@article {62979, title = {Simultaneous Determination of Timolol maleate and Brimonidine tartarate in their Pharmaceutical Dosage Form}, journal = {Analytical Chemistry Letter}, volume = {4 }, year = {2014}, pages = {132 - 145}, abstract = {

Three new simple and selective assays were developed for the analysis of binary mixture
containing timolol maleate (TM) and brimonidine tartarate (BT) in the presence of benzalkonium chloride
(BZ) as a preservative in eye drops. The first derivative ultraviolet spectrophotometry was used with zerocrossing
measurements at 313 nm for TM and 386 nm for BT, respectively. The second method depends on the
first derivative of the ratio spectra with zero-crossing measurements at 313 nm and 391 nm for TM and BT,
respectively using 0.25 μg/mL BZ as a divisor. The assays were linear over the concentration ranges 5-85 μg/
mL and 2-35 μg/mL for TM and BT, respectively. The third method was based on isocratic and mobile phase
saving micellar liquid chromatographic method with a Biobasic phenyl column (150 x 1.0 mm, 5 μm particle
size) and micellar mobile phase composed of 0.1M SDS, 10 \% of 1-propanol and 0.1 \% of TEA in 0.035M
ortho phosphoric acid. UV detection was adjusted at 298 nm and 250 nm for TM and BT, respectively performed
at room temperature. The linearity range for TM and BT was 2-100 μg/mL and 1-50 μg/mL, respectively. The
proposed methods showed high percentage recovery, good accuracy and precision.

}, author = {Mohamed S. Rizk and Hanan A. Merey and Shereen M. Tawakkol and Mona N. Sweilam} }