Glutathione dissolves in bacteriostatic water, and that is the standard solvent for our vials. It is strongly hydrophilic and needs no organic solvent. What sets it apart is mass: a 600 mg or 1500 mg vial is mixed at 100 mg/mL or more, far above most peptides, so it dissolves more slowly and needs patience rather than force.
Why glutathione dissolves in water
Glutathione is small and polar. Its three residues carry two carboxyl groups, one amine, a thiol and two amide bonds, with no hydrophobic side chain beyond cysteine’s short thiol arm. PubChem’s computed XLogP is minus 4.5 (PubChem CID 124886).
Counting the ionisable groups gives two carboxyls against one amine, with the thiol mostly uncharged near neutral pH. From that count we calculate a net charge of about minus 1 at pH 7 and an isoelectric point near pH 3.3. These are our calculations from standard pKa values, not a measured figure. A peptide is least soluble near its isoelectric point. Glutathione is itself acidic, so at very high concentration in unbuffered water it can pull the pH down toward that range, which may be one reason concentrated solutions dissolve slowly. That is our reasoning, not a measurement, and we have no measured pH for a mixed vial.
What the published figures say
Published water figures vary widely:
- About 20 mg/mL in water (Cayman Chemical, item 10007461, product information).
- 62.5 mg/mL in water, needing ultrasound (MedChemExpress, HY-D0187, data sheet).
- 100 mg/mL in PBS, with ultrasound and heating to 60 °C (same sheet, as a formulation note).
- 180 and 189 mg/mL in working solutions at pH 6.4, within a stated range of 10 to 400 mg/mL (Harbin and Stephens, US Patent 6,835,811, 2004).
- 292.5 mg/mL, listed in PubChem from the Human Metabolome Database.
No source explains the spread. Supplier figures are usually what they guarantee for their own stock, not a hard ceiling, and the high figures show that strong solutions are possible. Our Glutathione reconstitution page lists 100 to 200 mg/mL for the 600 mg vial and 150 to 250 mg/mL for the 1500 mg vial, which sits above both supplier water figures. The practical reading is that the top of those ranges leaves the least margin, so more water is the easy answer to slow dissolving. Heating is not: warmth is what speeds oxidation.
Bacteriostatic water first
Bacteriostatic water is sterile water with 0.9% benzyl alcohol, which allows a refrigerated vial to be accessed more than once. It is our solvent for glutathione, and the preservative supports repeated access over the fridge window described on how long glutathione lasts. Sterile water works for a vial that will be accessed once. The difference is explained in bacteriostatic water explained.
Why not acetic acid or base?
Laboratories sometimes add dilute acetic acid to coax basic or hydrophobic peptides into solution. Glutathione is neither, and it is already acidic, so acid would only move it closer to its calculated isoelectric point. Adding base to help it along is no better: thiols generally oxidise faster as pH rises. Plain bacteriostatic water and time are the method.
Saline and sodium chloride
Glutathione is expected to dissolve in 0.9% sodium chloride, and MedChemExpress’s PBS note shows it dissolves in a salt buffer, but we found no figure for saline itself and our vials are not specified for it. For a multi-access vial, bacteriostatic water remains the choice because of its preservative.
Concentrations in our vials
A 600 mg vial with 3 mL of bacteriostatic water gives 200 mg/mL, and with 6 mL gives 100 mg/mL. A 1500 mg vial with 6 mL gives 250 mg/mL, and with 10 mL gives 150 mg/mL. The tables are on the Glutathione reconstitution page. Check that the vial has headspace for the chosen volume. A larger water volume does not change the amount in the vial; it spreads it more thinly. Whatever volume is chosen, write the concentration on the vial.
Cloudiness and gelling: what causes them
A correctly mixed vial forms a clear, colourless solution. Because so much powder is going into so little water, undissolved material is the commonest cause of haze here:
- Not enough time. A large cake dissolves slowly. Swirl, wait a few minutes, and swirl again.
- Water jetted onto the cake. A strong stream can trap air and create foam, which looks cloudy and adds oxygen. Running the water down the inside wall of the vial avoids it.
- Shaking. This adds air to a compound that reacts with it.
- Cold water onto cold powder. Both at fridge temperature slows dissolving. Letting the vial and the water reach room temperature first helps.
- Haze appearing later in storage. This points to warm or bright storage, freezing or contamination, and the solution is discarded.
Brief cloudiness that clears with time is normal. The general causes are covered in why peptides gel or go cloudy, and the mixing method step by step is in how to reconstitute peptides with bacteriostatic water.
Related glutathione pages
How the dissolved peptide behaves over time is on the Glutathione stability page, and bench technique is on the Glutathione handling page.
All products supplied by Vistara Labs are intended for laboratory research use only. They are not drugs, are not approved for human or veterinary use, and are not intended to diagnose, treat, cure or prevent any condition. Nothing on this page constitutes medical advice or guidance for use in humans.
