DPG or TEC: which solvent should you choose in perfumery?

DPG and TEC are two highly useful technical solvents in the perfumer's practice. Both have a discreet odor, evaporate much more slowly than ethanol and can be used for dilutions, working solutions or as co-solvents. That does not, however, make them equivalent.

The useful question is not “which solvent is better?” but “which technical problem do I need to solve in this formula?”. The choice can change depending on the raw material being diluted, the final system — alcoholic, non-alcoholic or containing water — and the effect the solvent has on volatility, viscosity, clarity and diffusion.

DPG vs TEC: the difference at a glance

This table is a formulation guide. Actual compatibility must always be checked with the raw material and finished product.

What is DPG and why is it so widely used in the laboratory?

DPG — Dipropylene Glycol is a clear, almost odorless, low-volatility and slightly viscous liquid. In everyday practice it is particularly convenient for preparing dilutions and working solutions of very powerful raw materials, crystals, concentrated bases or ingredients that need to be dosed in very small quantities.

If, for example, a molecule needs to be studied at 1% or 10%, a properly prepared solution makes it possible to weigh more manageable quantities and compare the material in a formula more precisely. It is the same principle used when studying aroma chemicals by function rather than evaluating them only neat on a blotter.

An important technical advantage of DPG is its miscibility with both ethanol and water. This makes it flexible in the laboratory, but one distinction is essential: the fact that DPG mixes with water does not mean that it automatically makes essential oils, absolutes, resins, bases or hydrophobic aroma chemicals water-soluble.

When DPG is often the most practical starting point

• For preparing technical dilutions at 10%, 1% or other working concentrations.
• For handling very powerful raw materials when direct weighing would be insufficiently precise.
• For some crystals, viscous materials or concentrated bases, after checking their actual solubility.
• When a co-solvent compatible with a system that also contains water is useful, without confusing that compatibility with true solubilizing action.
• For laboratory trials where a low-volatility working solution is desirable.

What is TEC and when does it become interesting?

TEC — Triethyl Citrate is a low-volatility solvent and co-solvent, clear, low-odor and slightly oily in feel. It is miscible with ethanol but only slightly soluble in water.

TEC becomes particularly interesting when the same water compatibility as DPG is not required and a low-volatility technical carrier is needed for aromatic bases, concentrates, roll-ons and other predominantly non-aqueous or mixed systems. It can help make evaporation more controlled and the opening less aggressive.

Here too, however, “low volatility” does not automatically mean “better longevity.” If the amount is too high for the architecture of the formula, TEC can slow the opening, make the composition feel denser and reduce the prominence of bright notes.

When TEC may be the more logical choice

• When the system is not primarily aqueous and full water miscibility is not required.
• When a low-volatility co-solvent is wanted for concentrates, aromatic bases or non-alcoholic preparations.
• When you want to control and soften evaporation without adding an obvious odor.
• When a DPG solution feels too glycol-like or viscous for the intended formulation effect and you want to test an alternative with different behavior.

For raw-material dilutions: DPG or TEC?

For routine laboratory work, DPG is often the first solvent to test when the objective is simply to prepare an accurate working solution. Its common professional use, low volatility and miscibility with alcohol and water make it practical for many raw materials.

This does not mean TEC cannot be used for a dilution. It means the solvent should be chosen according to what happens next: will the solution be used only for study? Will it enter an alcoholic formula? A concentrate? A non-aqueous system? Will the amount of solvent eventually become significant in the finished composition?

Also, neither solvent universally dissolves every perfumery raw material. Resins, crystalline materials, complex naturals and particular molecules must be checked case by case.

Does an alcoholic perfume really need DPG or TEC?

Not necessarily. In an alcoholic fine fragrance, ethanol can remain the main carrier and there is no technical requirement to add DPG or TEC by default.

A co-solvent makes sense when it solves a concrete problem: it facilitates handling of a raw material, improves the compatibility of a solution, deliberately changes the evaporation curve or allows an existing working solution to be incorporated into the formula.

