Infrared detector (IRD) solutions for forensic sector - Manufacturing, Other
Due to the worldwide increase of illegal synthetic drugs and their legal definition, it is essential to differentiate between isomers of illicit drugs. To comply with accepted standards for identification, this typically requires a combination of instrumental and chemical techniques. Gas Chromatography- mass spectrometry (GC-MS) is a powerful tool used in forensic chemistry for the identification of the complex mixtures often encountered by forensic chemists. In GC analysis, compounds are separated from a mix and eluted from a column based on the structure’s affinity for the stationary phase. The elution is measured by retention time, and while the retention time of a given compound in a GC method can provide clues to identity, retention time is not unique to any compound.
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In MS, a molecule is bombarded with high energy electrons, creating charged ions. Typically, these ions are unstable and will undergo fragmentation producing a mass spectrum pattern based on mass to charge ratio. Libraries of known standards can then be compared to these fragmentation patterns. Many times, this mass spectrum is enough to identify the compound of interest in a forensic setting. In the case of positional isomers, the ions produced during fragmentation may not be unique, and the resulting mass spectra are indistinguishable in benchtop GC-MS instrumentation. The American Society of Crime Laboratory acknowledges the need to couple MS with other instrumentation to accurately identify positional isomers.
In infrared spectrophotometry (IR), molecules are exposed to infrared radiation. Based on the arrangement of the functional groups, it will either absorb or transmit the various wavelengths of radiation. The resulting IR spectra can then be compared to known Vapor Phase IR Libraries. Unlike in MS, where the movement of a functional group in a positional isomer cannot be differentiated, slight changes in the position of functional groups is detectable in the IR spectrum. GC-IRD allows for the characterization of these isomers with the advantage of the separation afforded by the GC.
The Vapor Phase (VP) GC-FTIR, IRD 3 manufactured by ASAP Analytical, is the best analytical technique to complement the most widely used analytical method for drugs of abuse GC-MS. Using the IRD 3 in tandem with GC-MS gives the forensic laboratories a versatile and reliable set of tools to identify unknowns and difficult isomers.