Ambient (desorption/ionization) mass spectrometry methods for pesticide testing in food: a review

Ambient mass spectrometry refers to the family of techniques that allows ions to be generated from condensed phase samples under ambient conditions and then, collected and analysed by mass spectrometry. One of their key advantages rely on the ability to allow the interrogation of samples with minimal to no sample workup. This feature map well against the requirements of food safety testing, in particular, those related with the fast determination of pesticide residues in foodstuffs. This review addresses the application of different ambient ionization methods for the qualitative and (semi)quantitative determination of pesticides in foods, attending to the different specific methods used and their ionization mechanisms. The more popular techniques used are those commercially available including Desorption Electrospray Ionization (DESI-MS), direct analysis on real time (DART-MS), paper spray (PS-MS) and low-temperature plasma (LTP-MS). Several applications described with ambient MS have reported limits of quantitation approaching reference methods, typically based on LC-MS and generic sample extraction procedures. Some of them has been combined with portable mass spectrometers thus allowing “in situ” analysis. In addition, these techniques have the ability to map surfaces (Ambient MS imaging) to unravel the distribution of the agrochemicals on the crop.