight irradiation and can support the catalytic cycle of horseradish peroxidase (HRP) without the need of H 2 O 2 to be present in the solution. Phenolic compounds, such as hydroquinone (HQ) and 4-aminophenol (4-AP), were detected amperometrically in flow-injection analysis (FIA) mode via the use of an electrode modified with TiO 2 impregnated with HRP. In contrast to the conventional detection scheme, no H 2 O 2 was added to the analyte solution. Basically, the inherited ability of TiO 2 to generate reactive oxygen species is used as a strategy to avoid adding H 2 O 2 in the solution during the detection of phenolic compounds. Electron paramagnetic resonance (EPR) spectroscopy indicates the presence of ROS on titania which, in interaction with HRP, initiate the electrocatalysis toward phenolic compounds. The amperometric response to 4-AP was linear in the concentration range between 0.05 and 2 μM. The sensitivity was 0.51 A M -1 cm -2 , and the limit of detection (LOD) 26 nM. The proposed sensor design opens new opportunities for the detection of phenolic traces by HRP-based electrochemical biosensors, yet in a more straightforward and sensitive way following green chemistry principles of avoiding the use of reactive and harmful chemical, such as H 2 O 2 .

A simple and low-cost continuous-flow (CF) electrochemical paper-based analytical device (ePAD) coupled with thermoplastic electrodes (TPEs) was developed. The fast, continuous flow combined with flow injection analysis was made possible by adding two inlet reservoirs to the same paper-based hollow channel flowing over detection electrodes, terminating in a fan-shaped pumping reservoir. The upstream inlet reservoir was filled with buffer and provided constant flow through the device. Sample injections were performed by adding 2 μL of the sample to the downstream sample inlet. Differences in flow resistance resulted in sample plugs displacing buffer as the solution flowed over the working electrodes. The electrodes were fabricated by mixing carbon black and polycaprolactone (50% w/w). CF-TPE-ePADs were characterized with chronoamperometry using ferrocenylmethyl trimethylammonium as the electrochemical probe. Optimized flow rates and injection volumes gave analysis times roughly an order of magnitude faster than those of previously reported flow injection analysis ePADs. To demonstrate applicability, the CF-TPE-ePADs were used to quantify caffeic acid in three different tea samples. The proposed method had a linear range from 10 to 500 μmol L -1 and limits of detection and quantification of 2.5 and 8.3 μmol L -1 , respectively. Our approach is promising for fabricating simple, inexpensive, yet high-performance, flow injection analysis devices using paper substrates and easy-to-make electrodes that do not require external mechanical pumping systems or complicated valves.

In this paper, a chemiluminescence (CL) method is proposed for retinol determination by combining flow injection (FI) methodology. The CL reaction is based on the oxidation of luminol by diperiodatoargentate(III) (DPA) in the presence of retinol. Under the optimum conditions, the relative CL intensity was linear to the concentration of retinol over the range 5.0×10 -3 -14 mg L -1 (y=347.26x+2.5944, R 2 =0.9999, n=8) with limit of detection (LOD) of 1.5×10 -3 mg L -1 (S/N=3) and limit of quantification (LOQ) of 5.0×10 -3 mg L -1 (S/N=10). The relative standard deviation (RSD) was from 1.04-3.4% over the range studied and injection throughputs of 150 h -1 . The method was satisfactorily applied to retinol in pharmaceutical formulation samples. The samples were saponified and extracted with liquid-liquid extraction using ether as an extractant. The possible CL mechanism is supported by CL and UV-visible spectrophotometric studies.

This paper presents a fast and automatic flow-based method to extract 131 I from biological samples and hospital waste, previous to liquid scintillation detection. 131 I is a radionuclide extensively used in Nuclear Medicine due to their beta and gamma disintegrations, whereby hospitals have to manage the associated waste generation. The automatic developed system is based on Lab-On-Valve (LOV) flow-technique exploiting Cl-resin (135 mg per extraction). This methodology allows performing sample extractions and measurements on the same day, since the extraction frequency takes 1.4-4 h -1 , depending on the analysed sample volume, plus up to 2 h of measurement for each vial. 131 I is retained as iodine ion and eluted with sodium sulphide 0.2 mol L -1 . The maximum sample volume that can be preconcentrated is 20 mL, reaching an extraction efficiency of 85 ± 5%. The minimum detectable activity (MDA) is 0.05 Bq, showing a precision of 7% RSD (n = 5). Both, biological samples (urine and saliva) and hospital waste samples can be satisfactorily analysed by the proposed system, obtaining recoveries between 90 and 110%. The developed method is then suitable to implement in hospitals, improving the surveillance of the 131 I environmental release., (Copyright © 2019 Elsevier B.V. All rights reserved.)

