A silica coated paper substrate: development and its application in paper spray mass spectrometry for rapid analysis of pesticides in milk

A novel silica coated paper substrate is developed through a facile vacuum filtration method by using the commercially available silica particles as the coating material and corn starch as the adhesive agent. Unlike the commercial silica coated paper (namely grade SG81 paper), the resulting paper substrate was covered by a layer of silica particles on the top side of the paper, and no cellulosic fibers were exposed at its surface. After loading a solution sample on its surface, the coated silica particles allowed the target analytes to remain at the top side rather than penetration through the substrate. Owing to this effect and the special interactions with analytes, the as-prepared silica coated paper demonstrated superior performance in the analysis of different pesticides in milk using paper spray mass spectrometry to the uncoated filter paper and grade SG81 paper. Compared to the other two papers, paper spray analysis using the as-prepared paper improved the estimated lower limit of quantitation of seven pesticides (alachlor, acetochlor, pretilachlor, butachlor, metolachlor, napropamid and benzeneacetamide) in milk by a factor of 2 to 19-fold depending on the pesticide. This study offers a novel paper substrate for paper spray in high sensitivity analysis of target analytes in a complex foodstuff matrix without any pretreatment.