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An aqueous two-phase system (ATPS) based on benzethonium chloride (BztCl) and sodium dihexyl sulfosuccinate (NaDHSS) was proposed for the first time for liquid-liquid microextraction of Cd(II), Co(II), Cu(II), Mn(II), Ni(II), and Pb(II) followed by ICP-OES determination. The mixture of cationic and anionic surfactants, BztCl and NaDHSS, showed liquid-liquid phase separation at the molar ratio of 1:1, and the total surfactant concentration of 0.01-0.2 mol L -1 forming ATPS that was investigated in the extraction process. The extraction efficiency for Cd(II), Co(II), Mn(II), Ni(II), and Pb(II) was nearly 100 %, and for Cu(II) - not lower than 88 % in the presence of 8-hydroxyquinoline as a complexing agent. The surfactant-rich phase containing analytes was subjected to back-extraction with 0.2 M HNO 3 before ICP-OES measurements. The preconcentration in the proposed BztCl-NaDHSS-H 2 O ATPS for 30 s and the high degree of back-extraction, which was achieved in 1 min, significantly reduced the sample preparation time, matrix effects and provided low LODs in the range of 0.04-1.0 μg L -1 , the preconcentration factor was 120. The analysis of a certified reference material sample of surface water and the real samples of tap, sea, and waste water verified the method accuracy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A rapid multi-residue LC-MS/MS method for the identification and determination of banned veterinary drugs in honey was developed. A total of 31 investigated veterinary drugs belonging to 4 classes including nitrofurans metabolites, nitroimidazoles, amphenicols, and quinolones were quantified by LC-MS/MS with ESI using one single injection. The sample preparation included treatment with 5-nitro-2-furaldehyde (5-NFA) in a thermostated ultrasonic bath (80 °C, 0.5М НСl, 20 min) to liberate matrix-bound residues of nitrofurans. Magnetic hypercrosslinked polystyrene (HCP/Fe 3 O 4 ) was proposed for the solid-phase extraction and clean-up of target analytes prior to LC-MS/MS analysis. To evaluate and validate the performance of method, the criteria of the Decision (EC) no 2002/657 were applied. The LOQs of the examined analytes range from 0.3 to 1 μg kg -1 , which indicates good sensitivity to quantify the target compounds in honey. The recoveries of veterinary drugs from 1 g of honey with 50 mg of the sorbent are 97-109% for nitrofuran metabolites, 84-115% for nitroimidazoles, 86-103% for amphenicols, and 97-118% for quinolones. The relative standard deviations of intra-day and inter-day precision analyses (RSD) are less than 16%. This methodology was applied to real honey samples and trace levels of some veterinary drugs were detected., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A possibility of the use of a common monitor calibrator as a portable and inexpensive tool for the fluorometric determination of sulfonamide drugs after their reaction with fluorescamine was examined. The luminescence measurements with a calibrator are based on irradiation of a test sample by the device lamp with a broadband spectrum in the visible and near UV regions and simultaneous registration of the secondary radiation by the device detector. Two types of cuvettes with black light absorbing sides eliminating the reflected self-radiation were tested. The commercially available Eppendorf-type black plastic microtubes ("LightSafe") were suggested as a good option for such measurements. It was shown that a monitor calibrator can be applied for optimization of the determination conditions. By the example of sulfanilamide and sulfamethazine, it was shown that the procedure should be carried out at pH 4-6 and fluorescamine concentration of 200 μmol L -1 , and 40 min of the interaction. The limit of detection of sulfanilamide and sulfamethazine using a monitor calibrator is 0.9 μmol L -1 and 0.8 μmol L -1 , respectively, which is comparable with their spectrophotometric determination., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this study, aqueous two-phase systems (ATPSs) containing a cationic and anionic surfactants mixture were used for the preconcentration of the synthetic food dyes Allura Red AC, Azorubine, Sunset Yellow, Tartrazine, and Fast Green FCF. A rapid, simple, low cost, affordable, and environmentally friendly methodology based on microextraction in ATPSs, followed by spectrophotometric/colorimetric determination of the dyes, is proposed. The ATPSs are formed in mixtures of benzethonium chloride (BztCl) and sodium N-lauroylsarcosinate (NaLS) or sodium dihexylsulfosuccinate (NaDHSS) under the molar ratio close to equimolar at the total surfactant concentration of 0.01-0.20 M. The density, viscosity, polarity, and water content in the surfactant-rich phases at an equimolar ratio BztCl:NaA were determined. The effects of pH, total surfactant concentration, dye concentration, and time of extraction/centrifugation were investigated, and the optimum conditions for the quantitative extraction of dyes were established. The smartphone-based colorimetric determination was employed directly in the extract without separating the aqueous phase. The analytical performance (calibration linearity, precision, limits of detection and quantification, reproducibility, and preconcentration factor) and comparison of the spectrophotometric and smartphone-based colorimetric determination of dyes were evaluated. The method was applied to the determination of dyes in food samples and food-processing industrial wastewater.

