Charge-based selectivity to resolve variants that can be difficult in RP-HPLC (GLP / ISO 13485 aligned, non-GMP).

IEX separates peptides by net charge at a selected pH. It is especially useful when the target and key impurities behave similarly in RP, or when charge variants are the primary risk.

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When to use Selectivity levers Pairing with RP Deliverables Related pages

When IEX is the right choice

Best fit

• Charge variants and terminal heterogeneity
• Impurities that co-elute in RP-HPLC
• Peptides where pH control changes selectivity

What IEX is not

• Not always ideal as a single-step “final purity” method
• Often best as pre-fractionation or orthogonal step

Key selectivity levers in IEX

pH selection

Controls peptide charge state and binding strength.

Salt gradient

Tuned to elute target away from charge-similar impurities.

Resin chemistry

Cation vs anion exchange based on peptide net charge behavior.

Common pairing strategy: IEX → RP-HPLC

A frequent high-success workflow is to use IEX to reduce mixture complexity and separate charge-driven variants, then use RP-HPLC to “polish” purity and improve hydrophobicity-based resolution.

• IEX: charge-based separation and pre-fractionation
• RP: final selectivity and purity confirmation

Deliverables

• Analytical HPLC chromatograms + purity assessment
• MS identity verification (as scoped)
• COA + supporting data package

Non-GMP: GLP / ISO 13485 aligned workflows. GMP manufacturing is not offered.

Related purification pages

RP-HPLC HILIC Desalting / SEC COA & QC Purification Overview