Identifying Drugs of Abuse Using Gas Chromatography-Time of Flight Mass Spectrometry (GC-TOFMS)

Illegal drug use worldwide is at an all time high. Forensic laboratories are seeing increased sample loads creating an immediate need for fast and accurate analysis to positively identify confiscated materials in criminal investigations. This application highlights the value of gas chromatography with time-of-flight mass spectrometry (GC-TOFMS) for drug testing in forensic laboratories. A method was developed to successfully identify twenty drugs of abuse in 4.5 min. This GC-TOFMS method shows good chromatographic peak shape for even the most challenging drug analytes; even the peak shapes for amphetamine and methamphetamine were exceptional considering they were analyzed underivatized. The total ion chromatogram (TIC) for the twenty drug analytes is shown in Figure 1.

Figure 1

This method was then used to analyze real world samples obtained from a collaborating forensic laboratory. The samples were residues collected by cotton swab that were taken at a suspected drug house.

Experimental

GC: Agilent 7890

Column: Phenomenex ZB-DRG1

Oven: 70 °C to 280 °C, hold 1.5 min

Injection: 2 μL, splitless at 250 °C

Carrier: He, ramped 0.43 to 2.0 mL/min

MS: LECO TruTOF HT

Acquired mass range: 30–500 m/z

Acquisition rate: 10 spectra/s

Source temperature: 300 °C

Samples

A standard containing twenty drugs of abuse was obtained from Alltech. This standard was analyzed by GC-TOFMS and the ChromaTOF software was used to create a reference containing both mass spectral and retention time criteria for each analyte.

Cotton swabs collected at various locations within the suspected drug house were extracted and resulting extracts were analyzed against the reference.

Results and Conclusions

The reference created using the ChromaTOF software was used to compare unknown materials against mass spectra and retention times of known drug substances.

The results showed the presence of cocaine on all cotton swabs collected at the drug house. Figure 2 shows overlaid extracted ion chromatograms (EIC) for the cocaine peak in both the reference standard and Swab #1. Spectra for the swab and cocaine reference standard and the peak table showing a match for cocaine are inset in the figure.

Figure 2

The use of the LECO TruTOF GC-TOFMS and ChromaTOF software offers significant advantages for analysis and positive identification of drug substances.

One major benefit of utilizing TOFMS for drug identification is the ability to acquire full mass range spectra without sacrificing sensitivity. This is essential for positive identification of materials that may be present at trace levels. This work has demonstrated the ability of GC-TOFMS to increase laboratory productivity and efficiency while providing positive identifications of illegal drug substances in criminal investigations.

LECO Corporation

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