A kinetic determination of ultramicro quantities of serotonin, 5-hydroxyindolacetic acid,L-dopa,methyl-dopa and carbidopa

Summary A kinetic method is presented for the determination of the biologically important substances serotonin, 5-hydroxyindolacetic acid, L-dopa, methyldopa and carbidopa. The method is based on the reaction between hydrogen peroxide, molybdenum(VI) and the substance to be determined, in carbonate buffer solution, the reaction rate being followed photometrically. In order to find optimum experimental conditions for these determinations the kinetics of the reactions were examined. The substances investigated were determined at concentrations ranging from 0.40 to 17.4 g/ml, with relative standard deviations ranging from 0.6 to 6.1%. The effect of some foreign species usually present in biological material has also been examined.

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Kinetische Bestimmung von Ultramikromengen Serotonin, 5-Hydroxyindolessigsäure, L-Dopa, Methyldopa und Carbidopa

Zusammenfassung Eine kinetische Methode zur Bestimmung der biologisch wichtigen Substanzen Serotonin, 5-Hydroxyindolessigsäure, L-Dopa, Methyldopa und Carbidopa wurde vorgeschlagen. Sie beruht auf der Reaktion zwischen Wasserstoffperoxid, Molybdän(VI) und der zu bestimmenden Substanz in carbonat-gepufferter Lösung. Das Reaktionsergebnis wird photometrisch gemessen. Um optimale Reaktionsbedingungen zu ermitteln, wurden die kinetischen Daten geprüft. Die genannten Substanzen wurden in Konzentrationen zwischen 0,40 und 17,4 g/ml bestimmt, wobei relative Standardabweichungen zwischen 0,6 und 6,1% auftraten. Die Wirkung mancher, in biologischem Material üblicherwiese anwesender Fremdsubstanzen wurde geprüft.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Determination of trace amounts of cobalt by solvent extraction--second derivative spectrophotometry

A sensitive derivative spectrophotometric method is described for the determination of microamounts of cobalt based on the integration of liquid-liquid separation and reaction, in dichloroethane, of the analyte with 3-(4-phenyl-2-pyridinyl)-5-phenyl-1,2,4-triazine (PPT) and 2,4,6-trinitro-phenol (picric acid). Cobalt was thus determined in the range 7.2-500 ng/ml. The method has a high selectivity with a detection limit of 2.2 ng/ml. The relative standard deviations were 3.2 and 1.5% for 20 and 100 ng/ml cobalt, respectively. The proposed method was applied to the determination of the analyte in vitamins.     

罗丹明B电极催化电位法测定微量锰的研究

本文基于在邻二氮菲（活化剂）存在下，Ｍｎ（Ⅱ）对高碘酸根氧化罗丹明Ｂ退色反应的催化作用，对于用罗丹明Ｂ电极（自制）以催化电位法测定微量锰进行了研究。实验表明，该方法测锰的线范围为１１－４８ｎｇ／ｍｌ。选择性较好，温度控制方便。本文在未经分离的情况下测定了标准钢样品的锰含量，结果满意。     

Flow-Injection Spectrophotometric Determination of Hydrazine

A flow-injection spectrophotometric method for the determination of hydrazine is described. The method is based on the inhibitory effect of hydrazine on the reaction of thionine with nitrite in acidic media. The decolorization of thionine by the reaction with nitrite was used to monitor the reaction spectrophotometrically at 602 nm. The variables that affected the reaction rate were fully investigated and the optimum conditions were established. Hydrazine can be determined in the range 2.0–40.0 μg/ml with a limit of detection of 1.0 μg/ml. The relative standard deviation for 10 replicate determinations of 7.0 μg/ml hydrazine is 3.3%. The method is simple, rapid, and widely applicable.     