BACKGROUND This feasibility study aimed to compare real-time two-dimensional contrast-enhanced ultrasound (2D-CEUS) and three-dimensional contrast-enhanced ultrasound (3D-CEUS) to quantify flow in an in vitro model. MATERIAL AND METHODS Five polyvinyl chloride (PVC) tubes were used for the perfusion models and used SonoVue ultrasound contrast agent with a perfusion volume ratio of 1: 2: 4: 8: 16. The contrast was injected at a constant speed to compare the raw quantitative data of 2D-CEUS and 3D-CEUS at angles of 0°, 45°, and 90°. The coefficient of variation (CV) of the peak intensity (PI) in the model were compared and the correlations between weighted PI and perfusion volume were analyzed. RESULTS In the three angles used, real-time 3D-CEUS resulted in a more comprehensive view of the spatial relationships in the perfusion model. Using real-time 2D-CEUS, the mean CV was 0.92±0.36, and the mean CV in the real-time 3D-CEUS model was significantly less at 0.48±0.32 (p<0.001). Quantitative 3D-CEUS parameters showed a good correlation with those of 2D-CEUS with an r-value of 0.93 (p=0.02). The r-value of weighted PI and the perfusion ratio using 2D-CEUS was 0.66 (p=0.23) compared with values in 3D-CEUS of 0.84 (p=0.08). CONCLUSIONS The combination of real-time 3D-CEUS and quantitative analysis identified the spatial distribution of the changes in angle in the model, which was less influenced by sectional planes, and was more representative of the perfusion volume when compared with 2D-CEUS. Quantitative real-time 3D-CEUS requires in vivo studies to evaluate the potential role in the clinical evaluation of vascular perfusion of malignant tumors.

A new method for the simultaneous determination of two tumour biomarkers, homovanillic (HVA) and vanillylmandelic acid (VMA), using flow injection analysis (FIA) with amperometric detection (AD) at a commercially available boron doped diamond electrode (BDDE) was developed. It was found that this method is suitable for the determination of HVA (in the presence of VMA) and VMA (in the presence of HVA) in optimum medium of Britton-Robinson buffer (0.04 mol L -1 , pH 3.0). Calibration dependences consist of two linear parts for both biomarkers, the first one being in the concentration range from 1 to 10 μmol L -1 and the second one from 10 to 100 μmol L -1 (with obtained LODs 0.44 μmol L -1 for HVA and 0.34 μmol L -1 for VMA, respectively). To minimize any negative effects related to the passivation of the working electrode, suitable cleaning pulses (+2.4 V for 30 s) were imposed on the working electrode after each measurement. An attempt to use FIA with multiple pulse amperometric detection to determine both analytes in one run was not successful. Changing potentials in short intervals in multiple pulse detection probably results in mutual interaction of analytes and/or products of their electrochemical oxidation, thus preventing the application of this approach., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Isothermal titration calorimetry (ITC) is conventionally used to acquire thermodynamic data for biological interactions. In recent years, ITC has emerged as a powerful tool to characterize enzyme kinetics. In this study, we have adapted a single-injection method (SIM) to study the kinetics of human soluble epoxide hydrolase (hsEH), an enzyme involved in cardiovascular homeostasis, hypertension, nociception, and insulin sensitivity through the metabolism of epoxy-fatty acids (EpFAs). In the SIM method, the rate of reaction is determined by monitoring the thermal power, while the substrate is being depleted, overcoming the need for synthetic substrates and reducing postreaction processing. Our results show that ITC enables the detailed, rapid, and reproducible characterization of the hsEH-mediated hydrolysis of several natural EpFA substrates. Furthermore, we have applied a variant of the single-injection ITC method for the detailed description of enzyme inhibition, proving the power of this approach in the rapid screening and discovery of new hsEH inhibitors using the enzyme's physiological substrates. The methods described herein will enable further studies on EpFAs' metabolism and biology, as well as drug discovery investigations to identify and characterize hsEH inhibitors. This also promises to provide a general approach for the characterization of lipid catalysis, given the challenges that lipid metabolism studies pose to traditional spectroscopic techniques.

Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a biophysical technique well suited to the characterization of protein dynamics and protein-ligand interactions. In order to accurately define the rate of exchange, HDX experiments require the repeated measure of deuterium incorporation into the target protein across a range of time points. Accordingly, the HDX-MS experiment is well suited to automation, and a number of automated systems for HDX-MS have been developed. The most widely utilized platforms all operate an integrated design, where robotic liquid handling is interfaced directly with a mass spectrometer. With integrated designs, the exchange samples are prepared and injected into the LC-MS following a "real-time" serial workflow. Here we describe a new HDX-MS platform that is comprised of two complementary pieces of automation that disconnect the sample preparation from the LC-MS analysis. For preparation, a plate-based automation system is used to prepare samples in parallel, followed by immediate freezing and storage. A second piece of automation has been constructed to perform the thawing and LC-MS analysis of frozen samples in a serial mode and has been optimized to maximize the duty cycle of the mass spectrometer. The decoupled configuration described here reduces experiment time, significantly improves capacity, and improves the flexibility of the platform when compared with a fully integrated system.

We report a novel amperometric flow-injection (FI) analysis of creatinine based on a sensor comprising copper oxide nanoparticles (CuO) coated with a molecularly-imprinted polymer (CuO@MIP) and decorating a carbon-paste electrode (CPE) to form the CuO@MIP/CPE electrode. The CuO@MIP was synthesized by using CuO as the supporting core, creatinine as the template, methacrylic acid (MAA) as monomer, N, N'-(1,2-dihydroxyethylene)bis(acrylamide) (DHEBA) as cross-linker, and 2,2'-azobis (2-methylpropionitrile) (AIBN) as initiator. Morphology and structural characterization reveal that CuO nanoparticle imprinted sites (CuO) synthesized using a precipitation method, exhibits features that are well suited to creatinine detection: high surface area, good analyte diffusion and adsorption characteristics that provide shorter response times, and large numbers of specific cavities for enhanced analyte capacity and sensitivity. Cyclic voltammetric measurements indicate that our sensor provides excellent performance toward electro-oxidation of creatinine. The amperometric FI system was used to quantitatively determine creatinine at the CuO@MIP/CPE sensor, in a phosphate buffer carrier. The imprinted sensor exhibits excellent performance for creatinine oxidation at an applied potential of +0.35 V and flow rate of 0.6 mL.min -1 . The as-prepared sensor exhibits a linear dynamic range for creatinine detection from 0.5 to 200 μM (r 2  = 0.995) with a limit of detection of 0.083 μM (S/N = 3). The system exhibits satisfactorily good precision (%RSD = 1.94%, n = 30) and selectivity toward creatinine. There is only approximately 20% loss from initial response after 2 weeks when stored at 4 o C. We successfully applied the FI detection system to detect creatinine in human urine samples., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Mycotoxins are secondary fungal metabolites produced by certain types of filamentous fungi or molds, such as Aspergillus, Fusarium, Penicillium, and Alternaria spp. Mycotoxins are natural contaminants of agricultural commodities, and their prevalence may increase due to global warming. According to the Food and Agriculture Organization of the United Nations, approximately 25% of the world's food crops are annually contaminated with mycotoxins. Mycotoxin-contaminated food and feed pose a high risk to both human and animal health. For instance, they possess carcinogenic, immunosuppressive, hepatotoxic, nephrotoxic, and neurotoxic effects. Hence, various approaches have been used to assess and control mycotoxin contamination. Significant challenges still exist because of the complex heterogeneous nature of food and feed composition. The potential of antigen-based approaches, such as enzyme-linked immunosorbent assay, flow injection immunoassay, chemiluminescence immunoassay, lateral flow immunoassay, and flow-through immunoassay, would contribute to our understanding about mycotoxins' rapid identification, their isolation, and the basic principles of the detection technologies. Additionally, we address other emerging technologies of potential application in the detection of mycotoxins. The data included in this review focus on basic principles and results of the detection technologies and would be useful as benchmark information for future research. © 2019 Society of Chemical Industry., (© 2019 Society of Chemical Industry.)

