DROPLET ELECTROSPRAY NEBULIZATION FOR PARTICLE BEAM LC-MS

Abstract

A new interface for particle beam liquid chromatography mass spectrometry (PB-LC-MS) was developed based on a droplet electrospray nebulizer (DESN). The DESN produced relatively monodisperse droplet aerosols of approximately 100 μm diameter. An efficient aerosol desolvation and transport system was also designed to optimize analyte mass transport efficiency. The DESN and desolvation system was coupled to an ion trap mass spectrometer via a three stage momentum separator (DESN-PB-LC-ITMS). The DESN provided several advantages over other nebulization techniques for PB-LC-MS. First, the resultant larger particles provided a high mass transport efficiency of analytes through the momentum separator, which resulted in a significant improvement of the sensitivity and calibration linearity of PB-LC-MS. Detection limits (3σ) ranging from 5.6 to 5.8 pg/μL were obtained for the tested compounds. Secondly, the lower dispersity of larger aerosols provided a better control of particle beam formation and significantly improved the peak shapes. The DESN method resulted in narrower and more symmetric peaks than those obtained with a thermospray nebulizer for PB-LC-ITMS. Compared with UV absorbance detection, no extra peak broadening, peak tailing, or asymmetry were observed with the DESN-PB-LC-ITMS method. Thirdly, the droplet aerosols were produced by applying a DC voltage to the electrode, which was easy to operate. In addition, the DESN could be operated well in both aqueous and organic solvents at flow rates up to 1 mL/min. The system design, optimization, and features of DESN-PB-LC-ITMS have been described in detail.