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Fabricating simple, accurate and user-friendly diagnostic device for “point of care testing” (POCT) applications is one of the most challenging objectives in the analytical field. Hemin detection is important for drugs monitoring, diagnosis, and forensic latent bloodstain imaging. Herein is developed, luminol chemiluminescence biosensor for hemin detection using artesunate as coreactant. A possible mechanism to account for the chemiluminescence reaction is discussed. Hemin was detected using both photomultiplier tube (PMT) and smartphone as detector. The detection limit for hemin using smartphone as detector is 20 nM, enabling the visual detection of hemin in blood sample with a dilution factor of blood up to 120,000. While PMT detector is used, the system is able to detect hemin down to 0.22 nM. In addition to high sensitivity, this sensing system exhibit high selectivity. It can successfully distinguish bloodstain from other stains while applying the system for point of care testing using smart phone as detector. Moreover, the system can detect artesunate with a linear range from 0.1 nM to 1.0 μM with a limit of detection of 0.078 nM.

In this study, we used nano-smectite (SMT) and multiwall carbon nanotube (MWCNT) as a recognition surface over the disposable pencil graphite electrode for the low-level detection of ascorbic acid (AA) and acetyl salicylic acid (ACA). Firstly, nano-semectit was obtained by the purification of natural bentonite clay. XRD patterns and Scanning electron microscopy (SEM) were employed to ensure the purity of the bentonite samples. Pencil graphite rodes were immersed into suspensions of SMT, MWCNT or the both.The surface morphology of the sensor was investigated by cyclic voltammery (CV), electrochemical impedance spectroscopy (EIS) and SEM techniques. The effect of pH, percentage composition of modifiers, immobilization time, accumulation time and accumulation potential was optimized for reaching the best electroanalytical response for AA and ACA. The sensor developed proved to give good recovery, notable electro-catalytic activity and appropriately distant signals for the simultaneous determination of the analytes. Common contaminates, uric acid, l-cysteine, dopamine, glucose, Na+, Cl- and citric acid were investigated for their interference effects. Uric acid, citric acid and dopamine were found to interfere to some extent. The electrode exhibited wide working ranges and a fairly satisfactory detection limit of 0.096 and 0.241 μM for AA and ACA, respectively. The electrode system proved to be practical for the analysis of pharmaceutical tablets and the recovery results are very satisfactory.

A novel non-enzymatic superoxide anion radical (O2•−) sensor was prepared by silver nanoparticles (AgNPs) decorated organic frameworks (MOFs) compound-derived metal oxide coated carbon material. Transmission electron microscopy (TEM) was employed to characterize morphologies and structures of the as-prepared samples AgNPs/Co3O4@C. Electrochemical studies indicated that the AgNPs/Co3O4@C/GCE exhibited excellent detection ability to O2•−. It offered a linear range of 8 orders of magnitude and a super low detection limits of 0.0564 pM. The sensor was successfully adapted to detection of O2•− released from living cells. Furthermore, the capacities of scavenging O2•− of food antioxidants were also studied by electrochemical method at cellular milieu. Accordingly, this work provided tremendous potential for reduction incidence of oxidative stress by intaking food antioxidants.

We report the colorimetric detection of dopamine (DA) on microfluidic paper-based analytical devices (μPADs) using an oxidation-reduction method. Here, dopamine reacts with ferric chloride forming reduced Fe2+ that subsequently reacts with phenanthroline to form the red tris(1,10-phenanthroline)iron(II) complex. The devices were fabricated by wax printing and changes in color intensity were recorded using a common cell phone. Subsequent analysis using Photoshop software, yielded a limit of detection (LOD) for DA of 0.37 μmol/L with a linear range of 0.527–4.75 μmol/L and relative standard deviation of 0.11% (inter-day) and 0.15% (intra-day) for n = 15 paper chips. The effects of detection conditions have been investigated and are discussed. Cow serum samples and human blood serum and plasma samples were detected. The work, herein, demonstrates the potential of this method as a low cost and rapid colorimetric technique to detect DA in real samples.

A non-invasive textile-based colorimetric sensor for the simultaneous detection of sweat pH and lactate was created by depositing of three different layers onto a cotton fabric: 1.) chitosan, 2.) sodium carboxymethyl cellulose, and 3.) indicator dye or lactate assay. This sensor was characterized using field emission scanning electron microscopy and fourier transform infrared spectroscopy. Then, this sensor was used to measure pH and lactate concentration using the same sweat sample. The sensing element for sweat pH was composed of a mixture of methyl orange and bromocresol green while a lactate enzymatic assay was chosen for the lactate sensor. The pH indicator gradually shifted from red to blue as the pH increased, whereas the purple color intensity increased with the concentration of lactate in the sweat. By comparing these colors with a standard calibration, this platform can be used to estimate the sweat pH (1−14) and the lactate level (0–25 mM). Fading of the colors of this sensor was prevented by using cetyltrimethylammonium bromide (CTAB). The flexibility of this textile based sensor allows it to be incorporated into sport apparels and accessories hence potentially enabling real-time and continuous monitoring of sweat pH and lactate. This non-invasive sensing platform might open a new avenue for personal health monitoring and medical diagnosis as well as for determining of the physiological conditions of endurance athletes.

This paper proposes a closed inline system for decomposition of wine, aiming at the determination of lead using electrothermal atomization atomic absorption spectrometry (ETAAS). The system is built using a 0.8 mm diameter PTFE tube, which is wrapped around an 8 W UV lamp. The sample in the presence of 70% hydrogen peroxide is circulated on an 8 W UV lamp at the flow rate of 1 mL min−1 for 45 min. Under these conditions, the carbon content varied from 10% to 2% for a red wine sample before and after digestion, respectively. The system has allowed the determination of lead in wine samples using the analytical line 283.306 nm in the presence of aluminum as the chemical modifier and pyrolysis and atomization temperatures of 800 and 1800 °C, respectively. Then, lead can be quantified employing the external calibration technique with limits of detection 0.27 and quantification 0.89 µg L−1, and characteristics mass of 18 pg. The precision expressed by relative standard deviation (RSD%) was 2.13%, calculated using six replicates of a digested solution of a wine sample with the lead content of 16.35 µg L−1. For evaluation of the accuracy method, two wine samples were analyzed simultaneously by the method proposed and also by inductively coupled plasma mass spectrometry (ICP-MS). A statistical test demonstrated no significant difference between the means obtained by these two techniques. Also, experiments involving addition/recovery tests confirmed the method's accuracy. The system was employed for digestion and determination of lead in four Brazilian wine samples. The lead content varied from 2.19 to 43.48 µg L−1.

