Calibration and calculationsA high performance liquid chromatographic method was developed for the quantitative analysis of organic acids in dairy products. A reverse-phase C8 column at room temperature, a mobile phase of 0.5% w/v buffer ((NH,)zHPO, at pH 2.24 with H,PO,)-0.4% v/v acetonitrile, UV detection at 214 nm and 1.2 mUmin flow rate were utilized. Formic, acetic, pyruvic, propionic, uric, erotic, citric, lactic and butyric acids were quantitated for raw milk, yogurt, Blue, Provolone, Port Salut and Quartirolo cheeses. Recoveries greater than '85.3% were observed for all acids.Five aqueous calibration standards covering a broad concentration range were prepared for each of the organic acids analyzed (formic, acetic, pyruvic, propionic, uric, erotic, citric, lactic, and butyric acids). At lcast triplicate 10 uL injections were made. The resulting peak area counts were determined; then, the best fit standard cutvc (peak area vs concentration) was prepared for each of the organic acids using linear regression. Quantitation was based on the external standard method.Retention times were first determined separately for each acid. Afterwards, individual standard solutions were added one by one to each sample to verify the correct identification of peaks.
