Emulsifiable Concentrate Formulation: Design and Testing

Emulsifiable Concentrate Formulation: What an EC Is and Where It Fits

CropLife International defines an emulsifiable concentrate, coded EC, as a liquid, homogeneous formulation to be applied as an emulsion after dilution in water. The FAO/WHO specification template adds that the technical active ingredient is dissolved in suitable solvents with other formulants, giving a stable liquid free from visible suspended matter and sediment. The solvent holds the active in solution, and the emulsifiers break the solvent phase into droplets when the tank is filled. A 2025 paper in the Journal of Pesticide Science notes that EC still holds a large proportion of the pesticide market.

The CropLife Technical Monograph 2 states that more than one formulation type can suit a product and that the most appropriate one should be chosen. For EC the first filter is simple, because the active ingredient has to dissolve in a water-immiscible solvent system. Our guides to starting an agrochemical formulation business and to the herbicide and pesticide formulation unit cover the commercial side of that choice.

The first design decision inside that clear liquid is the solvent.

EC Agrochemical Solvent Selection: Solvency, Flash Point and Toxicity

In emulsifiable concentrate formulation, the solvent decides whether the active ingredient stays dissolved at every temperature the product will meet. A 2018 patent lists the water-immiscible solvents commonly used for EC as aromatic hydrocarbons, paraffinic hydrocarbons and ester solvents such as methyl oleate. Aromatic hydrocarbons such as xylene remain the traditional choice, but the authors of a 2025 Journal of Pesticide Science paper describe aromatic solvents as having high toxicity and low biodegradability. They add that solvent toxicity is rarely considered in agrochemical risk assessment, so solvent choice balances solvency, safety and emulsifiability.

• Solvency for the active — the concentrate has to remain a homogeneous liquid free from visible suspended matter and sediment, which is the FAO/WHO description clause.
• Water immiscibility — the solvent has to form droplets in the tank, not dissolve into the water.
• Flash point — the FAO/WHO manual notes that flash point is largely determined by the solvents used and is therefore under manufacturing control.
• Toxicity and biodegradability — the 2025 paper argues that these are rarely considered in risk assessment, so they belong in the screening criteria.
• Emulsifier match — the emulsifier blend is chosen for the solvent and active together, so a new solvent means a new blend screen.

The same 2025 paper tested ethylene glycol diacetate, which its authors report has a flash point of 88 °C, as an alternative to xylene. They report that formulations of the herbicides cyhalofop-butyl and nicosulfuron gave better weed control than the xylene equivalents and lower cytotoxicity to human bronchial cells. Treat that as one study with two actives, not as a general substitution rule. Our guide to solvent-based versus waterborne formulations shows the same trade-off in coatings.

With the solvent chosen, the emulsifier system has to be matched to it.

EC Emulsifier Blend: Anionic and Nonionic Surfactant Systems

On dilution, the emulsifier system of an emulsifiable concentrate formulation turns the solvent phase into droplets that stay dispersed long enough to spray. The usual EC emulsifier blend pairs an anionic surfactant, such as a calcium salt of a sulfonated alkylbenzene, with nonionic surfactants from the classes in the table below. The balance between the water-loving and oil-loving parts of each surfactant is expressed as HLB, a scale devised by Griffin in 1949 and 1954. Wikipedia's summary of the HLB scale gives 8 to 16 as the range for oil-in-water emulsifiers.

Our guide to HLB values and emulsifier selection explains the scale in detail, and the principle is the same in agrochemicals even though the oil phases differ. The blend still has to prove itself in the test conditions that regulators and buyers use.

• Screen by HLB first — build a ladder of blends across the HLB range and test each against the solvent and active.
• Test in soft and hard water — the FAO/WHO manual states that dilution water hardness and temperature can affect the physical properties of formulations diluted before use.
• Test at both ends of the dilution range — the manual asks for the highest and lowest recommended use rates within the scope of the method.
• Watch foam — the persistent foam test limits the foam produced when the spray tank is filled.

Matching the blend to the water and to the dilution range is exactly what emulsion stability testing proves.

Emulsion Stability in Agrochemical EC: Hardness, Cream and Free Oil

Emulsion stability is the test that matters most for an emulsifiable concentrate formulation, because the spray tank is where the emulsion has to work. The FAO/WHO manual states the aim as ensuring that the active ingredient is uniformly dispersed in the emulsion, giving a satisfactory and effective mixture throughout spraying. The physical properties of formulations diluted with water can be affected by the hardness and temperature of the water, so the test uses CIPAC standard waters A and D. Results are read as cream and free oil at set times.

• Creaming — droplets rise and concentrate as a cream layer at the top of the emulsion.
• Coalescence — droplets merge, and the separated solvent phase forms free oil. Our guide to creaming and coalescence explains both mechanisms.
• Crystallisation — the active comes out of solution on dilution. The patent states that a diluted EC should stay free of crystallisation until spraying, preferably for at least two hours.
• Water hardness — the FAO/WHO manual says dilution water hardness can affect the physical properties of a diluted formulation, which is why the test uses two standard waters.

1. 0 hours — initial emulsification must be complete.
2. 0.5 hours — the volume of cream is measured against the specification limit.
3. 2 hours — cream and free oil are both measured.
4. 24 hours — re-emulsification must be complete, and the template notes that tests after 24 hours are needed only where the 2-hour results are in doubt.
5. 24.5 hours — cream and free oil are measured again.

