Extraction-photometric determination of bismuth in the ointment «Liniment balsamic» in the quaternary water – dithiopyrylmethane – trichloroacetic acid – orthophosphoric acid system

Abstract

The article is devoted to the investigation of the mutual influence of bismuth, dithiopyrylmethane, trichloroacetic and orthophosphoric acids in a four-stratified system with a single liquid component, water. The results of the developed alternative method for determining the microgram amounts of bismuth in pharmaceutical preparations using this system, which does not contain toxic organic solvents, are presented. The coloring complex of bismuth with dithioerythritol yellow allowed using photometry at 354 nm and 447 nm as a method of monitoring the concentration of bismuth. The appearance of two maxima on the absorption spectrum indirectly indicates the formation of Bi-DTM complexes in different tautomeric forms, namely, thion and thiol. Comparing the obtained data, it is found that the complexation of phosphate in the media is similar to sulfuric acid, and the formation of the red complex of bismuth with dithioerythritol prevents high value of acidity. The influence of extraneous ions on the determination of bismuth (III) was investigated. Selection of the ions was due to their presence in various alloys, pharmaceutical preparations, etc. objects, and containing trace amounts of bismuth. The results of the developed alternative methods are consistent with the stated content of bismuth in ointment A.V. Vishnevsky «Liniment balsamic».