Utility of Schiff's base Formation Reactions for the Spectrophotometric Determination of Pemetrexed Disodium in bulk and in its Pharmaceutical Formulations

Two simple, accurate, sensitive and extraction-free Spectrophotometric methods (A and B) have been developed for the determination of pemetrexed disodium in bulk and in pharmaceutical dosage forms. The methods A and B are based on the reaction of pemetrexed disodium with p-Dimethyl aminocinnamaldehyde (PDAC) and 4-Hydroxy-3-methoxybenzaldehyde (Vanillin) in the presence of dilute Sulphuric acid gives red colored chromogenes, which show maximum absorbance at 515nm and 470nm respectively. Beer's law is obeyed in the concentration range 2.5–40μg mL-1 for method A and 2.5–35 μg mL-1 for method B. The molar absorptivity and sandell's sensitivity values are 1.3 X104 Lit mo1-1cm-1 and 0.046 μg cm-2 for method A and 1.5 x104 Lit mo1-1cm-1and 0.039 μg cm-2 for method B. The results of the two methods are validated statistically and by recovery studies. The proposed methods are economical, sensitive and can be used for the determination of pemetrexed disodium in bulk and pharmaceutical formulations.