Wilson, Nicola Dawn; (2002) The application of near infrared spectroscopy to the characterisation and quality control of pharmaceutical materials of natural origin. Doctoral thesis (Ph.D.), University College London.

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Abstract

Natural products are of increasing interest as sources of novel pharmaceuticals and there are frequent questions as to their authenticity and purity. The use of Near Infrared (NIR) spectroscopy provides a method for rapid analysis of such materials and requires no sample preparation. Although there are many references detailing the use of NIR spectroscopy in the pharmaceutical industry, the majority of these are concerned with the analysis of pharmaceutically active drugs or pharmaceutical excipients. The aims of this PhD were to demonstrate the potential of NIR spectroscopy as a tool in the quality control of a variety of natural materials. The emphasis, therefore, was on studying a range of different products in both a qualitative and quantitative manner. Qualitative methods included the identification and qualification of natural products by the use of constructed spectral libraries. Statistical discrimination methods such as Correlation in Wavelength Space (CWS) and Maximum Distance in Wavelength Space (MDWS) were employed to create Library methods that allowed an unknown spectrum to be identified with, or distinguished from, spectra used to construct the Library. Quantitative methods included the quantification of certain analytes at different concentrations in certain materials by developing calibration equations using the Multiple Linear Regression (MLR) method. Methods of sampling, preparation and measurement were developed to carry out these investigations in the most appropriate manner and to overcome problems encountered with data acquisition and analysis. British and European Pharmacopoeia assays for the quantification of certain chemical constituents in essential oils such as Eucalyptus and Lemon oils have been used as standard reference methods and compared with NIR methods developed as part of this research and it has been shown that the NIR method is similar in precision and accuracy to the conventional assay methods. In addition, it has been demonstrated that NIR spectroscopy can be used to identify and distinguish between different essential oils and that the water content of Agar samples can be determined. Initial studies have also been carried out into the detection of adulteration of Rosemary oil with Eucalyptus oil and the contamination of Fennel with Hemlock. To summarise, the potential of NIR spectroscopy for the quality control of natural pharmaceuticals has been demonstrated and it is possible that this technique could replace more complicated and expensive traditional methods of analysis in the future.

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