This work presents a second-to-none method for Taxol isolation from the Endophytic fungus Cladosporium sphaerospermum (AUMC 6896) and the Entomopathogenic fungus Metarizium anisopliae (AUMC 5130). The extracts were analyzed by high performance liquid chromatography (HPLC) and Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) using positive electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode. This is rapid, consistent, reproducible, accurate, and sensitive for quantifying Taxol across multiple samples. The yield of crude Taxol product obtained from Potato Dextrose broth (PDB) medium inoculated with Cladosporium sphaerospermu and Metarizium anisopliae was found to be 3.732, and 0.0023 μg L−1 respectively. The yield can be improved by adding ammonium acetate or salicylic acid to the culture broth. Addition of ammonium acetate (AA) (20 mg L−1) to culture media resulted in an increase of Taxol yield to 30.365 and 27.289 μg L−1 respectively. Production of Taxol was 29.844 and 67.254 μg L−1 for the two fungus species when ammonium acetate was substituted by 90 mg L−1 salicylic acid (SA). Adding both AA (20 mg L−1) and SA (90 mg L−1) to the culture media resulted in an increase of the Taxol yield to 4.054 and 116.373 μg L−1 respectively. Our proposed analytical method offers very fast (3 min) quantitation of Taxol in comparison with other published methods. These findings represent a new bioprospecting of the endophytic fungi that may serve as a potential material for the production of Taxol for anticancer treatment.

Developing effective ways for controlling the quality of natural products that are sold in high volume worldwide is currently one of the most urgent goals of analytical chemistry. Black pepper (Piper nigrum) is a major spice that constitutes 34% of the global spice market. Black pepper is highly prone to quality variations, arising from alteration of the piperine content. Miniaturized NIR spectroscopy offers a high-throughput, cost-effective and laboratory independent technique for quality control of black pepper. Handheld NIR spectrometers differ in the implemented technology, with impact on their analytical performance and unit cost. In this work, the performance of three miniaturized NIR instruments in quantification of piperine in whole and milled seeds of black pepper was investigated. With HPLC method used as the reference analysis, partial least squares regression (PLSR) models were constructed for NIR spectra while the prediction accuracy with respect to the spectrometer used was monitored through root mean square error of prediction (RMSEP) determined for an independent test set validation. Prediction of piperine content in milled seeds was achieved with a RMSEP of 0.18% using the benchtop spectrometer Buchi NIRFlex N-500; while handheld instruments offered, respectively, 0.22% (microPHAZIR), 0.26% (MicroNIR 2200) and 0.42% (SCiO). In contrast, for the analysis of the whole pepper seeds, only the Buchi NIRFlex N-500 (RMSEP: 0.30%) and the Viavi MicroNIR 2200 (RMSEP: 0.37%) gained reliable results. The performance of Thermo Scientific microPHAZIR was satisfactory (RMSEP: 0.75%). The consumer-aimed spectrometer SCiO (Consumer Physics) was found adequate for milled samples, while the analysis of the whole seeds was unsuccessful. To gain better understanding of the features of PLSR models of piperine content in black pepper, quantum mechanical simulation of NIR absorption bands of piperine was performed. This step enabled elucidating the chemical information relevant to the calibration model, and interpreting the difference in the analytical performance of the compared spectrometers with statistical parameters of the calibration models below acceptable levels.

A pH colorimetric sensor array (CSA) with fast response time (

Herein a semi-quantitative and quantitative method for rapid determination of water hardness was introduced. The method was based on color change of silver nanoparticles (AgNPs) in the presence of real water samples. Carbon dots were prepared from mulberry in a hydrothermal procedure and used as reductant of silver ion for synthesis of AgNPs. A classification method based on the color change of AgNPs in the presence of different water samples was also founded. The analysis based of the proposed method was cheap and rapid. On site semi-quantitative determination of total hardness of water can be performed by the proposed method. A linear calibration model based on the color analysis of the images of AgNPs in the presence of water samples was constructed. The model was applicable for determination of total hardness of water in the range of 116-248 mg L−1 of calcium carbonate. A variety of real water samples were included in the calibration model. The calibration method can be used to predict total hardness of water in a critical range above the soft water and below the very hard water. The results were compared by the standard titrimetric method based on ethylenediaminetetraacetic acid. Prediction of total hardness of real water samples based on the color model was in most cases below 20%.

Colistimethate sodium (CMS) is a widely administrated old-generation prodrug for the treatment of the life-threatening infections caused by multi-resistant Gram-negative bacteria. Until now, the quality control procedure of the CMS commercial products is based on microbiological assays. The aim of the study is the development of a chemical analysis methodology based on liquid chromatography - mass spectrometry (LC-MS) that could be used for the quality control of CMS products. The careful optimization of the LC and QToF-MS parameters was deemed crucial, as CMS is known to be a very complex mixture. Thus, a two stage Design of Experiments (DoE) pipeline has been followed, aiming towards the separation of the mixture components. According to the DoE results, a baseline-resolved chromatogram revealing more than 20 compounds was achieved. The separation was performed using a Waters Acquity BEH C8 column employing gradient elution. The mobile phase consisted of aq. ammonium formate 0.005 M (pH 6) (solvent A) and methanol/acetonitrile 79/21 (v/v) (solvent B). A second optimization experiment for the MS signal was employed in order to achieve maximum sensitivity. The singly charged signals were monitored for the validation in the positive ion mode. The calibration curve range was 50 – 110 μg mL-1, corresponding to the 80-120 % of the nominal CMS amount in the commercial products. Due to the complexity of the CMS chromatograms and the corresponding spectrum of each chromatographic peak, untargeted and targeted approaches were performed employing the MZmine software. Furthermore, apart from the classical univariate statistical analysis, partial least square regression (PLS-R) model was also employed, as the variables were more than the observations. The developed methodology has been employed to analyze several batches and inconsistences have been discovered.

A novel ferricyanide/Prussian blue (PB) assay for total antioxidant capacity (TAC) determination was developed exploiting the formation of PB nanoparticles in the presence of polyvinylpyrrolidone (PVP) as stabilizer. This improved method, named as "nanoparticle-based ferricyanide/Prussian blue assay (PBNP)", was applied to the TAC measurement of Cynara Scolymus L. (globe artichoke). The calibration results of the novel (PBNP) method were compared with those of a similar nanoparticle PB method performed in the absence of PVP, and of a sodium dodecyl sulfate-modified and acid-optimized ferricyanide reference assay. Compared to similar common Fe(III)-based TAC assays, much higher molar absorptivities, pointing out higher response to different kinds of antioxidants, were obtained with PBNP for all tested antioxidants, and lower LOD and LOQ values were achieved for thiols. As an additional advantage, methionine, not responding to other electron-transfer based TAC reagents, could be measured. PBNP could detect various antioxidants with one-two orders-of-magnitude lower LOD values than those of widely used TAC assays like CUPRAC and Folin-Ciocalteau well correlating with the proposed assay.

Seed-growth synthesis is a common strategy to prepare silver nanoplates, whose peculiar plasmonic features can be exploited for surface enhanced Raman scattering (SERS) applications. Here we describe the fabrication and characterization of SERS chips using a peculiar in situ seed growth method, yielding a dense layer of nano-objects directly on a glass slide. In this way, geometric features (i.e. shape and dimensions) of the nano-objects can be tuned by controlling the growth time, obtaining a high concentration of hot spots on the surface. In particular, the SERS response of four kinds of chips were investigated to define the best SERS configuration in terms of size of the silver nano-objects, excitation wavelength and homogeneity of the SERS response. Silver nano-plates with a seeded growth time of 60 min demonstrated remarkable results both in terms of plasmonic enhancement, with an enhancement factor (EF) of 2 × 105 using a 532 nm laser excitation, and good homogeneity of the SERS response with intra- and inter-maps RSD of 10% and 5%, respectively. In order to demonstrate application of these chips for real sample analysis, an analytical procedure for the detection of a model pesticide, i.e. thiram fungicide, was developed and applied to its detection on green apples peels. SERS measurements on 60 min seeded growth silver nano-plates chip coupled with a multivariate PLS approach demonstrated high accuracy and repeatability for thiram detection in food matrix within the European law limits.

