Determination of chloride and nitrate in dimethyl carbonate using a column-switching ion chromatography system
Dimethyl carbonate (DMC) is widely used in solvents, fuels, monomers, and synthesis. The inorganic anions in DMC always have a big impact on product performance. Herein, improvement in the performance of the conventional column-switching technique and on-line elimination pretreatment system was achieved to automatically determine trace anions in DMC. In this study, a pretreatment column was applied to eliminate the DMC matrix on-line, and target anions were eluted from the pretreatment column and retained in the concentrator column. The collected anions were eventually separated in the analytical column using the column-switching technique. Eluent containing 100% acetonitrile was used to wash out DMC and regenerate the pretreatment column at the same time. A type of water-soluble solvent was added to the DMC samples before injection to help improve their solubility in the eluent, which was subsequently removed by extending the collection time in the concentration procedure. This method shows satisfactory linearity (R2 ≥ 0.9977) in the range of 0.1–8.0 mg L−1. The detection limit based on the signal-to-noise ratio of 3 (S/N = 3) is 2.79–5.66 μg L−1. The recovery rate for the anions is 85.09–99.07%. Good reproducibility was obtained with relative standard deviations less than 4.03% by injecting standard solutions 6 times.