title: The use of derivative and least-squares methods to analyse a polypharmaceutical product by UV spectrophotometry.
abstract: Derivative UV spectrophotometry is well established for analysing pharmaceutical products containing more than one drug. By contrast, the least-squares method for over-determined systems is rarely used, because it is assumed that measurements at a large number of wavelengths are needed to obtain good results. Both methods have advantages, and their use in combination is useful for analysing polypharmaceuticals. A combination of derivative and least-squares methods was used to analyse tablets containing pseudoephedrine hydrochloride, triprolidine hydrochloride and dextromethorphan hydrobromide. Pseudoephedrine was determined by derivative spectrophotometry. The other drugs were determined by the least-squares method at higher wavelengths where pseudoephedrine does not absorb. Satisfactory precision for the least-squares method was obtained with a manual spectrometer measuring at six wavelengths and calculating the results with a microcomputer.
authors.affiliation: Central Analytical Laboratories (Chemical), Wellcome Foundation Ltd., Temple Hill, Dartford, Kent DA1 5AH, UK.
authors.forename: R
authors.initials: R
authors.lastname: Jones
authors.forename: M J
authors.initials: MJ
authors.lastname: Orchard
authors.forename: K
authors.initials: K
authors.lastname: Hall