Detection and Quantification of Water-Soluble Inorganic Chlorine, Bromine and Iodine by MALDI-MS

Halogens are elements in soil and water that occur as organic and inorganic species. Studies have shown that inorganic halogens are closely related to animal and plant life. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) can achieve high-throughput and rapid analysis, which is also an essential characteristic in some environmental studies. However, there is currently no report on MALDI-MS analysis for water-soluble inorganic halogen compounds. In this study, we aimed to develop a reliable and reproductive method to detect inorganic halogens in soil and water by MALDI-MS. Based on sinapic acid (SA) and silver trifluoromethanesulfonate (SA/AgOTf) as the matrix in negative-ion mode, MALDI-MS showed excellent MS signals related to halogens. Under the optimum conditions, the method achieved satisfactory linearity ( R 2  > 0.99) and repeatability (RSD < 18%). The LODs for Cl − , Br − and I − were 0.76, 0.11 and 0.10 μg/mL, respectively. The concentration of inorganic halogens from 24 samples was successfully determined by MALDI-MS. In summary, an innovative method was developed for the analysis of inorganic halogens by MALDI-MS using a novel SA/AgOTf matrix, extending the application of MALDI-MS in inorganic compounds.