HPLC Determination of Zinc Pyrithione in Shampoo

Content of zinc pyrithione in shampoo was determined by HPLC. The sample was extracted ultrasonically with a mixture of acetonitrile-methanol (9+1). After centrifugation, the extract was filtered on 0.45 μm filtering membrane. MG C18 (4.6 mm×250 mm, 5 μm) chromatographic column was used as stationary phase, and mixtures of the following 3 components mixed in various ratios were used as mobile phase in the gradient elution: (A) mixed solution containing 0.01 mol·L-1 KH2PO4 and 0.5 mol·L-1 EDTA; (B) acetonitrile; (C) methanol. The eluate obtained was determined with DAD at the wavelength of 272 nm. Linear relationship between values of peak area and mass concentration of zinc pyrithione was kept in the range of 3.20-200.0 mg·L-1, with detection limit (3S/N) of 0.15 g·kg-1. Using blank sample of shampoo as matrix, values of recovery found by standard addition method were in the range of 87.2 %-89.1%., with RSD′s (n=6) in the range of 2.6%-6.2%.