Direct Determination of Pb in Cosmetics by Graphite Furnace Atomic Absorption Spectrometry with Suspension Sampling

There have been many difficulties surrounding cumbersome digestion processes and explosive boiling when attempting to detect metal elements in cosmetics. It is difficult to control the pretreatment process and it is necessary to use a lot of reagents, which easily leads to the high reagent blank. Content of lead (Pb) in cosmetics is far below the national limits (≤40 mg/kg), which cannot accurately be determined by flame atomic absorption spectrometric. In this paper a method is described for direct determination of Pb in cosmetics by Graphite Furnace Atomic Absorption Spectrometry with suspension sampling. Sample digestion was not required as the cosmetics samples to be determined were directly placed into the Graphite Furnace Atomic Absorption Spectrometer after suspension by 0.2% nitric acid and 0.1% Triton X-100. The instrument conditions were optimized and high pure argon was added to the drying compressed air in the graphite furnace ashing process, in order to eliminate the carbon residue when the number of samples was over 50, and to ensure the stability for long-term analysis. The matrix modifier was palladium nitrate. Palladium and Pb can form a stable palladium Pb metal compound, and significantly improve the atomic temperature. Standard addition method was conducted to eliminate the matrix interference. The detection limit of this method was 0.003 mg/kg.The recovery of Pb was in the range of 91.6%-106.8%, precision was in the range of 1.5%-2.1% (n=6). National standard reference materials GBW (E) 090028 (cream) and GBW(E) 090027 (powder) were determined by using this method and the results were consistent with the standard value. Compared with the results using the national standard method for detection, the results showed no significant difference. This method has low detection limit, can meet the testing requirements of trace Pb in cosmetics.