Chip-based liquid phase microextraction combined with electrothermal vaporization-inductively coupled plasma mass spectrometry for trace metal determination in cell samples

Metal determination in precious biological samples is critical to metallomics research. Microfluidic chips provide an excellent platform for the miniaturization of extraction. In this work, a chip-based liquid phase microextraction (chip-based LPME) device was fabricated and combined with electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the determination of trace Cu, Zn, Cd, Hg, Pb and Bi in cell samples and human serum samples. With sodium diethyldithiocarbamate (DDTC) as both the chemical modifier for low-temperature ETV-ICP-MS and the extracting reagent for the chip-based LPME, the chip parameters influencing the extraction efficiency including central channel width, branch channel ratio and central channel length were optimized by orthogonal design experiments. Under the optimized conditions, the limits of detection (LODs) are in the range of 6.6-89.3 pg mL(-1) with the RSDs ranging from 4.23-8.15% (n = 7, c = 1 ng mL(-1)) for the target metal ions. The linear range covers three magnitudes with correlation coefficients higher than 0.99. The proposed method was validated by analyzing the target metal ions in certified reference materials of GBW07605 human hair and GBW09152 human serum, and metal determination in HepG2 cells, Jurkat T cells and a human serum sample were achieved with the recoveries in the range of 86.6-119%. The developed method is fast, has a low sample and reagent consumption and is highly sensitive, thus it is quite suitable for the analysis of precious biological samples such as cells.