All GenScript peptides undergo Total Quality Management testing, including mass spectrometry and analytical high performance liquid chromatography (HPLC) analysis throughout the peptide synthesis and purification processes. These analyses are normally sufficient for custom peptide applications. However, peptides to be used in certain types of assays may require additional peptide analysis. For instance, peptides used in cellular assays or manufactured products may require TFA exchange or endotoxin control services. Hydrophobic peptides may require solubility testing. Click on a service below to learn more and to request a quote for your custom peptide and Accupep QC+ customized service.

Quick Reference AccuPep+QC Chart

Test Description
When to Request

Solubility Test

Qualitative solubility test Free: Genscript offers you qualitative test results for up to 3 solvents (default are Ultrapure water, 1 x DPBS(pH 7.1±0.1), DMSO) for free.

Quantitative solubility test New: Customized solvents are available and specified quantitative test report (the highest gross peptide concentration can be achieved) will be included.

Recommended for:
hydrophobic peptides > 5 AA long, and
containing >50%:

  • Tryptophan
  • Isoleucine
  • Leucine
  • Phenylalanine
  • Methionine
  • Valine
  • Tyrosine

TFA Exchange Service

TFA is often used in the final cleavage of custom peptides from the solid support. Hence, traces of TFA may be left behind in the final peptide preparation, even after purification. Ion exchange chromatography is used to separate and quantify TFA.

Recommended for:
peptides that will be used in:

  • cellular assays
  • API formulations
  • manufactured products

Counter Ion Quantification Analysis*

Counter ions used in the synthesis process such as acetate, hydrochloride, or trifluoacetate (TFA) may be present in your peptide preparation. Ion exchange chromatography is used to separate and quantify the various amounts of counter ions in the preparation.

Bundle with TFA Counter-ion Exchange for:
peptides that will be used in:

  • cellular assays
  • API formulations
  • manufactured products

Amino Acid Analysis*

Peptide is hydrolyzed under acid conditions into free, individual amino acid residues. Following derivation, reversed-phase liquid chromatography is used to separate the amino acid derivatives, followed by UV-detection and quantification.

Request this test:
1). to determine the amino acid composition in the peptide preparation.
2). to determine the precise amount of the net peptide in the preparation to ensure experimental accuracy and consistency.§

Peptide Content Analysis/Nitrogen Analysis*

Peptide content analysis involves quantifying the amount of elemental nitrogen in the gross peptide preparation.The amount of target peptide in the preparation is calculated using molar ratios.

Request this test to determine the precise amount of the net peptide in the gross peptide preparation to ensure experimental accuracy and consistency.§

Endotoxin Control & Analysis

Endotoxin, which can form throughout the process of peptide synthesis, can decrease cell viability or cause an immune response. Our endotoxin control service guarantees endotoxin levels in your custom peptide prep to be ≤ 0.01 EU/µg in order to improve your experimental results.

Recommended for peptides used in:

  • Cellular assays
  • Immunotherapy
  • Active pharmaceutical ingredients (APIs)

Moisture Content Analysis*

Even after lyophilization, water may still be present in a peptide preparation. The amount of water left behind depends on the hygroscopic nature of the peptide. Normally, hydrophilic peptides will retain the most water. Moisture content is determined by the Karl Fischer Titration method.

Water % contributes to the gross weight of the peptide preparation and may vary from batch to batch of the same peptide. It is important to know the exact amount of your target peptide in the gross peptide preparation to limit variability in results between batches of the same peptide.

Request this test to ensure precise dilution of your peptide to your desired stock concentration, which will limit batch to batch variability between different lots of the same peptide.

pH Test

Peptide is dissolved in water (additional solvents may be added in case of hydrophobic custom peptides) and a pH meter is used to determine the pH value of the peptide.

Acids (e.g. TFA) used during peptide synthesis can form salts with amino groups on side chains or the amino terminus of your peptide causing the pH of the preparation to become acidic. Low pH can interfere with assay results.

Request this test to ensure that your peptide preparation has your desired pH value.

NMR analysis

NMR is mainly based on a physical phenomenon, nuclear magnetic resonance (NMR) of atomic nucleus either to determine the purity and impurities of peptide samples or to characterize impurities, through the carbon spectrum and hydrogen spectroscopy
NMR is usually used for microcosmic physicochemical properties testing of peptides, and the carbon or hydrogen spectrum is provided for the determination of purity and impurities in peptides.

Request this test to determine the primary structure and the components of impurities in peptides.


LC-MS is used for the components analyses of peptide samples, which can measure molecular weight online of all peptide components.

Request this test for real-time characterization of the peptide components in peptide samples, which is commonly applied to confirm the target HPLC peak or the analysis of isomers.

Stability test

This test is used for the stability test of peptide samples under requested solvents. HPLC and MS characterization reports of peptide solution over a sustained period of time will be provided.

Request this test to compare the stability of peptide in different environments.

Peptide Sequencing

N-terminal amino acid of peptide samples is degraded step-by-step by Edman degradation method, and then separated and identified by HPLC. The whole N-terminal amino acid sequence of peptide is tested.determined.

Request this test to determine the primary structure of peptide samples.

Specific opticalrotation

The plane-polarized light would be rotated through the peptide solution if the peptide containing asymmetric carbon atoms, and the specific optical rotation is the measured value of the optical rotation.

Request this test to determine the optical activity and purity of peptides especially containing chiral amino acids.


HPLC-UV-fluorescence detection is beneficial for the detection of peptides containing fluorescence adsorption group, which provides more sensitive and specific signals than single UV detector.

Request this test for the purity or concentration determinations of peptide samples containing fluorescence adsorption groups(such as FITC, AMC, FAM, DABCYL, TMR and so on)


* Use the results of these tests to perform a mass balance calculation (% Target Peptide + % Peptidic Impurities + % Counter ion + % Water = 100%) to ensure that all peptide preparation components have been accounted for.

§ Net peptide refers to the combined fractions of the target peptide and peptidic impurities (i.e. deletion peptides). Counter ions and water are not considered part of the net peptide content. The amount of the target peptide is calculated by the multiplication of gross weight x net peptide content x HPLC purity.



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