Substance identification: the weak link in analytical toxicology

Although substance identification is a key factor in analytical toxicology, it is amazing that the subject is receiving very limited and often inappropriate attention. With regard to the latter, a “confirmation” approach is usually chosen, which does not yield unambiguous identification. Moreover, the criteria for establishing a “positive match” leave much to be desired. These observations are corroborated when comparing some recent guidelines for qualitative analysis (issued for various forensic areas by SOFT/AAFS, NCCLS, NLCP, WADA and EU). Apart from showing substantial differences between them on pivotal issues, the guidelines contain various elements that appear scientifically incorrect and/or legally untenable. Also, the guidelines focus primarily on mass spectrometry (MS) and pay little or no attention to other identification possibilities (such as chromatographic techniques, either in combination with MS or as stand-alone techniques. Moreover, they do not offer alternatives in situations where access to MS is not available. One must conclude, therefore, that substance identification is a neglected and misunderstood domain in analytical toxicology. Rapid and concerted actions are needed to: (1) improve the general knowledge; (2) to define uniform strategies in the analytical approach and in the interpretation of the results; and (3) to set up and maintain suitable banks of reference substances and computerized data bases to allow unambiguous identification.