Reading a Certificate of Analysis: What Every Number Means

A Certificate of Analysis (COA) is the batch-specific quality record for a research peptide — documenting identity (mass spectrometry), purity (HPLC), water content (Karl Fischer), bacterial endotoxin level, and batch traceability. Reading one properly is the single most important quality-verification skill a researcher can develop.

Research Highlights

Six fields define a real COA: Identity (MS), purity (HPLC ≥99%), water content (Karl Fischer), endotoxin (for in vivo), batch / lot number matching the vial, and named third-party lab with credentials.
Three immediate red flags: missing batch number, undated testing, or generic “professional testing” without a named lab — any one of these makes the COA insufficient.
Match-then-trust: Always confirm the batch number on the COA matches the vial before opening or reconstituting the peptide.

A Certificate of Analysis lands in your email inbox. It’s a PDF, dense with technical language, graphs, and numbers. You know it matters—it’s supposed to prove your research peptide is what you paid for. But decoding it feels like reading a foreign language.

This guide removes that friction.

A COA isn’t bureaucratic overhead. It’s the most detailed record you’ll ever receive about your peptide’s identity, purity, and manufacturing history. Understanding how to read it—what the numbers mean, what each section reveals, and which red flags demand attention—transforms it from a confusing document into your most powerful quality verification tool.

By the end of this article, you’ll know exactly what every section of a COA tells you, how to spot problems, and what separates a thorough COA from one that hides gaps in testing.

What Is a Certificate of Analysis? (And Why It Matters)

A Certificate of Analysis is a formal analytical report documenting the chemical, physical, and microbiological properties of a specific batch of product.

For research peptides, a COA serves three critical functions:

1. Proof of Identity
It confirms that the batch contains the peptide you ordered—not a different sequence, not a degradation product, not a manufacturing error. Mass spectrometry data proves the molecular weight matches your target peptide.

2. Quantification of Purity
It measures exactly how much of your sample is the target molecule (expressed as a percentage) and identifies what the remaining percentage consists of. This is done through HPLC peak analysis.

3. Documentation of Manufacturing Safety
It provides data on endotoxin levels, microbial contamination, and other safety parameters. This matters because contamination can invalidate research results or create other complications.

The COA is also a legal document. It’s a supplier’s formal claim about what they’re delivering. If the batch later proves deficient, the COA becomes evidence of whether the supplier delivered as promised.

In a market where regulations are loose and supplier standards vary wildly, a COA is often your only objective measure of what you actually received.

Key Takeaway: A COA Is Identity Proof + Purity Data + Safety Verification

A COA doesn’t just say “high quality.” It documents exactly how quality was measured, what was found, and traces each result back to a specific batch and testing date.

Anatomy of a Certificate of Analysis: Section by Section

A comprehensive COA includes multiple sections. Understanding each one prevents misinterpretation and reveals where suppliers cut corners.

Section 1: Header and Sample Identification

At the top of any COA, you’ll find:

Product Name: This should match exactly what you ordered. “Peptide XYZ [2-45]” not just “Peptide XYZ.” The bracketed numbers indicate the amino acid range and are critical to identity.

Lot/Batch Number: A unique identifier linking this COA to your specific shipment. This is non-negotiable. If the COA doesn’t include a lot number, or if the lot number doesn’t match your invoice, the data isn’t traceable to your batch.

Date of Analysis: When the testing was performed. A recent date (within 2 weeks of shipment) suggests the batch was tested immediately after synthesis. An old date (6+ months before shipping) raises questions: Was the peptide stored under proper conditions? Was it re-tested? If not, why not?

Testing Facility: The name and, ideally, the location of the lab that performed the analysis. A specific lab name (e.g., “Phoenix Analytical Laboratories, Tempe AZ”) is better than a vague “third-party testing facility.” You should be able to verify that the lab exists and has experience with peptides.

Manufacturer/Synthesis Facility: Which lab synthesized the peptide. If this section is blank or vague, you’re missing critical traceability data.

