CAPILLARY ZONE ELECTROPHORETIC ANALYSIS OF THE MINOR ANIONS PRESENT IN ORANGE JUICE AND ORANGE PULPWASH

Capillary zone electrophoresis (CZE) was used to determine the chloride, sulfate, and nitrate concentrations of 35 orange juice, 10 orange pulpwash, and 3 water samples from juice-processing plants. Chloride and sulfate concentrations were determined by indirect photometry at 254 nm, and nitrate concentration was determined by direct UV detection at 214 nm. The concentrations of the anions in these samples were as follows: 7.7-97.4 ppm (Cl-), 19.1-107.6 ppm (SO42-), <0.2-3.52 ppm (NO3-) for orange juice; 12.3-60.2 ppm (Cl-), 71.5-128.3 ppm (SO42-), <0.2-1.13 ppm (NO3-) for pulpwash; 21.7-92.9 ppm (Cl-), 19.1-96.2 ppm (SO42-), <0.2-13.3 ppm (NO3-) for processing plant water. The concentrations of these anions for two orange juice and two pulpwash samples were also determined by high-performance ion chromatography (HPIC), and these values were compared to those obtained by capillary zone electrophoresis. These results showed good correlation for chloride and sulfate; however, HPIC was unable to detect nitrate due to interference by other compounds in the orange juice/orange pulpwash and low concentration of nitrate in these samples. The effect of calcium and carbohydrate concentrations on the separation and quantitation of these three anions by CZE was also investigated. Calcium addition to the electrolyte caused retention time shifts which improved the separation of the aforementioned anions from citric acid. Carbohydrate addition had the effect of increasing retention times, peak broadening, and peak height reduction for each of the three anions. Results indicated that orange juice samples from Brazil had consistently lower levels of chloride than those from Florida, Israel, California, Arizona, Mexico, and Belize.