Kinetic determination of iodide, based on the chlorpromazine-bromate reaction

A kinetic method based on the catalytic effect of iodide on the chlorpromazine-bromate reaction is described. The reaction was followed spectrophotometrically by measuring the increase in the absorbance at 525 nm. Under optimal experimental conditions (10(-4)M chlorpromazine hydrochloride, 1.5(itM) phosphoric acid, 5 x 10(-4)M potassium bromate, 40 degrees ), iodide was determined between 5 and 70 ng/ml by the tangent method. The influence of reaction variables, the precision and accuracy of the method and the effect of foreign ions were studied. The procedure was applied to the determination of iodide in iodinated salts and in rat thyroid.     

Automatic ultramicro determination of iodine in natural waters

An automatic spectrophotometric reaction rate method is described for the ultramicro determination of iodine in natural waters. The method is based on the catalytic effect of iodine on the reduction of cerium(IV) by arsenic(III). The time required for a small fixed (about 0.06 unit) change in absorbance is measured automatically and related to the iodine concentration. Speed and the small size of the sample needed are the main advantages over other methods. Iodine in water in the range 1 to 15 μg/l in a total volume ot 4 ml is determined with errors smaller than ±0.3 μg /l.     

Spectrophotometric determination of trace amounts of selenium with catalytic reduction of bromate by hydrazine in hydrochloric acid media

A method is presented for the determination of selenium, based on the catalytic effect of selenium(IV) on the reduction reaction of BrO(-)(3) by N(2)H(4).2HCl. The decolourization of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. This method is precise, highly sensitive, simple, rapid, widely applicable and selective for the determination of selenium(IV) and total selenium. The variables which affected the reaction rate were fully investigated and the optimum conditions were established. Selenium, as low as 1 ng/ml, can be determined by this method. The relative standard deviation of 20 ng of selenium was 0.94% (N = 10). The method was applied to the determination of Se(IV) in a health-care product.     

Highly Selective Photometric Method for the Determination of Periodate

ABSTRACT

A simple and selective photometric procedure was developed for the micro-determination of periodate in aqueous media. The method is based on the reaction of periodate with Gallocyanine at pH = 4.8. The reaction was monitored photometrically by measuring the absorbance of the reaction mixture at 620 nm. The effects of reagent concentration, temperature and influence of other species for the determinations of periodate were investigated. Periodate can be determined in the range of 0.02-2.20 μg/ml, with a relative standard deviation of 1.96% for ten replicate measurements of 0.13 μg/ml periodate. Periodate can be determined in the presence of iodate or iodide.     

Spectrophotometric reaction rate method for the determination of osmium by its catalytic effect on the oxidation of gallocyanine by bromate

A simple kinetic spectrophotometric method was developed for the determination of osmium. The method is based on the catalytic effect of osmium as osmium tetroxide on the oxidation of gallocyanine by bromate at pH 7. The reaction is monitored spectrophotometrically by measuring the decreasing absorbance of gallocyanine at 620 nm by the fixed-time method. A detection limit of 0.01 ng/ml and linear calibration curve from 0.1 to 100 and from 100 to 1200 ng/ml Os(VIII) is reported. The relative standard deviation for 0.0100 microg/ml Os(VIII) is 0.8% (N = 10). The method is free from most interferences. Osmium in synthetic samples is determined by this method, with satisfactory results.     

Fluorimetric Determination of Trace Amounts of Scandium with Di-2-pyridyl-ketone 2-Furoylhydrazone

Abstract

The reaction of Di-2-pyridyl-ketone 2-furoylhydrazone (DPFH) with scandium in an aqueous ethanolic medium (4% v/v of ethanol) has been studied. A spectrofluorimetric method based on the formation of a fluorescent complex is proposed for the determination of scandium. With excitation at 387 nm, the scandium (III) chelate has an emission maximum at 492 nm; the reaction is carried out at pH 6.5–7.5. The accuracy and precision of the method are demonstrated by the analysis of synthetic mixtures containing various amounts of scandium. 10 – 140 ng/ml of scandium can be determined with a relative error of ±1.3%.     

