Z. A. Temerdashev

Determination of lead and cadmium by atomic absorption spectrometry coupled with slurry sampling of carbonized samples : Use of palladium-bearing activated carbon as a matrix modifier

The determination of Pb and Cd by electrothermal atomic absorption spectroscopy with the slurry sampling of carbonized samples into a graphite furnace was considered. Textural and chemical properties of new palladium-carbon modifiers based on activated carbon and carbonized nutshell were studied by high-resolution electron microscopy, x-ray photoelectron spectroscopy, and the adsorption of liquid nitrogen. Advantages of activated carbon as a modifier support were substantiated. Pyrolysis and atomization temperatures were selected for determining elements using matrix modifiers. The developed analytical procedure was tested with reference samples of plant materials. The results obtained agreed well with the certified analyte concentrations. The RSD values were no higher than 8% for lead and cadmium in the ranges 0.3–3.3 and 0.110–1.34 mg/kg, respectively.

Determination of phenolic compounds in medicinal herbs by reversed-phase HPLC

An HPLC procedure is proposed for the determination of 12 phenolic compounds in plant tissues by reversed-phase HPLC with gradient elution and UV detection. The influence of pH, composition of the mobile phase, concentration of the organic modifier, and temperature on the separation of gallic, protocatechuic, trans-ferulic, trans-caffeic acid, rutin, quercetin, dihydroquercetin, and (_)-epicatechin for 30 min is studied. The lower limit of quantification of phenolic compounds is 1–2.5 μg/L. The procedure was applied to the determination of phenolic compounds in aqueous extracts of Hypericum perforatum; its sample was found to contain protocatechuic acid, (_)-epicatechin, and also rutin.

Determination of phenolic compounds in medicinal plants from the Lamiaceae family

A procedure for the determination of Phenolic compounds in extracts from the medicinal plants of the Lamiaceae family—garden sage (Salvia officinalis L.), creeping thyme (Thymus serpyllum L.), wild marjoram (Origanum vulgare L.), and common balm (Melissa officinalis L.)—obtained under different extraction conditions was developed. The identification of the extracted compounds was performed and their qualitative and quantitative composition was established by HPLC with diode array and mass-spectrometric detection with consideration for the obtained characteristics of the standard samples of individual components. The test samples of medicinal herbs contained caffeic acid (0.19–0.62 mg/g) and rosmaric acid (4–23 mg/g); the highest rosmaric acid content (23 mg/g) was found in wild marjoram, and the lowest content (4 mg/g), in creeping thyme. The extracts of wild marjoram contained the greatest amounts of Phenolic compounds; rosmaric acid and luteolin-7-O-β-D-glucuronide were major components, whereas protocatechuic, 3-O-caffeoylquinic, and caffeic acids were minor components.

Permanent chemical modifiers in electrothermal atomic absorption spectroscopic analysis: A review

Publications on the use of permanent modifiers (PMs) in electrothermal atomic absorption spectroscopic analysis (ETAAS) were reviewed. Modifiers of thermally stable carbides (TCs), platinum group metals (PGMs), and their mixtures were characterized. The objects analyzed most frequently with the use of permanent modifiers were described in groups: organic solutions, suspensions and solid samples, materials after acid decomposition, and natural and drinking water. The results of the physicochemical studies of new sorbent modifiers and the thermodynamic and kinetic laws of thermochemical processes with their participation were presented.

Electrochemical behavior of Crystal Violet on glassy carbon electrodes

The electrochemical behavior of Crystal Violet (CV) on the surface of a glassy carbon electrode in potassium chloride, nitrate, and iodide supporting electrolytes was studied using stripping voltammetry. It was demonstrated that an electroactive complex of CV with iodine was adsorbed on the electrode in a KI solution. This property can be used for determining iodide by adsorption–stripping voltammetry.

