Multi-laboratory Method Validation on Determination of Salicylic Acid in Cosmetic Cream by ASEAN Cosmetic Testing Laboratory Network

Abstract

       Thailand proposed a testing for determination of salicylic acid in cosmetic cream using High Performance Liquid Chromatography (HPLC) method. There were 8 ASEAN laboratories participating in validation of the test. A sample of skincare cream containing 0.5% w/w salicylic acid and a protocol to perform the test were distributed to each laboratory. A total of five laboratories submitted their results while no results were obtained from the rest. However, only results from 4 participating laboratories could be analyzed due to the fact that one laboratory did not conduct the test according to the protocol provided. Cochran’s test and Grubb's test were used for statistical analysis. We found no outliers of the results and precision of the method was within acceptable criteria: repeatability standard deviation (S_r) was 0.002, repeatability relative standard deviation (RSD_r, %) was 0.43, repeatability limit (r₉₅) was 0.006, reproducibility standard deviation (S_R) was 0.039, reproducibility relative deviation (RSD_R, %) was 7.68, reproducibility limit (R₉₅) was 0.109 and a mean percentage of recovery was in a range of 95.60-101.38. Taken together, the proposed testing method “Determination of Salicylic Acid (Beta Hydroxy Acid) in Cosmetic Products by High Performance Liquid Chromatography (HPLC)” is approved to be used as a new ASEAN Cosmetic Method (ACM) entitled ACM 009. In addition, Thailand has been assigned as the Proficiency Testing Provider (PTP) for the ASEAN cosmetic laboratories on determining BHA using the ACM 009.