A homologous series of internal standards for near universal application in the discovery LC-MS/MS bioanalytical laboratory

Abstract

When using Liquid Chromatography-Tandem Mass Spectrometry (LC–MS/MS) to quantify In Vivo samples, an internal standard (ISTD) is key in correcting for variability within the sample extraction process and injection volume. Just as important is the ability of the internal standard to identify any matrix effects, which can artificially suppress or enhance the signal of the compound of interest. To properly do this, the internal standard should co-elute with the compound. A common source of potential matrix effects with In Vivo studies is from the excipient(s) used to formulate the compound for dosing. In the world of high-throughput discovery bioanalysis, a lab can quantitate over a hundred compounds each week, many of which are evaluated once, and rarely is a stable-isotope labeled (SIL) internal standard available (the industry gold standard). Finding a suitable and easy-to-use alternative LC–MS/MS method is important to providing high quality data. To overcome this challenge, a homologous series of compounds was synthesized to improve the chromatographic range for co-eluting ISTD’s. This novel mix of internal standards was shown to have key characteristics making it ideal for use as a near universal internal standard mix including but not limited to: they ionize in both positive and negative modes, they are susceptible to signal perturbation from common formulation excipients, and they cover a wide range of retention times.