Purification¶

TL;DR¶

Preparative HPLC is the standard method for peptide purification to ≥98% purity. Method development focuses on gradient selection, column choice, and fraction screening by analytical HPLC.

Why Peptides Need Purification¶

Crude peptide from SPPS typically contains: - Target peptide (60–85%) - Deletion sequences (missing one or more amino acids) - Truncated sequences (incomplete synthesis) - Scavenger residues from cleavage - Salts and organic impurities

Preparative HPLC Method¶

Column Selection¶

Parameter	Research Scale	Process Scale
Column ID	10–30 mm	50–200 mm
Particle size	5–10 μm	10–30 μm
Stationary phase	C18 (most common), C8, C4	C18
Length	150–250 mm	250–300 mm

Mobile Phase¶

Phase	Typical Composition
A (aqueous)	0.05–0.1% TFA in water
B (organic)	0.05–0.1% TFA in acetonitrile
Alternative A	0.1% formic acid or 20 mM NH₄HCO₃
Alternative B	Methanol or isopropanol

Gradient Profile (Typical)¶

Time	%B	Event
0–5 min	5–10%	Equilibration/loading
5–30 min	10–50%	Linear gradient
30–35 min	50–95%	Column wash
35–45 min	95–5%	Re-equilibration

Purification Process¶

flowchart LR
    A[Crude Peptide] --> B[Dissolve in<br/>Mobile Phase A];
    B --> C[Filter<br/>0.45 μm];
    C --> D[Inject onto<br/>Prep Column];
    D --> E[Gradient Elution];
    E --> F[UV Detection<br/>214/254 nm];
    F --> G[Fraction Collection];
    G --> H[Analytical QC<br/>of Fractions];
    H --> I{>98% Purity?};
    I -->|Yes| J[Pool & Lyophilize];
    I -->|No| K[Re-purify or Discard];

Key Parameters¶

Loading Capacity¶

Column Size	Maximum Load (crude)
10 mm ID	5–20 mg
20 mm ID	20–100 mg
30 mm ID	100–500 mg
50 mm ID	0.5–2 g
100 mm ID	2–10 g

Detection Wavelengths¶

214 nm: Peptide bond absorption (most sensitive)
254 nm: Aromatic residues (Phe, Tyr, Trp)
280 nm: Tyr and Trp

Flow Rate¶

Column ID	Flow Rate
10 mm	3–5 mL/min
20 mm	10–20 mL/min
30 mm	20–40 mL/min
50 mm	60–120 mL/min

Common Challenges¶

Issue	Cause	Solution
Poor resolution	Shallow gradient too fast	Extend gradient or adjust slope
Peak tailing	Column overload	Reduce load or use larger column
Multiple peaks	Deletion sequences	Optimize SPPS synthesis
Low recovery	Peptide precipitation	Add co-solvent or adjust pH

Alternative Purification Methods¶

Method	Use Case
Ion exchange	Charged peptides, removal of TFA counter-ion
Size exclusion	Desalting, buffer exchange
Flash C18	Fast initial purification
Reversed-phase	Industry standard for most peptides

Preparative HPLC for Peptide Purification — Review the section above for key parameters, methods, and quality criteria.
Why Peptides Need Purification — See the section for detailed parameters and specifications.
Preparative HPLC Method — Review the section above for key parameters, methods, and quality criteria.
Purification Process — Review the section above for key parameters, methods, and quality criteria.

🔗 Related: SPPS Process | Preparative HPLC System | HPLC Analysis | LC-MS Testing | Peptide Quality Control Guide

Key Takeaways¶

Why Peptides Need Purification — See the section above for detailed parameters and specifications.
Preparative HPLC Method — Review the section above for key parameters, methods, and quality criteria.
Purification Process — Review the section above for key parameters, methods, and quality criteria.
Key Parameters — Review the section above for key parameters, methods, and quality criteria.