Pharmaceutical controls are time-consuming and require extensive sample preparation. Process analytical technology (PAT) implementation in the pharmaceutical industry would reduce these time consuming operations. To perform this implementation, the use of analytical techniques capable of providing accurate results in a simple and rapid manner is necessary (1). Other advantages include little or no sample preparation (2, 3). Near infrared spectrophotometry (NIR) is a non-destructive and non-invasive technique that allows determination of chemical properties such as active pharmaceutical ingredient (API) or excipient content. The paper proposes a near infrared method able to directly and simultaneously quantify ascorbic acid and sodium ascorbate in powder blends for tableting and in vitamin C chewable tablets without any sample preparation. In the first step, calibration models for the quantification of ascorbic acid and sodium ascorbate in powder blends for tableting and subsequently in chewable vitamin C tablets (corresponding to 80-120 % active substance) were developed according to an experimental design with 2 variables and 5 levels. Then, using the best calibration models, the methods were fully validated in terms of recovery, precision and accuracy for both powder blends and vitamin C chewable tablets. NIR spectroscopy can be used to perform quantitative determinations of one, two or more compounds in complex matrices like, for instance, a pharmaceutical powder blend for tableting or tablets. A NIR assay method is usually not developed in the »traditional« way as UV spectrometry or HPLC assay methods (4). A major step to develop a NIR assay method is the calibration procedure for model development. Once calibration is developed and favourable predictions are expected, they must be validated to be accepted for routine use. For external validation, independent sets of samples are needed. There are several validation parameters that must be determined in order to be consistent with the recommendations of official guidelines: accuracy, precision (repeatability and intermediate precision), specificity, linearity and range of application (5, 6).Many papers report the determination of API content in powder blends or tablets by NIR methods (6, 7), but only a few are focused on the prediction of two or more APIs and/or excipients combined in powder blends or tablets (8, 9).The methods currently used to determine the amount of ascorbic acid and sodium ascorbate in tablets or powder blends for tableting are HPLC (10, 11) and titrimetry (12, 13), but they have the disadvantage of being rather time-consuming. Unlike the conventional methods, NIR-chemometric methods are faster and do not require prior preparation of the sample, so they can be a viable alternative for direct quantification of ascorbic acid and sodium ascorbate in powder blends for tableting and vitamin C tablets. The first objective of our research was to develop a NIR-chemometric method suitable for direct quantification of both APIs from powder blends f...