# Blends or Separate Vials: Fixed Ratios, Molar Arithmetic and Certificate Requirements

> A co-formulated vial locks its composition at manufacture. Everything that follows — the maths, the certificate, the design freedom — comes from that.

Web page: https://peptidemedixeu.com/en/learn/peptide-blends-vs-single-vials/ · Peptide Medix EU · 3 min read · Updated: 2026-11-03

Manufacture decides the ratio inside a blend; the experimenter decides it in a multi-vial stack. Every other difference, whether in certificate interpretation, concentration calculations or purity claims, flows from that single fact. Picking between blends and separate vials is a matter of study design before it is a matter of purchasing, and the category's most frequent mistake is handling a co-formulated vial as though it held one molecule. Below we describe the three formats, the ratio and molarity arithmetic a blend imposes, how a multi-component certificate must differ from a single-peptide one, and which format suits which purpose.

## Three formats, not two

The contrast between the [Wolverine blend](https://peptidemedixeu.com/en/products/bpc-157-tb-500-wolverine/) and the Wolverine Stack makes the point: one is a single vial of BPC-157 and TB-500 co-lyophilized at a fixed 1:1 mass ratio, the other is three separately sealed vials of BPC-157, TB-500 and [GHK-Cu, whose proportions](https://peptidemedixeu.com/en/products/ghk-cu/) you set yourself.

## Interpreting the label

Blend labels give total mass and, where the split is unequal, the per-component breakdown. A vial marked 10 mg (5/5) holds 5 mg of each of two peptides. A vial marked simply 80 mg, as with the four-component [KLOW Blend](https://peptidemedixeu.com/en/products/klow-blend/), leaves the certificate to reveal how those 80 mg divide, and in most four-component preparations the split is not equal. Any blend whose documentation refuses to state per-component mass cannot be used quantitatively.

### Working out concentration per component

1. Begin with the blend. Reconstituting a 10 mg (5/5) Wolverine vial in 2 mL of diluent gives 10 ÷ 2 = 5 mg/mL of total peptide.
2. Divide it. Since the vial holds 5 mg of BPC-157 and 5 mg of TB-500, the solution is 2.5 mg/mL of each rather than 5 mg/mL of either.
3. Per graduation. One unit on a U-100 syringe, 0.01 mL, holds 25 mcg of BPC-157 plus 25 mcg of TB-500. A 0.1 mL withdrawal gives 250 mcg of each, 500 mcg in total.
4. Against separate vials. Reaching the same 2.5 mg/mL of each from single vials means reconstituting 5 mg of BPC-157 in 2 mL and 5 mg of TB-500 in 2 mL: two reconstitutions and two septum entries per transfer, but the ability to change either concentration afterwards.

The mg/mL arithmetic beneath this is exactly what any vial requires and is covered in peptide reconstitution math explained.

### Where equal mass misleads

This is the point that trips up experienced researchers. Equal masses give equal moles only when the components share a molecular weight, which they seldom do.

- BPC-157 weighs 1,419.55 Da, so 2.5 mg/mL means 2.5 g/L ÷ 1,419.55 g/mol = 1.76 mM.
- TB-500 weighs 889.02 Da, so 2.5 mg/mL means 2.5 ÷ 889.02 = 2.81 mM.

Identical masses therefore supply roughly 1.6 times as many [TB-500 molecules](https://peptidemedixeu.com/en/products/tb-500/) as BPC-157 molecules. For questions of receptor occupancy or stoichiometry that is the figure that counts, and a fixed-mass blend offers no way to correct it. Designs requiring [equimolar](https://peptidemedixeu.com/en/learn/peptide-molecular-weight-and-moles/) components require single vials.

## Requirements for a blend certificate

A single-peptide certificate carries one [HPLC purity value](https://peptidemedixeu.com/en/learn/hplc-purity-explained/) and one mass-spectrometry identity confirmation. No blend can be summarised that way, so honest documentation looks different:

- Purity per component, determined before blending. Each peptide should be synthesised, purified and released against its own certificate before combination. "≥99% purity" on a blend normally means every input met that specification, not that the mixture yields one 99% peak.
- A chromatogram that separates the components. Under reversed-phase conditions, four peptides of differing hydrophobicity elute at four retention times, so a blend chromatogram should display the expected peak count with the expected area ratios. One broad peak is a warning sign.
- Per-component mass in the vial, determined gravimetrically at fill or by quantitative amino acid analysis.
- Identity confirmation for every component, since a blend has several molecular weights and MS should account for all of them.

