The role of gas chromatography/mass spectrometry. Instrumental techniques in forensic urine drug testing.

Appropriate GC/MS analytic techniques can provide conclusive confirmatory evidence for the presence of drugs and metabolites in forensic urine drug testing. Although forensic laboratories are required to utilize GC/MS, they have flexibility and freedom in selecting instrumentation, modes of operation, and actual analytic methods. It is incumbent on the laboratory to optimize analytic procedures so that reliability and accuracy are maximized. The laboratory needs to be aware of potential pitfalls in both the handling and the analyses of specimens. Specificity can be enhanced by utilizing mass spectrometric operating modes such as CI and full scan, which serve to complement SIM analyses. They are useful in solving difficult identification problems and in enhancing sensitivity as well as specificity. Newer types of GC/MS systems utilizing ion trapping or tandem mass spectrometry offer the promise of enhanced analytic performance and productivity gains. Knowledge of the advantages and potential pitfalls of different GC/MS systems as well as ionization and detection modes is helpful in optimizing the accuracy of compound identification.