ИСТИНА

Determination of organic anions in food and beverages such as fruit juices, vegetables, dairy products, coffee, and wine is an important task, because these compounds are responsible for the taste characteristics and organoleptic quality, and may also influence the stability of the product. Quantification of organic acids in wine is extremely important for quality and process control, while their determination in juice is also a way to identify the product authenticity. For instance, high concentrations of acetic and lactic acids in juice can be the evidence of microbial growth caused by the defective fruit processing or by using bad fruits. Due to its high sensitivity, ion chromatography (IC) is one of the most attractive methods for determining organic anions along with inorganic components in various samples. Modern anion exchangers for IC possess high selectivity, however, most of them suffer from incomplete resolution of some short-chain carboxylic acids. Therefore, determination of full organic acid profiles often requires additional efforts for optimization of separation conditions including addition of organic solvent into the eluent or application of other methods in addition to suppressed IC, namely, enzymatic and electrochemical methods. In the present work the possibility of determining full organic acid profiles in presence of inorganic anions by means of suppressed IC using home-made covalently-bonded poly(styrene-divinylbenzene)-based anion exchangers is demonstrated on the examples of some fruit juices (mango, blueberry, grape, etc.) and alcoholic beverages (beer and red wine). Improved selectivity of the prepared anion exchanger provided good resolution for low-molecular weight organic acids such as quinic, gluconic, glycolic, shikimic, acetic, lactic, formic, and galacturonic. The proposed method was validated with respect to linearity, recovery, limits of detection, and intra-day and inter-day precision. The obtained data show that the proposed approach is accurate and reliable, and can be a promising tool for the analysis of complex samples containing various inorganic and organic anions.