Liquid chromatography-mass spectrometry: difference between revisions
Diff·revision 8 → 9·18:12, 10 Jan 2025
Difference between revision 8 and revision 9 of Liquid chromatography-mass spectrometry. 6 lines changed; the page grew by 673 bytes.
| Revision 8 — 05:03, 24 Dec 2024 AnalyticalAnnie (talk) add the figure for the chromatogram and caption its axes 2,642 bytes ±0 | Revision 9 — 18:12, 10 Jan 2025 NauseaNoor (talk) clarify the difference between related substances and total impurities 3,315 bytes +673 | ||
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| 1 | {{Infobox method | 1 | {{Infobox method |
| 2 | | name = Liquid chromatography-mass spectrometry | 2 | | name = Liquid chromatography-mass spectrometry |
| + | 3 | | subtitle = Hyphenated technique | |
| 3 | | Abbreviation = LC-MS | 4 | | Abbreviation = LC-MS |
| 4 | | Combines = Chromatographic separation and mass detection | 5 | | Combines = Chromatographic separation and mass detection |
| ⋮ | ⋮ | ||
| 19 | 20 | ||
| 20 | Tandem operation — selecting a precursor, fragmenting it, and measuring the fragments — adds sequence information and can locate a modification to a residue rather than merely detecting it.{{r|aebersold2003}} | 21 | Tandem operation — selecting a precursor, fragmenting it, and measuring the fragments — adds sequence information and can locate a modification to a residue rather than merely detecting it.{{r|aebersold2003}} |
| + | 22 | ||
| + | 23 | == Quantification == | |
| + | 24 | LC-MS is not inherently quantitative: ionisation efficiency varies by orders of magnitude between species and with what else is eluting. Quantification requires calibration against a standard of the same substance, ideally with an isotopically labelled internal standard.{{r|aebersold2003}} | |
| + | 25 | ||
| + | 26 | This is why a purity figure is normally reported from ultraviolet detection rather than from mass detection: ultraviolet response at 214 nm is roughly proportional to the number of peptide bonds and is therefore a reasonable proxy for mass across related peptides, whereas mass-spectrometric response is not.{{r|usp1503}} | |
| 21 | 27 | ||
| 22 | == References == | 28 | == References == |