Section 2: Description of Product (Theoretical Properties)

This section lists the theoretical specifications—what the peptide should be, mathematically, before any real-world testing.

Molecular Formula: The exact atomic composition (e.g., C₁₂₅H₂₀₁N₃₀O₄₉S₁). This is calculated from the amino acid sequence and any post-synthesis modifications. It rarely changes between batches.

Theoretical Molecular Weight: Calculated from the molecular formula. For a peptide with sequence MVHLTPEEKS, the theoretical MW is calculated to high precision. The observed MW (from mass spectrometry) should match this number very closely—within 0.01-0.02% for peptides under 5 kDa.

Amino Acid Sequence: The exact order of amino acids. This must be identical to your order specification. If it differs by even one amino acid, it’s a different peptide—not a purity issue, but an identity failure.

Purity Grade Specification: Some suppliers list target purity ranges here (e.g., “Research Grade: 95%+ purity”). This is the claim the actual testing will verify.

Key Takeaway: The Header and Specification Sections Are Your Traceability Anchors

Before you look at any testing data, verify that the lot number matches your batch, the sequence matches your order, and the testing date is recent. If any of these are missing or inconsistent, stop. Contact your supplier. The testing data is meaningless without traceability.

Section 3: Identity Testing (Mass Spectrometry)

Mass spectrometry (MS) is the most direct way to prove you have the right molecule.

Method: Look for “MALDI-TOF MS,” “ESI-MS,” “Q-TOF MS,” or similar. The method type affects precision, but all modern approaches can confirm peptide identity accurately. Avoid suppliers relying only on HPLC (which measures purity, not identity) without MS.

Observed Molecular Weight: The actual molecular weight measured by the mass spectrometer. This is your proof-of-identity benchmark.

Theoretical Molecular Weight: Calculated from the amino acid sequence. The observed and theoretical values should match.

Percent Difference: Calculated as:

((Observed MW - Theoretical MW) / Theoretical MW) × 100

Acceptable ranges:
– Peptides <5 kDa: Within ±0.01% (e.g., theoretical 2,150 Da, observed 2,150.10 Da is acceptable)
– Peptides 5-10 kDa: Within ±0.02%
– Larger peptides: Within ±0.05%

If the observed MW differs from theoretical by more than these tolerances, it indicates a synthesis error, degradation, or modification that wasn’t disclosed.

Example of a Good MS Result:

Theoretical MW: 2,149.87 Da
Observed MW: 2,149.95 Da
Difference: +0.037% ✓ ACCEPTABLE

Example of a Red Flag:

Theoretical MW: 2,149.87 Da
Observed MW: 2,135.42 Da
Difference: -0.66% ✗ PROBLEM

The large discrepancy suggests the peptide is missing a portion (possibly a degradation or synthesis failure). This batch should be rejected.

Section 4: Purity Analysis (HPLC)

This is the most commonly cited section: the purity percentage.

Testing Method: Should state “Reverse-Phase HPLC” or “RP-HPLC” with specific technical details:
– Column type and dimensions (e.g., “Phenomenex Luna C18, 5 μm, 250×4.6 mm”)
– Detection wavelength (e.g., “214 nm”)
– Mobile phase composition (e.g., “Acetonitrile/water gradient with 0.1% TFA”)
– Flow rate (e.g., “1.0 mL/min”)
– Column temperature (e.g., “25°C”)

These details matter because they determine which impurities are separated and detected. A different column or wavelength might miss certain contaminants.

Chromatogram: A graph showing peaks plotted over time (retention time on the x-axis, UV absorbance on the y-axis). The largest peak is your target peptide. Smaller peaks are impurities.

