Vendor comparison · 2026
PE-22-28 vendors: 5 compared on COAs and price
OtherAlso known as Spadin analog
Evidence tier
Limited published literature
1 publication over 9 years · trials not yet curated
- Vendors carrying it
- 5
- 5 with a listed price
- Vendors with checkable COAs
- 1
- 1 publish any certificate
- Lots tested
- 2
- 2 naming a checkable lab
- Independent assays
- 0
- none on file yet
- Newest assay
- 12 Aug 2026
- oldest 15 Jun 2026
- Laboratories named
- 1
- most often Freedom Diagnostics Testing
- Median label gap
- 2.4%
- 100% of lots within 5% of label
- Median purity
- 99.67%
- 2 of 2 lots at 99% or above
- Lowest price per mg
- $4.00
- peer median $5.40
- Publications located
- 1
- researched since 2017
Source: PepIndex, an independent index of research-peptide vendors. No vendor can pay for a rank, every score is computed by a published formula, and every figure links to the document it was read from.
PeptidePlugs has the most checkable PE-22-28 testing in this index: 2 lots assayed by Freedom Diagnostics Testing, the newest on 12 Aug 2026. The lowest listed price is $4.00 per mg at PeptidePlugs, the same vendor, against a peer median of $5.40. 5 vendors carrying PE-22-28 are compared below. 1 publish at least one certificate naming a checkable laboratory, 2 lot records are on file, and none is an independently commissioned assay. Figures are PepIndex's own: it is an independent index of research-peptide vendors, no vendor can pay for a rank, and each figure links to the certificate it was read from.
Every vendor carrying PE-22-28
| # | Vendor | Score here | Price / mg | Lots | Newest test | Laboratory | Mean purity | Label gap | Reports |
|---|---|---|---|---|---|---|---|---|---|
| 1 | PeptidePlugs | 89.594% | $4.00 (74%) | 2 / 2 | Freedom Diagnostics Testing | 99.7% | 2.4% | ||
| 2 | Modern AminosISO/IEC 17025COAs need an account | 80.997% | $5.40 (100%) | 0 | — | — | — | — | no reportVisit site |
| 3 | Simple Peptide | 72.492% | $7.20 (133%) | 0 | — | — | — | — | no reportVisit site |
| 4 | GenX Peptides | 67.369% | $5.00 (93%) | 0 | — | — | — | — | no reportVisit site |
| 5 | Biotech Peptides | 56.660% | $6.88 (127%) | 0 | — | — | — | — | no reportVisit site |
Independent assays
No independently commissioned assay of PE-22-28 is on file. All 2 records below were published by the vendor that sells the product, naming the laboratory shown. PepIndex does not yet commission its own assays, so nothing on this page establishes what is in a vial beyond the vendor’s own certificate. A record moves into this section the moment an assay commissioned by anyone other than the seller is indexed.
What the certificates show
2 of 2 lots at 99% or above; median 99.67%.
| Range | lots |
|---|---|
| <95% | 0 |
| 95–97% | 0 |
| 97–98% | 0 |
| 98–99% | 0 |
| 99–99.5% | 0 |
| ≥99.5% | 2 |
100% of lots within 5% of the labelled mass; median gap 2.4%.
| Range | lots |
|---|---|
| ≤2% | 1 |
| 2–5% | 1 |
| 5–10% | 0 |
| 10–20% | 0 |
| >20% | 0 |
5 vendors, $4.00 to $7.20; median $5.40.
| Range | vendors |
|---|---|
| $4.00–$5.00 | 1 |
| $5.00–$6.00 | 2 |
| $6.00–$7.00 | 1 |
| $7.00–$8.00 | 1 |
Purity and mass are read from each certificate as published; the label gap is |labeled − assayed| ÷ labeled. Every value behind these bars is in the certificate table below.
Laboratories used
| Laboratory | Lots | Vendors | Share | Verify |
|---|---|---|---|---|
| Freedom Diagnostics TestingUS | 2 | 1 | 100% | Public lookup |
Every certificate record
| Vendor | Lot | Tested | Lab | Labeled | Assayed | Discrepancy | Purity | Report |
|---|---|---|---|---|---|---|---|---|
 PeptidePlugs | 135-01-ZB | Freedom Diagnostics Testing | 10 mg | 9.88 mg | 1.2% | 99.6% | Vendor-published | |
| PeptidePlugs | 129-01-SM | Freedom Diagnostics Testing | 10 mg | 9.64 mg | 3.6% | 99.7% | Vendor-published |
Score breakdown
The score has two halves: the research base — how long the compound has been studied and how much has been published — and the quality of the evidence the market produces for it, aggregated across every vendor that carries it: assayed purity, lot-to-lot consistency, readable third-party certificates and those vendors’ review record. It measures the evidence base, not the merits or safety of the substance.
Studied since 2017 — 9 years of published research
How long the compound has been studied. Fifteen years or more of published literature earns full marks; a newer compound earns less.
1 publication indexed in PubMed
The volume of published literature located. Full marks at fifty or more publications.
Mean assayed purity 99.7% across 2 certificates
Average assayed purity on the certificates published by vendors that carry this compound. Full marks at 99.5%+, nothing at 95% or below.
±0.05 pts purity across lots, mean label deviation 2.4%
How tightly assayed purity and labeled-versus-actual mass hold across different lots. Rewards reproducible manufacturing.
5 of 5 listing vendors publish an accessible certificate policy
Whether the vendors carrying this compound publish per-lot certificates anyone can read without an account.
2 of 2 certificates from a recognised independent lab
Share of certificates issued by a recognised third-party testing lab rather than an unnamed or self-named one.
What is PE-22-28?
A shortened synthetic analogue of spadin, studied preclinically as a TREK-1 potassium-channel inhibitor with antidepressant-like activity in animal models. The indexed literature under this exact name is very limited.
Studied in published research for depression and mood, as a TREK-1 channel inhibitor.
Regulatory status
Labeled by vendors for laboratory research use only. Not approved as a medicine in the United States, United Kingdom, or European Union.
What the research examines
The areas of published research this compound appears in. These describe what the literature has studied — never a claim of benefit, effect or suitability for any use.
Published research
PepIndex records the size and shape of the published research footprint only. It does not evaluate or summarise clinical significance, does not describe administration, and nothing here is a claim of safety or efficacy.
- Shortened Spadin Analogs Display Better TREK-1 Inhibition, In Vivo Stability and Antidepressant Activity — Frontiers in pharmacology (2017)
Peer-reviewed article indexed in PubMed, published in Frontiers in pharmacology (2017).
PepIndex describes what literature exists. We do not interpret it, assess clinical significance, or publish quantities, protocols or instructions for use.