Nitrofurans (NFs) are synthetic broad-spectrum antibacterial and antiparasitic drugs, which recently were extensively used in veterinary practice. In the body of animals, NFs are converted into carcinogenic and mutagenic metabolites that can be accumulated in foods of animal origin having an adverse effect on human health. Therefore, NFs are currently banned in animal husbandry and aquaculture of many countries. However, the data from monitoring the quality of food products indicate that, despite the prohibitions established by the law, they still are used not only in the developing countries but also in the European Union, due to their high antibacterial activity, low cost, and accessibility. Thus, it is of great importance for human health to develop reliable and sensitive analytical methods for monitoring NF metabolites in animal-derived foods. The objective of this review is to summarize the pretreatment strategies and chromatographic methods that have been reported during the last decade for the determination of NF metabolites in food samples, and to outline the future trends with an emphasis on the novel solutions in this area., 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.)

A quantitative multi-class multi-residue analytical method was developed for the determination of veterinary drugs in milk by high-performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS). A total of 132 veterinary drugs investigated belonged to almost 15 classes including sulfonamides, β-lactams, tetracyclines, quinolones, macrolides, nitrofurans, nitroimidazoles, phenicols, lincosamides, pleuromutilins, macrocyclic lactones, quinoxaline antibiotics, benzimidazoles, anthelmintics, coccidiostats and some others. A magnetic solid-phase extraction procedure was developed using magnetic hypercrosslinked polystyrene (HCP/Fe 3 O 4 ) for the sample preparation prior to HPLC-MS/MS without deproteinization step. The results indicated recoveries of 85-107% for 14 sulfonamides, 85-120% for 13 β-lactams, 89-115% for 4 tetracyclines, 82-119% for 14 quinolones, 82-115% for 8 macrolides, 97-109% for 4 nitrofurans, 84-115% for 10 nitroimidazoles, 89-114% for 3 phenicols, 86-111% for 3 lincosamides, 97-102% for 2 pleuromutilins, 72-88% for 4 macrocyclic lactones, 87-104% for 4 quinoxaline antibiotics, 76-119% for 21 benzimidazoles, 79-115% for 12 anthelmintics, 81-118% for 12 coccidiostats and 75-119 % for 5 unclassified drugs, with relative standard deviations (RSDs) of less than 20%, and the LOQs ranged from 0.05 to 1 μg kg -1 . This methodology was then applied to field-collected real milk samples and trace levels of some veterinary drugs were detected., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Microfluidic paper-based analytical devices (µPADs) represent one of the promising green analytical strategies for low-cost and simple determination of various analytes. The actual task is the development of such devices for quantitation of antioxidants, e.g., flavonoids. In this paper, possibilities of a novel three-reagent µPAD including silver nitrate, 4-nitrophenyldiazonium tetrafluoroborate, and iron(III) chloride as reagents are assessed with respect to the determination of dihydroquercetin. It is shown that all the three reagents produce different colorimetric responses that can be detected by a mini-spectrophotometer-monitor calibrator or by a smartphone. The method is applicable to direct measuring high contents of dihydroquercetin (the linearity range is 0.026-1 mg mL -1 , and the limit of detection is 7.7 µg mL -1 ), which is favorable for many dietary supplements. The analysis of a food supplement was possible with the relative standard deviations of 9-26%, which is satisfactory for quantitative and semiquantitative determinations. It was found that plotting a calibration graph in 3D space of the three reagents' responses allows us to distinguish dihydroquercetin from its close structural analogue, quercetin.

