Ambient ionization based on mesoporous graphene coated paper for therapeutic drug monitoring

Paper spray (PS), as a new ambient ionization method, has been applied for direct qualitative and quantitative analysis. The high sensitivity and minimum internal energy (low spray voltage) with optimized paper spray conditions is a significant request for real application in POCT. In this study, a simple and efficient ambient ionization method is developed by spraying from a mesoporous graphene foams (MGFs)-modified paper surface. The good electrical conductivity of MGFs results in obvious spray voltage decrease. Meanwhile, the MGFs-paper substrate has a well improvement in separation and elution efficiency ascribing to ultrahigh specific surface area and π-π electrostatic stacking property of graphene. In combination a commercial triple quadrupole mass spectrometer, the paper spray is successfully used for analysis of amphetamine in saliva. The linear dynamic ranges expand 10 fold in comparison with unmodified chromatography papers and the low limit of quantitation (LOQ) is as low as 1 pg/mL. A small sample volume (0.5 μL) could be analyzed immediately after spotting, without any pretreatment. The performance of this method was demonstrated for application in fast point-of-care mass spectrometry.