Ferrous(II) phosphate nanoflowers (Fe3(PO4)2·8H2O NFs) were synthesized by a facial co-precipitation method. The structure, composition and morphology were characterized by XRD, EDX, element mapping and FESEM. The as-prepared Fe3(PO4)2·8H2O NFs exhibited excellent intrinsic peroxidase-like activity. Steady-state kinetic studies showed that Fe3(PO4)2·8H2O NFs exhibited stronger affinities with 3,3,5,5-tetramethylbenzidine (TMB) and H2O2 as the substrates compared with the natural horseradish peroxidase (HRP) and the catalytic constant (kcat) value was even higher than HRP and other reported nanomaterial based peroxidase mimics. The investigation of the catalytic mechanism by cyclic voltammetry, fluorescence spectroscopy and ESR displayed the catalytic activity of Fe3(PO4)2·8H2O NFs originated from the generation of •OH. The Fe3(PO4)2·8H2O NFs also exhibited higher robustness and better storage stability than HRP. Then, a Fe3(PO4)2·8H2O NFs-based colorimetric platform was developed to determine H2O2 and glucose. The linear range of H2O2 and glucose was as broad as 1 × 10−5–2.5 mM and 8 × 10−4–1.2 mM, and the detection limit (LOD) was as low as 5 nM and 35 nM, respectively. This simple assay offered a highly sensitive and specific strategy for H2O2 and glucose determination, which had been successfully utilized for real sample analysis with good reproducibility and accuracy.

A simple and economical spectrofluorimetric alternative for aluminium determination in bivalve mollusks based on the fluorescent blue-green colour complex between Al(III) and salicylaldehyde picolinoylhydrazone (SAPH) has been studied. The factors that are most likely to affect were optimized with a Box-Behnken design. Optimum conditions were: pH 6.6, 0.9 mol L-1 acetic acid/acetate buffer, 3.0 mmol L-1 SAPH, and 50% ethanol. Detection and quantitation limits were found to be 2.7 μg L-1 and 9.1 μg L-1, respectively. The upper limit of application was assessed through the limit of linearity which was set as 300 μg L-1. Intra-day repeatability and inter-day repeatability were evaluated showing an excellent precision for the fluorescence method (both < 5%). The method was sensitive enough for the satisfactory determination of aluminium in several bivalve mollusk samples both fresh and canned seafood. The results showed that commercial fresh wild products presented the smallest Al concentration (6-27 mg per 100 g dry weight), while bivalves preserved in cans the concentration was considerably higher (75 mg per 100 g dry weight). Thus, differences between Al concentration related to processing were identified. The study shows a simple, cost-effective and reliable tool for routine aluminium determination in seafood for food quality control.

A simple, rapid, and ultrasensitive fluorescence strategy for adenosine triphosphate (ATP) detection was developed by using a FAM (carboxyfluorescein) labeled DNA (FAM-DNA). In this strategy, highly fluorescent FAM-DNA was used as a probe, and nanoceria (CeO2 NPs) acted as an efficient quencher. FAM-DNA attached to the surface of nanoceria through the coordination between the phosphate group of DNA and NP surface, which induced complete quenching in the FAM-DNA fluorescence due to a photo induced electron transfer (PET) process. It was found that ATP can readily displace adsorbed DNA from nanoceria surface because of the stronger coordination ability of ATP with nanoceria, and the nanoceria-based competitive binding resulted in over 7-fold fluorescence enhancement. Over a wide range from 0.1nM to 1.5μM, a good linear relationship between the fluorescence intensity and the concentration of ATP was obtained and the detection limit was estimated to be as low as 54pM. This method was successfully used to analyze ATP in a single drop of blood and human urine.

In this work, polypropylene hollow fiber was replaced by agarose gel in conventional electro membrane extraction (EME) to develop a novel approach. The proposed EME method was then employed to extract two amino acids (tyrosine and phenylalanine) as model polar analytes, followed by HPLC-UV. The method showed acceptable results under optimized conditions. This green methodology outperformed conventional EME, and required neither organic solvents nor carriers. The effective parameters such as the pH values of the acceptor and the donor solutions, the thickness and pH of the gel, the extraction voltage, the stirring rate, and the extraction time were optimized. Under the optimized conditions (acceptor solution pH: 1.5; donor solution pH: 2.5; agarose gel thickness: 7 mm; agarose gel pH: 1.5; stirring rate of the sample solution: 1000 rpm; extraction potential: 40 V; and extraction time: 15 min), the limits of detection and quantification were 7.5 ng mL−1 and 25 ng mL−1, respectively. The extraction recoveries were between 56.6% and 85.0%, and the calibration curves were linear with correlation coefficients above 0.996 over a concentration range of 25.0–1000.0 ng mL−1 for both amino acids. The intra- and inter-day precisions were in the range of 5.5–12.5%, and relative errors were smaller than 12.0%. Finally, the optimized method was successfully applied to preconcentrate, clean up, and quantify amino acids in watermelon and grapefruit juices as well as a plasma sample, and acceptable relative recoveries in the range of 53.9–84.0% were obtained.

Multivariate calibration coupled to RP-HPLC with diode array detection (HPLC-DAD) was applied to the identification and the quantitative evaluation of the short chain organic acids (malic, oxalic, formic, lactic, acetic, citric, pyruvic, succinic, tartaric, propionic and α-cetoglutaric) in fermented food. The goal of the present study was to get the successful resolution of a system in the combined occurrence of strongly coeluting peaks, of distortions in the time sensors among chromatograms, and of the presence of unexpected compounds not included in the calibration step. Second-order HPLC-DAD data matrices were obtained in a short time (10 min) on a C18 column with a chromatographic system operating in isocratic mode (mobile phase was 20 mmol L−1 phosphate buffer at pH 2.20) and a flow-rate of 1.0 mL min−1 at room temperature. Parallel factor analysis (PARAFAC) and unfolded partial least-squares combined with residual bilinearization (U-PLS/RBL) were the second-order calibration algorithms select for data processing. The performance of the analytical parameters was good with an outstanding limit of detection (LODs) for acids ranging from 0.15 to 10.0 mmol L−1 in the validation samples. The improved method was applied to the analysis of many dairy products (yoghurt, cultured milk and cheese) and wine. The method was shown as an effective means for determining and following acid contents in fermented food and was characterized by reducibility with simple, high resolution and rapid procedure without derivatization of analytes. Fil: Mortera, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina Fil: Zuljan, Federico Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentina Fil: Magni, Christian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentina Fil: Bortolato, Santiago Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina Fil: Alarcon, Sergio Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina

This paper discusses the development and implementation of a method based on NIR spectroscopy for the in-situ determination of the ammonia mass fraction of ammonia/water mixtures in an absorber test bench. The calibration model was established using a static measuring system. A cell was designed and constructed to prepare and measure samples at the ammonia mass fractions (0.332-0.482), pressures (3.4-4.6), bar and temperatures (25.0-35.5) °C typical in absorption refrigeration systems. A quadratic model for absorbance at 1041nm was established and validated. The root-mean-square deviation (RMSD) of the results was 2.1%. To implement NIR spectroscopy in the absorber test bench, a new flow cell was designed. The calibration model was transferred and used in the conditions of the absorber test bench. In these experimental conditions, the model was statistically validated using density measurements as a reference method for measuring the ammonia mass fraction. The root-mean-square deviation between the ammonia mass fractions obtained using the two methods was 1.1%.