Sorption properties of cellulose filters with covalently immobilized thiosemicarbazide

AbstractsA novel thin-layer cellulose adsorbent bearing chemically immobilized thiosemicarbaside is synthesized. The adsorbent is used for the preconcentration of cobalt(II), mercury(II), and cadmium(II) followed by their X-ray fluorescence quantification in the concentrate. The physicochemical parameters of metal sorption are determined.

Synthesis of novel silica-gel-supported thiosemicarbazide and its properties for solid phase extraction of mercury

ABSTRACT A new thiosemicarbazidе-modified silica gel (SG-THSC) sorbent was prepared. The sorbent was quantified by adsorption of mercury ions on silica gel, desorption and then spectrophotometry detection of mercury ions. The retention parameters (sample flow rate, eluent type, sample volume, presence of foreign ions, shaking time, sample flow rate and volume, eluent condition, interfering substances) were investigated. The quantitative recovery (>95%) of Hg(II) ions could be obtained by use of 5 mL of 6 mol L−1 HCl. The adsorption capacity of SG-THSC was found to be 98.3 mg g–1 at optimum pH. The maximum preconcentration factor was 400. The technique detection limit was 70 ng L–1, and the relative standard deviation was lower than 4.0% (n = 6). The studied sorbent was applied to preconcentrate the trace Hg(II) from the mineralised residues of fish and seawater samples.

Immobilization of Guanazyl Functional Groups on Silica for Solid-Phase Extraction of Metal Ions

Guanazyl groups were grafted on silica gel by 4-nitrobenzoyl chloride acylation, sodium dithionite reduction, diazotation, and reaction with 2-benzylidenehydrazinecarboximidamide. The modified silica gel was used for separation and preconcentration of Cu(II), Ni(II), Cd(II), and Co(II). Quantitative extraction of the ions was achieved after 30 min and at the optimal pH of 7.5–8 at an initial concentration of 2 mg L−1. Analysis of metal sorption isotherms allowed estimation of the sorbents interaction efficacy under static conditions at optimal pH. Distribution coefficients were determined to be 3 ± 0.3 L g−1 for Ni(II), 3 ± 0.3 L g−1 for Co(II), 1.6 ± 0.2 L g−1 for Cd(II), and 4.6 ± 0.4 L g−1 for Cu(II) at 20–60 µg analyte. The applicability of pseudo-second order kinetic equations for metal sorption kinetics description was investigated. Chemically modified silica was used for solid-phase extraction of the metal ions to improve the detection limit using X-ray fluorescence spectrometry. The method was employed for the determination of Cu(II) in water with a low limit of detection, high accuracy, and good precision.

Application of Ranging Analysis to the Quality Assessment of Wines on a Nominal Scale

This work is dedicated to wine quality assessment methods as a problem of considerable current interest. Well-known approaches to wine quality assessment are considered based on the concentrations of volatile substances in wines and on the results of their taste tests. Comparative analysis was carried out for the evaluation of wines on a nominal scale of quality (high, medium, low, and adulterated) by means of discriminant analysis. It was found that the classification of wines based on quality with the use of discriminant analysis as a ranging analysis method with consideration for the concentrations of volatile substances, which are responsible for their organoleptic properties, is highly competitive with their expert (tasting) evaluation. A mathematical model was constructed for the classification of wines into the above categories, and a program module was developed for the automation of calculations.

Suspension columns with grain sorbents retained in an ultrasonic field for separation and determination of rare-earth elements in wines

The properties of a Diasorb-130-IDK sorbent based on silica gel with a grain size of about 6 µm were studied in order to choose conditions for the separation of the rare-earth elements from the samples of natural wine and their subsequent determination by inductively coupled plasma mass spectrometry. The possibility of the quantitative separation of the elements with the use of an ultrasonic flow suspension column was demonstrated. The results were compared with data obtained with the use of other sample preparation methods. A procedure was proposed for the determination of the rare-earth elements and yttrium in the samples of wines.