Quality

NXPeptides Quality Assurance Standards

Quality is the foundation of everything we do at NXPeptides. When you order a peptide from us, you are trusting that what arrives at your lab is exactly what we say it is: the correct sequence, at the stated purity, in the specified quantity. We take that trust seriously, and we back it up with a comprehensive quality assurance program that spans every step from synthesis to your doorstep.

Our Quality Control Process

Every batch of peptide that ships from NXPeptides undergoes a multi-step quality control process:

Step 1: HPLC Purity Analysis

High-Performance Liquid Chromatography is our primary tool for measuring purity. Every batch is analyzed by reversed-phase HPLC using validated, standardized methods. We use C18 analytical columns with UV detection at 214 nm and gradient elution with acetonitrile/water/TFA mobile phases.

Our standard catalog products must meet a minimum purity of 98% as determined by HPLC. Batches that do not meet this threshold are either re-purified or rejected. We do not ship substandard material.

For a detailed explanation of how HPLC works in peptide analysis, see our HPLC Purification Methods guide.

Step 2: Mass Spectrometry Identity Confirmation

HPLC tells us how pure the peptide is, but mass spectrometry tells us what it is. Every batch undergoes MS analysis to confirm that the molecular weight matches the expected value for the target sequence. We use both ESI-MS and MALDI-TOF depending on the peptide.

A positive identity confirmation requires that the observed mass matches the theoretical mass within instrument specifications (typically within 0.1% or 1 Dalton for smaller peptides).

Learn more about mass spec in peptide QC in our Mass Spectrometry guide.

Step 3: Visual Inspection

Every vial is visually inspected before shipping. We check for proper lyophilized appearance (white to off-white powder), correct labeling, intact seals, and appropriate fill level. Vials that show any abnormalities are set aside for investigation.

Step 4: Documentation

All QC data is compiled into a Certificate of Analysis that accompanies every shipment. The COA includes HPLC purity data, mass spectrometry results, lot number, manufacturing date, and storage recommendations. This document serves as the quality record for your specific batch.

Additional Testing Available

Beyond our standard HPLC and MS testing, we can provide additional analytical services upon request:

Amino Acid Analysis (AAA): Determines the amino acid composition and net peptide content. Particularly useful for precise quantitative work.
Endotoxin testing: For peptides intended for cell culture or biological assays where endotoxin contamination could affect results.
Residual solvent analysis: Confirms that residual solvents from the synthesis and purification process are within acceptable limits.
Water content (Karl Fischer): Measures residual moisture in lyophilized peptides.

To request additional testing for your order, contact us at support@nxpeptides.com.

Equipment and Methods

We use modern, well-maintained analytical instruments and validated methods:

Analytical HPLC systems with UV and PDA detectors
ESI and MALDI mass spectrometers
Analytical balances calibrated to traceable standards
Controlled-environment storage (minus 20 C freezers, 2 to 8 C refrigerators) with temperature monitoring

Our methods are documented, standardized, and consistently applied across all batches. This ensures that QC results are reproducible and comparable from batch to batch.

Supply Chain Quality

Quality does not start in the QC lab. It starts with raw materials and extends through every step:

Raw material sourcing: We source amino acids, resins, and reagents from reputable suppliers with established quality track records.
Synthesis: Peptides are synthesized using optimized Fmoc solid-phase protocols with quality checks at key steps during production.
Purification: Preparative HPLC purification isolates the target peptide from synthesis impurities.
Lyophilization: Purified peptides are lyophilized under controlled conditions to produce a stable powder.
Packaging: Vials are sealed in a controlled environment to minimize moisture and oxygen exposure.
Storage: Finished products are stored at minus 20 C until they ship.
Shipping: Temperature-controlled packaging maintains cold chain integrity during transit.

Continuous Improvement

We regularly review and refine our processes. When we identify opportunities to improve quality, efficiency, or reliability, we implement changes and document them. Customer feedback is an important input to this process; if you ever notice anything that does not meet your expectations, please tell us.

Quality Guarantee

If you receive a product that does not meet the specifications stated on the Certificate of Analysis, we will replace it or issue a full refund. No questions, no hassle. See our Returns & Refund Policy for details.

All NXPeptides products are for research use only. Not for human consumption.