Paper spray ionization mass spectrometry: Study of a method for fast-screening analysis of pesticides in fruits and vegetables

• Paper spray is suggested for fast screening of pesticides.
• Post-harvest pesticides can be identified with a simple, rapid wiping method.
• Pre- and post-harvest pesticides can be identified from homogenized samples.
• Limit of detection for pesticides was below MRL.

New faster and simpler methods for determination of pesticides in agricultural products are necessary as requirements for food safety are becoming increasingly stringent. One possibility is to introduce a fast, easy and low-cost screening method before liquid chromatography mass spectrometry analyses. We hereby present a systematic proof of concept study of paper spray mass spectrometry method for pesticide detection as a screening method. Two sampling approaches – wiping the surface with paper and applying the sample homogenate directly on the paper – were used. The wiping method was more extensively studied for imazalil and thiabendazole originally present in oranges. For homogenized samples three matrices – oranges, tomatoes and grapes – and five pesticides of different chemical nature and polarity – thiabendazole, aldicarb, imazalil, methomyl and methiocarb – were chosen. It has been shown that limits of detection below maximum residue levels can be achieved for both methods (e.g. imazalil and thiabendazole detection limits were found to be lower than 5 mg/kg). The methods are therefore suitable for fast screening of samples. Moreover, the wiping method was also applied for 11 samples – oranges, grapefruits, lemons, limes, mandarins, tomatoes, apples, pears, strawberries, grapes and sweet peppers – from the local supermarket to screen for different pesticides. Three positive samples for thiabendazole and imazalil and one positive sample for imazalil were found.