A simple and efficient multi residue method was developed, for the analysis of 160 pesticides by GC-MS/MS in herbal plants. The developed method employs pesticide residue extraction by EtAC/ n. hexane (6:4) with a cleanup step using florisil/ PSA mixture. The optimized conditions have resulted in lower co-extracted matrix components than those extracted using EtAC or MeCN (QuEChERS method), according to FTIR and full scan GC/MS analyses. In addition, the developed method (EtAC/ Hexane) eliminates the evaporation step that is usually performed when using MeCN as an extraction solvent prior to the GC-MS/MS injection. The developed method was fully validated on chamomile, based on SANTE/11945/2015 guidelines. Where, intraday recoveries were estimated at three concentration levels of 10, 50 and 250 μg kg −1 . However, interday recoveries have also been carried out, at 250 μg kg −1 . In addition, intraday recoveries were estimated for two other herbal plants (thyme and marjoram), at 250 μg kg −1 . Three point calibration mixtures were prepared in ethyl acetate solvent and in the blank extracts of chamomile, thyme, and marjoram, in order to check the linearity and matrix effect. The average recoveries for most of the studied pesticides ranged from 70% to 100% at 50 and 250 μg kg −1 with relative standard deviations below 20%. The validated method was successfully applied for determination of pesticide residues in 20 herb samples, collected from the Egyptian market.

We designed two double quenching molecular beacons (MBs) with simple structure based on guanine (G base) and Black Hole Quencher (BHQ), and developed a new analytical method for sensitive simultaneous detection of two DNAs by synchronous fluorescence analysis. In this analytical method, carboxyl fluorescein (FAM) and tetramethyl-6-carboxyrhodamine (TAMRA) were respectively selected as fluorophore of two MBs, Black Hole Quencher 1 (BHQ-1) and Black Hole Quencher 2 (BHQ-2) were respectively selected as organic quencher, and three continuous nucleotides with G base were connected to organic quencher (BHQ-1 and BHQ-2). In the presence of target DNAs, the two MBs hybridize with the corresponding target DNAs, the fluorophores are separated from organic quenchers and G bases, leading to recovery of fluorescence of FAM and TAMRA. Under a certain conditions, the fluorescence intensities of FAM and TAMRA all exhibited good linear dependence on their concentration of target DNAs (T1 and T2) in the range from 4 × 10-10 to 4 × 10-8molL-1 (M). The detection limit (3σ, n = 13) of T1 was 3 × 10-10M and that of T2 was 2×10-10M, respectively. Compared with the existing analysis methods for multiplex DNA with MBs, this proposed method based on double quenching MBs is not only low fluorescence background, short analytical time and low detection cost, but also easy synthesis and good stability of MB probes.

Determination of chromophores of various classes—rosaniline (fuchsine), cyanidin-3-O-glucoside, tris(1,10-phenanthroline) iron(II), and phenol red — in their concentrated solutions near their solubility limits is performed with the optoacoustic technique for optically dense solutions; light-absorption coefficients of samples range from 0.5 to 500 cm–1. The assessment of these substances in organo-aqueous and organic solvents is possible up to ca. 0.1 mol L–1. Characteristic stability and rate constants of the chelation of iron(II) with 1,10-phenanthroline are determined. It was found that turbidities up to 200 FTU and dynamic viscosities up to 20 mPa s do not affect the determination. The determination of total anthocyanins (as cyanidin-3-O-glucoside) in bilberry and sweet-cherry juices agrees with the reference spectrophotometric method and demonstrates the possibilities of the optoacoustic technique for the analysis of real samples without dilution and with almost no sample preparation.

Electrochemical properties of eugenol were investigated on a graphene modified carbon paste electrode (CPE) by using voltammetric methods, which exhibited a well-defined irreversible peak at about 0.7V vs Ag/AgCl, NaCl (3M) in Britton-Robinson buffer at pH 2.0. Mechanism of the electrochemical reaction of eugenol was studied by performing density functional theory (DFT) computations and mass spectroscopic analysis. (CPCM:water)-wB97XD/aug-cc-PVTZ//(CPCM:water)-wB97XD/6-31G(d) level calculations predicted that the formation of product P2, possessing a para-quinoid structure, is preferred rather than the product P1, suggested in the literature, having an ortho-quinoid system. Determination of eugenol in a pharmaceutical sample was realized in the light of the electrochemical findings, and a validated voltammetric method for quantitative analysis of eugenol in a pharmaceutical formulation was proposed. The differential pulse voltammogram (DPV) peak currents were found to be linear in the concentration range of 1.0 × 10-7 to 1.7 × 10-5M. The limit of detection (LOD) and the limit of quantification (LOQ) were obtained to be 7.0 × 10-9 and 2.3 × 10-8, respectively.

In the current study, poly(MImEO8BS)-Ni nanocomposite was synthesized and applied to modify a glassy carbon electrode along with conductive polymeric ionic liquids. The electrochemical investigation of the modified electrode as well as its efficiency for voltammetric oxidation of warfarin is elucidated. The electrode was used to study the voltammetric oxidation of warfarin by employing cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry, and square wave voltammetry (SWV) as diagnostic techniques. It has been observed that warfarin oxidation at the surface of modified electrode occurs at a potential of about 230mV which is less positive than that of an unmodified glassy carbon electrode. SWV demonstrated a linear dynamic range from 1.0×10-6 to 1.0×10-4M and a detection limit of 1.5×10-7M for warfarin. In addition, this modified electrode was utilized for simultaneous determination of warfarin and tramadol. Finally, the modified electrode was employed for determination of warfarin and tramadol in pharmaceutical compounds.

This study analyses the presence of pesticides in 106 samples of raw propolis from Spain and Chile. The components detected and quantified using gas chromatography mass spectrometry were as follows: triamidefon present in 70.1% of the samples with concentrations between 0.35 and 42.17mg/kg, and dicofol detected in 7.5% of the samples with concentrations between 0.39 and 2.83mg/kg. Diclorofluanid, procymidone, folpet, propham and metazachlor were also detected but only in a small number of samples. Near infrared spectroscopy with a remote reflectance fibre-optic probe was used to detect samples contaminated with triadimefon via partial least squares discriminant, with a R2 value of 0.71. In addition, the presence of the pesticide triadimefon in propolis was quantified using the modified partial least squares (MPLS) regression method. The calibration results showed a coefficient of determination (R2) of 0.81, a root mean square error (RMSE) of 0.36, and a ratio of performance to deviation (RPD) of 2.5.

