No abstract

A simple isocratic HPLC procedure has been developed for simultaneous separation and quantitation of dopamine, glycine, tryptophan, valine, leucine and isolucine by pre-column derivatization with 4-dimethylaminobenzaldehyde and UV detection at 240 nm. The derivatives formed were examined spectrophotomatrically for the effects of pH, derivatizing reagent concentration and heating time in aqueousmethanolic solution. The analytes and excess of the derivatizing reagent separated completely from the column Kromasil 100 C-18 5 µm, (250 × 0.46 cm) when eluted with methanol-water-potassium chloride (1M) adjusted to pH 2 (55:44.75:0.25 v/v/v) with a flow rate of 0.4 mL min -1 . Linear calibration were obtained with 2-400 µg mL -1 and limits of detection within 13.2-533.2 ng/20 µL. A number of amino acids and pharmaceutical additives did not interfere to the determination. The derivatization, separation and quantitation was repeatable with RSD within 4.5 (n = 6). The method was used for determination of dopamine, tryptophan, valine, leucine and isoleucine from pharmaceutical preparation. The results were further supported by standard addition method. The recovery from pharmaceutical preparation of dopamine was 96.8 %, tryptophan 99.6 %, valine 98.7 %, leucine 98.8 % and isoleucine 99.3 % with RSD (n = 3) 3.4, 3.1, 1.3, 3.8 and 1.8 %, respectively. The results were further supported by standard addition method.