Sampling of micro-samples using Micro Sample Collector (2) - Qualitative analysis of unknown powders on table cloths -

Importance of the Topic

Rapid and sensitive identification of trace powders on surfaces is essential in forensic investigations, quality control of pharmaceuticals, and foreign material analysis. Micro-scale sampling combined with thermal desorption GC/MS enables direct analysis of minute residues without solvent extraction.

Objectives and Study Overview

This study demonstrates qualitative analysis of unknown powder residues collected from table cloths. The aim was to test a Micro Sample Collector (MSC1) for trace sampling and to apply thermal desorption GC/MS to identify powder constituents.

Methodology and Instrumentation

• Sampling: A micro coil tip of the MSC1 was gently touched to each powder spot on the cloth and retracted into a syringe needle.
• Thermal Desorption GC/MS Conditions: Injector temperature 330°C, split ratio 1/10. Two oven programs: 40→330°C (20°C/min, 5 min hold) and 60→330°C (20°C/min, 6.5 min hold). Column: Ultra ALLOY+-5 (5% diphenyl/95% dimethylpolysiloxane), 30 m×0.25 mm×0.25 µm, carrier gas flow 1 mL/min.

Main Results and Discussion

• Unknown Sample A: Chromatogram showed a single dominant peak identified as ibuprofen.
• Unknown Sample B: Major peaks included acetylsalicylic acid (aspirin), salicylic acid (hydrolysis product), and cyclic oligomers (dimers, trimers, tetramers). Minor components such as phenol and acetic acid appeared at low intensity (10× scale).
• The detection of common analgesics confirms both powders were pharmaceutical painkillers.

Benefits and Practical Applications

• Non-destructive micro-sampling directly from surfaces preserves sample integrity.
• Thermal desorption GC/MS offers rapid, solvent-free identification of drug residues.
• Technique is applicable to forensic casework, pharmaceutical QA/QC, and foreign particle analysis.

Future Trends and Potential Applications

• Coupling with high-resolution MS for enhanced structural characterization of trace compounds.
• Automation of micro-sampling workflows for high-throughput analysis in forensic and environmental laboratories.
• Extension of the method to other matrices, including solids, biological tissues, and environmental particulates.

Conclusion

The combination of micro coil sampling with TD-GC/MS provides a robust approach for qualitative analysis of unknown powder residues on surfaces. The method successfully identified ibuprofen and aspirin derivatives, demonstrating its utility in forensic and quality control applications.