Assi, Sulaf; (2010) Identification of Counterfeit Medicines By Near-infrared Spectroscopy. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The aim of this thesis is to investigate the identification and quantification of counterfeit medicines by near-infrared spectroscopy (NIRS) and Raman spectroscopy with no or minimal sample preparation. The background literature on the identification and quantification of counterfeit medicines using conventional analytical methods as well as spectroscopic methods is reviewed. The products used for investigation (including tablets, powders, pellets and liquids) were obtained from the world market. Both laboratory and handheld NIR and Raman instruments were used in these studies. The data were processed on the standard normal variate second derivative spectra (SNV-D2) for NIRS and on the baseline treated spectra for Raman spectroscopy. Optimisation of the method of determination of counterfeit pharmaceutical products by NIRS was made on the FOSS NIRSystems 6500 spectrometer using a model set of nine tablet products. The optimised identification method was effective for proprietary and generic tablets if an authentic sample from exactly the same manufacturer was available. Otherwise, a quantitative approach to determine the active pharmaceutical ingredient (API) amount in tablets had to be taken using partial least square regression (PLSR). In addition to conventional tablet models, it was best to use standard addition models with 0 and 100% sample spectra included. Handheld Raman spectroscopy (using Ahura Truscan instrument) showed it had better identification potential that handheld NIRS (using Polychromix PHAZIR instrument). However, laboratory based NIRS was better than laboratory based Raman spectroscopy (using the Kaiser Workstation instrument) as most often in the latter the signal of the pharmaceutical product was masked by the fluorescence of one of its components. Identification of tablets through their transparent blister packaging was possible using a FOSS NIRSystems 6500 spectrometer equipped with a Smart Probe by changing the conventional ceramic reference to a Spectralon of 20% reflectance. However, for analysis of intact tablets, Spectralon 20% and 80% were the best references for identification and quantification respectively.

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