Objective:

Assess whether atmospheric pressure solids analysis probe mass spectrometry (ASAP-MS) can rapidly screen surfaces for illicit drug residues, compared with laboratory liquid chromatography–mass spectrometry (LC-MS).

Approach:

• Sampling: Researchers collected 420 swabs over three weeks from bathrooms, tables, and a copper bar in an anonymous pub in southern England.
• Analytes and reference method: Samples were tested for cocaine, ketamine, amphetamine, diazepam, and tetrahydrocannabinol. LC-MS was used for confirmatory analysis.
• ASAP-MS workflows: The team compared direct, untargeted ASAP-MS screening with methanol extraction followed by targeted ASAP-MS analysis.

Key Findings:

• LC-MS detected 320 positive findings: 250 for cocaine and 70 for ketamine; 64 swabs contained both. No other tested drugs were detected.
• Cocaine was found on more than half of swabs. Bathrooms had the most cocaine and ketamine detections; tables and the bar had fewer residues.
• Direct ASAP-MS mainly detected samples with relatively high cocaine levels and missed many lower-level residues.
• Methanol extraction with targeted ASAP-MS yielded 118 positive findings: 104 for cocaine and 14 for ketamine. Sensitivity was 40.49% for cocaine and 11.43% for ketamine, compared with 27.16% and 4.88%, respectively, for direct untargeted analysis.
• The targeted extraction workflow missed 59.51% of LC-MS cocaine-positive samples and 88.57% of ketamine-positive samples. Across ASAP-MS workflows, researchers recorded 15 false-positive results.
• Some apparent ketamine signals were associated with procaine, a cocaine adulterant with a similar mass signal.

Interpretation:

The researchers concluded that ASAP-MS may be more suitable for initial screening than for confirming whether a drug is present or absent. Surface residues do not establish whether a substance was consumed at the venue, when it was deposited, how it arrived, or who was responsible.

Limitations:

• ASAP-MS had high false-negative rates, including after extraction and targeted analysis.
• A single-quadrupole instrument without chromatographic separation had difficulty distinguishing compounds with similar mass signals.
• The researchers identified a need to optimize temperature control, extraction volumes, matrix-matched controls, and data-analysis software before routine on-site screening.

Conclusion:

Direct ASAP-MS may rapidly identify larger quantities of unknown material, while extraction and targeted analysis can improve trace detection. Further method development is needed.

Sources:

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