Journal of Analytical Chemistry

A rapid method is proposed for the preparation of binuclear rhodium(II) tetraacetate [Rh2(OAc)4(HOAc)2] under the action of microwave radiation. This complex is potentially suitable for the coulometric determination of rhodium. The mechanism of the redox process Rh2(III, II) ⇄ Rh2(II, II) in acetic acid solutions of this complex has been characterized by cyclic voltammetry, controlled-potential coulometry, and spectrophotometry.

A method is proposed for the selective photometry determination of perchlorates in potable water with a detection limit of 2×10−3 mg/L is proposed based on the extraction of its ion pair with the astrafloxin cation and absorbance measurements at 540 nm. The following ratios of matrix ions are acceptable (in parentheses): ClO−, ClO 2 − , ClO 3 − , BrO 3 − (500); I− (1000); IO 3 − (7000); HCO 3 − , Cl−,SO 4 2− , NO 3 − , Br−, Na+, K+, Ca2+, Mg2+ (10000). The relative error of determination for ClO 4 − is 20% in the range 4 × 10-3-1 × 10−2 mg/L and 10% in the range 1 × 10-2–5 × 10−2 mg/L.

The adsorption of osmium(VIII) from sulfuric and hydrochloric acid solutions and gas phase on silicas chemically modified by dithiocarbamate, thiodiazolthiol, mercaptophenylpropylurea, and aminobenzothiazolpropyl groups is studied. A procedure is developed for the adsorption-photometric determination of osmium, including the adsorption of osmium(VIII) from the gas phase on silicas chemically modified by sulfur-containing groups and the determination of osmium in the adsorbent phase by diffuse reflection spectroscopy. The procedure was used to determine osmium in a certified reference material of the composition of a matte ore thermal melting and process waters.

The affinity of acetonitrile to different adsorbents used as modifiers of quartz crystal microbalance electrodes was estimated from quantitative sorption parameters. A piezoelectric quartz crystal microbalance with electrodes modified with a squalane solution in hexane was proposed for determining acetonitrile in air at a level of 0.5 MPC. The conditions of the formation of sensitive films (modifier weight and solvent) were optimized, and the interfering effect of alkyl acetates was studied.

Films based on arachic acid, alkylated calixresorcinarenes, and β-cyclodextrin were prepared on the surfaces of piesoresonance sensors using the Langmuir-Blodgett method. A linear relationship between the frequency shift of the piesoresonance sensor and the number of monolayers was found in all of the test diphilic compounds. The Langmuir-Blodgett films were used as surface modifiers in piesoresonance sensors for the determination of nitroalkanes. The reversibility of sensor signals, that is, the complete regeneration of the films after blowing with air for 1–3 min, was an important property of the sensors. The sensing coating proposed was characterized by a long lifetime: it withstood 80–100 sorption-desorption cycles. The sensor noise level was ±20 Hz.

The micellar extraction of barium with phases of nonionic surfactant Triton X-100 was studied in the presence of aliphatic monocarboxylic acids, crown ethers, and Carboxyarsenazo and its mixtures with cetylpyridinium chloride and octylamine. It was shown that the complete extraction of barium into the micellar phase was attained using Carboxyarsenazo and cationic surfactants in the presence of octylamine through the formation of a ternary hydrophobic complex. The conditions for the determination of the atomic absorption of barium in water with preconcentration into the nonionic surfactant phase at the cloud point temperature were developed.

Optimal conditions of the complexation of Sulfochlorophenol and Sulfochlorophenol S with lanthanum, terbium, and erbium were found, and molar absorptivities of the complexes were calculated. Chromaticity characteristics of the complexes and molar coefficients of chromaticity functions were determined. It was demonstrated that the use of the most sensitive chromaticity functions provides an increase in the sensitivity of the determination of rare-earth elements of 1–2 orders of magnitude in comparison with conventional spectrophotometry. Dissociation constants of the reagents were determined using optical and chromaticity methods.

A sensitive voltammetric method is developed for the determination of diazinon, an organophosphorus pesticide, using a Nafion®-coated glassy carbon electrode as an enrichment film. The analysis of diazinon in aqueous solutions using sensitive instrumental methods has gained importance. Investigation of the electrochemical behavior of diazinon on a Nafion®-coated glassy carbon electrode reveals the presence of a specific oxidation peak of analytical significance. The experimental parameters, such as pH, film thickness, preconcentration potential, preconcentration time, and square-wave voltammetric parameters were optimized. Using this method, a linear calibration curve for diazinon was obtained up to 5 μM range in pH 1 citrate buffer solution with a detection limit (S/N = 3) of 75 nM.

One of the possible methods for determining molecular masses of organic compounds is discussed. The method consists in the use of short-time chemical ionization of analyte molecules by incident pulses of an initiator compound. The possibility of the determination of molecular masses by this method was demonstrated with an example of organophosphorus compounds.