What a good chromatogram looks like:
– One dominant peak (your peptide) accounting for 95%+ of the total area
– Smaller, clearly distinct impurity peaks scattered across the trace
– Clean baseline with minimal noise

Red flags in a poor chromatogram:
– Multiple peaks of similar height (suggests degradation or synthesis impurity)
– Many small peaks scattered throughout (degradation or synthetic byproducts)
– Tall baseline noise (poor sample preparation or equipment malfunction)
– No clear separation between the main peak and impurities

Purity Percentage: Expressed as “Purity by HPLC: 99.2%” or similar. This is calculated as:

(Area of main peak / Total area of all peaks) × 100 = Purity %

Interpretation:
– 95-97%: Acceptable research grade, suitable for preliminary studies
– 98-99%: High purity, suitable for binding studies and detailed mechanism work
– 99%+: Premium grade, suitable for advanced biophysical characterization

Note: HPLC purity is specific to UV-detectable components. Non-UV-active contaminants (salts, some organic solvents) won’t be detected by HPLC alone. This is why mass spectrometry is essential—it catches identity problems that HPLC purity numbers might miss.

Impurity Table: A breakdown of individual impurities by retention time and percentage.

Example:

Main Peak (Retention time 12.3 min): 99.2%
Impurity A (Rt 8.1 min): 0.4%
Impurity B (Rt 14.6 min): 0.2%
Other peaks (<0.1% each): 0.2%
Total: 100%

What this tells you:
– The identity of each impurity (by retention time) is documented
– You can see if the same impurities appear in every batch (manufacturing consistency) or if they vary (quality control issues)
– Large single impurities (>1%) suggest synthesis or degradation problems
– Multiple tiny impurities (<0.1% each) suggest normal manufacturing variation

Key Takeaway: HPLC Purity Is Your Main Quality Metric, But It’s Incomplete Without MS

A 99% HPLC purity number proves cleanliness, but mass spectrometry proves you have the right molecule. Together, they answer: “Is this pure AND correct?”

Section 5: Endotoxin Testing

Endotoxins are pyrogens—heat-stable lipopolysaccharides from gram-negative bacterial cell walls. Even in trace amounts, they can cause fever, inflammation, and invalidate sensitive research.

Method: Usually “Limulus Amebocyte Lysate (LAL) Assay” or “Gel-Clot LAL.” These tests detect endotoxins at the parts-per-billion level.

Threshold: Most research labs expect <1 EU/mL (Endotoxin Units per milliliter). Some sensitive applications demand <0.5 EU/mL or <0.25 EU/mL.

Result: Should state a specific number or “Negative” (below detection limit).

Example:

Endotoxin Content: <0.5 EU/mL ✓ GOOD
Endotoxin Content: 2.3 EU/mL ✗ PROBLEM (High for research use)

If a COA claims the peptide is endotoxin-free but doesn’t specify the detection limit, it’s incomplete. “Negative” isn’t informative—you need to know the limit of detection.

Section 6: Sterility Testing

This section confirms the batch has no viable microorganisms (bacteria, fungi).

Method: “Membrane Filtration” or “Direct Inoculation” per USP <71>.

Result: Should state “Negative for microbial growth” or “No growth detected.”

Note: Sterility testing takes 14+ days to complete (microorganisms grow slowly in culture). If a COA was dated 2 days ago but includes sterility results, something’s wrong—either the date is incorrect, or the test was conducted in advance and released before confirmation.

Key Takeaway: Endotoxin and Sterility Data Prevent Contamination Problems

These tests aren’t always required, but they prevent silent contamination from invalidating your research. Premium suppliers include them as standard; others only test when asked.

Section 7: Physical Characterization

Additional properties that affect usability and stability.

Appearance: What the dried peptide looks like. “White powder,” “off-white solid,” “crystalline powder.” Discoloration (brown, yellow) can indicate oxidation or degradation.

pH (if applicable): For solutions or lyophilized products reconstituted with specific buffers. Should be within a narrow range. Deviation suggests improper storage or contamination.

Moisture Content: Percentage of water in the dried peptide (if lyophilized). Most research peptides should be <5% moisture. High moisture accelerates degradation.

Loss on Drying (LOD): Similar to moisture content; expressed as weight loss when the sample is heated under specific conditions.

Section 8: Batch Traceability and Storage Information

Batch/Lot Number Cross-Reference: Confirmation that the batch number in the header matches manufacturing records.

