IC-MS Determination of Etidronic Acid in Cosmetics

IC-MS was applied to the determination of etidronic acid in cosmetics. The cosmetic sample (0.500 g) was extracted ultrasonically with 50 mL of 3.0 mol·L^-1 acetic acid solution for 15 min. After cooling, the solution was diluted to 100 mL with 3.0 mol·L^-1 acetic acid solution. An aliquot (10 mL) of the above sample solution was taken and filtered on 0.22 μm nylon filtering membrane. The filtrate was purified with Oasis HLB solid phase extraction column. IonPac AS11-HC analytical column (250 mm×4 mm) was used for chromatographic separation, and potassium hydroxide solution was used as eluant. ESI^- and the selected reaction monitor mode were adopted in MS. Linear relationship between values of peak area and mass concentration of etidronic acid was kept in the range of 0.01-5.00 mg·L^-1, with detection limit (3S/N) of 0.5 mg·kg^-1. Tests for recovery were made by standard addition method at 4 concentration levels of 2.0, 4.0, 10.0, 1 000 mg·kg^-1, giving values of recovery and RSD's (n=6) in the ranges of 92.0%-103% and 3.9%-8.1% respectively.