In this study, 5-nitro-2-furaldehyde (5-NFA) was proposed as a new derivatizing agent for nitrofuran metabolites. It reacts with nitrofuran metabolites producing the parent nitrofurans (furazolidone, furaltadone, nitrofurantoin, and nitrofurazone). Magnetic hypercrosslinked polystyrene (HCP/Fe 3 O 4 ) was first used for magnetic solid phase extraction (MSPE) clean-up before the determination of nitrofuran metabolite derivatives in honey via LC-MS/MS. Main parameters affecting the derivatization and MSPE efficiency were investigated in detail and the optimal conditions were found. The method was validated using honey spiked with the four metabolites at 1, 2 and 200 μg kg -1 . Recoveries of >85% were achieved for the all analytes. The matrix calibration curve was fitted with the correlation coefficient (R 2 ) > 0.99 in the range of 1-200 μg kg -1 . Precision values expressed as relative standard deviation (RSD) were <12% and <15% for intra-day and inter-day precision, respectively. The limits of detection (LODs) for the nitrofuran metabolites were of 0.1-0.3 μg kg -1 and the limits of quantitation (LOQs) were of 0.3-1.0 μg kg -1 . The proposed LC-MS/MS method was applied to the analysis of real honey samples., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Effect of amines on formation of gold nanoparticles (AuNPs)/polymer nanocomposites has been observed and studied. Nanocomposites based on polyurethane foam and AuNPs were synthesized by interaction between the polymer modified with sodium borohydride and aqueous solution of tetrachloroauric acid. It has been shown that some amines cause a remarkable decrease of the surface plasmon resonance band of AuNPs in the nanocomposite material. Both aliphatic and aromatic amines as well as amines containing several amino groups were studied. A possible mechanism of the effect is discussed. It is probably based on stabilization of AuNPs with an amine that entails a decrease in the degree of their adsorption on PUF and appearance of the stabilized AuNPs in solution. The decrease of the nanocomposite surface plasmon resonance band is proportional to the concentration of amine in the solution. Based on this effect, a method for the determination of cetylamine, β-naphthylamine and neomycin in water and medical formulations using a monitor calibrator as a portable household tool is proposed. Under the selected conditions, the detection limits for amines were in the range of 0.7-1.5 μM, the determination ranges were approximately an order of magnitude. The observed color change of the nanocomposite samples also provides a good basis for semiquantitative determinations., (Copyright © 2021 Elsevier B.V. All rights reserved.)

An improved step-by-step colorimetric method for determination of halides has been developed. The method is based on successive selective oxidation of iodide, bromide and chloride into corresponding free halogens, their extraction by airflow and colorimetric detection with different paper test-strips. This procedure can be performed in a single analyzed solution and possesses high selectivity and good sensitivity due to the extraction step. Three types of paper test-strips were examined: paper modified with tetramethylammonium iodide and starch, paper modified with methyl orange and paper modified with silver triangular nanoplates. Limits of detection for iodide, bromide and chloride are 0.01, 0.02, and 0.04 mg L -1 respectively in case of the last mentioned paper. The method was applied to the analysis of samples having complex matrices, such as various seafood, preserves, bread, and natural waters, showing good accuracy of the analysis with recoveries of 95-105% and relative standard deviations not higher than 6%., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A novel method towards spectrophotometric determination of catecholamines and their metabolites differing in their functional groups has been developed. This method is based on a change in morphology of silver triangular nanoplates upon the action of cateсholamines and their metabolites, which is manifested by the decrease of the nanoparticle local surface plasmon resonance (LSPR) band intensity or its shift to the short-wavelength region of the spectrum. The shift value of the LSPR band or the change of its intensity increases with increasing concentration of catecholamines or their metabolites, which is proposed for their spectrophotometric determination. The limits of detection of catecholamines and their metabolites under selected conditions increase in the series homovanillic acid < vanillylmandelic acid < L-epinephrine < L-norepinephrine < dopamine and are 0.25, 1.2, 3.0, 64, and 130 μmol L -1 , respectively. The selectivity of the proposed method was assessed using vanillylmandelic acid as example. It was found that the determination of vanillylmandelic acid does is not interfered in the presence of 4000-fold excess of Na + , K + , CH 3 COO - , and 1000-fold excess of Mg 2+ , Ca 2+ , Al 3+ , NO 3 - . The method also allows for the selective determination of vanillylmandelic acid in the presence of a 1000-fold excess of structurally related substances that do not contain either a catechol fragment or an electron donor substituent. The proposed approach was successfully applied to the determination of catecholamines in pharmaceuticals and artificial urine. Graphical abstract.