Establishing a simple and accurate method for Hg 2+ detection is of great importance for the environment and human health. In this work, platinum nanoparticles (Pt NPs) with different capped agents and morphologies were synthesized. It was found that Pt NPs exhibited peroxidase-like activity that can catalyze the chemiluminescence (CL) of the luminol system without H 2 O 2 . The most intensive CL signals were obtained by using PVP-capped Pt NPs as catalysis. Based on the fact that Hg 2+ could further enhance the CL intensity in the Pt NPs-luminol CL system, a Pt NPs-catalyzed CL method based on a flow injection system is developed for the sensitive analysis of Hg 2+ . When the concentration of Hg 2+ in the system increases, the CL intensity would together increase, thereby achieving sensitive Hg 2+ detection. The limit of detection (LOD) was calculated to be 8.6 nM. This developed method provides a simple and rapid approach for the sensitive detection of Hg 2+ and shows great promise for applications in other complex systems., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work, we introduce a high-throughput quantitative multi-element method for biological fluids enabled by omitting sample preparation and an analysis time of a few seconds per sample. For the first time, flow injection of an undiluted cerebrospinal fluid (CSF) was combined to state-of-the-art ICP-TOFMS detection for multi-element analysis. Owing to the low sample volume and trace element concentrations of the CSF, flow injection methods with only 5 μL sample intake were used in combination with an icpTOF 2R TOF-based ICP-MS instrument. Due to the lack of certified reference materials for CSF analysis, a validated method employing open vessel digestion of the CSF material in combination with ICP-sectorfield-MS analysis was carried out and used as a reference. Additionally, the performance of the flow injection ICP-TOFMS was cross-validated by flow injection quadrupole-based ICP-MS/MS analysis using both external calibration and isotope dilution strategies. In the latter case, the sample had to be injected several times because of the need for tailored gas conditions for different elements. Overall, flow injection of biological fluids delivered quantitative values, which were in excellent agreement with the gold standard established by ICP-SFMS demonstrating the capability of ICP-TOFMS analysis in terms of resolution and sensitivity for the accurate quantification of trace elements in biological samples.

The sequential application of a polymer inclusion membrane (PIM), composed of poly(vinylidenefluoride-co-hexafluoropropylene) and the anionic extractant Aliquat 336, and a microporous polytetrafluoroethylene (PTFE) gas-permeable membrane was utilized for the first time to develop a flow analysis (FA) system, for the automatic determination of trace levels of arsenate (As(V)) in drinking water as arsine. The system incorporated a flow-through extraction cell for separation and preconcentration of arsenate and a gas-diffusion cell for the separation of arsine prior to its spectrophotometric determination based on the discoloration of a potassium permanganate solution. Under optimal conditions the FA system is characterized by a limit of detection of 3.0 μg L -1 As(V) and repeatability of 1.8% (n = 5, 25 μg L -1 As(V)) and 2.8% (n = 5, 50 μg L -1 As(V)). The newly developed FA method was successfully applied to the determination of arsenate in drinking water samples in the μg L -1 concentration range., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

An automatic mesofluidic system combining dynamic oral bioaccessibility with lab-on-valve (LOV)-based sorptive microextraction is herein proposed for the first time for exploring the kinetics of leaching of incurred rather than spiked organic emerging contaminants (viz., methyl paraben, butyl paraben, diclofenac, and triclosan) from exposed mussels on the basis of the Versantvoort's fed-state physiological extraction test. Our method capitalizes on programmable flow analysis, in which gastrointestinal extracts are obtained online by pumping a simulated biorelevant gastrointestinal fluid across a large-bore column (maintained at 37.0 ± 2.0 °C) loaded with 250 mg of freeze-dried and powdered mussel onto a polyvinyldiene difluoride filter membrane. The physiologically relevant extracts are then cleaned up, and the analytes are preconcentrated onto a dedicated reversed-phase solid-phase extraction (Oasis PRIME-HLB) microcolumn that is captured into the channels of an LOV mesofluidic platform. The aim behind this is to obtain analyte-laden eluates with ACN/MeOH (90:10, v/v) in unsupervised mode for direct injection into LC-MS. The LOV minicolumn (≤25 mg) is automatically disposed of and renewed for every individual fraction on account of the strong retention of (phospho)lipids by the copolymeric sorbent. The proposed dynamic bioaccessibility test features a significant shortening of the extraction time against the batch method (28 vs 240 min) while avoiding overestimation of potentially bioavailable fractions. The trueness of the online gastrointestinal extraction method was confirmed using mass-balance validation following ultrasonic-assisted solid-liquid extraction of the original mussel sample and the residual (nonbioaccessible) fraction of emerging contaminants.

