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.     

Flow-injection photometric determination of mercaptans in light oil products with chromatomembrane extraction

A procedure was developed for the flow-injection photometric determination of mercaptans in light oil products. The use of sodium nitroferricyanide as the photometric reagent at 540 nm provides a detection limit of mercaptan sulfur of 0.3 mg/L at a volume of the sample of 3 mL; the analytical range is from 1 to 50 mg/L.     

Cyclic flow-injection photometric determination of mercaptans in hydrocarbon gases

A procedure for the automated photometric determination of mercaptans in hydrocarbon gases was developed using sodium nitroprusside as a photometric reagent. The analytical range was from 10 to 150 mg/m³ at a sample volume of 0.4 L and preconcentration time of 2 min.     

Stepwise injection photometric determination of mercaptanes in air

An automated procedure is developed for the photometric determination of mercaptanes in air. To achieve the required selectivity of analyte determination, a scheme of sample preparation was elaborated, which includes the liquid absorption separation of interfering components (hydrogen sulfide and sulfur dioxide) and mercaptanes on two consequent chromatography columns with glass wool impregnated with a zinc acetate solution and an alkaline solution of cadmium chloride. Therein, the impurities specified were separated in the first column, while the target materials were gathered on the second one. The materials were detected with high sensitivity by their reaction with an iodine/starch complex under the conditions of step-wise injection analysis. The analytical range for mercaptane sulfur was from 0.5 to 7.5 μg/m³ for a sample volume of 1 m³.     

Stepwise injection photometric determination of ascorbic acid in drugs

A procedure is developed for the photometric determination of ascorbic acid in drug preparations. It is based on the rapid and highly selective reaction of ascorbic acid with a novel reagent, the guanidinium salt of 1-bismuto-11-molybdophosphoric heteropolyacid. The detection limit for ascorbic acid in stepwise injection analysis makes 15 mg/L, and the duration of single analysis, 5 min.     

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.     

Flow injection determination of trace vanadium with catalytic photometric detection

A catalytic photometric detection system based on the chromotropic acid—bromate reaction is adapted to a flow injection system for the rapid, simple and sensitive determination of vanadium. Vanadium in the range 0.3–4.8 ng (10–160 ppb) can be determined at a rate of ca. 60 samples per hour.     

Selective determination of orthophosphate and total inorganic phosphates in detergents by flow injection photometric method

A flow injection photometric system was developed for the determination of orthophosphate and total inorganic phosphates in detergents. While orthophosphate was directly determined in the presence of other phosphates by utilizing the kinetic discrimination of flow injection analysis, total inorganic phosphates was analyzed after on-line hydrolysis of polyphosphates in 2.5 mol l(-1) sulfuric acid for 50 s under 145 degrees C. Sodium dodecyl sulfate (SDS) was added to mask the interference of non-ionic surfactants. The detection limits and the sampling rates were 2.5 mg l(-1) P(2)O(5) and 40 h(-1) for total inorganic phosphates, and 1.0 mg l(-1) P(2)O(5) and 80 h(-1) for orthophosphate determination. The proposed method was applied to analyze orthophosphate and total inorganic phosphates in washing powders. The experimental results are in good agreement with those obtained by the Chinese national standard methods.     

Downscaling a multicommuted flow injection analysis system for the photometric determination of iodate in table salt

In this work a downscaled multicommuted flow injection analysis setup for photometric determination is described. The setup consists of a flow system module and a LED based photometer, with a total internal volume of about 170 μL. The system was tested by developing an analytical procedure for the photometric determination of iodate in table salt using N,N-diethyl-henylenediamine (DPD) as the chromogenic reagent. Accuracy was accessed by applying the paired t-test between results obtained using the proposed procedure and a reference method, and no significant difference at the 95% confidence level was observed. Other profitable features, such as a low reagent consumption of 7.3 μg DPD per determination; a linear response ranging from 0.1 up to 3.0 m IO₃⁻, a relative standard deviation of 0.9% (n = 11) for samples containing 0.5 m IO₃⁻, a detection limit of 17 μg L⁻¹ IO₃⁻, a sampling throughput of 117 determination per hour, and a waste generation 600 μL per determination, were also achieved.     

Flow injection determination of lactate based on a photochemical reaction using photometric and chemiluminescence detection

A photochemical method for the determination of lactate using a flow-injection system is proposed. The method is based on the decomposition of lactate in the presence of UO2(2+) and Fe3+ upon irradiation with UV or visible light. The Fe2+ produced in the photochemical process was monitored by measuring the absorbance after complexation with ferrozine (lambda max = 562 nm) or the chemiluminescence (CL) intensity in a luminol system without added oxidant. The range of measurements depended on the length of the irradiation time and the detection system used. The detection limits using CL and photometric detection were 2 ng ml-1 and 50 ng ml-1, respectively. The sample throughput was 45 samples h-1. The usefulness of the method was demonstrated by determining lactate levels in blood serum, milk, yoghurt, beer and pharmaceutical preparations.     

Utilization of flow injection with hydrazine reduction and photometric detection for the determination of nitrate in rain-water

The hydrazine reduction method for determination of nitrate at the parts per million level is adapted to flow injection sample processing of rain-water. Reagent composition and physical variables were evaluated and optimized. Forty samples per hour can be processed. A precision of better than 3% is possible in the range of 1.0–10.0 ppm nitrate. Results for nitrate obtained from 9 rain-water samples agreed favorably with those determined by ion chromatography.     