One of the possible ways for using silver nanoparticles (AgNPs) in spectrophotometry is their application for the determination of oxidizing agents, based on oxidative destruction of these nanoobjects. This process depends on the structure of AgNPs surface layer, which is essentially affected by the chosen stabilizer. To assess influence of the nanoparticle stabilizer and the nature of the analyte, possibilities of AgNPs covered with stabilizers of three types (citrate, polyvinylpyrrolidone, and polyhexamethylene guanidinium) for the spectrophotometric determination of hydrogen peroxide and differently substituted organic peroxides were studied. The approach is based on AgNPs oxidation leading to discoloration of the solution monitored spectrophotometrically. Different selectivity of the oxidation depending on the stabilizer was shown. Effects of various factors (time of interaction, pH, concentration of AgNPs) on the oxidation and analytical performance of the procedure were investigated. The method allows for the determination of hydrogen peroxide, peracetic acid, m-chloroperbenzoic acid, and t-butylhydroperoxide in the range of 0.3-1.5, 0.1-0.8, 1.0-7.5, and 1-7 μg mL -1 and with the limits of detection of 0.1, 0.04, 0.3, and 0.3 μg mL -1 , respectively. The analysis can be performed using either spectrophotometry or naked-eye detection., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A method is described for sensitive and selective detection of iodine by using a paper strip modified with silver triangular nanoplates (AgTNPs). It is based on the extraction of iodine from a solution into a flow of air via dynamic gas extraction and transferring it through a reactive paper modified with AgTNPs. The interaction of AgTNPs with iodine results in a color change from blue to white. This can be visually detected and monitored by digital colorimetry. The dynamic gas extraction is highly selective for volatile compounds so that a sample pretreatment is minimal. Due to the sensitivity of AgTNPs for iodine, the limit of its detection is as low as 7 μg L -1 , and the analytical range is of 20-200 μg L -1 . The method also was applied in a new approach for determination of organic compounds that can interact with iodine. The organic compound is exposed to an excess of iodine, and this is followed by detection of residual iodine as described above. The method was applied to the determination of ascorbic acid, caffeine and the drug metamizole. Graphical abstract Schematic representation of a procedure of organic iodine-interacting compounds (Org.) determination. It is based on their iodination followed by gas extraction of the residual iodine, its interaction with silver triangular nanoplates and colorimetric detection with a scanner.

Positively charged polyhexamethylene guanidine hydrochloride-stabilized silver nanoparticles (PHMG-AgNPs) were prepared and applied as a colorimetric probe for single-step determination of pyrophosphate and sulfate. The approach is based on the nanoparticles aggregation leading to change in their absorption spectra and color of the solution. Due to both electrostatic and steric stabilization these nanoparticles show decreased sensitivity relatively to many common anions, which allows for simple and rapid direct single-step determination of pyrophosphate and sulfate. Effects of different factors (time of interaction, pH, concentrations of anions and the nanoparticles) on aggregation of PHMG-AgNPs and analytical performance of the procedure were investigated. The method allows for the determination of pyrophosphate and sulfate in the range of 0.16-2μgmL -1 and 20-80μgmL -1 with RSD of 2-5%, respectively. The analysis can be performed using either spectrophotometry or naked-eye detection. Practical application of the method was shown by the example of pyrophosphate determination in baking powder sample., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The article describes a novel approach towards improving selectivity of volatile compounds detection using metal nanoparticles. It is based on combination of sensitive optical detection using convenient nanoparticle-modified paper test strips and dynamic gas extraction improving selectivity to volatile compounds. A simple and inexpensive setup allowing for realization of this combination is described. Analytical prospects of the approach are shown by the example of chlorine determination in highly salted aqueous solutions using silver triangular nanoplates and digital colorimetry. The limit of detection is equal to 0.03mgL -1 and the determination range is 0.1-2mgL -1 . This determination can be successfully carried out in solutions containing at least 2·10 5 greater molar amounts of Na + , K + , Zn 2+ , Cl - , SO 4 2- , and H 2 PO 4 - with no sample pretreatment. The approach seems to be compatible with different types of nanoparticles with respect to detection of various analytes, thus having good opportunities for further development., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A sorption-spectrometric method for determination of the anionic synthetic dyes based on their sorption on silica sorbent modified with hexadecyl groups (C16) followed by measuring the diffuse reflectance spectra on the surface of the sorbent has been proposed. Adsorption of sulfonated azo dyes Tartrazine (E102), Sunset Yellow FCF (E110), Ponceau 4R (E124) reaches maximum