Development of approaches to the analysis of elemental impurities in titanium dioxide (barium and lead definition)

Relevance. Due to its properties, substance of titanium dioxide is still widely used in the pharmaceutical industry as a drug excipient. However, from the point of view of the safe use of any component of drugs, one of the most important factors is the determination of its content of elemental impurities (PE). The pharmacopoeic requirements for titanium dioxide to contain elemental impurities are not harmonized today. It was therefore advisable to develop approaches to defining them under the strictest of standards.

Research objective. This work is devoted to the development of approaches to the analysis and further validation of the method of determination of antimony in the substance titanium dioxide at the level of 2 ppm.

Material and Methods. The method used in this paper is based on the extraction into the organic phase of ionic associates, in which the halogen complex SbCl₆-antimony acts as an anion and interacts with the triphenylmethane dye - diamond green. All the reagents and materials used were pharmacopoeic. A sample of titanium dioxide, produced by Venator Germany GmbH, Germany, was used as the research object. The validation of the methodology was carried out in accordance with the requirements of the SP RF on the following characteristics: specificity, linearity, LOQ, correctness, repeatability, intralaboratory precision and range of methods.

Results. The article shows applicability of the method of determination of antimony in the substance titanium dioxide, at the level of 2 ppm, using as a reagent diamond green. At the same time, the validation evaluation of the methodology showed that the obtained results met the criteria of acceptability for all the studied characteristics.

Conclusions. Control of PE is an important aspect of the safe use of any component of the drug.

Due to the wide variety of pharmacopeic requirements for PE content in the substance TiO₂, this study shows the possibility of using the extraction and photometric method with the use of a triphenylmethane dye (diamond green) to determine Sb at the most stringent standards (2 ppm).

At the same time, the validation of the methodology on such characteristics as specificity, linearity, LOQ, correctness, repeatability, intralaboratory precision and range confirmed the possibility of quantitative estimation of Sb content in the substance TiO₂ in the range of 50% (LOQ) up to 150% of the specification level.