A common mistake is to add a low-volatility solvent simply because it is expected to “fix” the perfume. DPG and TEC can influence the rate of evaporation, but they should not be treated as universal fixatives. In excessive quantities they can also reduce lift and brightness in the opening.

What about an oil-based or non-alcoholic perfume?

Both DPG and TEC can be used in non-alcoholic systems, but “oil-based” covers many different formulation types. A roll-on, a concentrated aromatic base and a system built with cosmetic oils do not necessarily have the same requirements for solubility, texture and compatibility.

DPG can be useful as a technical solvent and diluent; TEC can be interesting as a low-volatility carrier/co-solvent in predominantly non-aqueous systems. Neither should automatically be assumed to be compatible with every oil or every blend of raw materials. The complete formula must be checked for clarity, separation, viscosity and behavior over time.

And in water-based formulas?

Here the difference is important. DPG is miscible with water; TEC is only slightly soluble. But even when DPG is chosen, a perfume composition does not automatically become a stable aqueous solution.

Many odorant materials are hydrophobic. Cloudiness, sediment or separation can therefore appear even when the technical solvent itself is perfectly miscible with water. A water-based product may require a true solubilizing system designed for that specific formula and fragrance concentration.

This is why “DPG mixes with water” and “DPG solubilizes perfume in water” are two completely different statements.

Can DPG and TEC be substituted 1:1?

There is no universal 1:1 substitution rule. Although both are used as technical solvents, they have different properties and can affect the following in different ways:

• the speed of the fragrance opening;
• the brightness of more volatile notes;
• viscosity;
• clarity and solubility;
• behavior in the presence of water;
• the overall impression of the drydown and evaporation curve.

If a formula is already balanced with DPG, replacing it with the same mass of TEC does not guarantee the same result, and vice versa.

Can DPG and TEC be used together?

Yes. In principle they can coexist in the same formulation when each solves a specific technical function. For example, a raw material might enter the formula through a working solution in DPG while TEC is used separately as a co-solvent in the base.

There is, however, no standard DPG/TEC ratio that applies to every formula. The total amount of low-volatility solvents should be evaluated in the finished product, because what is useful on a small scale can become excessive when several technical solutions are added together.

The most useful test: control, DPG and TEC

To understand which solvent works better in your formula, prepare three small samples and change only one variable.

1. Sample A — control: the reference formula without the new co-solvent, when technically possible.
2. Sample B — DPG: the same formula with a controlled amount of DPG.
3. Sample C — TEC: the same formula with a comparable amount of TEC.

Do not evaluate only the immediate smell. Check:

• clarity immediately and after 24–48 hours;
• opening in the first few minutes;
• diffusion and brightness in the heart;
• drydown after several hours;
• viscosity and ease of dosing;
• any sediment or separation;
• stability after resting.

If the finished product is intended for sale, testing must then be extended to the normal stability, compatibility and compliance checks required for that product category.

A practical rule for choosing

Choose DPG as a first candidate when the main problem is preparing precise laboratory dilutions, handling very powerful materials or working in a system where water miscibility may be useful.

Choose TEC as a first candidate when you are working mainly in non-aqueous or concentrated systems and want a low-volatility co-solvent with behavior different from a glycol.

Do not automatically choose either one in an alcoholic formula that is already clear and performing well: first define which technical problem the solvent is supposed to solve.

You can find both materials in the Solvents collection, kept separate from technical additives because DPG and TEC perform a specific solvent/co-solvent function.

Conclusion

DPG and TEC are not two versions of the same solvent. DPG is often more practical for dilutions and everyday laboratory work, particularly because of its miscibility with alcohol and water. TEC is a low-volatility co-solvent that becomes particularly interesting in predominantly non-aqueous systems and when a different control of evaporation is desired.

The best choice comes from the function required and from comparison in the real formula, not from an absolute ranking between the two materials.

Technical note: always consult the current SDS and technical documentation for the solvents and raw materials being used. Solvent choice does not modify or replace any applicable IFRA limits, labeling requirements or other obligations for ingredients and the finished product.