# Matrix-Tolerant Quantification of THC and THCA in Complex Cannabis Products Using In-Sample Calibration with Multiple Isotopologue Reaction Monitoring

## TL;DR

This paper introduces a new method for accurately measuring THC and THCA in various cannabis products without needing external calibration.

## Contribution

The novel in-sample calibration curve (ISCC) with multiple isotopologue reaction monitoring (MIRM) eliminates the need for matrix-matched calibration.

## Key findings

- The ISCC method achieved a >600-fold dynamic range with high linearity (R² > 0.999).
- The method showed precision (<10% RSD) and accuracy (±10%) across diverse cannabis products.
- Results strongly agreed with traditional external calibration methods in all tested matrices.

## Abstract

Accurate quantification of Δ9-tetrahydrocannabinol
(THC) and Δ9-tetrahydrocannabinolic acid (THCA) across
diverse cannabis- and hemp-derived products remains challenging due
to severe matrix effects, wide concentration variability, and the
need for matrix-matched calibration in traditional LC–MS workflows.
Here, we develop an in-sample calibration curve (ISCC) method based
on multiple isotopologue reaction monitoring (MIRM) from stable-isotope-labeled
(SIL) analytes to enable robust quantification of THC and THCA without
external calibration curves. The approach leverages the theoretical
relative isotopic abundances of SIL calibrators to generate multiple
internal calibration points within each injection. By incorporating
two SIL calibrators for THC (THC-D3 and THC-D9), applying a response-correction factor to harmonize labeled and
unlabeled analytes, and utilizing native-analyte isotopologue transitions
at high abundance, the method achieves a >600-fold dynamic range.
The ISCC method demonstrated excellent linearity (R
2 > 0.999), precision (<10% RSD), and accuracy (±10%)
in commercial CBD oils, gummies, creams, waxes, dietary supplements,
and plant materials. Comparison with external calibration showed strong
agreement across all matrices. Collectively, this work develops the
ISCC–MIRM framework for heterogeneous consumer and forensic
samples and establishes a practical, matrix-tolerant calibration strategy
for routine cannabinoid analysis.