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Sterile Water Australia — Preservative-Free Diluent

Sterile Water research peptide vial — TXLABS, ≥98% HPLC

From $19 AUD · ≥98% HPLC purity · third-party COA · ships Australia-wide

What is Sterile Water?

Sterile Water — a research-grade peptide reference supplied lyophilized for laboratory use only.

Specifications

What the research covers

Sterile water for injection is exactly what the name says and deliberately nothing more: water, sterile and non-pyrogenic, containing no antimicrobial agent, no buffer, no tonicity adjuster and no added substance of any kind. Its defining property is what has been left out.

That compositional simplicity is the whole point, and it carries one direct consequence. With no preservative present, nothing inhibits the multiplication of organisms introduced during a withdrawal, so the vial is a single-use item. Once the closure has been entered, the contents are used and any remainder is discarded rather than kept for later. This is not a conservative recommendation; it follows from the composition. Storing an opened, unpreserved vial and returning to it converts a controlled product into an uncontrolled one.

There are three situations where preservative-free water is the correct choice rather than merely an available one. The first is analytical work, where benzyl alcohol is a contaminant: it is a small organic molecule that absorbs in the ultraviolet and elutes in a chromatogram, so a preserved diluent puts a peak in every run and a background in every spectrum. The second is preservative-sensitive material, since benzyl alcohol can interact with some peptides and with some container and device materials. The third is any context where the diluent must be compositionally simple so that anything detected can be attributed to the sample rather than to what it was dissolved in.

It is also the appropriate reference point for anyone asking what a diluent contributes to a measurement, because the answer here is nothing.

TXLABS supplies sterile water as a laboratory reagent for research use only. It is not supplied for human or veterinary administration.

Reading the certificate

For preservative-free water the certificate is shorter than for the bacteriostatic version and every remaining item carries more weight, because there is no preservative providing a second line of defence. Sterility is the central claim and the test method used to establish it should be named, since sterility asserted without a method is not a result. Bacterial endotoxin by the LAL method should be reported with the limit applied stated explicitly, because water is a classic endotoxin source and pyrogen-free is a measured property rather than an assumption. pH, particulate matter and container-closure integrity complete the picture. An HPLC purity percentage is not a meaningful measurement for water and its presence suggests a template rather than a test. TXLABS publishes third-party certificates for tested lots in the CoA library; none is published for sterile water, and the lot certificate is available on request to support@txlabs.bio.

Storage and handling

Aseptic technique carries more weight here than with a preserved diluent, because there is no chemical margin for error. Swab the septum with an appropriate agent and allow it to dry before entry, use a fresh sterile needle, and plan the work so that everything needed from the vial is withdrawn in one session rather than returning to it. Store at controlled room temperature, protected from light where the packaging directs it, and do not freeze: ice expansion stresses both the container and the closure, and the container-closure barrier is the only thing maintaining sterility. Inspect each vial before use against a light background for clarity, particulates and any damage to the seal or closure; with an unpreserved product a visible haze is a definitive reason to discard rather than a judgement call. In Australian conditions the practical caution is against leaving a 10 mL vial in a hot vehicle or letterbox where seal integrity may be stressed. Collect and store indoors.

Working out concentration

The arithmetic is identical to any other diluent: mass over volume. A 10 mg vial of lyophilised material reconstituted with 1 mL of sterile water gives 10 mg/mL; with 2 mL, 5 mg/mL; with 4 mL, 2.5 mg/mL. One consideration specific to an unpreserved diluent: because the vial is single-entry, a preparation should be planned around the volume actually needed rather than around a convenient round number, since a 10 mL vial partly used is a 10 mL vial finished. Note also that the lyophilised cake itself occupies volume, so final volume slightly exceeds added volume, which matters for concentrated preparations. The reconstitution calculator handles mass against volume. Concentration examples only, not a protocol.

How it relates to adjacent compounds

Bacteriostatic water is the same product with 0.9% benzyl alcohol added, and the choice between the two is a single decision about whether the vial will be entered once or repeatedly, weighed against whether the preservative would interfere with anything downstream. Acetic acid diluent covers the separate case of peptides that will not dissolve properly in water at neutral pH regardless of which water is used. Analytical work on any of the compounds in this catalogue, including copper complexes such as GHK basic where trace metal content matters, is where the compositional simplicity of sterile water counts most. These are functional relationships between reagents only.

Frequently asked questions

Why is sterile water single-use? +
Because it contains no preservative. Once the closure has been penetrated, any organism introduced during that entry can multiply without inhibition, and nothing in the vial slows it down. That is a consequence of the composition rather than a cautious recommendation. Use what is needed in one session and discard the remainder; keeping an opened unpreserved vial converts a controlled reagent into an unknown one.
When should sterile water be chosen over bacteriostatic? +
In three cases. Where the work is analytical and benzyl alcohol would appear as a chromatographic peak or an ultraviolet background. Where the material or the container is preservative-sensitive. And wherever the diluent must be compositionally simple so that anything detected can be attributed to the sample. Outside those situations, the repeated-entry convenience of a preserved diluent is usually the deciding factor.
What does non-pyrogenic mean? +
That the water has been tested and found to be below a specified limit for bacterial endotoxin, the fever-inducing lipopolysaccharide fragments shed by Gram-negative bacteria. Endotoxin survives sterilisation, so a solution can be sterile and still pyrogenic. Water is a classic endotoxin source in manufacturing, which is why the LAL result and the limit applied belong explicitly on a certificate rather than being implied.
Can sterile water be frozen for storage? +
It should not be. There is no benefit, since an aqueous reagent gains nothing from cold storage, and there is a real cost: water expands on freezing, which stresses both the container and the closure. Since the container-closure barrier is the only thing maintaining sterility in an unpreserved product, compromising it defeats the entire purpose. Controlled room temperature is the correct condition.
Does sterile water contain any buffer? +
No. It contains water and nothing else: no buffer, no tonicity adjuster, no antimicrobial agent, no stabiliser. That means it has no buffering capacity at all, so the pH of a solution made with it is determined entirely by whatever is dissolved into it. For a peptide with acidic or basic side chains, the resulting pH can differ substantially from neutral and is worth measuring rather than assuming.
How should a partly used vial be handled? +
By discarding it. With no preservative there is no basis for storing an entered vial, and the risk is not theoretical: an unpreserved aqueous solution at room temperature supports growth of anything introduced. Planning the volume actually required before entering the vial, rather than after, is the practical way to avoid the question arising in the first place.

Related compounds

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