Protein Quality Control

Peptide Purity Analysis Service

Quantitative purity determination for synthetic peptides by RP-HPLC, MALDI-TOF MS, and ESI-MS. Instrument-generated chromatograms and mass spectra with full traceability.

RP-HPLC Purity MALDI-TOF MS ESI-MS AAA

Service Scope

Orthogonal methods for quantitative peptide purity determination

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RP-HPLC

Quantitative purity by peak area normalization; C18 column.

MS Detection

MALDI-TOF and ESI-MS for molecular weight confirmation.

AAA

Amino acid analysis for composition verification.

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Certificate of Analysis with instrument data.

Orthogonal

HPLC + MS + AAA for independent purity verification.

Raw Data

Instrument-generated chromatograms and spectra.

Traceable

Every result linked to original instrument files.

Service Details

Deliverables

Case Study

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What Is Peptide Purity Analysis?

Peptide purity refers to the amount of correct peptides in a peptide product. The quality and purity of synthetic peptides are typically checked by analytical reversed-phase high-performance chromatography (RP-HPLC), followed by mass spectrometry (MS) with ultraviolet (UV) detection at 210-220 nm. The purity of peptides is a key factor affecting the results of research projects, which has led to the widespread use of peptide purity analysis in various industries.

Common contaminants in peptide products come from chemical synthesis, culture media, or incorporation from extraction and purification processes, including peptides with deleted sequences, truncated sequences, incomplete deprotection, and by-products generated during synthesis or final cleavage. To ensure the success of various peptide experiments, it may be necessary to remove trifluoroacetic acid (TFA), or to assess the solubility of hydrophobic peptides prior to performing the desired experiment.

Creative Proteomics provides professional peptide purity determination services using analytical reversed-phase HPLC coupled with mass spectrometry. Each peptide is rigorously monitored during the analytical cycle according to documented analytical protocols, with instrument-generated data provided for full traceability.

HPLC chromatogram showing a clean peptide main peak with baseline-resolved impurities, overlaid on a laboratory analysis workspace.

Our Peptide Purity Analysis Services

Orthogonal analytical methods for quantitative purity determination, each supported by instrument-generated data. Every peptide is rigorously monitored during the analytical cycle.

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RP-HPLC Purity Analysis

Advanced reversed-phase HPLC is used to determine the purity of client peptide samples. Peptide purity is quantified by the chromatogram produced by reversed-phase HPLC, and the number and relative amount of possible by-products are determined by calculating peak area.

C18 column — standard for most synthetic peptides
Water/acetonitrile gradient — optimized for peptide hydrophobicity
UV detection — 210–220 nm for backbone amide bond absorbance
Peak area normalization — quantitative purity determination

C18 Column UV 210-220 nm

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MALDI-TOF Mass Spectrometry

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry provides rapid molecular weight confirmation to verify that the correct sequence has been synthesized. Well-suited for high-throughput batch screening and peptides above 2 kDa.

Rapid screening — molecular weight in minutes
High throughput — ideal for multi-batch analysis
Mass accuracy — ≤50 ppm under standard conditions

Method 02

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ESI Mass Spectrometry

Electrospray ionization mass spectrometry provides accurate mass measurement via direct infusion, detecting multiple charge states for multiply charged peptides. Delivers precise molecular weight determination with mass accuracy ≤10 ppm.

Accurate mass — ≤10 ppm via direct infusion
Charge state detection — resolves multiply charged peptides
Compatible with LC — on-line LC-ESI-MS for complex mixtures

Method 03

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Amino Acid Analysis (AAA)

Amino acid analysis determines the amino acid composition in peptide or protein products, ensuring experimental accuracy and consistency. An MS-orthogonal method that verifies composition at the residue level.

Composition verification — molar ratios vs. theoretical
Leu/Ile resolution — distinguishes isobaric residues
Peptide content — quantitative mg peptide / mg powder

Method 04

Common Peptide Impurities We Detect

Our expert team begins by determining what level of purity you require, or rather, which impurities can be tolerated in your application. The most common impurities include:

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Deleted sequences

Missing amino acid residues in the peptide chain due to incomplete coupling.

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Truncated sequences

Shorter peptide chains resulting from premature termination during synthesis.

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Incompletely deprotected sequences

Residual protecting groups that were not fully removed during cleavage.

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Modified sequences

Side products from protecting group reattachment during cleavage.

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Side reaction products

Asparagine formation, oxidation products, and other synthesis-related byproducts.

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TFA (Trifluoroacetic Acid)

Residual counterion from peptide cleavage and purification; affects solubility and bioactivity.

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Acetic acid

Residual acetate from buffer exchange or counterion-exchange procedures.

How Our Peptide Purity Analysis Works

A systematic process from sample receipt to data delivery, with instrument calibration and quality controls at every stage.

Sample Receipt & Assessment

Sample purity requirements and the allowable impurity profile are confirmed. Method conditions are selected based on peptide sequence and properties.

RP-HPLC Analysis

Samples are analyzed by RP-HPLC with C18 column and water/acetonitrile gradient. UV detection at 210–220 nm monitors eluting peptides.

Mass Spectrometry

Molecular weight is confirmed by MALDI-TOF MS or ESI-MS. AAA is performed as an orthogonal composition check when required.

Data Review & Report

Results are reviewed by a senior analyst. Chromatograms, mass spectra, and a Certificate of Analysis are provided as the analytical report.

Analytical Instrumentation & Data Quality

High-performance liquid chromatography and mass spectrometry instrumentation in a clean analytical laboratory.

