Reconstitution Guide
How compounds are reconstituted
Research compounds ship as a lyophilised powder. Before handling, they are returned to solution by adding a sterile diluent. This guide covers the fundamentals, the arithmetic, and the measurement basics for laboratory work.
- Covers
- Diluent · Maths · Technique
- Reading time
- 8 minutes
- Companion
- Calculator
- Scope
- Laboratory handling
Choosing a diluent
Bacteriostatic water is the standard diluent for a multi-use research vial.
The diluent is simply the liquid that dissolves the powder. Its job is to carry the compound without degrading it and, ideally, to keep the vial usable across repeated withdrawals. Whichever you choose, the volume added is what sets the final concentration — the mass in the vial never changes.
Bacteriostatic water
0.9% benzyl alcohol
The preservative inhibits microbial growth across repeated withdrawals, which is what makes a multi-use preparation possible at all. The usual default.
Sterile water
No preservative
Adequate for a single session, but it offers no protection once the stopper is pierced. Reserved for same-session work.
Bacteriostatic saline
0.9% sodium chloride
Occasionally used, but the added salt can affect sensitive compounds. Bacteriostatic water is the safer default unless a record says otherwise.
The concentration arithmetic
Concentration is the compound mass divided by the diluent volume.
Finding the concentration
- Compound mass
- 10 mg
- Diluent added
- 2 mL
- Concentration
- 5 mg/mL
Finding the volume to draw
- Target quantity
- 0.25 mg
- Concentration
- 5 mg/mL
- Volume to draw
- 0.05 mL
Rather than working these out by hand, the calculator converts between vial size, diluent volume, target quantity and the markings on a syringe barrel.
Reading an insulin syringe
A U-100 barrel is marked in units, where 100 units is exactly 1 mL.
The conversion is fixed. So if a compound is reconstituted to 5 mg/mL and a protocol references 0.05 mL, that is 5 units on the barrel. Translating a concentration into a mark is exactly what the calculator automates.
| Units (IU) | Volume | Also written |
|---|---|---|
| 100 units | 1.0 mL | 1 cc |
| 50 units | 0.5 mL | 0.5 cc |
| 20 units | 0.2 mL | 0.2 cc |
| 10 units | 0.1 mL | 0.1 cc |
| 5 units | 0.05 mL | 0.05 cc |
Step by step
A clean, gentle technique preserves compound integrity.
- 01Prepare the materials
Work on a clean surface with the lyophilised vial, diluent, alcohol swabs and a sterile syringe. Allow refrigerated material to reach ambient temperature so atmospheric moisture does not condense onto the cake.
- 02Swab both stoppers
Wipe the stopper of the compound vial and of the diluent vial with separate swabs, and let both air dry before drawing.
- 03Draw the diluent
Draw the chosen volume. That volume is what sets the final concentration — more diluent yields less compound per unit on the barrel.
- 04Introduce it slowly
Insert the needle at an angle and let the stream run down the inner wall rather than directly onto the powder. A jet onto lyophilised material generates local shear and foaming.
- 05Dissolve gently
Swirl the vial, or roll it between your palms, until the solution is clear. Never shake or vortex — agitation at the air-liquid interface shears and aggregates peptide chains.
- 06Label and refrigerate
Record compound, batch, concentration and date on the vial, then store as the handling guide describes. A preparation without those four fields is not reconstructible.
Best practice
Small habits protect both the compound and the result.
- Swirl or palm-roll — never shake or vortex, which aggregates chains at the air-liquid interface.
- Run diluent down the vial wall, not onto the lyophilised cake.
- Use a fresh swab on the stopper before every withdrawal.
- Label every vial with compound, batch, concentration and reconstitution date.
- Observe the reconstituted interval on the batch certificate; discard if the solution turns cloudy or gels. For longer storage, aliquot rather than repeatedly freezing the parent vial.
This guide is educational and describes general laboratory handling. It is not medical advice and it is not a dosing protocol. This catalogue is presented for informational purposes only. It is not an offer of sale, and it makes no medical or therapeutic claim.
In more depth
Freeze-drying is not packaging convenience. Water is the medium in which hydrolysis, deamidation and oxidation proceed, and its removal slows all three by orders of magnitude. A lyophilised cake held at −20 °C is a compound in suspended animation. Adding diluent ends that state on purpose.
Before the seal is broken
- Bring the vial to ambient temperature. A vial opened cold draws in atmospheric moisture, which condenses onto a cake engineered to have none.
- Inspect the cake. Note collapse, discolouration or shrinkage against the appearance stated on the certificate.
- Confirm the batch number on the vial matches the certificate you intend to reference.
- Decide the diluent and the final volume before starting, and record both.
Introducing diluent
- Direct the stream against the vial wall, never onto the cake. A jet onto lyophilised material generates local shear and foaming.
- Swirl gently; do not shake. Agitation at an air-liquid interface denatures peptides — foam is that process made visible.
- Allow two to three minutes. Cakes that appear insoluble have usually simply not been given time.
- Do not force a cake into solution with heat unless the compound record explicitly permits it.
Choosing a diluent
Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits microbial growth and therefore permits a preparation to be drawn on more than once. Sterile water contains no preservative and is single-use by design. The choice determines how long a preparation remains valid and belongs in the record for that reason, not as bookkeeping.
When a solution looks wrong
Cloudiness, visible particulate, or unexpected viscosity are worth investigating rather than dismissing. Some peptides gel at concentration through intermolecular association — a physical phenomenon rather than degradation. Others cloud because they have exceeded solubility at the working pH. Check the concentration against documented solubility before concluding the material is at fault.
The record
Four fields make a preparation reconstructible: batch number, diluent, volume added, date of reconstitution. Any one missing and the concentration becomes an assumption rather than a measurement — an uncomfortable position when a result needs defending months later.
Enquiries
Preparing a specific batch?
Reconstituted stability is compound-specific and stated on the batch certificate. The desk can confirm the interval for the batch you hold.