Identification and Quantification of Illegal Drugs and Benzodiazepines in Human Plasma by LC–MS-MS After Solid Phase Extraction (SPE)

Catherine Roy¹, Fabrice Mangani², and Nouredine Sadeg¹, ¹Centre Hospitalier René Dubos and ²Gilson International BV

The identification and quantification of drugs of abuse in blood (plasma, serum, whole blood) has become very common in the forensic medicine laboratory. Liquid-liquid extraction (LLE) has been traditionally used at a basic pH (pH = 9) for the extraction of amphetamines, cocaine and its metabolites, and opiates from blood. LLE can be time consuming and difficult to automate compared to solid phase extraction (SPE). Poor reproducibility can also be a factor when using a manual method such as LLE.

This study describes an automated SPE protocol using a Gilson GX-271 ASPEC™ System for the simultaneous extraction of amphetamines, cocaine and its metabolites, and opiates as well as benzodiazepines prior to analysis by LC–MS-MS.

Experimental Conditions

Plasma (0.5 mL) was spiked with internal standards (LGC Standards, Molsheim, France).

Solid Phase Extraction (SPE) Protocol

The SPE procedure used 1 mL Waters Oasis™ HLB (30 mg) cartridges. The SPE protocol is entirely automated using the Gilson GX-271 ASPEC System. The SPE steps are summarized with the schematic provided in the GX-271 ASPEC control software, TRILUTION® LH (Figure 1).

Figure 1

Results

See Table I.

Table I: Recovery Values Obtained from Spiked Plasma Samples (n = 3)

Conclusion

The high quality of the automated SPE clean-up method allowed for the direct injection of extracts into the LC–MS-MS system. Recovery of all analytes was excellent. Automation of the SPE process increased recovery ranges 10 to 20% compared to results obtained using the manual liquid-liquid extraction method. Automation of the extraction process has the additional benefit of allowing scientists to spend more time developing new methods for the analysis of compounds of interest to the forensic laboratory.

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