CEI-MS-02 — procedure

§4Procedure

The procedure below is written in the second person, which is the only place in the Institute's document set where that register is used. A procedure is an instruction and is written as one.

1. Calibrate the mass analyser across the range spanning the expected charge states. Record the calibration residual.
2. Establish the expected average mass from the molecular formula. Where the formula is not public, record "expected mass not established" and do not proceed to a mass-agreement conclusion.
3. Acquire a full-scan spectrum. Identify at least two charge states of the analyte.
4. Deconvolute across the observed charge states. Record the deconvoluted average mass and the deconvolution charge-state range used.
5. Compare against the expected mass. Record the difference in daltons and in parts per million.
6. Where the analyte belongs to a near-isobaric pair recorded in the monograph series, confirm that the instrument resolution at the relevant m/z exceeds the threshold stated for that pair, and state the resolution achieved.
7. Select the most abundant charge state as precursor and acquire a fragmentation spectrum. Assign b- and y-ions and calculate sequence coverage as the proportion of interresidue bonds represented by at least one assigned fragment.
8. Report the deconvoluted mass, the mass difference, the resolution achieved, and the sequence coverage.

References cited on this page

References are numbered in order of first citation in this document. Each superscript in the text links to its entry below.

1. International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. ICH Q2(R2) Validation of Analytical Procedures. ICH Harmonised Guideline 2023;Step 4 version, 1 November 2023. identifier not held by the Institute

Identifiers are reproduced only where the Institute holds them. Where a digital object identifier or PubMed identifier is not shown, the Institute has recorded the journal and year and has not constructed an identifier.