The effects of four different ion-pair reagents (weak and strong volatile ion-pair reagents and nonvolatile strong ion-pair reagents) in positive and negative ionization modes are compared. The results show that the strength and volatility of the ion-pair reagent have a great influence on the formation of the ion pair and the resulting ion-pair effect. Strong volatile ion-pair reagents show good performance in both positive and negative ionization modes, while nonvolatile strong ion-pair reagents show good performance in positive ionization mode.
This document investigates the impact of ion-pair reagent selection on LC/MS analysis using various analytes. It compares the effects of volatile and nonvolatile reagents on both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) sources. The study utilizes an Agilent 1100 Series LC/MSD system to evaluate how reagent type and concentration influence analyte retention and ionization efficiency.
The APCI response for erythromycin is greatly reduced by heptane sulfonic acid because these ion-pair reagents trap the analyte in the dried droplets.
The ESI signals for direct yellow 50 and orange G are improved by the presence of tributylamine, as a result of a pH effect in the drying ESI droplet.
Tetrabutylammonium hydroxide causes significant suppression for all analytes because the nonvolatile ion-pair hinders the escape of analyte from the droplets during electrospray ionization.