Metal–organic framework coated paper substrates for paper spray mass spectrometry†
Metal–organic frameworks (MOFs) have emerged as novel materials owing to their inherent structural characteristics, i.e., a large surface area and a well-ordered porous structure, but there are no reports on their application to paper spray mass spectrometry. Herein we explore the capability of paper substrates coated with three types of MOFs [e.g., MIL-53(Al), ZIF-8 and UiO-66(Zr)] for paper spray, in which the as-prepared UiO-66(Zr) coated paper demonstrated the highest sensitivity in the analysis of therapeutic drugs in dried blood spots relative to MIL-53(Al) and ZIF-8 coated paper substrates. To get a better understanding on the interactions between drugs and MOF coated papers, much effort has been focused on the elution behaviors of target drug verapamil from the MOF coated papers and the adsorption ability of the studied analyte to MOF particles in solution systems. Due to the more favorable elution behaviors and weaker adsorption ability of the tested drugs at the surface of UiO-66(Zr) coated paper relative to the other two papers, the estimated lower limit of quantitation (LLOQ) values of the examined drugs with UiO-66(Zr) coated paper have improvements of 8.5–46.6-fold relative to those from uncoated filter paper, and the values were in the range of 0.04–0.65 ng mL−1. Based on the high sensitivity of UiO-66(Zr) coated paper in drug quantitative analysis, the developed paper has also been successfully applied for the analysis of five anti-psychotic drugs (e.g., clozapine, amisulpride, quetiapine, risperidone and aripiprazole) in 40 human blood samples.