Simultaneous determination of inorganic anions and carboxylic acids in wine using isocratic separation on a permanently coated reversed-phase column and UV indirect detection

A method for the separation and determination of both inorganic anions and carboxylic acids using a Nova-Pak C-18 column permanently coated with n-cetylpyridinium chloride is described. A 0.4 mM (pH 4.9) aqueous potassium phthalate acid solution was used as the mobile phase. By careful selection of the eluent pH (the factor which mostly affects retention) isocratic separation of both inorganic anions (chloride, nitrite, bromide, nitrate and sulphate) and carboxylic acids (lactic, succinic, malonic, malic, maleic and tartaric) in wine was carried out in about 20 min. These analytes were determined at ng level using indirect UV detection. Satisfactory reproducibility of the results was obtained even after a 4 month period of continual use of the column. Subsequently, re-coating the column did not produce any changes in the expected analytical results. Accuracy and precision of the results were checked by determining recoveries of spiked samples for each analyte. Average recoveries between 97.4% and 108.3% were obtained.