Comprehensive Automation of the SPEGC/ MS Analysis of Opioids, Cocaine and Metabolites from Serum and Other Matrices

Importance of the Topic

The analysis of opioids, cocaine and their metabolites in biological samples is central to forensic toxicology, clinical monitoring and anti-doping applications. Reliable detection and quantification in complex matrices such as serum, urine and tissues ensure accurate legal and medical decisions while minimizing human error and laboratory workload.

Objectives and Study Overview

This study aimed to fully automate a validated partially-automated SPE-GC/MS workflow for the determination of opioids, cocaine and key metabolites. It compared performance characteristics and results between the conventional routine method and a new fully automated approach using GERSTEL’s MultiPurpose Sampler (MPS) across nearly 170 serum samples and over 50 additional matrices, including urine, tissue homogenates and post-mortem blood.

Methodology and Instrumentation

The sample preparation combined:

• Manual protein precipitation of serum, urine or homogenized tissues using acetonitrile/isopropanol and internal standards.
• Automated steps in the MPS: solid phase extraction (SPE) with mixed-mode cation exchange cartridges, elution, mVAP evaporation, MSTFA derivatization with isooctane/pyridine/MSTFA (14/5/1, v/v/v), and transfer to GC/MS.
• Instrumental analysis by GERSTEL CIS 4 coupled to Agilent 7890 GC/5975 MSD operating in splitless mode and SIM detection for eight target compounds.
• Reference method: Agilent 7683 autosampler and bench-top SPE for comparison.

Main Results and Discussion

Comparable analytical performance was achieved in terms of limits of detection (0.3–9 ng/mL), quantification (0.8–47 ng/mL) and linear upper limits (150–1500 ng/mL) for all eight analytes. Correlation plots demonstrated equivalence across the full concentration range, including near the LOQ. Derivatization time was reduced from 30 to 5 minutes without loss of yield by adding pyridine and shaking at 90 °C. The automated fraction collection was optimized to elute key analytes between 0.6 and 1.9 mL. Throughput reached approximately 26 samples per day with negligible carry-over.

Benefits and Practical Applications

• Full automation minimizes manual handling and potential errors, enhancing laboratory safety and consistency.
• Workflow flexibility allows straightforward adaptation to other GC or LC methods.
• Maintained throughput and analytical quality support routine forensic, clinical and QA/QC laboratories.

Future Trends and Potential Applications

Further integration of centrifugation and sample dilution on the MPS, expansion to LC–MS/MS methods and incorporation of real-time data processing will extend automation benefits. Emerging micro-extraction techniques and machine-learning-based data evaluation hold promise for increased sensitivity, selectivity and decision support.

Conclusion

The fully automated SPE-GC/MS method matches the validated reference in accuracy, precision and robustness while reducing manual workload. Its high flexibility and throughput make it an ideal platform for forensic toxicology and other analytical settings requiring reliable multi-analyte quantification.

Used Instrumentation

• GERSTEL MultiPurpose Sampler (MPS) with SPE module, mVAP evaporation station, Agitator, Solvent Filling Station 2.
• GERSTEL Cooled Injection System 4 (CIS 4).
• Agilent 7890 GC with Rxi-5Sil MS column and 5975 MSD in SIM mode.

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