No sample pretreatment?

Do you want to screen the pesticides presence on your orange? Or do you want to determine if person has used illegal drugs? Or maybe you want to determine the contamination level of trees in the park across the street?

How many sample preparation methods do you need for this? The answer is simple. Just one.

You need a PSI/MS. This means a mass-spectrometer (MS) with a paper spray ionization (PSI) source.

Paper spray was invented approximately 5 years ago in Prof. G.R. Cooks lab. This is a technique that allows to analyse samples that have been collected on a paper with MS.

A PSI/MS setup. Author Hanno Evard.

You can analyse dried blood spots and determine metabolites indicating some disease or determine doping chemicals. Just from this one small blood spot. The beauty of the method is that you really do not need to do anything more than place the blood spot bunched out from the collection paper to the cartridge (placed in front of the MS entrance and to which the ionization voltage is applied to) and add solvent. Both sample preparation and ionization occurs then on the paper and in the spray. Sample preparation can be modified by choosing different paper type (chromatographic papers, eg containing silica or C18 modified silica).

I our lab we have mostly used PSI for pesticide determination. The easies application is for pesticides that are located on the peel of the fruit (the ones that are applied after harvesting). For example thiabendazole and imazalile on oranges, lemons, grapefruits etc. You just need to wipe the peel of the fruit with a paper wetted with solvent and put this paper into PSI/MS. It is a bit trickier for compounds that have been applied during cultivation. For these compounds a slice (or a mush) onto the paper and then apply the solvent.

You can find more about our work on paperspray here.