Two simple, rapid, accurate and economical methods have
been developed for the estimation of valdecoxib and tizanidine
HCl in the mixture. Valdecoxib has an absorbance maximum
at 243 nm in methanol: 0.1 mol L1 HCl (1:1) mixture. The linearity
was observed in the concentration range 5.0–
30 lg mL1
. First method is based on Q absorbance ratio
and second method is based on the simultaneous equations
(Sankar et al., 2007). Two methods for simultaneous estimation
of valdecoxib and tizanidine in combined dosage form
have been described. The first method; involves formation of
Q-absorbance equation at 239.6 (isoabsorptive point) and at
241 nm, while the second method; involves formation of simultaneous
equation at 241 and 229 nm, using methanol as solvent
(Devarajan and Sivasubramanian, 2006). A