Developing of sunscreen formulation for proficiency testing scheme

Abstract

       Participation in appropriate interlaboratory proficiency programme is naormally required by accreditation body to comply with ISO/IEC 17025. Since 2005, the Bureau of Cosmetic and Hazardous substances, Department of Medical Sciences had provided proficiency testing scheme for sunscreen agents. The commercial sunscreen cream and lotion adding withtwo sunscreen agents, benzophenone-3 and octyl methoxycinnamate, that were mostly used in the sunscreen products in Thailand, were used as the samples in the proficiency testing scheme for sunscreen agents. Because of unknown formulation of those commercial sunscreen products, the quality of prepared samples for proficiency testing was not consistent and their stability was not good. Therefore, in 2010, sunscreen cream formulation adding 4 sunscreen agents had been developed in order to get the homogenous and stable samples. The formulation with 2 more sunscreen agents were developed in 2013. Totally, samples for 6 sunscreen agents were developed. The samples were tested for homogeneity by assessing within sample variation using Cochran's test and assessing between sample variation by the analysis of variance (ANOVA) at a 95% confidence interval. Test for stability of the samples at room temperature (25+5 C) was also done. The results showed that the sunscreen samples from this formulation have appropriate homogeneity and stability to be used as proficiency testing samples in determination of sunscreen products.