Simultaneous Determination of Sulfadiazine and Sulfamethoxazole in Synthetic Samples and Pharmaceutical Tablets Using HPLC-DAD Combined with Second-Order Calibration Method

The overlapped chromatograms and spectra of sulfadiazine (SD) and sulfamethoxazole (SM) in both synthetic samples and pharmaceutical tablets even in the presence of uncalibrated and interfering sulfanilamide (SN) were resolved by HPLC-DAD combined with a novel second-order calibration method. Their elution time was set from1.077 min to 1.624 min and the detection wavelength was chosen from 230 nm to 316 nm. The recoveries of SD and SM were (99.3 ± 1.3)% and (99.2 ± 3.1)%, respectively. The satisfying results show this method can be easily performed and applied to solving second-order calibration problems quickly and accurately.