4-Aminoantipyrine as an Analytical Reagent for the Colorimetric Determination of Tetracycline and Oxytetracycline

Abstract

A spectrophotometric method is proposed for the determination of tetracycline and oxytetracycline and their dosage forms. The suggested method depends on the reaction with 4-aminoantipyrine in the presence of an alkaline oxidising agent. A red antipyrine dye is produced. The reaction ratio has been determined. Variables such as pH, temperature, reagent concentration, stability of the colour produced have been evaluated to permit selection of the most advantageous technique. Beer's law was obeyed over the concentration range 0.04 - 0.12 mg/ml and 0.04 - 0.16 mg/ml for tetracycline and oxytetracycline respectively.     

A catalytic method for the determination of cobalt impurities in reactor cooling-water circuits

Metal impurities in reactor cooling-water circuits must be kept to a minimum. A method is described for the determination of trace levels of cobalt in water samples, based on catalysis of the hydrogen peroxide oxidation of Alizarin Red S. The determination is carried out at pH 11.0 in a phosphate buffer under conditions where the reaction rate is a maximum. Interfering impurities are removed by an ion-exchange separation. The method enables cobalt to be determined in water samples down to 10(-4)mug ml , or 5 x 10(-5)mug ml in samples where an ion-exchange separation is not required.     

Kinetic determination of Hg(II) in different materials, based on its inhibitory effect on a catalysed process

A new kinetic method for the determination of Hg(II) based on its inhibitory effect on the Pd(II)-catalysed reaction between Co(III)-EDTA and hypophosphite is proposed. The reaction is followed spectrophotometrically at 540 nm by measuring the induction period. Both the influence of the reaction variables and the interference of many ions have been studied. A mechanism for the inhibition process is also proposed. Under the selected experimental conditions of 2.7 x 10(-1)M Co(III)-EDTA, pH-3.2 Britton-Robinson buffer, 0.3M H(2)PO(-)(2), 0.35 mug/ml Pd(II), and temperature 18 +/- 0.2 degrees , Hg(II) was determined in the range 13-120 ng/ml. The method was applied to the determination of Hg(II) in sphalerites and pharmaceuticals.     

Kinetic determination of selenium, based on inhibition of the Pd(II)-catalysed reaction between pyronine G and hypophosphite

A new kinetic method for determination of selenium is based on its inhibitory effect on the Pd(II)-catalysed reaction between Pyronine G and hypophosphite. Under the optimum experimental conditions (6 x 10(-5)M Pyronine G, 0.4M hypophosphite, 0.4 mug/ml Pd(II), pH 2.8, temperature 22.0 +/- 0.2 degrees ), Se can be determined in the concentration range 0.033-0.50 mug/ml. The method suffers from numerous interferences and is thus limited in application. It has been applied to the determination of selenium in spring waters and pharmaceutical preparations.     

A fluorimetric kinetic method for the determination of organophosphorus and organocarbonyl compounds

A direct reaction rate method is proposed for the rapid, sensitive determination of organophosphorus and organocarbonyl compounds, based on a fluorimetric SCHOENEMANN reaction. From 0.02 to 100 μg/ml of benzoyl chloride, benzoyl bromide, phthalic anhydride, diisopropyl phosphorofluoridate, parathion, methyl parathion, diethyl chlorophosphate and dimethyl chlorothiophosphate can be determined with an accuracy and precision of about 1.5%.     

Simultaneous stopped-flow determination of 1- and 2-naphthol

A kinetic method for the simultaneous determination of 1- and 2-naphthol based on their different rate of coupling with diazotized sulphanilic acid in a weakly acid medium is reported. The reaction is performed by a stopped-flow technique and monitored spectrophotometrically at 475 nm. On the basis of this reaction, mixtures of these naphthols can be determined by measuring the reaction rates at two reaction times which gave maximum discrimination between the two naphthols. Theoretical equations are used in order to evaluate the accuracy of the proposed method. Mixtures of these naphthols at the mug/ml level and in 2-naphthol/ 1 -naphthol ratios from 20:1 to 1:5 can be determined with a relative standard deviation of 1.5%. Ternary mixtures of carbaryl, 1-naphthol and 2-naphthol can also be resolved.     

