Publications

In our experience, we have found a significant number of situations that force us to have to QC a much greater percentage of our LC/MS UV, ELSD compound QC results than we feel should be really necessary. This oftentimes means a 100% QC. Some of the reasons are summarized as: Target(s) Found (Green) but the purity or concentration of the sample being too low to be of practical usage. Targets found but eluting in a region of significant level impurities and therefore more challenging for auto-purification. Targets eluting within the solvent front or end of the chromatographic run typically with poor integration. Targets being poorly classified as found, maybe or not found due to challenges in the signal processing, baselining, peak integration, MS peak classification, poor assignment of adducts and so on. The major issue of course, was that we were not really sure to what level these issues were prevalent or were causing us to over QC results. To better understand these effects we have undertaken a relatively large scale review of our results to determine where most of the problem situation occurs and to remedy as many as possible. We were also looking to increase the trust we have our processing and to be able to trap those situations where an analyst needs to make an informed decision and communicate this effectively. This presentation summarizes some of our finding and how we have attempted to solve these issues.

Previously, within our research and services as a Clinical Research Organization we were constantly challenged with how to accurately and reliably determine the presence or absence of target substances within minimal analyst intervention. Most of these types of studies were in support of our customers performing corporate library management, support for synthetic chemists and process chemistry. While the principle and acquisition of the typical array of LC/MS, UV, ELSD and/or CLND data is relatively simple, our experience shows that reliable analysis across vendors, instruments, analytical methods and sample types creates a more intractable challenge. In the process of analyzing running millions of samples, we found a number of areas that were cause for deeper evaluation as follows: Baseline accuracy – affecting directly the integration accuracy which in turn affects area under the curve calculations (AUC) used for both purity and concentration calculations. Spectral analysis and characterization issues which often led to incorrectly assigned adducts and ionized molecules. Issues with accurate analysis and differentiation of real peaks and noise. Quantitation calculation flexibility to deal with single and multiple zone mobile phase correction and calibration. Ability to quickly find those samples which had deeper hidden issues that would actually affect the final results. For example just because a well in a microtitre plate was colored green, often did not signify that the sample was free of issues. This could be for multiple reasons including: inconclusive peak analysis for potential isomeric compounds eluting as multiple peaks. Low level extracted mass chromatograms with low signal and/or low signal to noise. Challenging elution profiles of the target substance say within a narrow time window of the major impurities where a more select purification methodology was needed. Our research and this presentation details how we approached many of these issues and brought them together into a practical application for our and other analysts. Our expectation of this poster presentation is to gather additional insights through discussion, into the issues that have been faced by other researchers in this area, how they have been solved and what additional areas of challenge remain.