In forensic sciences, positive results are reported when compounds or drugs are identified chemically and their quantity is measured. Therefore, confirmation of these results needs scientific methods to recognize the chemical structure of the compound which distinguishes it from other compounds. This therefore includes isomers i.e. compounds having different structure with the same molecular formula like methamphetamine and phentermine. The identification of a drug forensically from initial screening requires another method to check for its confirmation. So, the other method adopted for confirmation must be different than the initial screening and be more specific, providing exclusive structural information about the compound’s identification other than some exceptions. This is stated in SOFT – Society of Forensic Toxicologists and the AAFS – American Academy of Forensic Sciences’ Toxicology Section’s Laboratory Guidelines and the Federal Workplace Drug Testing Programs’ Guidelines which are set up by the Department of Health and Human Services.
MS – also known as mass Spectrometry can accurately identify and quantify drugs and their metabolites in forensic toxicology. Therefore, the combination of mass spectrometer and a GC – Gas Chromatograph is now synonymous with the confirmatory methods of drug testing programs. The proper use of this method was mandated in 1988 in the Federal Workplace Drug Testing Program’s Guidelines which made it the sole confirmatory test to be used for workplace drug testing.
Much advancement in computer technology, electronics and engineering have emerged which has resulted in a new generation of compact, sensitive and more quicker mass spectrometers. These mass spectrometers are more capable of discovering and measuring many drug compounds at different concentrations in different biological tests. The advancements in the ionization of the sample and ion transmission have led to an immense increase in the use of liquid chromatography mass spectrometry (LC-MS). Mass spectrometers having a high resolution such as ToF – Time of Flight and FTICR – Fourier Transform Ion Cyclotron Resonance are those which can give accurate calculations up to 5-decimal places. These technologies have greatly enhanced the S/N – Signal to noise ratios, accuracy, LoD – Limits of Detection, sensitivity, LoQ – Limits of Quantitation and the robustness of the techniques which are used in forensic sciences.
This chapter will be focused to describe the conventional and the latest analytical techniques which are used to confirm drugs and their metabolites. Their theory, application and the limitations is also discussed in this chapter.