How to approach substance identification in qualitative bioanalysis

The ultimate goal in qualitative analysis in the biosciences is to demonstrate with acceptable probability that for an unknown constituent in a sample only one substance comes into consideration and that all other substances can be rejected. In the biosciences, identification of relevant substances in complex matrices through database retrieval is frequently required. Yet, despite its importance, the subject has not received much attention, so that progress has been limited and relevant literature is scarce. As a result, one can conclude from many publications and reports that qualitative analysis in practice is often not being addressed properly. In this paper, some fundamental aspects of qualitative analysis will be discussed and a general approach is provided for the correct identification of organic substances in complex matrices through database retrieval. Special attention is given to the choice of proper analytical techniques and their inter-laboratory standard deviations, as well as to match factors and decision criteria based on applying multiple analytical techniques, also if the latter have different dimensions (e.g. retention data and spectral data). In addition, the requirements for suitable databases are outlined and the need for inter-laboratory cooperation is emphasized.