Deuterated Analogues as Internal Standards in the Accuracy of Quantitative Pesticide and Mycotoxin Analysis between Differing Cannabis Matrices

Significance of the Topic

Modern cannabis products span a wide range of formulations, from inhalable flower to edibles, concentrates and topicals. Ensuring patient safety requires accurate quantitation of pesticide and mycotoxin residues in these diverse matrices. Matrix effects can compromise measurement accuracy when standard calibration in one matrix is applied to another. The use of deuterated analogues as internal standards addresses these challenges by compensating for variable recovery and ion suppression, leading to more reliable results across complex cannabis-based samples.

Objectives and Study Overview

This study aimed to evaluate the impact of matrix effects on quantitative analysis of 59 pesticides and 5 mycotoxins in four cannabis matrices (oil, gummy bear, flower, topical cream) and to demonstrate how deuterated internal standards improve accuracy and precision. A single LC-MS/MS method was developed to perform simultaneous positive and negative mode analysis with rapid polarity switching, enabling high-throughput screening in under 16 minutes.

Methodology and Sample Preparation

Calibration standards (0.5–1000 ppb) and QC samples (1, 10, 50 ppb) were prepared by spiking 0.5 g of each cannabis matrix with target analytes and deuterated internal standards. Extraction employed 9:1 methanol:water with 0.1% acetic acid, followed by agitation, centrifugation and direct injection of 10 µL of supernatant.

Used Instrumentation

• Shimadzu Nexera X2 UHPLC system
• Trap column: Restek Raptor Biphenyl (3.0 × 30 mm, 2.7 µm)
• Analytical column: Restek Raptor ARC-18 (2.1 × 100 mm, 2.7 µm)
• Shimadzu LCMS-8060 triple quadrupole mass spectrometer (5 ms polarity switching, 30 000 u/s scanning)
• 24 isotopically labeled internal standards (e.g., imidacloprid-D4, chlorpyrifos-D10, permethrin-D5)

Main Results and Discussion

Direct calibration based on analyte peak areas showed significant variability between matrices, with RSDs exceeding 50% and accuracy deviations over 60%. When analyte responses were normalized to their corresponding deuterated standards, accuracy improved to within 25% and RSDs dropped below 20% for all analytes. This demonstrates that internal standard normalization effectively compensates for matrix-induced suppression and recovery differences, ensuring consistent quantitation across diverse sample types.

Benefits and Practical Applications

• Enhanced accuracy and precision in multi-matrix pesticide and mycotoxin analysis
• High throughput: 16-minute total run time for 64 analytes
• Robust, reproducible method adaptable to additional analytes and matrices
• Automated workflow minimizes operator variability

Future Trends and Opportunities

As regulatory requirements evolve, incorporation of additional deuterated standards will further expand method coverage. Ongoing improvements in UHPLC-MS/MS sensitivity and scanning speed may reduce run times and lower detection limits. Integration with automated sample preparation and data processing pipelines will enhance throughput for large-scale testing laboratories. Emerging matrix-matched calibration strategies and machine learning–based signal correction hold promise for further mitigating complex matrix effects.

Conclusion

The presented UHPLC-MS/MS method employing deuterated internal standards successfully overcomes matrix challenges in quantitative pesticide and mycotoxin analysis across multiple cannabis preparations. This approach delivers reliable accuracy and precision, supporting regulatory compliance and safeguarding patient safety in the rapidly expanding medical cannabis industry.

Reference

No external literature references were provided in the original text.