A passive sampler inspired from previous devices was developed for the integrative sampling of a broad range of contaminants in the water column. Our primary objective was to improve the performance of the device to provide accurate and averaged pollutant water concentrations. For this purpose, an agarose diffusive gel was used as the boundary layer that drives the analyte uptake rate. Contrary to conventional passive samplers, the developed device does not require the sampling rates to be corrected for exposure conditions (e.g. hydrodynamic flow) because the diffusive gel boundary layer selected was sufficiently large to control the pollutant diffusion rate from the aqueous phase. The compounds diffusion coefficients in agarose gel and the gel thickness are the only required data to accurately calculate the time weighted averaged water concentration of pollutants. The performance of the developed sampler was evaluated in the laboratory under two contamination scenarios and in the field in 8 contrasting exposure sites for a selection of 16 emerging pollutants and pesticides. The results show that detection limits of this method are environmentally relevant and allow the determination of the averaged pollutant concentrations. Additionally, the ability of the device to sense very short contamination pulses (5-320min) was evaluated through a theoretical approach and laboratory tests. Results show that the device is suitable for sampling contamination pulses as short as 5min without deviation from the actual average concentrations of pollutants.

Nowadays, a deep eutectic solvent (DES) has recently been considered as a green ion liquid analogue. In this study, a new compound of DES has been synthesized as an extraction solvent in air assistedemulsification liquid-liquid microextraction method (DES-AAELLME) for preconcentration and extraction of methadone followed by gas chromatographyflame ionization detector (GC-FID). To obtain an efficient water-miscible deep eutectic solvent, choline chloride (ch-cl) and 5,6,7,8-Tetrahydro-5,5,8,8-tetramethylnaphthalen-2-ol (TNO) were mixed at a molar ratio of 1:2 and tetrahydrofuran (THF) was used as a demulsifier solvent into homogeneous solution for providing a turbid state. The solution was rapidly sucked up and injected 10 times using a 10-mL glass syringe to enhance the turbidity of solution and disperse the aggregated DES droplets into aqueous phase. Some important parameters affecting extraction recovery were investigated. Under optimum conditions, the calibration curve was linear in the concentration range from 2 to 8000µgL-1. The limit of detection and the limit of quantification were found 0.7µgL-1 and 2.3µgL-1 respectively with preconcentration factor of 270. The precision, as the relative standard deviation (RSD) (n=6), was

The present paper reported an one-pot synthesis of Co nanoparticles doped amino-graphene nanocomposites (Co-amino-Gr), involving in situ generation of Co nanoparticles (NPs). The simultaneous reduction of graphene oxide (GO) and Co2+ to produce Co-amino-Gr had been achieved under mild reaction conditions using an environmentally benign reducing agent, glycine. By combining the merits of amino-Gr and the Co NPs, a highly sensitive electrochemical sensor was erected to detect baicalin based on the Co-amino-Gr nanocomposites. Under optimum conditions, the response peak currents were linear related with baicalin concentrations in the range of 1.0×10-8-8.0×10-7molL-1 with a lower detection limit of 5.0×10-9molL-1 (S/N=3). Additionally, the proposed method was used to detect baicalin in the medicinal capsules with satisfactory results.

A fast and simple analytical method was developed to fully understand the chemical diversity of pentacyclic triterpenes: lupane, oleanane and ursane type, using multiple neutral loss markers scanning combined with substructure recognition (MNLSR). This procedure was performed on ultra-high performance liquid chromatography coupled to electrospray ionization quadrupole Orbitrap high resolution mass spectrometry (UHPLC/ESI Q-Orbitrap). Hippophae rhamnoides was used as an example. This approach includes three systematic workflows: (i) targeted identification of 25 reference standards in order to deduce the mechanism of fragmentation in both positive and negative modes. (ii) statistical analysis for neutral loss markers and structural fragment markers of pentacyclic triterpenes by fragmentation mechanism information. (iii) untargeted identification using multiple neutral loss markers scanning technique to discover new compounds and then confirming structural characterization by structural fragment markers. This mass spectra data analysis approach was successful to identify and confirm 15 new compounds from Hippophae rhamnoides samples. This study extended the application of mass spectrometry to satisfy the requirements of high-throughput identification for pentacyclic triterpenes in new medicine or food resources and could help chemists rapidly discover novel similar substructure compounds from a complex matrix.

A completely new voltammetric method has been developed for quantitative determination of food additive Taurine (Tau) in energy drinks. This electroanalytical method is based on voltammetric oxidation of o-phthalaldehyde-ethanthiol derivative of Tau at glassy carbon electrode in 95% methanol containing 0.1 mol L−1 lithium perchlorate. Working conditions necessary for quantitative Tau derivatization reaction and electrochemical detection using square wave voltammetry were optimized. Linear range from 1.0 × 10−5 to 1.0 × 10−4 mol L−1 characterized by coefficient of determination 0.9998, limits of quantification 6.8 × 10−6 mol L−1 and detection 2.1 × 10−6 mol L−1 were obtained at pulse amplitude 50 mV and frequency 80 Hz. Analytical method of calibration curve was used for evaluation of Tau content in several commercially available energy drinks. The procedure was validated using standard reference high performance liquid chromatography (HPLC) method. Both methods showed nearly identical Tau content, around 0.35% (w/w). Besides its reliability to the Tau determination, that is totally comparable to reference method used, present voltammetric approach is more advantageous on the economic and simplicity basis. Finally, developed voltammetric method could find employment in food quality control.

The endocrine disrupting chemicals bisphenol A (BPA) and 4-nonylphenol (NP) were simultaneously quantified through third-order/four-way calibration. Excitation-emission fluorescence matrix-kinetic (EEFM-K) third-order data were generated by measuring the EEFMs of these priority xenoestrogens as a function of reaction time during their Fenton degradation. Third-order/four-way calibration notably improves the sensitivity of the method and provides the required selectivity for quantifying analytes with critically overlapped fluorescence signals. In fact, collinearity between BPA and NP emission spectra prevented their quantification using EEFM second-order data and three-way PARAFAC (parallel factor analysis); however, the addition of a third instrumental mode allowed the correct chemometric modeling with four-way PARAFAC. In this way, the compliance of Kruskal´s theorem extended to higher-order data was verified. The method was applied for the determination of the analytes in samples of different plastic materials, which are in contact with food and/or beverages. In these cases, where unmodelled constituents are present, good results for BPA were achieved with four-way PARAFAC, but the predictions for NP using this model were deficient. A better predictive capability for NP in real samples was achieved when either U-PLS/RTL (unfolded partial least-squares combined with residual trilinearization) or MCR-ALS (multivariate curve resolution with alternating least-squares) was applied for data processing, demonstrating the power of these latter models for the resolution of more complex systems. Fil: Carabajal, Maira Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina Fil: Arancibia, Juan Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina Fil: Escandar, Graciela Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina

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.

2-(2H-Benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV 328; CAS: 25973-55-1) is a benzotriazole ultraviolet light (BUV) absorber which is applied to plastics and other organic substances to prevent discoloration and enhance product stability. Therefore, UV 328 is frequently used as a plastic additive and may lead to an exposure of consumers. For a reliable assessment of UV 328 metabolism, an analytical method applying dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography tandem mass spectrometry and advanced electron ionization was developed which allows the determination of UV 328 and six of its metabolites in human whole blood. Sample preparation was optimized with respect to DLLME parameters. A critical aspect of the procedure was the application of spiked human blood for calibration, which proved to be essential for achieving accurate results. Validation of the method resulted in limits of detection of 0.1 μg/L for all analytes. Variation coefficients ranged from 2 to 9% for intraday precision and from 3 to 11% for interday precision. Furthermore, relative recovery rates between 80 and 100% were calculated. Afterwards, the procedure was successfully applied to blood samples collected from a volunteer orally exposed to a single dose of UV 328. The method proved to be highly sensitive, repeatable and robust for all compounds and may further be used for studies to elucidate the human metabolism and kinetics of UV 328 and for biomonitoring of specific, environmental and occupational exposure to this UV stabilizer.

