Sample preparation
Dissolve a known mass in a known volume of LC-grade water or buffer; centrifuge to remove particulates; inject a fixed volume to keep peak area comparable across runs.
Method selection
Reverse-phase C18 gradient with TFA or formic acid modifier is the default. For very hydrophilic or charged peptides, HILIC may resolve better.
Reporting
Include method parameters, system suitability, the chromatogram itself, the integration table, and the calculated purity percentage. Sign and date the report.
Frequently asked questions
What modifier should I use — TFA or formic acid?+
TFA gives sharper peaks but suppresses ESI; formic acid is friendlier for LC-MS.