Background: Congenital disorders of glycosylation (CDG) represent 1 of the largest groups of metabolic disorders with >130 subtypes identified to date. The majority of CDG subtypes are disorders of N -linked glycosylation, in which carbohydrate residues, namely, N -glycans, are posttranslationally linked to asparagine molecules in peptides. To improve the diagnostic capability for CDG, we developed and validated a plasma N -glycan assay using flow injection-electrospray ionization-quadrupole time-of-flight mass spectrometry., Methods: After PNGase F digestion of plasma glycoproteins, N -glycans were linked to a quinolone using a transient amine group at the reducing end, isolated by a hydrophilic interaction chromatography column, and then identified by accurate mass and quantified using a stable isotope-labeled glycopeptide as the internal standard., Results: This assay differed from other N -glycan profiling methods because it was free of any contamination from circulating free glycans and was semiquantitative. The low end of the detection range tested was at 63 nmol/L for disialo-biantennary N -glycan. The majority of N -glycans in normal plasma had <1% abundance. Abnormal N -glycan profiles from 19 patients with known diagnoses of 11 different CDG subtypes were generated, some of which had previously been reported to have normal N -linked protein glycosylation by carbohydrate-deficient transferrin analysis., Conclusions: The clinical specificity and sensitivity of N -glycan analysis was much improved with this method. Additional CDGs can be diagnosed that would be missed by carbohydrate-deficient transferrin analysis. The assay provides novel biomarkers with diagnostic and potentially therapeutic significance., (© 2019 American Association for Clinical Chemistry.)

An amperometric biosensor compatible with a flow injection analysis (FIA) for highly selective determination of acetaminophen (APAP) in a sample of human urine was developed. This biosensor is also suitable for use in the routine pharmaceutical practice. To prove this statement, two different commercially available pharmaceutical formulations were analyzed. This nano-(bio)electroanalytical device was made from a commercially available screen-printed carbon electrode covered by a thin layer of non-functionalized graphene (NFG) as amperometric transducer. A biorecognition layer was prepared from mushroom (Agaricus bisporus) tyrosinase (EC 1.14.18.1) cross-linked using glutaraldehyde, where resulting aggregates were covered by Nafion ® , a known ion exchange membrane. Owing to the use of tyrosinase and presence of NFG, the developed analytical instrument is able to measure even at potentials of 0 V. Linear ranges differ according to choice of detection potential, namely up to 130 μmol L -1 at 0 V, up to 90 μmol L -1 at -0.1 V, and up to 70 μmol L -1 at -0.15 V. The first mentioned linear range is described by the equation I p [μA] = 0.236 - 0.1984c [μmol L -1 ] and correlation coefficient r = 0.9987; this equation was used to quantify the content of APAP in each sample. The limit of detection of APAP was estimated to be 1.1 μmol L -1 . A recovery of 96.8% (c = 25 μmol L -1 , n = 5 measurements) was calculated. The obtained results show that FIA is a very selective method for APAP determination, being comparable to the chosen reference method of reversed-phase high-performance liquid chromatography.

