A Novel Method Based On 3D Hydrodynamic Focusing Microfluidic For High Resolution Chip Coupled With Nanoelectrospray Ionization Mass Spectrometry

Microfluidic chip own low sample consumption and the probability to integrate various samples treatment(such as mixing,filtration,separate,etc.).There for it has been widely used in the research of proteomics,single cell analysis and so on.Mass spectrometry(MS)own high sensitivity and powerful qualitative.Because of which it has been widely reported to be a good detector of microfluidic chip.Coupling microfluidic chip with MS has attracted interest.In all kinds of ionization resource,ESI source could be realized ionization for samples in liquid,and it is capable with normal air pressure(vacuum is not strictly required).There for it had been widely utilized.Conventional ESI resource could only be coupled with those sample flow which own a suitable flow rate such as several microliters per minute,and it is could not realize the ionization for nano sample flow.In recent reports,most usual strategy was focused on the fabrication for spray emitters which own a very small size,while those interfaces are difficult to be made,as well as its repeatability.Under these kinds of situations,our research utilized microfluidic three dimension hydrodynamic focusing strategy to inhibit the sample expansion in the ESI spray,and modulated the distribution of sample ions in the pattern.Moreover,MS reference solution was integrated into the sample flow to improve the resolution for the proposed MS strategy.The final aim for over research was to realize an ESI ionization for nano sample flow with a decent MS resolution.Generally,our research was reported as following:1.Based on the reasonable design for microfluidic chip,focusing solution was used to focus the sample flow in 3D.Under these kinds of treatments,the sample flow was controlled to be in the center of the general flow puffier,based on which the sample ion expansion in the taylor cone was highly inhibited.In addition,the proposed 3D ESI resource chip was used to determine rhodamine B and reserpine.Experimental result indicated that 3D hydrodynamic focusing in chip was indeed capable of low sample consumption.2.In order to realized the high resolution for MS,the reference solution in standard high resolution MS was used to take place of conventional hydrodynamic focusing solution in both vertical and horizontal direction.More over nitrogen flow rate was integrate into the chip in four directions to improve the ionization efficience.The ESI resource based on the microfluidic chips which own both MS reference function and nitrogen flow function was used to determine rhodamine B and reserpine.It was shown that the proposed microfluidic chip could be realized a high MS resolution determinations,and its sensitivity as well as its ionization efficience was rather satisfactory.3.PDMS was used to fabricate the proposed chip,and the oligomers in the chip would be dissolution in the sample flow,because of which the background ions in MS determination would be rather high.Our strategy was to use octadecyltrichlorosilane to coat channels in the chip,based on which organic solution was prevented from the PDMS.Generally oligomers in PDMS would not indicate strong interference in the proposed combination for microfluidic chip and MS.In a sum,our research achieved a strategy to couple focusing chip and MS,which was based on 3D hydrodynamic focusing.This kind of method owns high resolution and it is suitable to realize the excitation for low sample flow in nano skill.It would be a satisfactory theoretical and experimental foundation for further research.