Manufacturing Date: When the peptide was synthesized.

Storage Conditions: Recommended storage (e.g., “2-8°C in amber vial, protect from light”).

Shelf Life/Expiration: How long the peptide remains stable under recommended conditions. Research-grade peptides typically have 1-3 year shelf lives.

Stability Data (if available): Some premium suppliers include data showing how purity changes over time under various storage conditions.

Key Takeaway: Traceability Data Connects Your Batch to Manufacturing Records

A COA without batch traceability is disconnected from the actual product. Always verify that your lot number matches the COA lot number and that both match your invoice.

What “99% Purity” Actually Means (The Full Picture)

A common misconception: “99% purity” means the sample is 99% pure. The reality is more nuanced.

HPLC-measured purity tells you that 99% of the UV-detectable compounds in the sample are the main peak (your target peptide). It doesn’t detect:
– Non-UV-active salts or buffers
– Residual solvents that don’t absorb at 214nm or 280nm
– Some synthetic byproducts without chromophores

HPLC + MS measured purity adds identity confirmation: the main peak’s molecular weight matches the target, proving it’s the right molecule, not an impurity masquerading as it.

Combined interpretation: When a COA shows HPLC purity of 99.2% AND mass spec confirmation of correct molecular weight, you have high confidence that the sample is 99.2% of your target peptide, with 0.8% being various impurities and degradation products.

This is the gold standard for research peptides.

Reading HPLC Chromatogram Results: The Visual Language

An HPLC chromatogram is a line graph. Learning to read it helps you spot quality issues that purity percentages alone don’t reveal.

Peak Anatomy

Each peak represents a compound exiting the HPLC column. The x-axis is retention time (minutes). The y-axis is UV absorbance (measured in millivolts, mV).

Peak Area: The area under the peak (integral). This is what’s used to calculate purity percentages. Larger area = more of that compound.

Peak Height: The maximum absorbance value. This is less useful for quantification (two peaks with the same area can have different heights) but is used visually to assess signal quality.

Peak Shape: An ideal peak is smooth and symmetrical, rising to a point and descending smoothly. A peak with a shoulder (extra bump on one side) or a split main peak suggests:
– Isomers (different structural forms of the same molecule)
– Incomplete separation of similar compounds
– Degradation products chemically similar to the target

Interpreting a Complex Chromatogram

A complex example:

Retention Time    Compound           Area        % of Total
8.1 min          Impurity A         500 mV·s    0.3%
10.5 min         Unknown            400 mV·s    0.2%
12.3 min         Main Peak (Target) 165,800 mV·s 99.2%
14.7 min         Impurity B         350 mV·s    0.2%
16.2 min         Unknown            100 mV·s    0.1%
                                    TOTAL:      100%

What this tells you:
– The target peptide is dominant (99.2%)
– Impurities are diverse (different retention times) and small—suggesting normal manufacturing variation, not a major synthesis problem
– No single impurity dominates
– The profile appears realistic for a high-quality batch

Compare this to a red flag profile:

Retention Time    Compound           Area        % of Total
12.1 min         Possible Degraded Form 15,000 mV·s  8.5%
12.3 min         Main Peak (Target) 165,800 mV·s 91.5%
                                    TOTAL:      100%

What this tells you:
– The main peak is lower than ideal (91.5% vs. 99.2%)
– A significant impurity at nearly the same retention time suggests a closely-related degradation product
– This could indicate storage stress, synthesis issues, or age

Key Takeaway: The Chromatogram Shows You What Impurities Are Present

A single purity number (99%) is incomplete without the chromatogram. The chromatogram reveals the quality of those impurities and whether they suggest degradation, synthesis problems, or normal variation.

Contaminant and Degradation Peaks: What They Signal

Not all impurities are equal. Understanding what they represent helps you assess whether a batch is usable for your research.

Synthesis Residues

Byproducts created during the chemical synthesis of the peptide.