in acidic medium (1M HCl - pH 1). For the quinophthalone type dye Quinoline Yellow (E104), the adsorption is also maximal in an acidic medium (1M HCl - pH 2). The triphenylmethane dye Fast Green FCF (E143) is absorbed in the wider area of pH (1M HCl - pH 6). Increasing concentration of the dyes in a solution led to the increase in absorption band intensity in diffuse reflectance spectra of the adsorbent, which was used for their direct determination. The proposed method was applied to the determination of dyes in beverages and pharmaceuticals., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In this paper, we report on a novel type of nanocomposites based on gold nanoparticles (AuNPs) and polyurethane foam (PUF), which represents an ability of AuNP aggregation on solid polymer matrix with the strongly different selectivity in comparison with aggregation of the same AuNPs in solution. This may indicate that a new type of aggregation takes place, which can be called solid-phase aggregation. A systematic study using diffuse reflectance spectroscopy revealed features of the solid-phase aggregation. The PUF-AuNPs nanocomposites can be synthesized by a simple and low cost procedure based on adsorption of different type AuNPs from aqueous solution onto PUF. Prospects of obtained composite materials for sensing some organic compounds using diffuse reflectance spectroscopy or colorimetry are shown. This nanocomposites have the increased selectivity to thiols allowing for their determination with limits of detection of 0.01-0.05μgmL -1 and relative standard deviations of 3-5%. Charged species that affect AuNPs in solution do not influence them on PUF., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Gold nanorods (AuNRs) stabilized by cetyltrimethylammonium bromide (CTAB) were synthesized and an interaction of catecholamines (CAs) with silver ions in the presence of the obtained AuNRs was studied. The reaction results into formation of core-shell Au@Ag nanorods (Au@AgNRs) and leads to a hypsochromic shift of the long-wave surface plasmon resonance (SPR) band in the absorption spectrum of AuNRs. The influence of a CA structure, excess of CTAB, interaction time, pH, concentration of AuNRs, silver ions and CAs on this interaction was studied. Based on correlation of the NRs spectral characteristics with the concentration of CAs, a method for spectrophotometric determination of dobutamine, epinephrine, norepinephrine and dopamine with detection limits 27, 18, 16 and 13 μg L(-1), respectively, has been developed. The method can be applied to the analysis of medicines., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this study, a novel magnetic solid-phase extraction (MSPE) sorbent, magnetic hypercrosslinked polystyrene (HCP/Fe3O4), was prepared and used for preconcentration of four sulfonamides (sulfamethoxypyridazine, sulfamethazine, sulfamethoxazole and sulfachloropyridazine) from natural water and milk samples. This material was prepared by sorption of pre-synthesized Fe3O4 nanoparticles (NPs) onto HCP. A number of sorbents with varying Fe3O4NPs content were prepared, and their structural, magnetic and sorption properties were studied. Various experimental parameters affecting the extraction efficiencies such as the amount of the magnetic nanocomposite, extraction time, pH of the sample solution and desorption conditions were studied and optimized. Under the optimal conditions, a convenient and efficient method for the determination of sulfonamides in water and milk samples was developed by combining MSPE and high-performance liquid chromatography with amperometric detection. The results showed that the recoveries of these compounds were in the range of 84-105% with the relative standard deviations ranging between 3% and 10%; the limit of detection were in the range of 0.21-0.33 ng mL(-1) for water and 2.0-2.5 ng mL(-1) for milk., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A simple screening method for isolation and determination of the total content of some sulfonamides in milk using solid-phase extraction and a color reaction is described. This procedure is based on SPE of sulfonamides on hypercrosslinked polystyrene, elution with acetonitrile and off-line derivatization with p-dimethylaminocinnamaldehyde in acetonitrile followed by spectrophotometric determination. The reaction produces intense violet-red color and can be easily used both for quantitation of sulfonamides using spectrophotometry and for naked-eye semi-quantitative estimation. Maximum absorption of the reaction product was determined at 540 nm. The Lambert-Beer's law was obeyed in the range of 0.07-3.0 μg mL(-1) in eluate, with the squared correlation coefficient (R(2)) of 0.9875-0.9995, and the relative standard deviation (RSD) of 3-4%. The limits of SAs detection using preconcentration were of 0.02-0.03 μg mL(-1). The proposed method can be recommended as a routine screening method for quantitation of sulfonamides in milk., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Desensitized ionene-stabilized gold nanoparticles have been prepared and applied as a colorimetric probe for the single-step test for sulfate ions at the relatively high concentration level. The approach is based on aggregation of the nanoparticles leading to the change in absorption spectra and color of the solution. These nanoparticles are characterized by the decreased