A spectrophotometric method is described for the assay of thioctic acid. The method is based on the reaction between the drug and palladium(II) chloride. In this reaction, a yellow-colored, water soluble product with a 1:1 stoichiometric ratio and an absorption maximum at 365 nm was formed. The stability of the formed complex depends on various factors (pH, reaction time, concentration of reagents, ionic strength). Based on these findings, a new method is suggested for the spectrophotometric determination of thioctic acid in pharmaceutical formulations. This method is simple, sensitive and reproducible. .

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The effect of plastics as polyurethane foams and polyvinyl chloride on the metabolism of tryptophan was investigated by determining the concentration of 5-hydroxyindolacetic acid (5-HIAA) as its metabolic end product excreted in the urine. Investigation of persons occupationally exposed to polyurethane and polyvinyl chloride showed that these plastics inhibit the metabolism of tryptophan, causing increased excretion of its easily measurable metabolite 5-HIAA. This fact points to the possibility of practical use of this laboratory test which, together with other biological parameters, could improve methods for early detection of occupational exposure to polyurethanes and polyvinyl chloride. "TRODUCTION EXPERIMENTALDuring the production of plastics or their use in manufacturing, several million workers in the world are exposed to hazardous substances either directly or indirectly. The use of polyvinyl chloride (PVC) in chemical and other modern industries is widespread. Polyvinyl chloride is produced by the polymerization of vinyl chloride (CH,= CHCl).Polyurethanes are formed by the interaction of diisocyanates or polyisocyanates, with polyhydroxy compounds.Depending on the finished product required, other products (such as water, catalyst, foaming agents and stabilizers) may be added.It is known that the essential amino acid tryptophan is a dietary precursor of 5-hydroxytryptamine' and therefore of 5-hydroxyindoleacetic acid (5-HIAA). Finding 5-HIAA in milligram quantities in the urine indicates that an appreciable proportion of tryptophan was metabolized via the 5-hydroxyindole route.' As yet, little is known about the normal functions of 5-hydroxytryptamine (serotonin) or its implications in pathological states and behaviour during some intoxications.Bearing in mind that polyvinyl chloride and polyurethanes can induce more subtle derangements in the metabolism of some essential amino acids, we paid special attention to the metabolism of tryptophan. The toxic effect of plastics on workers employed in the production of polyurethane foams and polyvinyl chloride bags was investigated by measuring the concentrations of 5-hydroxyindolacetic acid excreted in the urine.The main goal of this study was to determine whether the 5-hydroxyindolacetic acid excretion in the urine was a useful test for evaluation of occupational exposure to polyvinyl chloride and polyurethanes.Three groups of workers from a chemical plant were examined. The control group consisted of 50 persons chosen from the general city population, and included students.The exposed groups were as follows:Group 1 -a group of 28 workers involved in the production of PVC bags; Group 2 -a group of 45 workers involved in the production of polyurethanes foams; and Group3 -a group of 20 persons working in the finalization (cutting, sorting, packing, etc.) of polyurethane foams.Urine samples (as the first morning sample) were taken from workers employed in everyday production. They urinated at home into laboratory bottles prepared and washed in our laboratory, and b...

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