A facile approach to improve the spray time and stability of paper spray ionization mass spectrometry with a Teflon tube

Methanol plays a significant role in paper spray ionization mass spectrometry (PSI MS) analysis as a spray solvent. Nonetheless, using pure methanol as a spray solvent would lead to rapid evaporation of solvent and a short spray time. Herein, we present a facile approach to enable PSI to use pure volatile solvents with a Teflon tube, which could extend the spray time by reducing solvent evaporation in PSI MS analysis. An around three times longer spray time was found for PSI with a Teflon tube over conventional PSI. Other than longer spray time, the stability of PSI was found to be improved with a Teflon tube. The detection of a mixture of methylene blue and methyl violet consumed 20 L methanol by PSI with a Teflon tube and 60 L methanol by conventional PSI, and the MS analysis results of R-bv (R-bv = ratio of methylene blue-to-methyl violet signal intensity) were consistent for PSI with a Teflon tube and conventional PSI. In addition, the RSDs for quantitative analysis were from 0.38 to 8.75% for PSI with a Teflon tube, which was illustrated via analysis of amitriptyline in blood and fetal bovine serum samples. This approach could provide a longer spray time and better stability for PSI, which could potentially benefit PSI MS analysis in various applications.