sensitivity due to both electrostatic and steric stabilization, which allows for simple, and rapid direct single-step determination of sulfate at the relatively high concentration level in real water samples without sample pretreatment or dilution. Influence of different factors (the time of interaction, pH, the concentrations of sulfate ions and the nanoparticles) on the aggregation and analytical performance of the procedure was investigated. The method allows for the determination of sulfate ions in the mass range of 0.2-0.4 mg with RSD of 5% from the sample volume of less than 2 mL. It has a sharp dependence of the colorimetric response on the concentration of sulfate, which makes it prospective for indicating deviations of the sulfate concentration regarding some declared value chosen within the above range. The time of the analysis is 2 min. The method was applied to the analysis of mineral water samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Formation of plasmonic silver nanoparticles by flavonoid reduction was studied. Effects of the nature and the concentration of a flavonoid and a stabilizer, composition of the solution and the interaction time were revealed. It was found that quercetin, dihydroquercetin, rutin and morin produced an intense surface plasmon resonance band of silver nanoparticles at 415 nm which was linearly related to the concentration of a flavonoid, while chrysin, naringenin and naringin did not produce any remarkable changes. It was used for the spectrophotometric determination of the former four flavonoids with the detection limits of 0.03; 0.06; 0.09 and 0.1 μg mL(-1), respectively. The developed method was applied for the determination of flavonoids in biologically active food additives., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Sulfonamides (SAs) have been the most widely used antimicrobial drugs for more than 70 years, and their residues in foodstuffs and environmental samples pose serious health hazards. For this reason, sensitive and specific methods for the quantification of these compounds in numerous matrices have been developed. This review intends to provide an updated overview of the recent trends over the past five years in sample preparation techniques and methods for detecting SAs. Examples of the sample preparation techniques, including liquid-liquid and solid-phase extraction, dispersive liquid-liquid microextraction and QuEChERS, are given. Different methods of detecting the SAs present in food and feed and in environmental, pharmaceutical and biological samples are discussed., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A new spectrophotometric method for the determination of neomycin has been developed. The method is based on aggregation of label-free gold nanoparticles leading to change in absorption spectra and color of the solution. Influence of different factors (the concentration of ethylenediaminetetraacetate (EDTA), pH, the concentrations of neomycin and the nanoparticles) on the aggregation and analytical performance of the method was investigated. EDTA plays an important role not only as a masking agent to eliminate interferences of metal cations but strongly affects the sensitivity of the nanoparticles relative to neomycin. The method allows to determine neomycin with detection limit of 28ngmL(-1). It was applied to analysis of eye- and ear-drops. The sample pretreatment is simply done by diluting the formulation with water., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Sorption preconcentration of flavonoids quercetin, rutin, chrysin, morin, naringenin and naringin on polyurethane foam was investigated. Several parameters that could affect the preconcentration efficiency were evaluated. The preconcentration efficiency is more than 75% for all the flavonoids except for those that are carbohydrate substituted (preconcentration efficiency less than 11%). This can be used for the separation of these two types of flavonoids. An ability of some flavonoids to absorb light in PUF phase allows their direct determination by diffuse reflectance spectroscopy. Validation of calibration linearity, reproducibility, limits of detection and quantification was performed. The method developed allows to determine flavonoids with detection limits 0.01-0.2 μg mL(-1). The method was utilized for the determination of quercetin in some plant extracts., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Polyurethane foam (PUF) has been suggested as a solid polymeric reagent for determination of nitrite. The determination is based on the diazotization of end toluidine groups of PUF with nitrite in acidic medium followed by coupling of polymeric diazonium cation with 3-hydroxy-7,8-benzo-1,2,3,4-tetrahydroquinoline. The intensely colored polymeric azodye formed in this reaction can be used as a convenient analytic form for the determination of nitrite by diffuse reflectance spectroscopy (c (min) = 0.7 ng mL(-1)). The possibility of using a desktop scanner, digital camera, and computer data processing for the numerical evaluation of the color intensity of the polymeric azodye has been investigated. A scanner and digital camera can be used for determination of nitrite with the same sensitivity and reproducibility as with diffuse reflectance spectroscopy. The approach developed was applied for determination of nitrite in river water and human exhaled breath condensate.