The simultaneous determination of eugenol (EU), thymol (Ty) and carvacrol (CA) in honey samples, employing square wave voltammetry (SWV) and chemometrics tools, is informed for the first time. For this purpose, a glassy carbon electrode (GCE) was used as working electrode. The operating conditions and influencing parameters (involving several chemical and instrumental parameters) were first optimized by cyclic voltammetry (CV). Thus, the effects of the scan rate, pH and analyte concentration on the electrochemical response of the above mentioned molecules were studied. The results show that the electrochemical responses of the three compounds are very similar and that the voltammetric traces present a high degree of overlap under all the experimental conditions used in this study. Therefore, two chemometric tools were tested to obtain the multivariate calibration model. One method was the partial least squares regression (PLS-1), which assumes a linear behaviour. The other nonlinear method was an artificial neural network (ANN). In this last case we used a supervised, feed-forward network with Levenberg-Marquardt back propagation training. From the accuracies and precisions analysis between nominal and estimated concentrations calculated by using both methods, it was inferred that the ANN method was a good model to quantify EU, Ty and CA in honey samples. Recovery percentages were between 87% and 104%, except for two samples whose values were 136% and 72%. The analytical methodology was simple, fast and accurate.

A simple and rapid HPLC method using 2-chloro-1-methyllepidinium tetrafluoroborate (CMLT) as a derivatization reagent was developed for simultaneous determination of homocysteine (Hcy), glutathione (GSH), γ-glutamylcysteine (γ-GluCys), cysteinylglycine (CysGly), N-acetylcysteine (NACys) and cysteine (Cys) in human saliva, plasma and urine. Separation of the analytes was achieved in just 7min using an HPLC, followed by UV detection at 355nm. Chromatographic separation was accomplished on Aeris PEPTIDE XB-C18 (150mm×4.6mm, 3.6µm) column from Phenomenex with a gradient elution: 0-4.0min, 7-30% B; 4.0-5.5min, 30-7% B; 5.5-7.5min, 7% B; (A: B, v/v); (A) 0.5% CH3COOH and (B) EtOH. Mobile phase was delivered at a flow rate 1.0mLmin(-1). Linearity in detector response for total thiols was observed over the range of 0.1-20μmolL(-1) for Hcy, GSH and γ-GluCys, 0.25-50μmolL(-1) for NACys and CysGly and 5-300 for Cys. The LOQ values for Hcy, GSH, γ-GluCys, NACys, CysGly and Cys were 0.05, 0.05, 0.10, 0.06, 0.12 and 0.08μmolL(-1), respectively. The method was successfully implemented to analysis of the samples donated by 15 apparently healthy volunteers and 10 patients.

The feasibility of predicting total antioxidant capacity (TAC) in maize flours by NIRS was assessed in a set of 391 samples, comprising Italian and public inbred lines, F1 seeds, commercial hybrids and traditional varieties, using ABTS direct assay as reference value. A subset of 81 samples were also used to test the development of a calibration model for soluble phenolic content (SPC), whereas 101 samples were analysed by DPPH assay. The models obtained for TAC by ABTS in different genetic materials were characterized by a good stability of the regression coefficients and showed a RER>2, allowing to develop both global and specific predictive models for this trait. On the contrary, only specific models were developed for SPC, and no predictive models were obtained for TAC by DPPH assay. These results demonstrated that NIR spectroscopy could be applied efficiently to the screening of the genotypes currently selected for the food industry.

A novel multi-wavelength nonaqueous capillary electrophoresis (MW-NACE) technique based on wavelength-dependent laser-induced fluorescence (LIF) detection was investigated for the simultaneous screening of various synthetic organic dyes. Multi-wavelength excitation light sources were utilized to excite different organic dyes [e.g., 543 nm for crystal violet (CV), methyl violet B (MVB), methyl violet B base (MBB), rhodamine 6G (R6G), and rhodamine B base (RBB); 635 nm for nile blue A (NBA) and methylene blue (MB)] simultaneously. Using a nonaqueous buffer system composed of 15 mM sodium borate and 835 mM acetic acid in 100% ethanol (pH=5.4), all dyes were analyzed within 15 min with excellent resolution (R≥4.0) under an electric field of 500 V/cm. Calibration curves showed excellent linearity with square of correlation coefficients (r(2)) greater than 0.9908 over wide dynamic ranges of 0.4-50 μM for CV, 0.8-50 μM for MVB, 1.5-50 μM for MBB, 0.08-5 nM for R6G, 0.06-10 μM for MB, 0.02-10 μM for NBA, and 0.13-10 pM for RBB. The detection limits (S/N=3) of 40 fM to 0.5 μM were 10-200,000 times lower than those of previous detection methods. While adjacent peaks were not well distinguished with baseline separation in a single capillary, the devised technique was faster and more sensitive than conventional aqueous and nonaqueous CE approaches, thereby enabling the quantitative analysis of various dyes based on wavelength-dependent fluorescence detection with different excitation wavelengths.

A passive sampler based on stir bars coated with polydimethylsiloxane (PDMS) was calibrated for the measurement of time-weighted average concentrations of hydrophobic micropollutants, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls and organochlorine pesticides, in water. Stir bar/water partition coefficients were measured by equilibrating bars with sheets made of silicone rubber material for which partition coefficients had been reported previously. Kinetic parameters characterising the exchange of analytes between stir bars and water were determined under controlled exposure conditions using a passive dosing system. The dosing system consisted of silicone rubber sheets with a large surface area, spiked with analytes. During stir bar sampler exposure, analytes partitioned from dosing sheets to water in the exposure tank and maintained constant exposure concentrations. Reversible and isotropic exchange kinetics of analytes between sampler and water was confirmed by measuring the release of a range of performance reference compounds (PRCs) from stir bars. Application of a two-resistance model confirmed that, except for hexachlorocyclohexane isomers, uptake of the test compounds under the experimental conditions was controlled by diffusion in the water boundary layer. This permits the application of PRCs for in situ calibration of uptake kinetics of test compounds to stir bars.

Propylene carbonate (PC) is a non-toxic solvent currently used in various pharmaceutical formulations. Consequently, a simple, cost-effective and most accurate analytical method for the quantification of this optical inert solvent is of major interest. Based on a consecutive three-step reaction 3,5-diacetyl-1,4-dihydro-2,6-lutidine was obtained from PC and used for quantification by either UV and fluorescent detection. Data were compared with results from LC-ESI-MS as a reference method. After using Mandel's test for linearity assessment of the calibration curves, linear fitting was used for LC-ESI-MS and spectrofluorimetry, while a polynomial 3rd order curve fitting was used for spectrophotometry. High intra- and inter-day precision as well as high accuracy were confirmed for all three analytical methods (spectrophotometry, spectrofluorimetry and LC-ESI-MS). The comparison of all three methods was assessed using correlation coefficients and Bland-Altman plots, both showing satisfying results with a high degree of agreement. The new method confirmed its applicability for PC quantification in two formulations, namely a PC-enriched cream and polyester microimplants. This new quantification method for PC is a reliable alternative to highly sophisticated chromatographic methods.