Examples:
– Truncated peptides (missing one or more amino acids)
– N-terminal or C-terminal protected forms (protecting groups incompletely removed)
– Diketopiperazines (a cyclic dimer formed when two amino acids bond instead of the full sequence)

Signature: These typically appear as distinct peaks at different retention times than the target. They often represent 1-5% of the total.

Assessment: Some synthesis residue is normal. If synthesis residues exceed 5-10% of the total, it suggests poor synthesis conditions (temperature, pH, reagent quality) or inadequate purification.

Oxidation Products

Peptides containing methionine or tryptophan are susceptible to oxidation. The sulfur in methionine is especially reactive with atmospheric oxygen.

Signature: Oxidized methionine appears as a peak at a slightly different retention time (often slightly later, as oxidized forms are slightly more polar). It’s typically 0.5-3% of the total if present.

Assessment: Small amounts of oxidation (0.5-2%) are expected and acceptable, especially if the peptide has been stored for weeks or months. Significant oxidation (>5%) suggests either poor storage conditions (exposed to light, heat, or humidity) or age.

Dimer and Aggregation Products

Peptide molecules sometimes bond to each other (dimer) or form larger aggregates. This is common in basic peptides with exposed cysteine residues.

Signature: Dimer peaks appear at nearly double the retention time of the monomer and typically show much lower UV absorbance (because two molecules elute together but produce the same UV signal intensity as one molecule, creating a larger but structurally different peak).

Assessment: Small amounts (<2%) are usually acceptable. Larger amounts suggest the peptide wasn’t properly handled during synthesis or storage (excess heat, pH stress).

Epimerization

Amino acids exist in two stereoisomers: L-form (left-handed) and D-form (right-handed). Peptide synthesis produces L-amino acids. Under certain conditions (heat, alkaline pH), L-amino acids can convert to D-forms (epimerization).

Signature: Epimerized forms appear as separate peaks at slightly different retention times. Detection requires high-resolution chromatography.

Assessment: Epimerization at levels <0.5% is usually negligible. Higher levels suggest synthesis was conducted at improper pH or temperature.

Key Takeaway: Impurity Peaks Tell a Story About Handling and Storage

A 99% pure batch with mostly synthesis residues suggests good manufacturing but poor purification. A 99% pure batch with 2% oxidation suggests good synthesis but suboptimal storage. Reading impurity profiles helps you understand batch history.

Batch Traceability: Following Your Product Back to Its Source

One of the most overlooked aspects of a COA is traceability—the ability to connect your physical product back through manufacturing records, testing data, and storage history.

What Good Traceability Looks Like:

Lot Number Matching: Your invoice says “Lot #20260325-001.” The COA header also says “Lot #20260325-001.” Your physical product vial is labeled “20260325-001.” All three match. This confirms the COA describes your batch, not someone else’s.
Manufacturing Date: The COA includes the synthesis date. If the COA is dated March 25, 2026, and you receive the product on April 5, 2026, the timeline makes sense. If the COA is dated January 2026 but you’re receiving it in April, it’s worth asking: Why was it stored for 3 months? Where? Under what conditions?
Testing Facility Confirmation: The COA identifies the independent testing lab. You can contact that lab directly to verify they tested this batch on the stated date.
Chain of Custody (if available): Premium suppliers include notes on storage temperature, handling conditions, and any re-testing or stability monitoring conducted.

What Poor Traceability Looks Like:

Lot numbers don’t match between invoice and COA
Multiple different lot numbers listed in a single COA (suggests batches were combined)
No testing date or vague date (“tested this quarter”)
No testing facility named or identifiable
COA is undated or the date is much older than the shipping date

Key Takeaway: Traceability Prevents Fraud

Matching lot numbers, recent testing dates, and named testing facilities are your defense against reused COAs and batch switching. Always verify traceability before trusting the data.

Red Flags: When a COA Hides Problems

Knowing what to look for helps you spot COAs that seem legitimate but contain hidden gaps or inconsistencies.

Red Flag #1: Reused COAs Across Multiple Lot Numbers

The same purity percentage (99.2%), identical impurity breakdown, and identical mass spectrometry results across six different batches is statistically impossible. Batches vary. If they don’t, the COA is probably reused.

