Yury A. Zolotov

Recent advances in sample preparation techniques and methods of sulfonamides detection - A review

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.

Facile synthesis of magnetic hypercrosslinked polystyrene and its application in the magnetic solid-phase extraction of sulfonamides from water and milk samples before their HPLC determination.

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.

Determination of the total content of some sulfonamides in milk using solid-phase extraction coupled with off-line derivatization and spectrophotometric detection.

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-Beers 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.

Kinetic approach for evaluation of total antioxidant activity

We propose a novel approach for assessment of total antioxidant activity by monitoring kinetics of hydrogen peroxide (H(2)O(2)) scavenging after its injection into liquid sample under study. H(2)O(2) is known to be the strongest oxidant, really presented in human body in contrast to the majority of the model oxidative systems used for evaluation of antioxidant activity. In addition, kinetic approach, being more informative than the commonly used determination of the final product, obviously provides better discrimination of potential antioxidants. Prussian Blue based sensor due to its high sensitivity and operational stability allowed to monitor kinetics of hydrogen peroxide consumption in turbid and colored samples. The pseudo-first order kinetic constants of hydrogen peroxide scavenging in the presence of different food additives correlated with total antioxidant activity of these samples evaluated via standard procedure based on lipid peroxidation. However, in contrast to the standard method, the proposed kinetic approach is expressed and does not require fresh biological tissues.

Cellulose fibrous sorbents with conformationally flexible aminocarboxylic groups for preconcentration of metals

New cellulose fibrous sorbents, containing a diethylenetriamine tetraacetate groups, are proposed for the preconcentration of heavy metals. Quantitative extraction of heavy metals from river and sea water is achieved in a wide pH range (3–8) at a high solution flow rate (up to 100–150 volumes of sorbent per minute). Quantitative desorption of metals is achieved with a very small volume of the acid.

Label-free gold nanoparticles for the determination of neomycin

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.

Phosphoryl containing podands as carriers in plasticized membrane electrodes selective to quaternary ammonium surfactants

Open chain polyethers with phosphoryl-containing terminal groups have been studied as carriers in plasticized membrane electrodes that are selective towards cationic surfactants. Host–guest complexation has also been studied by means of batch extraction and bulk membrane transport experiments. For the various guests, the bulk membrane (chloroform) transport rate decreases in the series tetraalkyl ammonium > alkyl pyridinium > alkyl ammonium, while the series of solvent extraction efficiency is exactly opposite; an explanation for this behaviour is proposed. The performance of electrode membranes follows the series for bulk membrane transport. Among the ISE membranes of various composition, one containing the longest (seven oxygen atoms) podand, o-nitrophenyl octyl ether (plasticizer), and sodium tetraphenyl borate (anionic additive) performs the best. The slope of the electrode function equals 58.5 mV/decade, the detection limit for dodecyltrimethylammonium is 3.2 × 10-6 M. ISE response time is 5–10 s, the working pH range is 2–11 and lifetime is at least 6 months. The electrode selectivity is significantly better than that of conventional ion-association and crown ether based electrodes.

Sorbents with non-covalently immobilized β-diketones for preconcentration of rare earth elements

A comparison of the efficiency of sorbents obtained by different methods of non-covalent immobilization of β-diketones on some low-polar matrices with respect to extraction of rare earth elements (REEs) was carried out. It was shown that sorbents containing reagent amounts of 1-8mmol/g can be obtained by sorption of reagents on low-polar matrices from aqueous and aqueous-organic solutions, and the value for the maximum capacity of the sorbent correlates with the specific surface of the matrix. Similar sorbents were also prepared by impregnating the matrix with reagent. It was found out that, under the chosen conditions, sorbents modified by extracting reagent from the aqueous solutions are more stable and extract lanthanum with higher distribution coefficients than those obtained by impregnation. We have found conditions for quantitative extraction of REEs from seawater in the proposed preconcentration systems (pH 4.0, minicolumn dimensions 2×10mm, v=4ml/min). It was shown that all REE may be quantitatively recovered in both ways: on modified sorbents and as complexes with reagents on unmodified matrices. We have proposed a sorbent for lanthanum preconcentration from large volumes of water samples (500ml). The sorbent is stable in dynamic conditions and is based on hyper cross-linked polystyrene modified with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (PMBP). Desorption could be carried out with 1-2M HNO3. REEs were determined by ICP-MS, LODs achieved were in ng/l range.

Towards highly selective detection using metal nanoparticles: A case of silver triangular nanoplates and chlorine

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 2·105 greater molar amounts of Na+, K+, Zn2+, Cl-, SO42-, and H2PO4- 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.

Early stages in the history of gas chromatography

The creation of gas chromatography is traditionally associated with the names of Nobel Prize winner Archer Martin and his colleagues Richard Synge and Anthony James. However, sometimes references to their predecessors can be found. An investigation conducted by the authors of this article not only confirmed the reliability of these references; but in fact led to the conclusion that by 1952, which is commonly believed to be the year when gas chromatography was born, many research papers had already been devoted to this method, mainly, in its gas-solid version. These papers are considered in this article.