Droplet electrospray nebulization for particle beam LC-MS

A new interface for particle beam liquid chromatography mass spectrometry ( PB-LC-MS) was developed based on a droplet electrospray nebulizer (DESN). T he DESN produced relatively monodisperse droplet aerosols of approximately 100 Irm 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 adva ntages over other nebulization techniques for PB-LC-MS. First, the resultan t larger particles provided a high mass transport efficiency of analytes th rough the momentum separator, which resulted in a significant improvement o f the sensitivity and calibration linearity of PB-LC-MS. Detection limits (3 sigma) ranging from 5.6 to 5.8 pg/mu L were obtained fo r the tested compounds. Secondly, the lower dispersity of larger aerosols p rovided a better control of particle beam formation and significantly impro ved the peak shapes. The DESN method resulted in narrower and more symmetri c peaks than those obtained with a thermospray nebulizer for PB-LC-ITMS. Co mpared 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, w hich was easy to operate. In addition, the DESN could be operated well in b oth aqueous and organic solvents at flow rates up to 1 mL/min. The system d esign, optimization, and features of DESN-PB-LC-ITMS have been described in detail.