The manual says the test is normally carried out before and after the heat stability test, at 30 ± 2 °C or 25 ± 5 °C. Limits for cream and free oil are product specific, so each specification sets its own values and the template leaves them blank.

The emulsion test is one clause in a longer template, and the full list shows what a buyer or regulator can ask for.

EC Specification Tests: What the FAO/WHO Template Requires

FAO and WHO publish a specification template for EC that buyers and regulators use as the benchmark for emulsifiable concentrate formulation. Its clauses cover description, active ingredient content, relevant impurities, physical properties and storage stability, and each clause is tied to a CIPAC method. The FAO/WHO manual fixes the test conditions, and the product specification supplies the limits. A manufacturer who builds the test plan on this template can answer most buyer questions before they are asked.

Flash point is not a clause in the current template. The manual explains that flash point measures hazard, not performance, and that the risk depends on climate and on the uses registered in each country. FAO and WHO therefore withdrew the flash point clauses that appeared in some older guideline specifications and rely on national authorities. A formulator should expect national requirements to apply to whatever solvent system the product uses.

Passing these tests on a fresh laboratory batch proves the design, and storage then tests it over time.

EC Storage Stability: Cold Crystallisation, Heat Ageing and Foam

Storage tests exist because a batch that passes at release can still change over time. At low temperature the main problems are precipitation or separation of liquid phases, and the FAO/WHO manual requires the original properties to be restored on warming and mixing. The accelerated test at elevated temperature protects the active ingredient content and the physical properties, and it gives an early prediction of long-term stability at more moderate temperature. Foam is the third failure, and the persistent foam test limits the foam produced while the spray tank is filled.

• Cold storage — MT 39.3 holds the sample at 0 ± 2 °C for 7 days, and the manual allows a lower temperature where buyer and seller agree.
• Heat storage — MT 46.4 holds the sample at 54 ± 2 °C for 14 days. The formulation must still comply with the clauses for by-products, acidity or pH, and emulsion stability, with the active content held above its limit.
• Degradation above 5 percent — the manual requires further information, such as identification and quantification of the degradation products, where active ingredient degradation exceeds 5 percent.
• Foam — MT 47.3 is run at the highest rate of use the supplier recommends, and it is not repeated after heat storage except for products packed in water-soluble bags.
• Polar co-solvents — they can prevent cold crystallisation, but the patent background says such combinations often lead to crystallisation in the diluted formulation.

Once the design survives storage, the remaining task is to make it reliably at scale.

Making EC: Process Steps, Safety and Scale-Up

Emulsifiable concentrate formulation reaches the plant as a blending operation, but the solvent makes it a flammable-liquid operation. The FAO/WHO manual notes that flash point is largely determined by the solvents used for formulation and is therefore under manufacturing control. That makes solvent selection the first safety decision as well as the first performance decision. Scale-up then has to keep dissolution, emulsifier addition and clarity checks consistent as batches grow.

1. Charge the solvent — add the solvent system, and any co-solvent, to a stirred vessel designed for flammable liquids.
2. Dissolve the active ingredient — confirm complete dissolution before continuing, because undissolved material fails the description clause.
3. Add the emulsifier blend — mix to a homogeneous liquid.
4. Check clarity — the finished liquid has to be free from visible suspended matter and sediment.
5. Sample for release testing — measure active content, water content, acidity or pH, and emulsion stability.
6. Fill and retain samples — keep retained samples for the cold and heat storage programme.

• By-products — the template limits by-products of manufacture or storage relative to the active content, so the technical grade quality matters.
• Water control — the template lists water as a relevant impurity where required, so raw material moisture belongs in the plant controls.
• Scale-down models — our guide to scale-down models that predict the plant explains how to carry bench results across.
• Toll formulation — many brand owners use contract capacity, and our guide to manufacturing without a factory explains the model.

Making the product correctly is only part of the commercial path, because the product also has to be registered.

Registration and Compliance Context in India

In India, pesticide formulations are registered through the Central Insecticides Board and Registration Committee under the Insecticides Act, 1968. The CIB&RC pages on the PPQS website publish the lists of registered formulations, banned or restricted pesticides, and approved manufacturers and import sources. This article covers formulation science only and gives no crop doses, label claims or registration advice for a specific active ingredient. A formulation consultant supports the technical work that sits behind a filing, but the registration decision belongs to the authority.

With the regulatory frame clear, the next question is who does the development work.

Working With an Agrochemical Formulation Consultant

Emulsifiable concentrate formulation development means screening many solvent and emulsifier combinations against one active ingredient and several waters. An agrochemical formulation consultant runs that screen against the FAO/WHO test template and keeps the data in a form a buyer can audit. Agrochemical product development services also cover specification writing and stability protocols. A contract formulation agrochemical manufacturer then carries the product into a plant that handles flammable liquids.

1. Profile the active ingredient — measure its solubility in candidate solvents at ambient temperature and at 0 °C.
2. Shortlist solvents — rank them on solvency, flash point, toxicity and biodegradability.
3. Screen emulsifier blends — test them in both CIPAC standard waters at the highest and lowest dilutions.
4. Run storage trials — complete the cold and heat tests and repeat the emulsion test after each.
5. Check foam and water content — confirm the persistent foam and moisture results.
6. Write the specification — use the FAO/WHO template with product-specific limits.
7. Transfer to the plant — verify scale-down batches against the laboratory results.

Our agro chemicals range and our guide to agrochemical formulation and safety show where EC sits among the other formulation types. Global Formulation provides EC solvent and emulsifier screening, stability protocols, specification support and scale-up for agrochemical manufacturers.