Ambient Ionization Mass Spectrometry Based Methods For Small Volume Sample Analysis And Components Identification

Small volume sample refers to sample with volume 10 pL to nanoliter level.The research of small volume sample mainly concerns the bio-chemical reactions and procedures happened in or between several cells,which could be quite important for the further understanding of life activities in cells and cell niche.Mass spectrometry is a useful tool for simultaneous multiple components analysis.The use of tandem mass spectrometry could provide the structure information,which is capable for the unknown components structure identification in sample analysis.Due to the limited sample amount,the current mass spectrometry based small volume sample analysis methods could only obtain very short or even instantaneous mass spectrometry signal.This makes it impossible to perform tandem mass spectrometry analysis to identify unknown components in small volume sample.In addition,it is also difficult to perform sample pretreatment of small volume sample.This makes the matrix effect quite obvious in small volume sample analysis and restrict the sensitivity.In this thesis,we had developed two ambient ionization sources,step-voltage nanoelectrospray(SV-Nano-ESI)and pulsed direct current electrospray ionization(Pulsed-DC-ESI)to solve the above problems.The main concepts of the thesis are as follows.1.SV-Nano-ESI was designed and established.This ionization source was developed to solve the matrix effect in small volume sample analysis.At the higher voltage stage,ions migration in sample solution was enforced and compounds with different apparent charges were separated in different zones.This made a matrix free zone for target molecule analysis in the followed low voltage stage for Nano-ESI analysis.Sv-Nano-ESI had improved the sensitivity for the analysis of small volume sample with complicated matrix.2.Pulsed-DC-ESI was designed and established.This ionization source used static electrical field to induce the pulsed electrospray of liquid sample remotely.Sample and electrode no longer needed to be contacted in Pulsed-DC-ESI.This solved the dead volume problem in while using ESI for small volume sample analysis.By controlling the electrical field strength,we could adapt the pulsed electrospray frequency to fit the mass spectrometry sampling frequency,enhancing the sample economy and reducing the flow rate.This solved the mass spectrometry signal duration problem.We also developed methods for sampling and reserving small volume liquid sample in nanoelectrospray emitters for Pulsed-DC-ESI analysis,making this source a convenient tool for small volume sample analysis.3.By using Pulsed-DC-ESI,we had performed single cell metabolomics and lipidomics analysis of Allium cepa and HeLa cell.Methods for single cell sampling had been developed to be coupled with the used of Pulsed-DC-ESI.A new strategy based on two dimension mass spectrometry was proposed for the metabolomics and lipidomics analysis.Using the above methods,we had successfully identified more than 1000 components in single cell and examined the saccharides modification while metabolizing.As to our knowledge,no similar result has been reported yet in the world.