Basic Information
Abstract Number: 470-4    
Author Name: Jason S Page Affiliation: Pacific Northwest National Laboratory
Session Title: MS-Bioanalytical
Event Type: Oral
Event Title: Increasing MS Sensitivity by Overcoming Ion Transmission Biases and Inefficiencies in the ESI MS Interface
Presider(s): Kaiser, Mary A Start Time: 09:00 AM ( Slot # 4 )
Date: Monday, March 1st, 2010 Location: 310A
Keywords: Electrospray, Instrumentation, Mass Spectrometry, Sample Introduction

Kelly, Ryan TPacific Northwest National Laboratory
Marginean, IoanPacific Northwest National Laboratory
Smith, Richard DPacific Northwest National Laboratory
Tang, KeqiPacific Northwest National Laboratory

Abstract Content
Detailed characterization of an electrospray ionization (ESI) mass spectrometry (MS) interface showed that the heated capillary inlets typically found in many commercial instruments incur large ion losses, which are biased towards low m/z species. This can lead to reduced analytical sensitivity and mass spectra not representative for the true chemical content in a sample, decreasing both the ability to identify low level species and to quantify them. The ion transmission biases were observed to depend strongly on the inlet length. The transmitted electrospray current increased when shorter lengths were used due to reduced losses to the inside walls of the capillary. Surprisingly, while the transmitted electrospray current more than doubled, some analytes showed little or no increase in sensitivity, while others showed as much as a 15 – fold gain. The variation was shown to be correlated with analyte mobilities, with considerable biases against higher mobility species but also affected by solution conductivity, flow rate, and inlet temperature. Besides showing strategies to overcome these ion losses, a new low pressure ESI source will be presented which operates the electrospray in a reduced pressure chamber of the mass spectrometer, and thus removing the need for the capillary inlet and the associated inefficiency and bias of ion transmission into the mass spectrometer.