Improve The Detection Performance Of Laser Desorption/Ionization Mass Spectrometry By Using Superwetting Materials

Taking advantages of short analysis time,small sample volume and high throughput,laser desorption/ionization mass spectrometry?LDI-MS?has received increasingly attention.The most common-used techniques in LDI-MS include matrix-assisted laser desorption/ionization mass spectrometry?MALDI-MS?and surface-assisted laser desorption/ionization mass spectrometry?SALDI-MS?.They can detect various analytes?such as peptides,nucleic acids and sugars?,have promote LDI-MS in fields of medicine,materials,environment,etc.Various superwettabilities exist in nature widely.Superwetting material has greatly promoted industry and facilitated people's life,for example,superhydrophobic material.Water has large contact angle on it,and analyte in aqueous solution can be confined to small area.This confinement effect greatly increases the density of molecules and improves detection signal of analyte.Various superhydrophobic substrates have been used in LDI-MS for improving the signal-to-noise ratio?S/N?and limit of detection?LOD?of analyte.Herein,this work improved the performance of LDI-MS by applying superwetting materials.The main research content is summarized as the following three parts:Firstly,a superhydrophobic candle soot/poly?dimethyl siloxane??C/PDMS?substrate was fabricated for analysis of peptide with MALDI-MS.Superhydrophobic C/PDMS substrate can enrich and desalt peptide simultaneously,due to the weak interaction of superhydrophobic surface with water/salt and the strong hydrophobic affinity between PDMS and peptide.Though there were salt contaminants in peptide solutions?2 M or saturated Na Cl?,superhydrophobic substrate can achieve significantly better performance than the commercial Zip Tip C₁₈ pipette tip.When analyzed the tryptic digests of protein,the number of assigned peptides and sequences coverage on superhydrophobic substrate were higher than Zip Tip C₁₈ pipette tip.The LOD of bacitracin A in milk on this substrate was 100 p M,which was nearly 360 times lower than LOD of the standard test method.Secondly,a superwetting porous silicon?p Si?substrate was prepared,combined with liquid-phase microextraction?LPME?technique,for rapid separation of analytes and onsite detection with SALDI-MS.The front surface of p Si was superhydrophobic in air/underwater superlipophilic,while the back surface was superhydrophilic in air/underwater superoleophobic.Organic extract was directed to the front surface due to oil-water separation.The application of superwetting p Si simplified analysis steps,can detect analytes?such as malachite green,verapamil and methadone?in various complex samples with shorter operating time,less required sample volumes,lower LODs and wider linear quantitative ranges than work reported.Thirdly,the washed carbon soot nanoparticles?WCS NPs?was obtained by physically washing the superhydrophobic CS NPs from candle flame and used as a new SALDI-MS matrix.Due to the confinement effect of near superhydrophobicity and the synergistic effect of multiple carbon components,analyte with WCS NPs had higher laser desorption/ionization efficiency and less background than common-used matrices.WCS NPs can quantitatively analyze urine glucose,visualize latent fingerprint and image it with SALDI-MS.