Study On The Atomization Experiment And Flow Field Numerical Simulation Of Electrospray Extraction

Electrospray extractive ionization(EESI)can rapidly and in real time ionize target molecules in complex matrix samples without complex sample pretreatment,which has been widely used in food quality monitoring,drug detection,drug and explosive detection and other research fields.The sampling efficiency of the EESI source is composed of ionization efficiency and transmission efficiency,which affects the mass spectrometry sensitivity of the EESI source in directly.The ionization efficiency is directly related by atomization flow field of EESI source.In the paper,the atomization flow field of EESI source is taken as the research object.The investigation was carried out to study the effect of different factors on the atomization flow field of EESI source through experiment and simulation analysis.First of all,atomization experiments were carried out on sample channel of electrospray ionization source,and the effects of auxiliary gas pressure,relative position of gas-liquid outlet and liquid flow rate on atomization effect were investigated.And the atomization cone angle as the evaluation standard of atomization effect.Then,the atomization experiment was based on sample channel,the method of computational fluid dynamics was used to simulate the atomization flow field of the sample channel,and the influence of auxiliary gas pressure and liquid flow rate on the atomization flow field were simulated.Finally,the numerical simulation and experimental study of the two-channel electrospray extraction ionization source were carried out respectively.The main research results are listed.(1)The experimental results of sample channel atomization experiment of EESI source show that the atomization cone angle first decreases and then increases,and finally tends to be stable with the increase of the auxiliary gas pressure,under the experimental condition of liquid flow rate of 5 ul/min.With the increase of the relative position of the gas-liquid outlet,the atomization cone angle increases first and then remains constant.When the relative position of gas-liquid outlet is 0.06 mm,the atomization cone Angle increases with the increase of liquid flow rate.When the relative position of gas-liquid outlet is 0.26 mm and 0.46 mm,the atomization cone angle of liquid flow rate of 10 ul/min is greater than that of liquid flow rate of 5 ul/min and 15 ul/min.The variation range of cone angle is smaller than that of 5 ul/min and 15 ul/min.For flow rates of 5 ul/min and 15ul/min,the gas pressure of 0.8 MPa and the relative position of 0.46 mm were prefered.For the flow rate of 10 ul/min,the gas pressure of 0.8 MPa and the relative position of 0.26 mm are preferred.(2)The simulation results of the atomization flow field in the sample channel of EESI source show that the gas velocity on the axis increases first and then decreases with the increase of the distance when the liquid velocity is 5 ul/min.The Sotel mean droplet size(SMD)of atomized flow field decreases with increasing auxiliary gas pressure.SMD decreased with increasing pressure at different flow rates.When the auxiliary gas pressure is 0.5-0.7 MPa,the particle size of atomized droplet increases with the increase of liquid velocity.When at pressure of 0.8-1.2 MPa,SMD of the three flow rates have no significant difference.The atomization model of sample passage is verified by comparing with the results of single passage experiment.(3)Through the EESI dual-channel simulation study,it is concluded that under the condition of the liquid flow rate of 5 ul/min,the SMD of the atomization flow field decreases with the increase of the auxiliary gas pressure.At the pressure of 0.8 MPa,the SMD in the atomization field increases with the increase of the spray distance,and the SMD values of the three were basically the same at the cross-sections 2 mm,3 mm and 4mm away from the center of the gas inlet.At the same time,the accuracy of the model was verified by two-channel atomization experiment.In this paper,the influence of different factors on the atomization flow field of single and double channels were studied by combining numerical simulation and experiment,which provides a certain theoretical basis for the further research on EESI sources.