Herbicide metolachlor (MET) and insecticide buprofezin (BUP) were determined in natural waters by means of a newly-developed, simple and sensitive thermochemically-induced fluorescence derivatization (TIFD) method. The TIFD approach is based on the thermolysis transformation of naturally non-fluorescent pesticides into fluorescent complex O-phthalaldehyde-thermoproduct(s) in water at 70°C for MET and at 80°C for BUP. The TIFD method was optimized with respect to the temperature, pH, complex formation kinetic and pesticides concentrations. The limit of detection (LOD=0.8ngmL(-1) for MET and 3.0ngmL(-1) for BUP) and quantification (LOQ=2.6ngmL(-1) for MET and 9.5 ngmL(-1) for BUP) values were low, and the relative standard deviation (RSD) values were small (between 1.2% and 1.8%), which indicates a good analytical sensitivity and a great repeatability of TIFD method. Recovery studies were performed on spiked well, sea and draining waters samples collected in the Niayes area by using the solid phase extraction (SPE) procedure. Satisfactory recovery results (84-118%) were obtained for the determination of MET and BUP in these natural waters.

Using the carminic acid assay, we determined the concentration of boron in oilfield waters. We investigated the effect of high concentrations of salts and dissolved metals on the assay performance. The influence of temperature, development time, reagent concentration, and water volume was studied. Ten produced and flowback water samples of different origins were measured, and the method was successfully validated against ICP-MS measurements. In water-stressed regions, produced water is a potential source of fresh water for irrigation, industrial applications, or consumption. Therefore, boron concentration must be determined and controlled to match the envisaged waste water reuse. Fast, precise, and onsite measurements are needed to minimize errors introduced by sample transportation to laboratories. We found that the optimum conditions for our application were a 5:1 mixing volume ratio (reagent to sample), a 1 g L(-1) carminic acid concentration in 99.99% sulfuric acid, and a 30 min reaction time at ambient temperature (20 °C to 23 °C). Absorption values were best measured at 610 nm and 630 nm and baseline corrected at 865 nm. Under these conditions, the sensitivity of the assay to boron was maximized while its cross-sensitivity to dissolved titanium, iron, barium and zirconium was minimized, alleviating the need for masking agents and extraction methods.

Electrochemical detection provides a simple, rapid, sensitive and inexpensive method for DNA detection. In traditional electrochemical DNA biosensors, the probe is immobilized onto the electrode. Hybridization with the DNA target causes a change in electrochemical signal, either from the intrinsic signal of the probe/target or through a label or a redox indicator. The major drawback of this approach is the requirement for probe immobilization in a controlled fashion. In this research, we take the advantage of different electrostatic properties between PNA and DNA to develop an immobilization-free approach for highly sequence-specific electrochemical DNA sensing on a screen-printed carbon electrode (SPCE) using a square-wave voltammetric (SWV) technique. Anthraquinone-labeled pyrrolidinyl peptide nucleic acid (AQ-PNA) was employed as a probe together with an SPCE that was modified with a positively-charged polymer (poly quaternized-(dimethylamino-ethyl)methacrylate, PQDMAEMA). The electrostatic attraction between the negatively-charged PNA-DNA duplex and the positively-charged modified SPCE attributes to the higher signal of PNA-DNA duplex than that of the electrostatically neutral PNA probe, resulting in a signal change. The calibration curve of this proposed method exhibited a linear range between 0.35 and 50 nM of DNA target with a limit of detection of 0.13 nM (3SD(blank)/Slope). The sub-nanomolar detection limit together with a small sample volume required (20 μL) allowed detection of

The effect of the molecular weight of polyethyleneimine (PEI), defined as a compound having two or more ethyleneamine units, and of its carboxymethylation rate (CM/N), represented by the ratio of ion-exchange capacity to the amount of N on the resin, on the selective solid-phase extraction ability of the chelating resin immobilizing carboxymethylated (CM) PEI was investigated. The chelating resins (24 types) were prepared by immobilization of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, PEI300 (MW=ca. 300), and PEI600 (MW=ca. 600) on methacrylate resins, followed by carboxymethylation with various amounts of sodium monochloroacetate. When resins with approximately the same CM/N ratio (0.242-0.271) were used, the recovery of Cd, Co, Cu, Fe, Ni, Pb, Ti, Zn, and alkaline earth elements increased with increasing the molecular weight of PEIs under acidic and weakly acidic conditions; however, the extraction behavior of Mo and V was only slightly affected. This was probably due to the increase in N content of the resin, resulting in an increase in carboxylic acid groups; the difference in the molecular weight of PEIs immobilized on the resin exerts an insignificant influence on the selective extraction ability. The CM/N ratio considerably affected the extraction behavior for various elements. Under acidic and neutral conditions, the recovery of Cd, Co, Cu, Fe, Ni, Pb, Ti, and Zn increased with increasing CM/N values. However, under these conditions, the recovery of alkaline earth elements was considerably low when a resin with low CM/N ratio was used. This is presumably attributed to the different stability constants of the complexes of these elements with aminocarboxylic acids and amines, and to the electrostatic repulsion between the elements and the protonated amino groups in the CM-PEI. The recovery of Mo and V decreased or varied with increasing CM/N values, suggesting that the extraction of these elements occurred mainly by the anion-exchange reaction. For the separation and preconcentration of trace elements in samples containing large amounts of alkali and alkaline earth elements, the CM-PEI600 resin with CM/N=0.131 (Cu(II) extraction capacity, 0.37mmol g(-)(1)) was found to be the most suitable because it scarcely extracts alkali and alkaline earth elements under acidic and neutral conditions. This resin proved to be convenient for separating and preconcentrating Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn in the certified reference materials (EnviroMAT EU-L-1 wastewater and ES-L-1 ground water) and commercially available table salt.

A magnetic ion-imprinted polymer (Fe3O4@TiO2@SiO2-IIP) functionalized with -NH groups for the selective determination of Co(II) ions from environmental and biological samples is presented. This sorbent was synthesized by surface imprinting technique combined with sol-gel process using 3-(2-aminoethylamino) propyltrimethoxysilane (AAPTS) as a functional ligand, tetraethyl orthosilicate as across-linking agent, and Co(II) ion as the template. The prepared magnetic ion-imprinted polymer was characterized by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), dynamic light scattering (DLS), and X-ray diffraction (XRD). Fe3O4@TiO2@SiO2-IIP showed higher capacity and selectivity than that of Fe3O4@TiO2@SiO2-NIP. The important parameters influencing the recovery such as pH, the volume and eluent concentration, contact time, and the amount of sorbent on extraction percentage of Fe3O4@TiO2@SiO2-IIP were studied and optimized. The linear range (LR), relative standard deviation(RSD) and limit of detection (LOD=3 S(b)/m) for flame atomic absorption spectrometric determination of Co(II) ion, after its selective extraction by the prepared IIP polymer, were evaluated as 1-130 µg L(-1), 1.22% and 0.15 µg L(-1), respectively. The maximum capacity of Fe3O4@TiO2@SiO2-IIP and Fe3O4@TiO2@SiO2-NIP is 35.21 mg g(-1) and 10.34 mg g(-1), respectively. The separation factor of Fe3O4@TiO2@SiO2-IIP for Co(II)/Pb(II), Co(II)/Ni(II), and Co(II)/Cd(II) are 41.17, 79.74, and 56.48, respectively. In addition, the spent magnetic ion-imprinted polymer can be refreshed by simply washing with an aqueous HNO3 solution, and there is no significant decrease in adsorption capacity after a test of upto seven cycles, demonstrating that the Fe3O4@ TiO2@SiO2-IIP is stable and reusable.

