Determination of Chloride and Nitrate in Dimethyl Carbonate with Column-Switching Ion Chromatography System
Dimethyl carbonate (DMC) has been widely used in solvent, fuels, monomers and synthesis. Inorganic anions in DMC always have a big impact on product performance. An improvement has been performed in conventional column-switching technique and on-line elimination pretreatment system to determine trace anions in DMC automatically. In this work, the pretreatment column was applied to eliminate DMC matrix on-line and target anions were eluted out from pretreatment column and reserved in concentrator column. The collected anions were eventually separated in analytical column by using column-switching technique. Eluent containing 100% acetonitrile was used to wash out the DMC and regenerate the pretreatment column at the same time. A kind of water-soluble solvent was added to DMC samples before injection to help improving solubility in eluent and was removed subsequently by extending collection time in concentration procedure. The method showed 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) was 2.79-5.66 μg L-1. Recovery rate for the anions were 85.09-99.07%. Good reproducibility was obtained with relative standard deviations less than 4.03% by injecting standard solutions for 6 times.