CEI-MS-10 — 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. Establish from the sequence whether the peptide is net basic or net acidic. A net acidic peptide is analysed for cations; a net basic peptide for anions.
2. Prepare a calibration series of the expected counter-ion spanning the anticipated range.
3. Dissolve a weighed sample in eluent-compatible diluent.
4. Separate and quantify. Report as a percentage of sample mass.
5. Calculate the theoretical maximum counter-ion content from the number of protonatable sites and compare. A determined value substantially above the theoretical maximum indicates free acid in the preparation rather than salt.
6. Where trifluoroacetate is found and the material is intended for cell-based work, note that trifluoroacetate is cytotoxic at the concentrations arising from unexchanged material and that an acetate exchange should be performed and documented.
7. Report counter-ion identity, content, the theoretical maximum, and whether an exchange was performed.

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. United States Pharmacopeial Convention. General Chapter ⟨1225⟩ Validation of Compendial Procedures. United States Pharmacopeia — National Formulary (USP–NF) 2024;USP 2024 Issue 1. 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.