Evaluation of Dispersive and Cartridge Solid Phase Extraction (SPE) Cleanups for Multiresidue Pesticides in QuEChERS Extracts of Finished Tobacco Using GCxGC-TOFMS

Importance of the topic

The intensive use of pesticides in tobacco cultivation leads to residual contaminants on finished products. Unlike food crops, tobacco lacks regulated maximum residue limits, raising concerns for consumer exposure, analytical laboratories, and import regulations. Reliable, efficient methods are needed to monitor multiresidue pesticides in complex tobacco matrices.

Objectives and overview of the study

This work assessed the performance of Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction coupled with two cleanup strategies—dispersive solid phase extraction (dSPE) and cartridge SPE (cSPE)—for multiresidue pesticide analysis in finished tobacco. Comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (GCxGC-TOFMS) was employed to compare cleanup efficiency and recovery at fortification levels of 500 ppb and 50 ppb.

Methodology and instrumentation

Samples of light and dark bulk tobacco (2 g) were fortified with a custom pesticide standard, extracted via QuEChERS using EN 15662 salts, then cleaned by:

• dSPE A: 150 mg MgSO₄, 50 mg PSA, 50 mg GCB, 50 mg C18
• dSPE B: 150 mg MgSO₄, 25 mg PSA, 7.5 mg GCB
• cSPE: 500 mg CarboPrep® 90 and 500 mg PSA cartridge, eluted with acetone:toluene

Cleanup efficacy was evaluated by GC–FID overlay and gravimetric measurement of nonvolatile residue. Pesticide recoveries were quantified by GCxGC-TOFMS on a LECO Pegasus 4D system with an Rxi-5Sil MS primary column and an Rtx-200 secondary column.

Main results and discussion

The dSPE formulation B (7.5 mg GCB, 25 mg PSA) yielded the highest average recoveries—92% (RSD 13%) at 500 ppb and 91% (RSD 22%) at 50 ppb—outperforming dSPE A (82%/81%) and matching the cSPE cleanup in nonvolatile residue removal (70%) but in only 20 minutes versus three hours. GC-FID showed cSPE removed more fatty acids via higher PSA content, while GCxGC-TOFMS contours demonstrated that two-dimensional separation effectively isolated pesticides from remaining matrix, exemplified by clear detection of incurred piperonyl butoxide obscured in one-dimensional GC.

Benefits and practical applications

The optimized QuEChERS-dSPE approach provides rapid, solvent-efficient cleanup with robust recovery across diverse pesticide chemistries. Coupled to GCxGC-TOFMS, it enables sensitive, selective trace analysis and non-target screening in complex dry matrices such as tobacco, reducing instrument maintenance and improving data reliability.

Future trends and potential applications

Broader adoption of GCxGC-TOFMS will address demanding regulatory and quality-control needs for pesticide monitoring. Further adaptation of high-throughput dSPE protocols for other dry botanicals, combined with archived full-scan data re-interrogation, will expand non-target residue surveillance. Emerging guidelines for tobacco residues may standardize these advanced workflows.

Conclusion

An optimized QuEChERS extraction with 7.5 mg GCB/25 mg PSA dSPE, paired with GCxGC-TOFMS, delivers fast, efficient cleanup and reliable quantitation of multiresidue pesticides in finished tobacco. This streamlined workflow outperforms traditional cSPE in speed and matches its cleanup efficiency, enabling routine application in analytical and regulatory laboratories.

Reference

• World Health Organization, The Tobacco Atlas, 2013
• U.S. Government Accountability Office, Pesticides on Tobacco: Federal Activities to Assess Risks and Monitor Residues, GAO-03-485, 2003
• Anastassiades M., Lehotay S., Stajnbaher D., Schenck F., J. AOAC Int. 86 (2003) 412
• Kowalski J. et al., Application Note PHAN1242A, Restek Corp., 2010
• Cochran J. et al., Application Note GNAN1338, Restek Corp., 2011
• Cochran J., ChromaBLOGraphy, Restek Corp., 2011