Detection of dicarboxylic acids in aqueous samples using membrane inlet mass spectrometry with desorption chemical ionization

In order to detect highly polar organic compounds in water using membrane inlet mass spectrometry (MIMS), we designed a desorption chemical ionization ion source with a tubular polyacrylonitrile membrane positioned in the center of the chemical ionization (Cl) ion plasma. With this system we have for the first time been able to detect dicarboxylic acids (malonic and succinic acid) in aqueous samples with a MIMS system. The dicarboxylic acids were detected with both standard MIMS and trap‐and‐release MIMS methods. The trap‐and‐release MIMS method gave the best signal to noise ratio spectra with detection limits down to 50 mg/L. Although the results presented are very preliminary, they suggest that rapid detection or even on‐line monitoring of this important group of biological metabolites might be possible with a MIMS system.