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HPLC Systems

UV/Vis and photodiode array (PDA) detection. C18, C8, and C4 stationary phases matched to peptide hydrophobicity and length. Method conditions — column, gradient, wavelength — tailored to each peptide.

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Mass Spectrometers

MALDI-TOF for rapid molecular weight screening and high-throughput batch analysis. ESI-MS for accurate mass measurement via direct infusion, detecting multiple charge states.

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Amino Acid Analyzers

Post-column ninhydrin or pre-column derivatization-based amino acid composition analysis, providing an MS-orthogonal verification of peptide identity and content.

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Data Quality & Integrity

System suitability testing and instrument calibration before each sample sequence. Blank injections and reference standards in every analytical batch. Raw instrument files archived and provided.

Peptide Purity Analysis Deliverables

Every purity analysis project includes a complete analytical package with instrument-generated data and a summary Certificate of Analysis.

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High Quality Peptide Purity Assessment

Quantitative purity determination by RP-HPLC with peak area normalization. Purity values calculated from instrument-integrated chromatograms, not manual transcription.

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MS and HPLC Report Files

Original instrument data files (chromatograms, mass spectra) and processed results. Full traceability from reported purity values back to raw detector signals.

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Certificate of Analysis (CoA)

A summary of purity results with methods used and instrument information — suitable for documentation and publication supporting information.

Certificate of Analysis document with HPLC chromatogram and mass spectrum printouts on a laboratory desk.

For comprehensive peptide characterization beyond purity — including peptide content, counterion profiling, residual solvent analysis, and sequencing — see our peptide testing services.

Published Research

Quantification of a Peptide Standard Using Intrinsic Tyrosine Fluorescence

Journal

Anal Bioanal Chem

Year

2016

DOI

10.1007/s00216-016-9334-1

Study Overview

Preston and Phillips (Analytical and Bioanalytical Chemistry, 2016) addressed a fundamental challenge in peptide purity analysis: conventional UV absorbance-based quantification cannot distinguish the target peptide from co-eluting impurities that share the peptide backbone. They developed an orthogonal HPLC method with intrinsic tyrosine fluorescence detection (HPLC-FD_Tyr) for a synthetic 21-residue peptide standard (Cam-iT3), comparing results against traditional UV absorbance and Ellman's derivatization assay.

Analytical Methods

RP-HPLC with diode array (DAD) and fluorescence (FD) detection in series — C18 column, water/acetonitrile gradient with 0.1% formic acid.
ESI-MS and MS/MS for peptide identity confirmation and identification of co-eluting impurities in the commercial preparation.
Ellman's assay (DTNB derivatization) as an independent chemical verification of thiol content for the reduced peptide form.

Relevance to Purity Analysis

Demonstrates the value of orthogonal detection methods beyond UV absorbance for peptide purity assessment.
Shows that co-eluting impurities can confound single-wavelength UV purity determinations.
Highlights the importance of mass spectrometric identity confirmation alongside chromatographic purity.

Key Finding

The orthogonal HPLC-FD_Tyr quantification results agreed with the Ellman's assay after correction for response differences between the calibrant and analyte. The study confirmed that impurities in commercial peptide preparations complicate quantification regardless of detection method — reinforcing the need for multi-method purity assessment that combines chromatographic separation, mass spectrometric identity, and orthogonal quantification.

Publication Reference

Preston GW, Phillips DH. Quantification of a peptide standard using the intrinsic fluorescence of tyrosine. Anal Bioanal Chem. 2016;408(9):2187–2193. DOI: 10.1007/s00216-016-9334-1.

Frequently Asked Questions

How is peptide purity calculated by HPLC?expand_more

Peptide purity is quantified by peak area normalization: the area of the target peptide peak is divided by the total area of all peaks in the chromatogram, expressed as a percentage. This calculation is performed using instrument software from the UV absorbance trace at 210–220 nm, which detects the peptide backbone amide bond. The number and relative amount of possible by-products are determined from individual peak areas.

What is the difference between RP-HPLC purity and mass spectrometry?expand_more

RP-HPLC determines the percentage of the total UV-absorbing material that is your target peptide — it is a quantitative purity measurement. Mass spectrometry (MALDI-TOF or ESI-MS) provides molecular weight confirmation, verifying that the peak assigned as the target peptide has the expected mass. Together, they answer two complementary questions: "how pure is it?" and "is it the right molecule?"

What sample quantity is required for purity analysis?expand_more

For RP-HPLC purity analysis alone, approximately 1 mg of lyophilized peptide is sufficient. For a combined purity + MS identity package, we recommend 2–3 mg. For full characterization including amino acid analysis, 5 mg is recommended. Please provide the peptide sequence and any modifications (acetylation, amidation, phosphorylation, etc.) with your sample.

Can you analyze peptides with modifications or non-standard amino acids?expand_more

Yes. We routinely analyze peptides with phosphorylated residues, acetylated and amidated termini, fluorescent labels, biotin, PEG, fatty acid conjugates, D-amino acids, and cyclic peptides. Providing the complete sequence and modification details helps us select the most appropriate HPLC column, gradient, and detection wavelength for your sample.

What is included in the analytical report?expand_more

Each report includes the HPLC chromatogram with peak table and purity calculation, the mass spectrum (MALDI-TOF or ESI-MS) with observed vs. theoretical mass comparison, and a Certificate of Analysis summarizing all results. Raw instrument data files are provided alongside the processed report.