RESUMO
New methods were developed to determine glyphosate, N-(phosphonomethyl)glycine, and its major metabolite, (aminomethyl)phosphonic acid in groundwater and soil. The methods involve ligand-exchange, anion-exchange and derivatisation and final identification and quantification by GC-MS. The limits of quantification in this experiment were 0.1 microg l(-1) for both compounds in water and 0.006 microg g(-1) for both compounds in soil. Decomposition in soil and occurrence in groundwater of the herbicide glyphosate was studied after its application for weed control on a Swedish railway embankment.
Assuntos
Glicina/análogos & derivados , Herbicidas/análise , Compostos Organofosforados/análise , Poluentes do Solo/análise , Poluentes Químicos da Água/análise , Calibragem , Cromatografia Gasosa-Espectrometria de Massas , Glicina/análise , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , GlifosatoRESUMO
A new method has been developed to determine a number of sterols in urine using non-chlorinated solvents, namely methyl tert.-butyl ether and methanol (the MTB method). The method involves liquid-liquid extraction, saponification, reextraction, silylation and final identification and quantification by GC-FID. The sterols determined were coprostanol, epicoprostanol, cholesterol and dihydrocholesterol. 5Alpha-cholestane was used as internal standard. The limit of detection for the sterols in this experiment was 2 microg l(-1) urine. Recovery of coprostanol over the range 5-100 microg l(-1) urine by this method was between 80 and 92%.
Assuntos
Fezes/química , Metanol , Éteres Metílicos , Esgotos/análise , Esteróis/urina , Colestanol/urina , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Sensibilidade e Especificidade , SolventesRESUMO
A controlled-potential coulometric iodometric method previously developed for the accurate determination of small amounts of nitrite has been extended for the determination of nitrate after its reduction on a coppered cadmium reductor. The conditions for quantitative reduction have been investigated with respect to type of reductor and pH. Nitrate-nitrogen in the range 0.01-100 mug ml may be determined with high accuracy in less than 10 min, including the reduction step. The method has been applied with good results to a large variety of samples such as meat products, juices and waste waters.
RESUMO
A controlled-potential coulometric method using iodine as an intermediate has been devised for the determination of nitrite. Nitrite is reduced by iodide and the iodine formed is then reduced coulometrically. The reduction of nitrite in the pH range 0-6 has been studied and the optimum conditions for an accurate determination are stated. The time of analysis for a determination in the range 0.005-5 mg of nitrite is about 2-5 min and the error +/- 0.1%. The method is applied to the determination of nitrite in some meat products.
RESUMO
The oxygen content of air-saturated distilled water has been determined at between 10 and 40 degrees by using a controlled-potential coulometric method based on an earlier published method for the iodometric determination of nitrite. The maximum error for the determinations was +/- 0.3% over the whole range, and the time of analysis about 3 min. An equation is given for the solubility in the measured range, and some thermodynamic functions are calculated.
RESUMO
A controlled-potential electroanalytical method has been devised for the accurate determination of small amounts of thiols. An adequate excess of iodine is generated, the sample is added and the unreacted iodine is then electrolytically reduced. The iodine consumed is calculated from the measured number of coulombs. Amounts of thiols in the range 0.2-5 mg may be determined with an error of +/- 0.05 %. A coulometric cell has been constructed which permits very high electrolysis rates, owing to efficient stirring by a large rotating platinum electrode combined with a high electrode-area to solution-volume ratio. A constant of 0.11 sec(-1) is found for the reduction of iodine. The necessity of careful control of background currents and current efficiency in coulometric determinations is discussed.
