Determination of organic acids by using hplc with UV-Visible detection

Careful monitoring and analysis of organic acids in the food and beverage industry is very important to enables the industry to implement stringent quality control measures, comply with regulatory standards and meet consumers' demands for safe, authentic and high-quality food and beverages. In this study, a simple and effective one-step pre-column derivatization method for reversed-phase HPLC-UV determination of the major organic acids (citric, malic, tartaric, and succinic acids) in fruit juices has been developed. Organic acids generally have poor spectral properties, which make their direct determination by HPLC-UV very difficult. Therefore, targeted organic acids have been derivatized using 1-naphthylamine in the presence of N,N'-diisopropylcarbodiimide as a coupling agent. The resulting organic acid amide derivatives were successfully separated on an AQ-C18 reserve phase column with isocratic elution using mobile phase with the composition (37 acetonitrile: 4 methanol: 1 tetrahydrofuran: 58 water) at a flow rate of 2,0 mL/min. A sufficient separation of organic acid derivatives was achieved within 22 minutes at room temperature and they were detected by a UV detector at 222 nm. Detection limits were 0.69 µg/mL, 0.18 µg/mL, 0.48 µg/mL, and 0.14 µg/mL for citric acid, tartaric acid, malik acid, and succinic acid, respectively. The developed method was successfully applied to three different widely consumed fruit juice samples without the need for any extraction procedures. Recoveries of organic acid derivatives from the sample of 1 mL of orange juice were 88.97–92.52 %, with relative standard deviations between 2.95 % and 4.56 %; for the sample of 1 mL of apple juice, recoveries were 85.46 %–93.14 %, with relative standard deviations of 2.98–4.55 %; and recoveries for the 1 mL mixed fruit juice sample were 85.71–89.15 %, with 2.99–4.55 % relative standard deviations.