Organic acid analysis by ion chromatography—particle beam mass spectrometry

Abstract

Ion chromatography—mass spectrometry (IC-MS) has been investigated, using the particle beam interface, as an analytical technique for the analysis of weak organic acids. Ion-exclusion chromatography is a technique for separating weak acids. Using dilute HCl as the mobile phase, weak acids are separated on a cation-exchange resin. IC-MS was used to detect and identify weak acids in commercial grape juices and red wine. Analyses were performed using both electron (EI) and chemical ionization (CI). Isobutane CI readily produced protonated molecular ions, and combined with structural information obtained from EI analyses, identification of weak acids was possible. A main advantage of this technique is that co-eluting acids can be identified, whereas with conductivity and UV detection this is difficult. To simplify these analyses, solid-phase extraction was used to remove sugars from the juice and wine samples.