Confirmation of identity
Confirmation of identity may be required if the product is not identified uniquely or if the consequences of an error demand that identification be confirmed. The analysis can be quite challenging for some products, such as multivitamins and minerals, herbal products, homeopathic remedies and steroids. Colour tests have been promoted for use by purchasers of ecstasy tablets at dance venues, either by organisations that offer a service or by the users themselves (Spruit 2001; Winstock et al. 2001). The Marquis reagent and more recently the Mecke or modified Mecke reagent and Mandelins reagent are available to the public for this purpose on the internet (Winstock et al. 2001). Confirmation of identity may be required for a variety of reasons:
• identification of illicit products
• unequivocal identification for forensic purposes
• detection of adulteration
• detection of the substitution of capsule contents
• identification of products not in commercial databases
• investigation of counterfeit or substandard products.
It may often be achieved by suspending a whole tablet or a scraping from a tablet or a portion of a capsule contents in a solvent, such as ethanol or methanol, and analysing it by spectroscopic methods (UV, IR, MS) or chromatographic methods (TLC). Analysis can present significant analytical challenges and may require structural elucidation using proton NMR spectroscopy. The analysis of non-active ingredients (excipients in legitimate medicines or diluents in illicit drugs) may be of value in investigating counterfeit medicines or the origin of illicit drugs. Near IR spectroscopy, particularly when linked with microscopy, is a valuable technique for this purpose (see Chapter 16). Polarised-light visible microscopy may be used to identify excipients such as the starches (e.g. maize, potato) used as disintegrants. The confirmation of identity of herbal products is difficult and may require microscopic examination for plant fragments by a specialist and chromatographic analysis (often TLC) for indicator compounds. The genetic characteristics of traditional Chinese herbal drugs are under investigation at the Royal Botanic Gardens at Kew (London, UK) and may be of value for the confirmation of their identity in the future.
