Analysis of low-molecular-mass organic acids using capillary zone electrophoresis–electrospray ionization mass spectrometry

A capillary zone electrophoresis–electrospray ionization-mass spectrometry (CZE–ESI-MS) method was developed to facilitate identification and determination of eleven low-molecular-mass (LMW) organic acids (i.e. oxalic, lactic, malonic, maleic, citric, tartaric, adipic, glutaric, gluconic, isosaccharinic and succinic acid) in different sample matrices. This CZE method was adapted to suit MS conditions. Sheath liquid, sheath flow and MS parameters were optimized to achieve high mass spectrometric sensitivity. The CZE–ESI-MS procedure showed good sensitivity (limit of detection of <0.05–0.7 mg/l for all acids), linearity (r2=0.9925–0.9998) and reproducibility (2.09–5.34% RSD). The applicability of the CZE–ESI-MS was demonstrated on LMW organic acids in an ale sample. In addition the (here presented) method also provided quantification of fumaric, galacturonic and 2-ketoglutaric acid with high sensitivity.