“…Therefore, simultaneous determination of the analytes in biological samples is important in studying pharmacokinetics. However, to our best knowledge, no analytical method has been described in the literature which simultaneously determines these three analytes in biological samples, even though several methods exist, which separately determine either triamterene [1][2][3][4][5], hydrochlorothiazide [6][7][8], reserpine [9][10][11][12][13], or determine triamterene and hydrochlorothiazide simultaneously [14,15]. Though many kinds of analytical methods such as spectrophotometry, spectrofluorimetric, potentiometry, capillary electrophoresis, HPLC-UV, LC-MS were used in these literatures, it is tedious to determine three analytes separately for each sample using two different HPLC conditions or even two different detection methods.…”