Meeting the International Conference on Harmonisation's Guidelines on Validation of Analytical Procedures: quantification as exemplified by a near-infrared reflectance assay of paracetamol in intact tablets.

This Perspective explains how the International Conference on Harmonisation's Guidelines on Validation of Analytical Procedures for quantitative methods can be met by near-infrared (NIR) assays of intact pharmaceutical products. Each of the validation characteristics (accuracy, precision, specificity, detection limit, quantification limit, linearity, range, robustness and system suitability testing) is defined, examined for their relevance to quantitative methods and examples given on how they may be used to demonstrate that near-infrared assays are fit for purpose. Methods for preparing samples for calibration are given in detail. The intention is to provide information so that a pharmaceutical manufacturer could validate a method suitable for an application for a variation of a marketing authorisation for an existing product and use a NIR assay instead of the previous method. The perspective is illustrated in detail using a NIR reflectance assay of paracetamol in intact tablets. This proven assay gives results comparable to the British Pharmacopeia ultraviolet assay for paracetamol, the standard errors of calibration and prediction for the NIR method being 0.48% w/w and 0.71% w/w respectively. The method is also precise, the standard deviation and coefficient of variation for six NIR assays on the same day being 0.14% w/w and 0.16% w/w respectively, while measurements over six consecutive days gave 0.31% w/w and 0.36% w/w respectively.