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

Capillary electrophoresis (CE) is used with electrospray-mass spectrometry (ES-MS) to analyze a mixture of succinic, maleic, malonic, and glutaric aci ds 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 solu tion of naphthalene disulfonate (NDS), pyromellitic acid, and methanol, wit h diethylene triamine (DETA) as an electroosmotic flow modifier. Compromise experimental parameters for the CE separation and ES-MS detection are eval uated. Detection limits for CE-ES-MS determination of the sample are 1-10 p pm or 60-600 pg. The carboxylic acid sample is injected directly into the C E column with little or no preparation. (C) 1999 Elsevier Science B.V. All rights reserved.