||Chromatography systems can separate complicated sample then sequentially importing to detector, so now are widely used in various fields. Generally, gas chromatograph ( GC ) is suitable for analysis of volatile small molecules, and liquid chromatography ( LC ) is suitable for analysis thermal instability molecular, biochemical macromolecules. Traditional gas chromatography and liquid chromatography mass spectrometry utilize electron, chemical ionization or fast atom bombardment techniques for ionization. However, sample analysis using these techniques is performed under a vacuum. Thus, the flow rate of mobile phase in GC and LC is limited. Coupling GC and LC to atmospheric pressure ionization ( API ) methods is therefore of interest to scientists.|
API methods such as electrospray ionization ( ESI ) , atmospheric pressure chemical ionization ( APCI ) , and atmospheric pressure photoionization ( APPI ) would generate intact analyte ions. In the recent year, new ESI/plasma-APCI source that combines an ESI and plasma-APCI has been developed to simultaneously characterize polar and non-polar compounds, greatly improving the capability of MS detector
In this study, a new GC+LC/MS that integrated GC/MS and LC/MS interfaces together was developed. The aforementioned, ESI/ plasma-APCI source was utilized for ionization of analytes from GC and LC columns. The gaseous analytes from GC column were delivered to the ionization region through a heated transfer line; whereas effluent from LC column was sprayed by a nebulizer. The ESI/ plasma-APCI ion source was operated in ESI-only, dual ESI/plasma-APCI, or plasma-APCI-only mode to analyze the separated compounds.
This GC-ESI/plasma-APCI/MS interface was used to analyze straight-chain alkanes and fatty acid methyl esters (FAMEs). Straight-chain alkanes were generated by plasma-APCI, protonated FAMEs were generated by ESI. In ESI/plasma-APCI mode, [M+O-3H]+ ion of analytes characterize in ESI-only and plasma-APCI-only mode were all detected. LC-ESI/plasma-APCI/MS was used to detect peptide mixtures. Because the peptide multiply-charged ions generated by ESI were reacted with negative species generated by plasma, the peptide ions with lower charge number were detected. Singly and multiply-charged analyte ions can be detected in ESI/plasma-APCI mode. In addition, gasoline, essential oil and leaf extract were tested.