Analysis of toxicological samples

Toxicology is the study of poisons (toxins) and indeed many compounds can act as a poison. The forensic toxicologist is required to identify and quantitate these in virtually any matrix. A high percentage of analysis performed are for drugs and their metabolites in body fluids, e.g. blood, urine, liver, stomach contents, etc. However, food, drinks and many 

To undertake the analyses of drugs and metabolites in body fluids the analyst is faced with several major problems. Firstly, due to the complex nature of the body fluid, the drugs must be isolated by an extraction technique which ideally should provide a relatively clean extract, and the separation system must be capable of resolving the drugs of interest from any co-extractives. Secondly, both selective and sensitive detection techniques are essential because of the small sample sizes available (typically less than 500 pi), and the extremely small quantities of drug often present. 

In general, the analysis of acidic and neutral drugs does not present too many difficulties with detection because their therapeutic and, hence, overdose levels are relatively high (pg ml range). Therefore, many of these drugs can be monitored in an HPLC eluate with a UV detector. 

On the other hand, detection difficulties are often experienced with basic drugs because their therapeutic levels are in the low ng ml range. Some of the problems can be alleviated by employing either an electrochemical or fluorescence detector, since it is possible to achieve detection levels of sub-nanogram with these instruments, if operated under favourable conditions. Furthermore, both of these detection methods can enhance selectivity because analytes will only be detected if they contain an electrochemically active group or fluoresce. 

To perform electrochemical detection the analyte should contain a functional group which is capable of either oxidation or reduction if subjected 

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