Method Validation of Silica Dispersive Solid Phase Extraction Combined with Spectrophotometer UV-Vis for the Determination of Allopurinol in Herbal Medicine

A facile sample preparation method based on silica dispersive solid-phase extraction combination with spectrophotometer UV-Vis for the extraction of allopurinol in herbal medicine was successfully developed. Silica was used as a solid sorbent. The extraction process was carried out by inserting and dispersing silicas in a 30 mL sample solution that contained allopurinol, then stirred using a hot plate stirrer. At the end of the extraction process, silicas were collected and desorbed using ethanol by utilizing a vortex. The desorption solution was analyzed by spectrophotometer UV-Vis at a maximum wavelength of 250 nm. Several essential parameters such as silica mass, extraction time, desorption time, and pH of sample solution were optimized. The results showed that the optimum extraction condition was achieved: silica mass. 0.8 grams; extraction time, 45 minutes; desorption time, 2 minutes; and pH of sample solution, pH 7. The optimum extraction condition was then applied for the standard curve and analyzed of allopurinol in herbal medicine samples. The results of the method validation method were obtained the correlation coefficient (R2), 0.9961; the detection limit, 0.6871 ppm; the quantitation limit, 2.2902 ppm, the percent of recovery (% R) in the range of 96.42-110.25%, percent coefficient of variation (% CV) in the range of 0.0361- 0.1322%. The application method in 3 real samples showed that the concentrations of allopurinol were 56.0221 ppm, 54.8706 ppm, and 63.6719 ppm, respectively. The values of % R in the analysis of real samples by using the spiking method were obtained in the range of 49.52-89.74%.