Nucleosides and their analogues play a crucial role in the treatment of several diseases including cancers and viral infections. Their therapeutic efficiency depends on their capacity to be converted to the active nucleoside triphosphates form through successive phosphorylation steps catalyzed by nucleoside/nucleotide kinases. It is thus mandatory to develop an easy, rapid, reliable and sensitive enzyme activity tests. In this study, we monitored the three-step phosphorylation of thymidine to thymidine triphosphate respectively by (1) human thymidine kinase 1 (hTK1), (2) human thymidylate kinase (hTMPK) and (3) human nucleoside diphosphate kinase (hNDPK). Free and immobilized kinase activities were characterized by using the Michaelis-Menten kinetic model. Flow Injection Analysis (FIA) with High-Resolution Mass Spectrometry (HRMS) was used as well as capillary electrophoresis (CE) with UV detection. The three-step cascade phosphorylation of thymidine was also monitored. FIA-HRMS allows a sensitive and rapid evaluation of the phosphorylation process. This study proposes simple, rapid, efficient and sensitive methods for enzyme kinetic studies and successive phosphorylation monitoring with immobilized enzymes., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A simple and miniature analytical system was developed to determine Hg and Cd in small amounts of samples by integrating flow injection capillary liquid electrode discharge (CLED) optical emission spectrometry (OES) and microplasma-induced vapor generation (PIVG) atomic fluorescence spectrometry (AFS). With the assistance of the inherent capillary driving force and the force arising from the solution vaporization in the microplasma, the sample solution was automatically transported into the discharge chamber wherein analytes were simultaneously excited to generate their atomic emission lines and converted to their volatile species. Subsequently, the volatile species were further swept into AFS for their further determination. Therefore, the same sample could be successively analyzed by OES and AFS. Owing to the unique independent linear-range and sensitivity of CLED-OES and PIVG-AFS, the developed system not only significantly extended its linear range to 6 orders of magnitude but also remarkably reduced the sample consumption to several microliters. Thus, wide linear-range and ultrasensitive determination of Hg and Cd in limited amounts of samples were accomplished simply by sharing one single capillary liquid electrode discharge source. Under the optimized conditions, limits of detection (LODs) of 10 μg L -1 were obtained for both Hg and Cd when CLED-OES was used as a detector, whereas the LODs for Hg and Cd were improved to 0.03 μg L -1 and 0.04 μg L -1 with AFS detector, respectively. In addition, the extremely wide linear-range of 0.001-100 mg L -1 and 0.001-40 mg L -1 were obtained for Hg and Cd, respectively. The potential application of this method was validated by successfully analyzing three Certified Reference Materials (ZK021-1, GBW(E)090033, and GBW(E)090034) and six human blood samples.

A flow injection based chemiluminescence process has been reported for vitamin D 3 determination without using especial chemiluminescence reagent. Vitamin D 3 shows enhancement on the CL intensity of diperiodatocuprate(III) with surfactant (Triton X-100) solution. The calibration curve was found to be linear over the concentration range 0.01-40 mg/L (R 2  = 0.9997, n = 8) tested. A limit of detection (S/N = 3), limit of quantification (S/N = 10) and sample injection throughput of 2.5 × 10 -3 , 8.3 × 10 -3  mg/L and 150 h -1 respectively were obtained. Various experimental variables were tested to get most suitable response, e.g., the concentrations of reagents, and their flow rates, sample injection volume and photomultiplier tube voltage. The effect of potential interferences was also examined. Vitamin D 3 determination was successfully carried out in pharmaceutical formulations. The recoveries from the formulations were obtained in the range of 96 ± 4-108 ± 2%. The reaction mechanism discussion for diperiodatocuprate(III) complex-Triton X-100-vitamin D 3 was also included., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A simple, reliable flow injection analysis (FIA)-tandem mass spectrometric (MS/MS) method was developed for the determination of gemini surfactants, designated as 16-3-16, 16(Py)-S-2-S-(Py)16 and 16-7N(GK)-16, as gene delivery agents in cellular matrix. 16-3-16 is a conventional gemini surfactant bearing two quaternary amines, linked by a 3-carbon spacer region, 16(Py)-S-2-S-(Py)16 contains two pyridinium head groups, while 16-7N(GK)-16 bears a glycine-lysine di-peptide in the space region. The method was fully validated according to USFDA guidelines. It is the first time that FIA-MS/MS method was developed for the quantification of gemini surfactants, belonging to different structural families. The method was superior to existing liquid chromatographic (LC)-MS/MS methods in terms of sensitivity and time of analysis. Positive electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode were used on a triple quadrupole-linear ion trap (4000 QTRAP ® ) instrument. Deuterated internal standards were used to correct for matrix effects and variations in ionization within the ESI source. Isotope dilution standard curves were established in cellular matrix, with a linear range of 10 nM-1000 nM for 16-3-16 and 16(Py)-S-2-S-(Py)16, and 20 nM-2000 nM for 16-7N(GK)-16. The precision, accuracy, recovery and stability were all within the acceptable ranges as per the USFDA guidelines. The method was successfully applied for the quantification of target gemini surfactants in the nuclear fraction of PAM 212 keratinocyte cells treated with nanoparticles, which varied significantly and may explain differences in the observed efficiency and/or toxicity of these gemini surfactants in gene delivery., (Copyright © 2018 Elsevier B.V. All rights reserved.)