Use of automated sample preparation techniques with GC-SQ, QQQ, and QTOF for aqueous samples

Importance of the Topic

Automated sample preparation techniques integrated with gas chromatography and advanced mass spectrometry are indispensable for trace analysis in environmental water, food and beverage, pharmaceutical and forensic applications. They enhance throughput, reproducibility and detection limits for challenging analytes in aqueous and complex matrices.

Objectives and Study Overview

This work evaluates established automated workflows—instrument top sample preparation, stir bar sorptive extraction, automatic tube exchange and dynamic headspace sampling—coupled to GC single quadrupole, triple quadrupole and QTOF mass spectrometers. Key aims include achieving low ng/L quantitation of NDMA and metaldehyde in water and extending methods to taste and odour compounds and volatiles in distilled spirits.

Methods and Sample Preparation Techniques

Several automated sample preparation workflows were applied:

• Instrument Top Sample Preparation (ITSP): small‐scale SPE cartridges (15–35 mg) for enrichment of aqueous samples and large volume injections
• Stir Bar Sorptive Extraction (SBSE) with PDMS twisters: concentration of hydrophobic analytes via passive stirring, enabling up to 1000-fold enrichment
• Automatic Tube Exchange (ATEX): thermal desorption of volatiles in solid or viscous matrices, isolating non-volatile residue
• Dynamic Headspace Sampling (DHS): controlled incubation and dual needle trapping for efficient volatile capture from beverages

Used Instrumentation

• Gerstel MPS robotic sample preparation platform with dual head and thermal desorption unit (PTV inlet)
• Agilent gas chromatograph coupled to single quadrupole, triple quadrupole and quadrupole time-of-flight mass spectrometers
• ITSP SPE cartridges packed with C18 and specialty sorbents
• PDMS twister stir bars (20 mm × 1.0 mm id and 2 cm × 0.5 mm)
• Dynamic headspace module with double needle trap and trap desorption interface
• Centrifuge and mixer CF200 for pre-treatment of viscous samples

Main Results and Discussion

Robust calibration and sensitivity were achieved:

• NDMA quantitation to 0.125 ng/mL with 25× enrichment and R2 > 0.9995
• Metaldehyde quantitation from 40 to 800 ng/L with R2 = 0.9993, recoveries > 94 % and RSD < 6 %
• Taste and odour compounds monitored from 1 to 120 ng/L with R2 > 0.992 in collaboration with Severn Trent Water
• SBSE delivered precision (RSD 1.7–8.7 %) and linearity (R2 0.989–0.997) for malodourants at 0.02 μg/L
• GC-QTOF provided accurate mass filtering (≈5 ppm mass accuracy) and deconvolution for pesticide residues in complex fruit extracts
• DHS outperformed static headspace in volatile profiling of gin, revealing enhanced peak intensities and richer compound coverage

Benefits and Practical Applications

The automated platforms reduce manual handling, boost sample throughput beyond 200 samples/week and ensure consistent quantitation at trace levels. They support regulatory compliance for water quality, flavour profiling in the beverage industry, pesticide residue screening in food and process control in petrochemical and pharmaceutical sectors.

Future Trends and Potential Applications

Emerging developments include miniaturized and green sorbents, multi-dimensional separations, inline process analytics and advanced chemometric tools for pattern recognition. Integration with high-resolution MS and real-time monitoring will expand applications in metabolomics, forensics and personalised exposure assessments.

Conclusion

Combining automated sample preparation with GC-MS technologies offers a powerful, high-throughput approach for reliable trace analysis across diverse matrices. The validated workflows deliver exceptional sensitivity, selectivity and reproducibility, meeting the demands of modern analytical laboratories.