SAN JOSE, Calif.—During the discovery phase, researchers are typically called upon to monitor the pharmacokinetic characteristics of a drug candidate mixed with dosing vehicles such as Tween, PEG, or methyl cellulose. Unfortunately, these compounds can confound mass spectra both by complicating the spectra with numerous peaks as well as causing significant ion suppression. While LC is often indicated to alleviate this problem, recent research suggests that atmospheric pressure separation using high-field asymmetric waveform ion mobility spectrometry (FAIMS) may be helpful.

 

In an application note, researchers at Thermo Fisher Scientific describe their efforts to analyze the drug loperamide in the presence of large excesses of PEG 400. Without pre-separation by FAIMS, PEG-related MS peaks occur throughout the mass range of interest (m/z 300-1000) and a particularly strong PEG peak at m/z 476 dominates the loperamide peak at m/z 477. Using FAIMS, however, the PEG and loperamide peaks are clearly distinguished and the signal-to-noise ratio over the full scan mass spectrum is improved by more than one order of magnitude.