On Jul 05, 2011 Anneli Kruve defended her PhD thesis Matrix effects in liquid-chromatography electrospray mass-spectrometry (LC-ESI-MS) at the Institute of Chemistry, University of Tartu.

Electrospray ionization (ESI, ESI ion source) is currently the most popular ionization mode in LC-MS (Liquid chromatography mass spectrometry, LCMS). LC-ESI-MS has become the premier technique for a large number of different analytical tasks, ranging form pesticides determination in fruit and vegetables to drug residues in sewage sludge. However, a major drawback of LS-ESI-MS is the so-called matrix effect – ionization suppression or enhancement of the analyte of interest by other compounds present in the sample and co-eluting with the analyte (see here for the definition of matrix effect). The matrix effect, if present, can cause large uncertainties in quantification using the LC-ESI-MS technique.

The thesis presents four original approaches for combating the LC-MS matrix effect developed by Anneli:
1. Extrapolative dilution;
2. Multilinear (PLS) calibration using background ions;
3. Taking matrix effect into account in measurement uncertainty of the analysis result;
4. Reducing matrix effects by optimization of ESI-MS parameters.

The first two approaches are essentially approaches for correcting for matrix effect. The third approach permits accounting for matrix effect via measurement uncertainty. The last one is about reducing matrix effect. These approaches, together with an investigation of the effect of sample preparation on ESI MS matrix effect and a comprehensive overview of LC-ESI-MS matrix effect in the introduction part make this thesis a genuine “LC-ESI-MS Matrix Effect Toolbox” for practitioners.

If you wish to read the above cited articles but do not have online access, please contact us.

(Sometimes the term matrix effect is used synonymously to “matrix suppression”. This is incorrect: matrix effect can sometimes also mean matrix enhancement. Sometimes the ESI-MS matrix effect is termed simply as MS matrix effect. These terms are not synonymous, as different effects are inherent in different ion sources.)
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