Net analyte signal based statistical quality control

Net analyte signal statistical quality control (NAS-SQC) is a new methodology to perform multivariate product quality monitoring based on the net analyte signal approach. The main advantage of NAS-SQC is that the systematic variation in the product due to the analyte (or property) of interest is separated from the remaining systematic variation due to all other compounds in the matrix. This enhances the ability to flag products out of statistical control. Using control charts, the analyte content, variation of other compounds, and residual variation can be monitored. As an example, NAS-SQC is used to appreciate the control content uniformity of a commercially available pharmaceutical tablet product measured with near-infrared spectroscopy. Using the NAS chart, the active pharmaceutical ingredient (API) content is easily monitored for new tablets. However, since quality is a multivariate property, other quality parameters of the tablets are also monitored simultaneously. It will be demonstrated that, besides the API content, the water content of the tablets as well as the homogeneity of the other compounds is monitored. © 2005 American Chemical Society

Identifying counterfeit medicines using near infrared spectroscopy

Counterfeit medicines are a growing threat to public health across the world and screening methods are needed to allow their rapid identification. A counterfeiter must duplicate both the physical characteristics and the chemical content of a proprietary product to avoid it being detected as a counterfeit product and this is almost impossible to get right. Counterfeit proprietary medicines are, therefore, relatively easy to identify by near infrared (NIR) spectroscopy which can detect physical as well as chemical differences between products by simple spectral comparison. Identifying generic products is more difficult as they use different excipients in the tablet or capsule matrix. Nevertheless, using appropriate models and a large library, NIR spectroscopy can detect counterfeit generic versions. Detecting sub-standard proprietary medicines can be carried out with NIR spectroscopy models and the most widely used is partial least squares regression (PLSR). General rules for generating accurate quantitative models are easy to describe. Quantifying the active pharmaceutical ingredient (API) in generic products can also be carried out using PLSR models with calibration samples generated by manufacturing laboratory samples or by collecting many generic versions of a medicine so as to obtain a good range of the API content in tablets and capsules. Using hand-held instruments or mobile laboratories allows NIR spectrometers to be taken to places where analyses may be made quickly, rather than taking the samples to a laboratory. This has the enormous advantage that the screening of large numbers of samples may be made in pharmacies and wholesalers. Imaging can bring a whole new dimension to NIR spectroscopy to allow the identification of the API and individual excipients as well as measuring the particle sizes of components and giving a measure of the homogeneity of the matrix. The effect of water on potential misidentifications may be obviated by only using blister-packed samples, having large spectral libraries subjected to different humidities or omitting the spectral region where water absorbs.Peer reviewe