Nitrate ions is a very common contaminant in drinking water and has a significant impact on the environment, necessitating routine monitoring. Due to its chemical and physical properties, it is hard to directly detect nitrate ions with high sensitivity in a simple and inexpensive manner. Herein with amino group modified graphene oxide (GO) as a sensing element, we show a direct and ultra-sensitive method to detect nitrate ions, at a lowest detected concentration of 5 nM in river water samples, much lower than the reported methods based on absorption spectroscopy. Furthermore, unlike the reported strategies based on absorption spectroscopy wherein the nitrate concentration is determined by monitoring an increase in aggregation of gold nanoparticles (GNPs), our method evaluates the concentration of nitrate ions based on reduction in aggregation of GNPs for monitoring in real samples. To improve sensitivity, several optimizations were performed, including the assessment of the amount of modified GO required, concentration of GNPs and incubation time. The detection methodology was characterized by zeta potential, TEM and SEM. Our results indicate that an enrichment of modified GO with nitrate ions contributed to excellent sensitivity and the entire detection procedure could be completed within 75 min with only 20 μl of sample. This simple and rapid methodology was applied to monitor nitrate ions in real samples with excellent sensitivity and minimum pretreatment. The proposed approach paves the way for a novel means to detect anions in real samples and highlights the potential of GO based detection strategy for water quality monitoring.

Given the threat that ostreid herpesvirus 1 (OsHV-1) poses to shellfish aquaculture, the need for rapid, user-friendly and cost-effective methods to detect this marine pathogen and minimise its impact is evident. In this work, an electrochemical biosensor for the detection of OsHV-1 based on isothermal recombinase polymerase amplification (RPA) was developed. The system was first tested and optimised on maleimide microtitre plates as a proof-of-concept, before being implemented on miniaturised gold electrodes. Amperometric detection of the isothermally amplified product was achieved through a sandwich hybridisation assay with an immobilised thiolated capture probe and a horseradish peroxidase (HRP)-labelled reporter probe. Calibration curves were constructed using PCR-amplified OsHV-1 DNA, achieving a limit of detection of 207 OsHV-1 target copies. The biosensor was applied to the analysis of 16 oyster samples from an infectivity experiment, and results were compared with those obtained by qPCR analysis, showing a strong degree of correlation (r = 0.988). The simplicity, rapidity, cost-effectiveness and potential for in-situ testing with the developed biosensor provide a valuable tool for the detection of OsHV-1 in aquaculture facilities, improving their management. info:eu-repo/semantics/acceptedVersion

A prototype of a handheld optical molecular analyzer based on household laser pointers of medium power (50–200 mW) equipped with a focusing lens is proposed. Its operating principle is based on the dependence of the attenuation of the laser beam by chromophore, luminophore or suspension on the analyte concentration in the solution. The possibilities of the proposed device are demonstrated by the determination of riboflavin in an injection solution and acetylsalicylic acid and magnesium hydroxide in a Cardiomagnyl® drug. The accuracy of the results is confirmed by fluorimetric, photometric and nephelometric methods. The lower limit of detection of riboflavin, salicylic acid and magnesium hydroxide is 3.5 μg mL−1, 1.2·10−5 mol L−1, 0.4 g L−1 respectively. The linearity range of the calibration dependences obtained in our work is about 1.5 order. The relative standard deviation of the determination results is less than 0.1.

Sensitive detection of copper is valuable for environment and human healthy. Herein, we reported a smartphone-based ratiometric fluorescent device for field analysis of soluble copper in river water samples, which is based on the fluorescence quenching effect of Cu2+ to N-doped carbon quantum dots. The fluorescent images in the sample and reference areas in a twin cuvette were captured by the camera in a smartphone. The non-linearity response of the image brightness to the exposure was corrected by (B−B0)/(255 −B), where B and B0 are the brightness with and without luminophore, respectively. It was shown that corrected brightness ratio is insensitive the variation in light source intensity, ambient temperature, shooting parameters and focus of the camera, which is helpful to improve the stability and reliability of the cheap portable detection device. By using a balanced calibration method, the accuracy for concentration estimation is improved further. Under optimized conditions, the proposed method was applied to detect Cu2+ in the range from 1 to 200 nM with the detection limit of 0.43 nM. This simple fluorescence device offers the advantages of portability, reliability and accuracy for field analysis.

Nucleoside-adduct analysis by liquid chromatography mass spectrometry is a powerful tool in genotoxicity studies. Efforts to date have quantified an impressive array of DNA damage products, although methodological diversity suggests quantification is still a challenging task. For example, inadequate co-examination of normal nucleosides, cumbersome sample preparation and large DNA requirements were identified to be recurring issues. A six-minute ultra-performance liquid chromatography method is presented which adequately separates seven candidate nucleoside-adducts from the four unmodified nucleosides. The method was sensitive to 1 adduct per 108 normal bases with 20 µg DNA input for most targets. The method was shown to be accurate (81–119% across quintuplets of six tissue types) and precise (relative standard deviation 4–13%). The fast method time facilitated a second quantitation for normal nucleosides at an appropriate dilution, allowing DNA damage concentrations to be contextualised accurately sample-to-sample. From DNA samples, the analytical processing time was

Phenanthrene is the most released polycyclic aromatic hydrocarbon into the environment by anthropogenic action. Because of the absorption and biotransformation pathways, this compound is metabolized and the most abundant metabolites are hydroxylated derivatives, such as 1-, 2-, 3-, 4- and 9-hydroxyphenanthrene, which are excreted through biological fluids, included mammals milk. For the resolution and quantitation of co-eluted analytes, elution time-emission fluorescence matrices were analysed with different second-order calibration algorithms: n-way and unfolded partial least squares, both coupled with residual bilinearization (N-PLS/RBL and U-PLS/RBL), and multivariate curve resolution-alternative least squares (MCR-ALS). Once optimized the chromatographic parameters, in isocratic mode, the elution time was of 5.5 min. The second-order data were obtained exciting at 250 nm, with an emission range from 330 to 430 nm, each 1 nm, and elution time from 0 to 5.5 min each 5.4 s. The ranges for the second-order multivariate methods in validation samples were from 1.0 to 9.0 ng mL−1 for 1-, 2-, 3- and 4-hydroxyphenanthrene, and from 5.0 to 45.0 ng mL−1 for 9-hydroxyphenanthrene. Root mean square errors of prediction between 0.45 and 1.82 ng mL−1 (relative errors of prediction 7–22%) were obtained. The optimized procedures were applied in the analysis of human breast milk and in whole and semi-skimmed commercial cow milk. N-PLS/RBL and U-PLS/RBL algorithms show satisfactory results for the five metabolites with recoveries ranging between 82% and 115%.