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SEM surface images of paper spray and ps-modifications. (a) Unmodified paper spray [3]. (b) Wooden tip spray [27]. (c) Silica coated paper (d). Close-up of silica coated paper [15] (e) Graphene coated paper [31]. (f) Polystyrene microspheres. (g) Comparison of PS-MS/MS of clozapine with uncoated paper and PS-coated paper with polystyrene microspheres. Quantitation curves are compared for coated and uncoated PS, showing improved detection limits for PS coated paper[30].
