Implementation and study of dopant‐assisted photoionization with a miniature capillary inlet ion trap mass spectrometer

Abstract

Rationale Dopant‐assisted photoionization (PI) has been widely used in the mass spectrometric analysis of volatile compounds. Exploring simple doping methods will benefit parameter optimization and promote the application of this technique. Methods A previously built miniature ion trap mass spectrometer was used to study dopant‐assisted vacuum PI. The sampling system of this device was modified to provide three inlets for the simultaneous introduction of analytes, dopants, and auxiliary air. Then, dopant solution was directly injected into the ion trap chamber through a self‐aspirating capillary inlet and rapidly evaporated without heating. Various dopant solutions were prepared and switched during the experiments. Results When analyzing some aniline compounds, the signals of all analytes were improved by more than 10 times after the injection of 2% anisole solution as a dopant. In addition, anisole can provide analyte signals more than three times stronger than those provided by the other dopants. On the basis of the ionization energy selectivity of dopant‐assisted PI, some isomers in the mass spectrometric analysis were distinguished using different additives. Conclusions In general, liquid doping is as feasible and as effective as other traditional methods, and using appropriate dopants with high PI efficiency or feeding more dopants contributes to the ionization of analytes. The proposed method also offers several unique merits, such as simple operation, low consumption, and smooth switching with minimal residue.

Ion Mobility Mass Spectrometry for the Separation and Characterization of Small Molecules

“…Ruskic et al found that the selectivity of DMS for separating isomers depends on the concentration of chiral selectors. Other common chiral selectors are cyclodextrin with metal cations, − methanol, anisole, and so on.…”

Portable Digital Linear Ion Trap Mass Spectrometer Based on Separate-Region Corona Discharge Ionization Source for On-Site Rapid Detection of Illegal Drugs

“…Ion trap mass spectrometer has been considered an optimum choice because of its moderate vacuum requirements, simple structure, and tandem analysis capability [ 9 ]. The development of ambient ionization methods without sample preparation or separation such as desorption electrospray ionization (DESI) [ 10 , 11 ], direct analysis in real-time (DART) [ 11 , 12 ], photoionization (PI) [ 13 , 14 , 15 ], low temperature plasma (LTP) [ 16 , 17 ], paper spray ionization (PSI) [ 18 , 19 ], further paved the way for MS technology from the laboratory use to onsite applications. The feasibility of combining these ambient ionization methods and miniaturized ion trap mass spectrometer for rapid on-site illegal drugs detection has been demonstrated [ 13 , 14 , 20 , 21 , 22 , 23 ].…”

High-Throughput Screening Using a Synchronized Pulsed Self-aspiration Vacuum Electrospray Ionization Miniature Mass Spectrometer

“…In terms of the injection method, self-aspiration sampling is a simple and feasible strategy, − which has the advantages of easy operation, small dead volume, and less sample consumption. In particular, using the native vacuum chamber of the mass spectrometer to self-pump liquid or gaseous samples can further simplify the assembly. − For miniature MS instruments, self-aspiration sampling should be combined with vacuum ionization technology to exhibit practical significance. The common in-vacuum ionization sources, such as electron ionization and photoionization, are typically used for the analysis of gaseous samples.…”