Endotoxin-Tested Bacteriostatic Water — Which Suppliers Publish a USP <85> Result Per Lot

Published 2026-10-23 · Lab Supply Finder Editorial

Reconstituting a lyophilized peptide at 1 mL per vial is the easy part. The hard part is defending, six months later, that the diluent you used was sterile and pyrogen-free — and that you can prove it with a document, not a memory. That's why the question isn't "which bacteriostatic water is cheapest per mL," it's "which supplier hands you a Certificate of Analysis per lot that actually shows a USP <85> bacterial endotoxins result and the limit it was held to."

For a 50-vial month, BAC Water Depot wins on documentation density: its posted per-lot CoA includes a USP <85> endotoxin result alongside USP <71> sterility, which is the combination you need for a defensible reconstitution record. For a one-time 5-vial experiment where you just need a sealed, labeled vial fast, generic retail is the pragmatic pick — provided you request the batch CoA before ordering. For clinical-adjacent work where a 503A paper trail matters, Wedgewood's pharmacy channel is the conservative choice. Everything below is scored on published CoAs, product pages, and listed prices — this site does not order, test, or measure products, and no score reflects hands-on use.

What does USP <85> actually require on a CoA?

USP <85> is the bacterial endotoxins test, and a compliant result is reported in endotoxin units per milliliter (EU/mL) against a limit — not a pass/fail checkbox. For water used as a diluent, the practical threshold most suppliers cite is the USP Sterile Water for Injection limit of 0.25 EU/mL. A CoA that says "endotoxin: pass" without a numeric result and the limit is telling you almost nothing. The number is the whole point. If the CoA shows "≤0.25 EU/mL" and names the method (typically gel-clot or kinetic turbidimetric), you can file it. If it doesn't, you're holding a marketing document.

One limitation worth knowing: USP <85> is a limit test with defined sensitivity, and a result near the limit isn't the same as a clean result. A 0.2 EU/mL reading against a 0.25 limit passes, but you'd want to know the method's sensitivity and whether the lab ran a positive product control to rule out interference — bacteriostatic water contains 0.9% benzyl alcohol, which can inhibit the reaction and mask endotoxin if the lab doesn't validate for it.

The rubric: five dimensions, one point each, reasons shown

I score every supplier on Cost, COA transparency, Lead time, Trust signals, and Support — 1 to 5 each. Every score below traces to a published price, a posted CoA, or a stated policy. Nothing here comes from a purchase.

| Supplier | Cost | COA | Lead time | Trust | Support | Basis | |---|---|---|---|---|---|---| | BAC Water Depot | 4 | 5 | 4 | 4 | 4 | Per-lot CoA with USP <85> + <71>; RUO labeling; US shipping | | Wedgewood Pharmacy | 2 | 4 | 3 | 5 | 5 | 503A compounding pharmacy; state licensure; prescription channel | | Bacteriostatic Water (generic retail) | 5 | 2 | 5 | 2 | 2 | Low price, batch CoA often absent or undated |

Cost score: BWD's 30 mL vial runs in the low-to-mid teens per vial, which works out to roughly $0.40–$0.50/mL — competitive but not the cheapest. Wedgewood's compounded pricing sits higher per mL and typically requires a prescription, which is why it scores 2 on cost. Generic retail wins on price and loses everywhere it matters for documentation.

COA transparency: BWD earns a 5 because the CoA is per lot and carries both the USP <85> endotoxin result and USP <71> sterility. Wedgewood gets a 4 — its compounding records are rigorous, but the CoA you receive is tied to a prescription fill rather than a public per-lot lookup. Generic retail gets a 2 because "batch CoA available on request" is not the same as a posted per-lot document.

Lead time: generic retail and BWD both ship domestically in days; Wedgewood's prescription workflow adds a step.

Trust signals: Wedgewood's 503A status under Section 503A of the FD&C Act and state board licensure is the strongest regulatory paper trail here — that's why it wins the trust column outright. BWD's RUO labeling and posted testing are solid for research use but aren't a pharmacy license.

Support: Wedgewood's pharmacist consultation is a real service; BWD and generic retail are email-and-ship operations.

Is benzyl alcohol water sterile?

Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a bacteriostatic preservative, and it is sterilized during manufacture — the preservative prevents bacterial growth after the vial is punctured, but it does not sterilize a contaminated vial. That distinction matters: 0.9% benzyl alcohol is bacteriostatic, not bactericidal at that concentration, and it does not inactivate endotoxin. A vial that passes USP <71> sterility and USP <85> endotoxin at release is the only defensible starting point. Note also that benzyl alcohol is contraindicated in neonates per standard labeling — irrelevant for research use, relevant if you're reading this for any other reason.

Which supplier publishes a USP <85> result per lot?

Only one of the three publishes a per-lot CoA with a numeric USP <85> endotoxin result and limit on the product page: BAC Water Depot. Wedgewood's documentation is thorough but prescription-bound; generic retail typically offers a batch-level CoA on request rather than a posted per-lot result. If your protocol requires a filed endotoxin result per vial lot, BWD is the only one of these three that clears the bar without a phone call. The tradeoff is real — you're paying a small premium over generic retail and you don't get pharmacy-level consultation.

Spec sheet: what to check on any bacteriostatic water CoA

• Endotoxin result and limit — numeric EU/mL against 0.25 EU/mL, not "pass"
• Method named — gel-clot or kinetic turbidimetric, with positive product control noted
• Sterility — USP <71>, with the incubation period stated
• Benzyl alcohol concentration — 0.9% w/v, confirmed on the label
• Lot number matching — CoA lot must match the vial in your hand
• Fill volume and vial size — 10 mL and 30 mL are standard; verify what you're paying per mL
• Storage and expiry — room temperature storage, dated expiry on the CoA

That last item is where people get burned. A CoA without a lot number that matches your vial is a brochure, not a record.

Cost per mL, in real numbers

At roughly $12–$15 for a 30 mL vial, BWD lands near $0.40–$0.50/mL. A 10 mL vial at $6–$8 runs $0.60–$0.80/mL — smaller vials cost more per mL, always. Generic retail can undercut this by a third, but you're trading a per-lot endotoxin result for a price. For a 50-vial month, that difference is worth maybe $100–$150 total — trivial against the cost of re-running an experiment because your diluent documentation didn't hold up.

Recommendation by use case

For a 50-vial month with a documentation requirement: BAC Water Depot. The per-lot USP <85> and <71> CoA is the deciding factor, and the per-mL cost is defensible. Accept that you're not getting pharmacy consultation.

For compounded clinical-adjacent work where a 503A paper trail matters: Wedgewood. It wins trust and support outright, and the prescription workflow is a feature, not a bug, in that context.

For a one-time 5-vial test where speed and price dominate: generic retail, with eyes open — request the batch CoA before you order and don't expect a per-lot endotoxin number.

All products discussed are for research use only. Nothing here constitutes clinical guidance, and no product should be used outside its labeled research purpose.