Detection of Hydrocarbons by Laser Assisted Paper Spray Ionization Mass Spectrometry (LAPSI MS)

作者：Pallab Basuri, Depanjan Sarkar, Ganesan Paramasivam, Thalappil Pradeep · 发表于：Analytical Chemistry · 年份：2018 · DOI：10.1021/acs.analchem.7b05213 · 被引用次数：32 · 研究领域：Mass Spectrometry Techniques and Applications、Analytical chemistry methods development、Isotope Analysis in Ecology

Here we introduce a new ambient ionization technique named laser assisted paper spray ionization mass spectrometry (LAPSI MS). In it, a 532 ± 10 nm, ≤10 mW laser pointer was shone on a triangularly cut paper along with high voltage, to effect ionization. The analyte solution was continuously pushed through a fused silica capillary, using a syringe pump, at a preferred infusion rate. LAPSI MS promises enhanced ionization with high signal intensity of polycyclic aromatic hydrocarbons (PAHs), which are normally not ionizable with similar ionization methods involving solvent sprays. LAPSI MS works both in positive and negative modes of ionization. A clear enhancement of signal intensity was visualized in the total ion chronogram for most analytes in the presence of the laser. We speculate that the mechanism of ionization is field assisted photoionization. The field-induced distortion of the potential well can be large in paper spray as the fibers comprising the paper are separated at tens of nanometers apart, and consequently, the analyte molecules are subjected to very large electric fields of the order of 10 7 Vcm –1 . Ionization occurs from their distorted electronic states of reduced ionization energy, using the laser. Negative ion detection is also demonstrated, occurring due to the capture of produced photoelectrons. LAPSI MS can be used for monitoring in situ photoassisted reactions like the decarboxylation of mercaptobenzoic acid in the presence of gold and silver nanopar...