SIMULTANEOUS DETERMINATION OF NICOTINAMIDE AND INOSINE IN OPHTHALMIC SOLUTIONS BY UV SPECTROPHOTOMETRY AND PLS-1 MULTIVARIATE CALIBRATION

The use of UV spectrophotometry is reported for the analysis of nicotinamide and inosine in ophthalmic solutions. The resolution of these mixtures has been accomplished without prior separation or derivatisation by using: 1) first-derivative measurements at two appropriate zero-crossing points:?1 = 248 nm, where the absorption corresponding to inosine and excipients is negligible, and ?2 = 261 nm, where the contribution of nicotinamide and excipients to the overall absorption is also negligible, and 2) partial least-squares (PLS-1) regression analysis of zero-order spectral data. Although the components show an important degree of spectral overlap, they have been simultaneously determined by using the latter method with high accuracy (recoveries for nicotinamide and inosine are 101.2% and 100.0 % respectively), with no interference from ophthalmic solution excipients.