The general framework for reading such documents is in how to read a peptide COA. Where a supplier's blend certificate offers a single purity number and one mass with no per-component detail, the document is not describing the product.

## Matching format to purpose

### Reach for a blend when

- The protocol fixes a ratio you have no intention of changing, as with CJC-1295 + Ipamorelin, where two secretagogues act at different receptors on one cell and the pairing is the established research configuration.
- Handling steps contribute meaningful error. Each reconstitution brings pipetting variance, a septum puncture and a contamination risk, and a four-component blend removes three of each.
- Cost per milligram of material matters and the supplied ratio is acceptable.

### Reach for separate vials when

- One component must be varied against the others, the defining feature of a concentration-response design.
- The comparison has to be equimolar rather than equal-mass.
- Components differ substantially in stability. Copper peptides, methionine-bearing sequences and disulfide-bonded peptides degrade on different schedules, and once co-formulated in solution the whole vial is governed by its weakest member.
- Lot traceability per component is needed for publication or internal quality control.
- Components require different diluents or pH ranges to dissolve properly.

The [NAD+ Longevity Stack](https://peptidemedixeu.com/en/products/nad-stack/) typifies the second list: three individually sealed vials sold as a kit and reconstituted independently.

## Frequent errors

- Reading total vial mass as per-component mass. An 80 mg four-component vial holds 80 mg of nothing in particular.
- Presuming an equal split when the label says nothing about one.
- Quoting molar concentrations for a blend without recalculating each component against its own molecular weight.
- Accepting one purity figure for a multi-component vial.
- Trying to split a blend to recover a single component. Once co-lyophilized, separation demands preparative chromatography; if you need one peptide alone, buy it alone from the lyophilized vial range.

The complete co-formulated and multi-vial range is in peptide blends and stacks.

## Frequently asked questions

### What is meant by "10 mg (5/5)" on a label?

The vial holds 10 mg of peptide in total, divided as 5 mg of each of two components. Reconstituted in 2 mL of diluent it gives 5 mg/mL overall but 2.5 mg/mL of each component, and the latter is what belongs in your calculations.

### Does a 1:1 blend contain equal moles?

Only by chance. Equal masses are equimolar solely when both peptides weigh the same. BPC-157 is 1,419.55 Da and TB-500 is 889.02 Da, so 2.5 mg/mL of each yields 1.76 mM and 2.81 mM respectively, about 1.6 times more TB-500 molecules. Equimolar designs need separate vials.

### What must a blend certificate report?

Purity for each component measured before blending, a chromatogram separating every component at its own retention time with the expected area ratios, the mass of each component in the vial, and mass-spectrometry identity confirmation for every molecular weight present. One purity value and one mass cannot describe a multi-component product.

### Can a blend be taken apart again?

Not in practice. Separating co-lyophilized components requires preparative chromatography and a re-purification workflow. If a study needs a single peptide, order that peptide on its own rather than trying to fractionate a blend.

### In which situations is a blend preferable?

When the protocol uses a fixed ratio that will not change, when handling steps add meaningful variance, and when the components are stable in each other's company. Every reconstitution avoided removes a pipetting error, a septum puncture and a contamination opportunity, which counts for a lot in a four-component preparation.

### When are separate vials the better option?

Whenever one component is varied against the others, whenever the comparison must be equimolar rather than equal-mass, whenever the components differ appreciably in stability, whenever per-component lot traceability is required, and whenever different diluents or pH ranges are needed for clean dissolution.

### What distinguishes a stack from a blend?

A stack supplies several individually sealed and individually tested vials as one catalogue item at a kit price. Nothing is co-formulated, so every vial has its own certificate and can be reconstituted to its own concentration. Only the pricing is bundled, not the chemistry.

### Do blends degrade more quickly than single vials?

They can once in solution. When components share a vial, the working life of the whole preparation is dictated by its least stable member, and copper complexes, methionine-containing sequences and disulfide-bonded peptides all decay on different timescales. Lyophilized and frozen, the gap is much narrower.

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For laboratory research use only. This page is provided for scientific and educational information. Materials referenced here are sold strictly for in-vitro laboratory research by qualified professionals — not for human or veterinary use, and nothing on this page is medical advice.