Extractive photometric determination of zinc traces in water

Summary Traces of zinc in water are determined by extracting diethyldithiocarbamates into chloroform at about p_H 9, and stripping lead, zinc and cadmium with 0.16M hydrochloric acid. The cadmium is masked with iodide and the zinc determined spectrophotometrically with Zincon at 620 nm. Iron is masked with citrate before the extraction.

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Zusammenfassung Zinkspuren in Wasser werden als Diäthyldithiocarbamat mit Chloroform bei p_H 9 extrahiert. Blei, Zink und Cadmium werden dann mit 0,16-n Salzsäure der Chloroformphase entzogen. Cd wird mit Jodid maskiert und Zink spektrophotometrisch mit Zineon bei 620 nm bestimmt. Eisen wird vor der Extraktion mit Zitrat maskiert.

     

催化光度法测定水中痕量亚硝酸根

利用在硫酸介质中亚硝酸根催化溴酸钾氧化吖啶橙的褪色反应 ,建立了测定痕量亚硝酸根的新方法。方法检出限为 7.6× 1 0 -8mol/ L,线性范围 0～1 .1 2× 1 0 -6mol/ L。本法可用于测定雨水和自来水中的痕量亚硝酸根     

Selective photometric determination of selenium in aqueous media

A procedure is developed for the photometric determination of selenium in aqueous media using 2-(p-nitrophenyl)-3,5-diphenyltetrazolium chloride. To selectively determine selenium, a two-stage scheme of sample preparation is chosen. It includes the gas extraction of selenium liberated as hydrogen selenide, its extraction from the gas phase to a solution of lead nitrate by liquid absorption and repeated extraction of hydrogen selenide, followed by its absorption with an aqueous reagent solution to form water-insoluble formazan. The formazan is extracted with chloroform. The concentration of selenium is determined from the absorbance of the chloroform extract of formazan. The procedure involves no special preconcentration operations and allows from 10 to 100 μg/L selenium to be determined.     

A simple turbidimetric flow injection system for saccharin determination in sweetener products

A new method for saccharin determination in liquid sweetener products was developed. The method is based on the precipitation reaction of Ag(I) ions with saccharin in aqueous medium (pH 3.0), using a flow injection analysis system with merging zones, the suspension was stabilized with 5 g L⁻¹ Triton X-100. All experimental parameters influencing the flow injection system were optimized by means of chemometric approaches. The linear analytical curve was built from 2.4 g L⁻¹ up to 9.64 g L⁻¹ (r = 0.9968) with a quantification limit of 2.40 g L⁻¹. The precision assessed as relative standard deviation (n = 10) was found to be 1.75 % for the saccharin concentration of 7.20 g L⁻¹. Based on interference studies performed with the substances commonly found in liquid sweeteners, such as sodium cyclamate, methylparaben, sodium aspartame, and benzoic and citric acids, at the analyte to interferent mole ratio of up to 1: 10, no interference with the saccharin determination was observed. The presence of chloride ions interferes with the method, but a preceding liquid-liquid saccharin extraction with ethyl acetate was successfully employed to overcome this drawback. Accuracy of the method in sweetener products was evaluated by a comparison with the HPLC method.     

X-ray fluorescence determination of sulfur and other elements in customs control of oil and liquid oil products

Results of an X-ray fluorescence determination of sulfur and other elements in oils and liquid oil products are presented, obtained using a Spectro-Xepos energy-dispersive spectrometer with the excitation of the fluorescence spectrum immediately in the liquid samples under investigation. It is shown that the amount of trace elements considerably varies not only in different types of oil products, but also in different samples of the same product. An experimental evaluation of the metrological characteristics of the determination of sulfur in oil products showed that they met the requirements of GOST (Russian State Standard) R 50442-92 Oil and Oil Products: X-ray Fluorescence Method for Determining Sulfur.     

Sequential injection method for the direct spectrophotometric determination of bismuth in pharmaceutical products

A spectrophotometric method is reported for the determination of bismuth in pharmaceutical products using sequential injection analysis. Methylthymol blue (MTB) was used as a color forming reagent and the absorbance of the Bi(III)-MTB complex was monitored at 548 nm. The various chemical and physical variables that affected the reaction were studied. A linear calibration graph was obtained in the range 0.0-75.0 mg l⁻¹ Bi(III) at a sampling frequency of 72 h⁻¹. The reagent consumption was considerably reduced compared to conventional flow injection systems, as only 150 μl of MTB were consumed per run. The precision was very satisfactory (s_r=0.5%, at 50.0 mg l⁻¹ Bi(III), n=12) and the limit of detection, c_L, was 0.250 mg l⁻¹. The developed method was applied successfully to the analysis of various pharmaceutical products containing Bi(III). The relative errors e_r, were <1.5% in all cases and were evaluated by comparison of the obtained results with those found using atomic absorption spectrometry as the reference method.     

Indirect flame photometric determination of sulphate ions

In this paper the possibilities have been studied of determining sulphate ions by indirect flame photometry by difference. Barium and Strontium in constant concentration were used as background elements. By means of the methods proposed sulphate ions can be determinined in the concentration range 0 to 70 p.p.m. with barium and 0 to 110 p.p.m. with strontium. The determinations can be carried out in dilute solutions of alkali metal sulphates and sulphate ions can also be estimated in the presence of macroquantities of other compounds. This may prove useful for the quantitative estimation of sulphate as an impurity in Chemical reagents. Some examples are given of the determination of the degree of purity of substances containing sulphate as impurities.