A. L. Moskvin

Automated procedure for determination of ammonia in concrete with headspace single-drop micro-extraction by stepwise injection spectrophotometric analysis

A novel automatic stepwise injection headspace single-drop micro-extraction system is proposed as a versatile approach for automated determination of volatile compounds. The system application is demonstrated for ammonia determination in concrete samples. An ammonia gas was produced from ammonium ions and extracted on-line into 5 μL 0.1M H3PO4 to eliminate the interference effect of concrete species on the ammonia stepwise injection spectrophotometric determination. The linear range was 0.1-1 mg kg(-1) with LOD 30 µg kg(-1). The sample throughput was 4 h(-1). This system has been successfully applied for the determination of ammonia in concretes.

Flow Analysis: A Novel Approach For Classification

ABSTRACT We suggest a novel approach for classification of flow analysis methods according to the conditions under which the mass transfer processes and chemical reactions take place in the flow mode: dispersion-convection flow methods and forced-convection flow methods. The first group includes continuous flow analysis, flow injection analysis, all injection analysis, sequential injection analysis, sequential injection chromatography, cross injection analysis, multi-commutated flow analysis, multi-syringe flow injection analysis, multi-pumping flow systems, loop flow analysis, and simultaneous injection effective mixing flow analysis. The second group includes segmented flow analysis, zone fluidics, flow batch analysis, sequential injection analysis with a mixing chamber, stepwise injection analysis, and multi-commutated stepwise injection analysis. The offered classification allows systematizing a large number of flow analysis methods. Recent developments and applications of dispersion-convection flow methods and forced-convection flow methods are presented.

Photometric cyclic-injection determination of arsenic in aqueous solutions

A procedure for the photometric on-line determination of trace arsenic in aqueous solutions was developed. The procedure is based on the reaction gas extraction of arsenic as arsine followed by liquid-absorption separation from a gas phase into a solution of a photometric reagent (2-(p-nitrophenyl)-3,5-diphenyltetrazolium chloride). The determination limit was 10 μg/L at a sample volume of 50 mL.

Simultaneous cyclic-injection spectrophotometric determination of aluminum and iron in petroleum products

A procedure is developed for the cyclic-injection spectrophotometric determination of iron and aluminum in petroleum products; it includes microwave sample mineralization followed by the determination of analytes as their complexes with Chrome Azurol S at pH 5. The classical least-squares technique is used for the simultaneous determination of iron and aluminum. The analytical range for elements covers from 10 to 100 mg/kg at a sample weight of 1 g. The limits of detection for both elements are 3 mg/kg. The developed procedure was used for the determination of iron and aluminum in the spent engine oil and marine fuel.

Determination of the phenol index of water by stepwise injection analysis with offline preconcentration by extraction chromatography

A procedure for the photometry determination of the phenol index of aqueous media is developed, which involves the preliminary separation of alkylphenols and their derivatives from water samples in sampling. Samples are filtered through an extraction chromatography column containing tributyl phosphate as an active component of the stationary phase followed by their quantification under the conditions of stepwise injection analysis. The detection limit of the method is 0.1 μg/L for simple phenol.

Generation of urinary steroid profiles in patients with adrenal incidentaloma using gas chromatography–mass spectrometry

A method is developed for the determination of steroid hormones in urine using gas chromatography with mass-spectrometric detection. Sample preparation procedure and the conditions of chromatographic analysis were optimized, and characteristic urinary steroid profiles of patients with adrenocortical cancer were obtained. Criteria for the evaluation of the deficiency of 21-hydroxylase and 11β-hydroxylase in patients with adrenal incidentaloma are proposed.

Stepwise injection photometric determination of nickel in air aerosols

A procedure is developed for the automated determination of nickel in air aerosols; it involves the adhesive separation of aerosols on a fiberglass column in the on-site mode followed by the photometric determination of analytes with dimethyl glyoxime under the conditions of stepwise injection analysis of aerosol concentrates. The analytical range for nickel is 1.5–38 μg/m3; the detection limit of the method is 0.5 μg/m3 at an air sample volume of 30 L. The duration of sampling to an adhesive column and concentrate analysis were 15 and 10 min, respectively.

Cyclic injection photometric determination of silicon in oil products

A photometric procedure is developed for determining silicon in oil products involving the preliminary conversion of organic and inorganic silicon into silicate ions followed by their determination by the formation of reduced silicomolybdic heteropolyacid and cyclic injection analysis. The detection limit for silicon is 1 μg/g for a sample weight of 1 g.

‘Lab-in-reaction-cell’ cyclic injection analysis as an opportunity for the miniaturization of flow analysis

The method of cyclic injection analysis in the ‘lab-in reaction-cell’ mode has been proposed for the miniaturization of flow analysis; the hydraulic scheme of this mode assumes the formation of the analytical forms of the analytes and their detection directly in the reaction cell of the cyclic injection analyzer through the combination of the latter with the measurement cuvette of a fiber optic spectrophotometer. The possibilities of the proposed solution are illustrated by the example of the determination of ‘active chlorine’ in aqueous media. A procedure has been developed for the automated photometric determination of ‘active chlorine’ in the range from 0.2 to 1.3 mg/L in aqueous media in a 125 μL sample, the duration of one analysis being 2.5 min.

Stepwise injection photometric determination of phosphorus in light oil products

A procedure has been developed for the automated photometric determination of phosphorus in light oil products. It includes the preliminary conversion of covalently bound phosphorus into phosphates followed by their determination by stepwise injection analysis using the reaction of the formation of reduced phosphomolybdic heteropoly acid in the presence of Murphy-Riley reagent. The limit of detection for phosphorus appeared to be 1 mg/L for a sample volume of 3 mL.