Two chemometric assisted spectrophotometric methods; multivariate calibration and zerocrossing
first derivative analysis were applied for the determination of ascorbic acid (vitamin
C) in its single pharmaceutical formulations and its simultaneous determination in mixtures
with either acetyl salicylic acid (aspirin), salicylamide or dipyrone (novalgin). The components
of the three mixtures show a considerable degree of spectral overlapping. Resolution of the
binary mixtures under investigation has been accomplished by using classical least squares
(CLS) or by using the first derivative analysis. Good recoveries were obtained by both methods.
In the CLS determintions, the recoveries for the first mixture were 98.761.24 and 98.521.48
for ascorbic acid and acetyl salicylic acid respectively. In the second mixture, the recoveries
were 100.38 0.38 and 100.630.63 for ascorbic acid and salicylamide respectively. In the
third mixture, the recoveries were 100.480.48 and 98.53 1.47 for ascorbic acid and dipyrone
respectively. On application of the first derivative method, the recoveries were 97.762.24 and
98.601.40 for ascorbic acid and acetyl salicylic acid mixtures; 102.60 2.60 and 100.38 0.38
for ascorbic acid and salicylamide; 98.531.47 and 99.28 0.72 for ascorbic acid and dipyrone
mixtures. Wavelengthes are given at which ascorbic acid and either of the three combined
drugs were simultaneously determined by the first derivative spectrophotometry. The mixtures
were simultaneously determined in many commercial dosage forms with high accuracy without
interference from the commonly encountered excipients. Good agreement was found between
results obtained with the two suggested methods and those obtained by the reported
pharmacopoeial methods.