Purge-and-Trap Extraction with a Miniaturized Extraction Capillary for the Determination of Aqueous Formic Acids in Ion Chromatography

Abstract

Aqueous formic acid (FA) was determined by purge-and-trap extraction with a miniaturized extraction capillary using ion chromatography (IC). The extraction capillary was prepared by packing particulate activated carbon in a stainless-steel capillary (0.8 mm i.d., 1.6 mm o.d.). FA was purged from the sample solution and extracted on the extraction medium in its molecular form. Following extraction, the extraction capillary was connected directly to a six-port valve of the IC. The extracted analyte was eluted with sodium hydroxide solution as the formate ion and introduced to a conventional IC. The extraction capillary can be reused after conditioned by passing hydrochloric acid solution. The limit of detection of FA in a standard aqueous sample is 0.5 mg/L. The method was successfully applied to determine FA in fruit juices without significant interference.