Raman and infrared spectroscopy used to spot fake malaria tablets
UK scientists have demonstrated a suite of analytical techniques that can be used to distinguish genuine from fake antimalaria tablets. The problem of counterfeit drugs is growing in many parts of the world and in Southeast Asia large quantities of forged tablets of the antimalarial medicine artesunate are in circulation, posing a serious health risk.
Artesunate is a semi-synthetic derivative of artemisinin, a compound found in a shrub. ’Artemisinin drugs are remarkably rapid in their antimalarial effects and they are very well tolerated,’ said Paul Newton a tropical medicine expert from the University of Oxford, and a co-author of the new study. ’So where these medicines are available they are sought after. But as they are relatively expensive, a demand is created for cheaper versions amongst the poorest and most vulnerable people upon whom the counterfeiters have preyed - with fatal results.’
As the forgers have become more sophisticated, fake packaging - including detailed holographic labels - have become increasingly difficult to detect. Analytical techniques such as thin-layer chromatography and high-performance liquid chromatography can detect contaminants and levels of active compound in the tablets but are time-consuming.
Camilla Ricci and colleagues from Imperial College London the Rutherford Appleton Laboratory and the University of Oxford have shown that Fourier transform infrared imaging and Raman spectroscopy can provide detailed information about a tablet’s composition within a few seconds.1 Furthermore, a technique called spatially offset Raman spectroscopy (SORS), reported earlier this year by Pavel Matousek at the Rutherford Appleton Laboratory, allows the chemical composition of the tablets to be probed while they remain in their packaging, such as blister packs or plastic bottles.2
’What we are able to do is take a chemical snapshot of different components within the sample,’ Sergei Kazarian of Imperial College told Chemistry World. ’If there is a compound present that should not be there we can detect it very quickly.’
The UK researchers are currently evaluating a portable Raman spectrometer to find out if it could be used in the field.
’There is no single panacea, but we believe these methods provide a complementary approach for the non-invasive and non-destructive characterization of fake antimalarial drugs,’ Kazarian said.
Facundo Fernandez of the Georgia Institute of Technology in the US is an expert on counterfeit malarial drugs. ’I believe these techniques have a tremendous potential to help in the forensic characterization of counterfeit antimalarial drugs,’ he told Chemistry World. ’I am looking forward to see further developments in this area, mostly related to the miniaturisation and field-use of these techniques.’
1 C Ricci et al, Anal. Bioanal. Chem., 2007, DOI: 10.1007/s00216-007-1543-1
2 P Matousek.and C Eliasson, Anal. Chem., 2007, 79, 1696 (DOI: 10.1021/ac062223z)