How to check: Ask for COAs from several lot numbers of the same product. Compare purity percentages, impurity profiles, and mass spec data. If they’re identical to three decimal places, demand batch-specific re-testing.

Red Flag #2: Missing Batch Numbers or Testing Dates

A COA without a batch number is untraceable. You can’t verify it describes your product. A COA without a testing date raises questions: Was it tested recently, or is it an old report reused? If it was tested months ago, has the stability been verified since then?

Red Flag #3: No Third-Party Testing Facility Named

“Third-party tested” is meaningless without specifics. Who is the third party? Where are they located? What are their credentials?

Legitimate independent labs (university analytical centers, specialized CROs, ISO-17025-accredited facilities) can be verified. If a supplier won’t name the lab, they’re hiding something.

Red Flag #4: No Chromatogram Image

A COA claiming 99% purity without showing the actual HPLC chromatogram is unverifiable. You can’t assess peak quality, impurity distribution, or baseline noise. The number exists in isolation, disconnected from evidence.

Red Flag #5: Incomplete or Omitted Sections

Missing endotoxin data, sterility results, or mass spectrometry confirmation suggests incomplete testing. This might be acceptable for some applications, but premium suppliers include comprehensive data.

Red Flag #6: Vague Purity Claims

“Exceeds expectations,” “very high purity,” or “pharmaceutical-grade quality” are marketing language, not data. A COA should state a specific number: “Purity: 99.2%,” not subjective assessments.

Red Flag #7: Inconsistent Testing Methodology

If one COA uses HPLC at 214nm and another uses 280nm for the same peptide, the testing methods differ. This can result in different purity percentages for the same batch if impurities absorb differently at the two wavelengths. This shouldn’t happen for a single product unless there’s a documented reason (e.g., “280nm is more appropriate for this sequence due to high tryptophan content”).

Key Takeaway: Detailed, Specific, Traceable COAs Are Your Best Defense

Vague claims, missing data, and untraceable batch numbers are red flags. Demand specificity.

What Makes a GOOD Certificate of Analysis

Not all COAs are equal. A truly good COA is specific, detailed, and transparent about methodology.

Essential Elements of a Good COA:

✓ Batch-Specific Identity
– Lot number matches your product
– Testing date is recent (within 1-2 weeks of shipping)
– Manufacturer and testing facility are named

✓ Dual Identity + Purity Confirmation
– HPLC purity percentage is specific (99.2%, not “very pure”)
– Chromatogram image is provided and shows clear peaks
– Mass spectrometry confirms correct molecular weight within acceptable tolerances
– Impurity breakdown is itemized, not lumped

✓ Safety Testing
– Endotoxin level is quantified (<1 EU/mL or specific value)
– Sterility testing is included or explicitly omitted with reason
– Physical properties (appearance, pH, moisture) are documented

✓ Transparency About Methods
– Testing methodology is explicitly stated (e.g., “Reverse-Phase HPLC, Luna C18, 214nm”)
– Equipment and column specifications are included
– Detection limits and sensitivities are documented (e.g., “endotoxin detection limit <0.25 EU/mL”)

✓ Realistic Batch Variation
– Purity percentages vary between batches (not perfectly consistent)
– Impurity profiles show normal manufacturing variation
– No signs of data reuse or copying

✓ Accessibility
– COA is provided without login walls or special requests
– Data is presented in both graphical and tabular formats
– Contact information for the testing lab is included for verification

Using the COA to Evaluate Your Supplier

A COA reveals not just product quality but supplier philosophy. A supplier who publishes detailed, batch-specific COAs is demonstrating commitment to transparency and traceability.

Ask yourself:
– Does this COA provide specific, verifiable data or marketing language?
– Are impurities identified or lumped together?
– Is the testing facility named and verifiable?
– Does the batch number trace back to my invoice?
– Are there signs of incomplete testing or reused data?

A supplier who consistently provides detailed, batch-specific COAs with transparent methodology is one worth trusting. Conversely, suppliers offering vague claims or refusing to share full COAs are likely cutting corners elsewhere.

