1. Investigación

Short chain organic acids play an important role in different areas such as biochemistry, clinical chemistry, or the food industry. The enantiomeric ratio of chiral metabolites is an important parameter for the understanding of metabolic processes and in many cases it can serve diagnostic purposes. On the other hand, the presence of racemates in food products could indicate the use of organic acids as additives; this is not always permitted and needs to be controlled. The short chain of these acids makes difficult the three point interaction generally accepted as necessary for chiral recognition. Relatively recent publications have demonstrated the feasibility of their direct chiral separation in capillary electrophoresis by various techniques utilizing exchange capillary electrophoresis, macrocyclic antibiotics, cyclodextrins, ion-pair method, and transition metal complexes. The present article describes existing methods and strategies proposed to advance these areas.

Fruit juices each have very distinct organic acids profiles that can be used as fingerprints for establishing authenticity. A method has been developed, optimised and validated for measuring by capillary electrophoresis citric, isocitric, malic and tartaric acids as authenticity markers in orange juices, without any sample treatment other than dilution and filtration. Final conditions were phosphate buffer 200 mM, pH 7.50, 214 kV as applied potential, and 57 cm length neutral capillary. Detection was direct UV at 200 nm. Different kinds and marks of orange juice, chosen from the great variety existent in the market, were analysed and clear differences could be found between them and just pressed orange juice.  2000 Elsevier Science B.V. All rights reserved.

Fruit juices have very distinct organic acid profiles that can be used as fingerprints for establishing possible adulteration. Recently, our group developed and validated a capillary electrophoresis method using UV detection for determining citric, isocitric, tartaric, and malic acids in natural and commercial orange juices. Sample treatment consisted of only dilution and centrifugation or filtration. This method has been applied to evaluate these acids and their ratios in 63 samples of Navelina, the most common variety of Spanish oranges, over a three month period. This evaluation has been conducted to establish ranges of acid concentrations and to compare them with those found in commercial juices. The more reliable parameter, because of the lower variability in fresh samples, was found to be the citrate/isocitrate ratio with a value of 113 (RSD ) 10%). Only one of nine ramdonly selected commercial juices presented values within the range of those of the population of just-pressed Navelina orange juice. Moreover, three of them had measurable tartrate values, which is not a natural component of orange juice, showing mixtures with cheaper fruits.