Spray Solvent Dependence Observed During the Analysis of Synthetic Cannabinoids Via Paper Spray Ionization-Mass Spectrometry

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Christopher Mulligan

Mentor Department



Paper spray ionization (PSI), a newer ambient mass spectrometric ionization method, employs a paper substrate to allow the direct analysis of deposited or swabbed samples through simple addition of high voltage and an appropriate spray solvent. During PSI investigation, analyte ions are generated through an electrospray-like process directly from the paper substrate itself. To date, PSI-MS has been shown highly applicable to forensic evidence screening, particularly for drugs of abuse. While a majority of drug classes have been shown broadly robust to the spray solvent system employed for PSI analysis, recent research has shown that successful analysis of synthetic cannabinoid and related evidence is highly dependent on the solvent employed. In this presentation, a systematic study of spray solvent composition and its effect on broad synthetic cannabinoid screening will be discussed. For comparison, ∆9-THC and several synthetic cannabinoids of diverse classification were investigated. Solvent systems examined included variable ratios of methanol (MeOH), acetonitrile (ACN) and water and acidification via addition of dilute formic acid (0.1% v/v). For every solvent combination, each cannabinoid was analyzed via PSI-MS using a 2 µg deposited mass, and the maximum signal intensity was collected. Using the entire dataset, a heat map was produced that allows the visual inspection of relative performance of each spray solvent system in regards to obtained signal intensity, allowing a user to optimize their intended experiment. Authentic samples of synthetic marijuana evidence were analyzed through interactions with local law enforcement agencies to show similar solvent constraints for plant-based samples. Results obtained show that polarity and solubility of the target analyte can dramatically affect experimental results, and care must be taken in regards to establishing PSI-MS method protocols for synthetic cannabinoid/marijuana evidence.



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