Key Takeaway: A COA Is a Window Into Your Supplier’s Standards

The detail, specificity, and transparency of a COA reveal whether your supplier is serious about quality or just checking a box.

The Bottom Line: Master the COA, Master Your Quality Control

A Certificate of Analysis is far more than a compliance document. It’s your primary verification tool—proof that your research materials are what they claim to be.

Mastering COA interpretation gives you several powers:

1. Spot Counterfeits and Fraud
Reused COAs, inconsistent batch numbers, and missing data are red flags that something’s wrong before the product ever reaches your lab.

2. Assess Real vs. Marketing Quality Claims
You’ll see through vague “pharmaceutical-grade” language and understand what “99% purity” actually means in practical terms.

3. Track Batch Variation
By comparing COAs across multiple lots, you’ll understand normal variation and catch batches that fall outside acceptable ranges.

4. Demand Better From Suppliers
When you ask specific questions about testing methodology and require detailed data, you incentivize suppliers to invest in real quality assurance rather than marketing spin.

At Artemis Labs, we publish detailed, batch-specific COAs for every product because we believe your research deserves transparency. Not vague claims. Not reused data. Real, current, specific evidence of quality.

When you evaluate any peptide supplier, let your COA requirements be non-negotiable. Demand specificity. Verify traceability. Ask questions. Your research depends on it.

Common Questions

Q: What’s the most important number on a COA?
HPLC purity is the headline metric (target ≥99% for high-value peptides), but the COA’s value as a verification tool depends entirely on the batch number matching your vial. A 99.5% purity number means nothing if it’s from a different lot.

Q: What does Karl Fischer water content tell me?
Karl Fischer measures residual water in the lyophilized powder. <5% is typical for research-grade peptides; lower (<2%) is preferred for sensitive compounds. High water content (>10%) suggests poor lyophilization and stability concerns.

Q: Do I need endotoxin testing if I’m only doing in vitro work?
For purely in vitro work, endotoxin matters less than for in vivo. For animal models or cell culture sensitive to LPS contamination, demand endotoxin ≤0.5 EU/mg. Cell-culture work often sets even stricter thresholds.

Q: My COA shows 99.2% HPLC purity — is that good?
Yes. ≥99% is the gold standard for research-grade peptides. Be cautious of 100% claims (impossible by HPLC accuracy) and of any purity below 95%, which suggests inadequate purification.

Q: How do I verify the lab on the COA is real?
Search the lab name + accreditation (ISO/IEC 17025 is the international standard for testing labs). Most legitimate third-party labs have public websites confirming their services. Contact the lab to confirm the work was performed if any doubt remains.

Q: What does “in-house testing” mean on a COA?
It means the supplier tested the peptide themselves rather than sending it to an independent lab. In-house testing is acceptable as supplementary QC but cannot substitute for third-party verification. Demand third-party testing for any high-value research compound.

Q: How recent should the COA’s test date be?
Within 30 days of shipment. Peptides degrade over time, so months-old test data shipped with current material is not a valid quality representation. Recent testing is non-negotiable for research integrity.

HPLC Testing Explained: 99%+ Purity Verification
Peptide Quality Assurance & Supplier Evaluation
Research Peptides & FDA Regulations Explained
Retatrutide Quality Crisis Report
Complete Guide to Research Peptides 2026 — root pillar
COA Interpretation Quick Reference — printable
USP <825> — General Chapters: Radiopharmaceuticals
ISO/IEC 17025 — General requirements for the competence of testing and calibration laboratories

Featured Products (with batch-specific COAs)

Tirzepatide — batch-specific HPLC + MS documentation
Retatrutide — independently re-tested
BPC-157 + TB-500 — combination repair peptide with full COA

Last updated: May 20, 2026 (originally published April 19, 2026)
Author: Artemis Labs Research & Quality Team
All content for educational and informational purposes. Products are for research use only. Not for human consumption. These statements have not been evaluated by the FDA.