Speciation of mercury in liquid cosmetic samples by ionic liquid based dispersive liquid–liquid microextraction combined with high-performance liquid chromatography-inductively coupled plasma mass spectrometry

Abstract

Ionic liquid based dispersive liquid–liquid microextraction (IL-DLLME) combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for the determination of mercury species in liquid cosmetic samples is described. Firstly mercury (Hg²⁺), methylmercury (MeHg⁺) and ethylmercury (EtHg⁺) were complexed with ammonium pyrrolidinedithiocarbamate (APDC), and then the complexes were extracted into 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) using DLLME. Under the optimized conditions, the enrichment factors of 760, 115, 235 for Hg²⁺, MeHg⁺ and EtHg⁺ were obtained from only 5.00 mL sample solution. The detection limits of the analytes (as Hg) were 1.3 ng L⁻¹ for Hg²⁺, 7.2 ng L⁻¹ for MeHg⁺ and 5.4 ng L⁻¹ for EtHg⁺, respectively. The relative standard deviation (n = 10) of 0.5 ng mL⁻¹ Hg²⁺, MeHg⁺ and EtHg⁺ were 7.4%, 5.2% and 2.3%, respectively. Finally, the developed method was successfully applied for the speciation of mercury in four liquid cosmetic samples, Hg²⁺ was found as the main species in these samples, and a spike test was performed to verify the accuracy of the method.