The polarography of 2-mercaptoethylguanidine (RSH), 2-mercaptopropylguanidine (R~SH), 2-mercaptoethylamine (R~SH), and 2-mercaptoethanol (RmSH) and their disulfides (RSSR, R~SSR~, RHSSR~ and R~SSRnD has been studied. The mercaptans behave in the same way as other mercaptans described previously in the literature. RSSR gives well-defined reduction waves. The characteristics of the RSSR waves in the absence and presence of RSH are the same as those of oxidized glutathione and can be accounted for by the sequence of the two reactions: RSSR ~ e + H + ~ RS + RSH, RS ~ e ~ H +--> RSH in which the first reaction is the rate and potential determining step. R~SSR~, RnSSR~, and RI~SSR~,~ are reduced irreversibly at the dropping mercury electrode.In recent years a large number of mercaptoalkyl compounds have been studied with regard to their properties as radiation protective drugs for animals. In the course of systematic investigations of reactions of these compounds with metal ions and proteins it appeared to be useful to study the polarographic behavior of a few typical mercaptoalkyl compounds under various experimental conditions. This paper deals with a polarographic study of 2-mercaptoethylguanidine (denoted as RSH), 2-mercaptopropylguanidine (R~SH), 2-mercaptoethylamine (R~SH), and 2-mercaptoethanol (R~HSH) and their disulfides which for the sake of brevity will be referred to as RSSR, R~SSR~, R~SSRH, and R~I~SSR,m respectively. The results obtained for these compounds are compared with each other and with those obtained for other mercaptans and disulfides described in the literature (1-3). ExperimentalMaterials.--Solutions of mercaptoalkyl guanidine were prepared from S,2-aminoalkylisothiouronium bromide hydrobromide which undergoes rearrangement in neutral solution to form mercaptoalkylguanidine (4). Stock solutions of 10-~I mercaptan were prepared by weighing an appropriate amount of the isothiouronium compound in a glass cap which together with the compound was introduced into a bottle provided with metal screw cap into which a few holes were bored. In order to obtain an airtight seal the cap was fitted with a self sealing Buna N rubber gasket. Now a given volume of air free sodium hydroxide solution containing an amount of sodium hydroxide exactly equimolar to the isothiouronium salt was added in order to neutralize the liberated hydrobromic acid. The bottle was sealed immediately and after dissolution of the sample the solution was purged thoroughly with nitrogen introduced by means of a hypodermic needle which pierced the cap of the bottle. Samples were withdrawn from the bottle by means of a 2 ml calibrated syringe. When not in use the solution was stored in a refrigerator. The mercaptan solutions were found to be stable for a week. Stock solutions of mercaptoethylamine and mercaptoethanol were prepared in the same way as described for RSH and R~SH except that no sodium hydroxide was added to the solution.The isothiouronium compounds were obtained from Dr. D. G. Doherty of the Biology Division, Oak Ridge Nati...
Method validation guidelines, which provide an organizational structure for the design and evaluation of a validation procedure, are presented for a wide range of pharmaceutical applications. The validation guidelines are based on the analyte concentration/sample matrix combination to which the method will be applied. These guidelines include the selection of appropriate validation parameters, design considerations for evaluation, and a discussion of acceptance guidelines for the determination of acceptable method performance. A set of tables is included which illustrates the selection and testing procedure and tailors the entire validation process to the specific characteristics of the determination to be made.
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