Spectrophotometric determination of phenol and resorcinol by reaction with p-aminophenol

Based on the reaction with p-aminophenol, a series of procedures have been developed for the spectrophotometric determination of phenol and resorcinol. Three basic approaches have been studied: (i) a batch procedure, using the dissolved oxygen as oxidant, (ii) a stopped-flow procedure by use of KIO(4) as oxidant and (iii) a flow injection (FI) procedure developed in the presence of KIO(4). Phenol can be accurately determined at 626 nm, in the stopped-flow mode, after a reaction time of 45 min in 0.005M NaOH, 0.004M KIO(4) and 500 mug/ml of PAP. The development of a manifold, which incorporates a sample parking, is a convenient approach which makes it possible to measure, in the stopped-flow mode, four solutions in one hour. The limit of detection of this method corresponds to 64 ng/ml of phenol Resorcinol can be determined by FI at 540 nm in 0.006M NaOH, 0.0002M KIO(4) and 50 mug/ml PAP with a limit of detection of 6.6 ng/ml and a sample throughput of 300 injections per hour. A combination between the FI procedure for the determination of resorcinol and the stopped-flow procedure for phenol determination provides accurate results in the analysis of spiked samples containing both phenol and resorcinol.     

Effects of Some Parameters on Particle Size Distribution of Chitosan Nanoparticles Prepared by Ionic Gelation Method

In this research, chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions. Effects of parameters such as chitosan concentration, tripolyphosphate concentration, and reaction time on the particle size distribution were investigated. In order to determine optimum conditions, tests were designed by Qualitek-4 software, using Taguchi method. The best conditions were determined based on three factors at three levels. Therefore, the main object was to investigate the effect of some parameters on particle size distribution and determine the optimum conditions for preparing chitosan nanoparticles by ionic gelation, followed by evaluation of the physicochemical and structural properties. The size distribution of original chitosan and chitosan nanoparticles were determined by Laser Diffraction and Dynamic Light Scattering, respectively. The physicochemical properties of the chitosan nanoparticles were studied using SEM, TEM, XRD pattern, FTIR, UV–vis, TGA, and NMR spectra. The optimum chitosan concentration, tripolyphosphate concentration, and reaction time were found to be 1.0 mg/ml, 1.0 mg/ml, and 60 min, respectively.     

Catalytic-kinetic determination of trace amount of formaldehyde by the spectrophotometric method with a bromate-Janus green system

A new simple and rapid catalytic kinetic method for the determination of trace amount of formaldehyde is described. The method is based on the catalytic effect of formaldehyde on the oxidation of Janus green by bromate in the present of sulfuric acid. The reaction monitored spectrophotometrically by measuring the decrease in absorbance of the reaction mixture at 618 nm. The fixed-time method was used for the first 150 s. For initiation of the reaction, under the optimum conditions, in the concentration range of 0.003-2.5 microg ml(-1) formaldehyde can be determined with a limit of detection 0.0015 microg ml(-1). The relative standard deviation of five replicate measurements is 2.3% for 1.0 microg ml(-1) of formaldehyde. The method was used for the determination of formaldehyde in real samples with satisfactory results.     

Spectrophotometric determination of platinum in glass after extraction with polyurethane foam

A spectrophotometric method has been developed for determination of trace amounts of platinum in glass. The method is based on the extraction of platinum(II) from 1M hydrochloric acid containing 0.2M stannous chloride and 4 x 10(-4)M dithizone onto polyurethane foam, elution with acetone (containing 3% v/v concentrated hydrochloric acid) and measurement of the absorbance of the eluate at 530 nm. Beer's law is obeyed up to 10.0 microg/ml Pt. The minimum platinum level in the eluate that can be determined by this method is 0.1 microg/ml.