Need to Improve Database Scoring for LC/MS Metabolomics? Try ACQUITY PREMIER Columns!
After another wrong assignment, I knew there had to be a better way to improve my database matching! Spectral library matching is an integral component in the workflow of untargeted, or high resolution mass spectrometry, analyses such as urine or plasma metabolomics. The comparison of non-disease and disease state samples can give insights to potential biological pathways that are important in disease progression. Scientists are then able to focus on these areas for potential new therapies and/or diagnostic tests. However, to identify these metabolites, we subject our data to database searches. There are several commercial databases for purchase; some with curated spectra and others with structures subject to theoretical fragmentation within software. An important factor in library matching is the quality of the data you are matching from your analysis. Too few or too many peaks relative to the reference can impact your score negatively. The implication for incorrect assignments means you could be barking up the wrong tree and miss a critical clue.
Let’s look at citric acid. It is present in cells as part of the Tricarboxylic acid (TCA) cycle. Citric acid is well-known for interacting with metals, most notably, iron. The presence of iron in the system can be problematic by causing loss of analyte or adducts in the mass spectrum. With the PREMIER class of columns, we are able to mitigate the interaction of these compounds with metals. Figure 1 shows the high energy (or fragmentation) spectra of citric acid from a diluted human urine sample as analyzed on a column in standard hardware (top), and one with PREMIER hardware (bottom). Immediately we see the difference in the spectra where the PREMIER column presents a cleaner and less complicated spectrum. Notably, we see much less of the known Fe-Citrate complex, 435.9 m/z , using the PREMIER column. This translates to higher fragmentation scores when searching a spectrum library (Figure 2) and certainly makes your life easier in the lab.
Challenging analyses such as these make it a no brainer to switch to PREMIER.
Silva A et al. Dalton Transactions. 2009(40), 8616-8625
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