Directly ionizing foods for mass spectrometric (MS) analysis can be a quick way to screen for contaminants. Techniques, such as DART-MS, can rapidly detect intentional (melamine) or inadvertent food contaminants (photoinitiators) without chromatography or sample preparation.  Using direct ionization the entire sample is ionized, yielding a complex MS response.  Assigning a signal to an analyte can be difficult since measuring m/z does not provide structural information.  Direct MS can even 'lose' selectivity by mixing ion signals. Ion fragmentation and high resolution MS (HRMS) can 'add back' selectivity/specificity of direct MS, but may diminish the speed or ease of screening for food contaminants. Little experimental data exists demonstrating the adequacy or figures of merit for these direct MS approaches. Similarly, it has not been established whether direct HRMS sample screening will reduce time or effort for food contaminant analysis.DART-MS was used to screen food, packaging, and cosmetics for targeted (photoinitiators, plasticizers) and untargeted (food contact materials) contaminants.  Traditional chromatography-MS analysis (including quantification) of these samples was compared to DART-MS screenings. The effect of DART-MS criteria was examined, including thresholds, and mass accuracy/resolution on accuracy of the direct-MS screening, and the workload.  Semi-targeted, unknown identification of compounds in food packaging was conducted by comparing the results to library matching GC-MS analysis.Unknown identification in food packaging by DART-MS yielded a broader range of compounds than GC-MS library matching. No false positive or false negative identifications were observed for 51 package/molecule identifications by DART-MS.  However, targeted screening of other food and packaging by DART-MS missed many true positive samples (>20% false negative) when more than two characteristic ions were required to be detected and/or when one of the ions was required to be a pseudo-molecular ion (M+/-X). DART-MS data and screening accuracy for foods, cosmetics, and food packaging will be presented.

False or not: Direct mass spectrometric screening for food contaminants

248th National Meeting (2014)

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