Determination of small carboxylic acids by capillary electrophoresis with electrospray-mass spectrometry Original Research Article

Capillary electrophoresis (CE) is used with electrospray-mass spectrometry (ES-MS) to analyze a mixture of succinic, maleic, malonic, and glutaric acids as the negative parent ions ([M–H]−). The CE is coupled with the ES-MS via a make-up sheath flow. The CE mobile phase consists of an aqueous solution of naphthalene disulfonate (NDS), pyromellitic acid, and methanol, with diethylene triamine (DETA) as an electroosmotic flow modifier. Compromise experimental parameters for the CE separation and ES-MS detection are evaluated. Detection limits for CE–ES-MS determination of the sample are 1–10 ppm or 60–600 pg. The carboxylic acid sample is injected directly into the CE column with little or no preparation.