A high-performance thin-layer chromatographic (HPTLC) method
was performed for simultaneous quantification of four angiotensin
II receptor antagonists, namely, losartan, irbesartan, valsartan, and
olmesartan. The method based on HPTLC separation of the four
drugs using reflectance–absorbance mode at 255 nm. Separation
was carried out on pre-coated silica gel HPTLC plates, using chloroform–
glacial acetic acid (7.5:2.5, v/v) as mobile phase. The four
drugs have been satisfactorily resolved with RF values of 0.23 ± 0.01,
0.36 ± 0.01, 0.45 ± 0.01, and 0.78 ± 0.01 for olmesartan, losartan,
irbesartan, and valsartan, respectively. The method was validated
according to the International Conference on Harmoni zation (ICH)
guidelines. The linear regression analysis data for the calibration
plots of all studied drugs produced a good linear relationship with
correlation coefficients ranging from 0.9988 to 0.9996 and coefficients
of determination ranging from 0.9976 to 0.9990 over the concentration
range of 90–750 ng per band. The limits of detection and
quantification for all studied drugs ranged from 14.85 to 30.42 and
from 45.00 to 92.18 ng per band, respectively. The developed
method was applied successfully for the determination of the studied
drugs in pharmaceutical formulations and spiked human plasma
with good precision and accuracy.