How to compare research peptide vendors

Research peptide listings can look alike: a compound name, a milligram figure and a price. This checklist covers what actually differs between vendors, so you can compare them on evidence rather than on the headline price. It applies to any supplier, including us.

1. Purity and identity testing

The single biggest difference between vendors is how much they tell you about what is in the vial. Look for:

• The method, not just a number. A purity figure normally comes from HPLC as an area percent. See reading an HPLC chromatogram for what that number does and does not mean.
• Identity confirmation. Purity says how much of the detected material is one molecule; mass spectrometry says whether it is the right molecule. See mass spectrometry for peptide identity.
• Who tested it and when. An independent laboratory and a test date that plausibly matches current stock carry more weight than an undated figure.
• Purity versus content. A powder can be highly pure and still be only part peptide by mass, because of water and counter-ions. See purity vs net peptide content.

Be cautious with round numbers repeated across every product, figures with no method, and wording that implies approval by an agency. Research peptides are not approved drugs.

2. True price per milligram

Vial sizes differ, so the sticker price is not comparable. Work it out per milligram:

• Divide the price by the stated mass in the vial. Our price-per-mg table and calculator does this for every vial size we list.
• Add shipping, then divide again. A low price with a high shipping charge can cost more per mg than a higher price that ships free.
• Check quantity pricing. Many labs order several vials of one item; see how volume pricing changes the per-vial cost.
• Compare like with like: same compound, similar vial mass, similar stated purity, and whether the mass is gross powder or net peptide.

3. Shipping

• Where it ships from and how. Domestic shipping with tracking avoids customs delays and the temperature swings of long transit.
• Dispatch time. Look for a stated handling time, not just a carrier name.
• Packaging. Sealed vials, padding and discreet outer packaging reduce breakage and exposure.
• Total cost. Flat rates, free-shipping thresholds and express options vary widely. Ours: free USPS Priority Mail at $199.99+; details on the shipping page.

4. Storage on arrival

Lyophilized (freeze-dried) peptides are comparatively stable, but heat, light and moisture still matter. A good vendor publishes storage conditions for each product and ships in a way that respects them. When the parcel arrives:

• Check that vials are sealed and the cake or powder looks intact.
• Store as the product page states, typically cold and dark, and let a vial reach room temperature before opening to avoid condensation.
• Record the receipt date and storage location. Our free Peptide Lab Handbook includes storage tables and log sheets, and the storage and stability guide covers the chemistry.

5. Policies and transparency

• Damaged or wrong items. Is there a written policy, and how quickly must you report a problem? See our returns policy as one example of the detail to expect.
• Payment. Which methods are offered, and is it clear when an order counts as paid?
• Privacy. A published privacy policy that says what is stored and for how long.
• Research-use-only terms. A responsible vendor states clearly that products are for laboratory research only, not for human or veterinary use, and requires buyers to be adults. A vendor that makes health or results claims is a red flag.
• Contact. A working support email and real answers to technical questions.

A quick comparison checklist

1. Testing method stated (HPLC purity, mass spectrometry identity) and dated.
2. Price per mg, including shipping, for the vial size you need.
3. Quantity pricing for multiple vials.
4. Domestic, tracked shipping with a stated dispatch time.
5. Storage conditions published per product.
6. Written policies for damage, payment and privacy.
7. Clear research-use-only terms and no health claims.

Questions

What is the most important thing to compare between peptide vendors?

Whether the vendor explains how identity and purity are tested, and with which methods. HPLC gives purity as area percent; mass spectrometry confirms the molecular mass. Price only means something once you know what is in the vial.

How do I compare prices fairly?

Divide the price by the stated milligrams in the vial to get price per mg, then add shipping and any minimums. Compare like for like: the same compound, similar vial sizes and similar stated purity.

Is the cheapest vendor per mg the best value?

Not necessarily. Missing test information, slow or warm shipping, or a vial mass that is gross weight rather than net peptide all change what you actually receive.

What policies should a vendor publish?

Shipping times and carriers, what happens with damaged or wrong items, payment methods, privacy handling, and clear research-use-only terms with an age requirement.

All Sealed Peptides products are for laboratory research use only. Not for human or veterinary use. Must be 21 or older.