Detection of anticoagulant rodenticides by direct analysis in real time time-of-flight mass spectrometry: novel screening techniques and rapid semi-quantitative determination

Environmental monitoring of rodenticide contamination is often required to address public concern of off-target poisoning, which threatens animal populations and disrupts related ecology. This study aimed to address the shortcomings of current analytical methods for testing water-soluble anticoagulant rodenticide by application of direct analysis in real time in tandem with time-of-flight (DART-ToF) mass spectrometry (MS), an alternative analytical technique offering rapidity, low cost, and robustness. Both positive and negative ion modes were investigated with the aim of establishing a quick screening and semi-quantitation workflow. Screening was conducted by development of a custom DART-ToF MS library with selected rodenticide spectra, and data was analyzed using the National Institute of Standards and Technology/National Institute of Justice DART-MS Data Interpretation Tool (NIST/NIJ DART-MS DIT). The developed methodology readily identified five rodenticides from complex mixtures at 1 mg L^-1 and one rodenticide at 10 mg L^-1. Semi-quantitation was conducted through the internal standard method and negative mode ionization, with linear relationships from <i>R</i>² = 0.98 to 0.99. While further optimization with alternative internal standards may be considered, this study revealed the analytical potential in DART-ToF for rapid identification and quantitation of many environmental contaminants.