Co-Formulant Change Control – Changing “Inerts” Without Changing the Product

This topic is part of the SG Systems Global regulatory & operations glossary.

Updated December 2025 • Change Control, MOC, QRM, Supplier Qualification, COA Verification • Formulation, QA, Regulatory, Supply Chain, Manufacturing

Co‑formulant change control is the structured process for evaluating, approving, implementing and verifying changes to non‑active formulation components (solvents, surfactants, dispersants, thickeners, antifoams, preservatives, wetters, adjuvants, carriers and other “inert” ingredients) without unintentionally changing product performance, safety profile or compliance status. In agricultural chemicals, co‑formulants are rarely truly inert. They drive emulsification, suspension stability, viscosity, pourability, sprayability, tank‑mix compatibility, packaging interaction and, in some cases, hazard communication and labeling outcomes. A weak change process turns co‑formulant substitution into silent reformulation: the batch might still meet a narrow lab spec today, but drift later as field performance complaints, stability failures, or regulatory questions you can’t answer cleanly.

“If switching a surfactant is treated like changing a bolt, your ‘same product’ claim won’t survive real-world use.”

1) What Co‑Formulant Change Control Actually Is

Co‑formulant change control is more than updating a purchase spec. At its core, it answers three questions: (1) What exactly is changing (supplier, grade, composition range, impurity profile, physical properties, regulatory listing, packaging compatibility)? (2) What could that change affect (stability, efficacy, safety, manufacturability, labeling, customer use behavior)? (3) Can we prove the change is acceptable through defined evidence and controlled implementation? A controlled change has a clear scope, risk assessment, testing plan and release criteria. An uncontrolled change is a purchasing decision that becomes a manufacturing experiment, and the “evidence” becomes hindsight after something fails.

2) Why Co‑Formulants Are Not Inert in Practice

Co‑formulants may not carry the primary pesticidal claim, but they frequently determine whether the product behaves like the registered formulation in real conditions. Surfactant chemistry drives emulsification and tank‑mix behavior. Polymer systems control viscosity, suspension stability and pourability. Solvent selection impacts solubility, crystallisation risk and flash point. Preservatives control microbial growth in water‑based systems. Even small shifts in these components can change performance outcomes without immediately changing assay. That is why co‑formulant changes require technical and quality governance, not just procurement approval.

3) Regulatory Reality – “Same Label” Can Still Mean “Not the Same Product”

Across jurisdictions, formulation changes can trigger different regulatory obligations depending on the product type and the nature of the change. Even when a change is allowed operationally, you still need internal evidence that the product remains within the intended formulation envelope and hazard communication remains correct. The practical message is: treat regulatory assessment as a required checkpoint in the change workflow. If your process doesn’t force a regulatory review step, you will eventually ship a “minor” co‑formulant change that creates a major compliance conversation.

4) Change Triggers – What Should Automatically Start a Control Process

Good governance starts with triggers. Events that should automatically route into change control include: supplier change; grade substitution; formulation tolerance widening; any change in composition range of a multi‑component co‑formulant (e.g., ethoxylate distribution); impurity profile shifts; changes to stabiliser packages; changes to physical properties that affect processing (viscosity, density, melting point); and any rebranding that masks “same name, different thing.” If the trigger list is vague, the plant will discover changes only after complaints or batch drift.

5) Risk Assessment – QRM Before You Test, Not After You Fail

Change control should begin with quality risk management (QRM). The point is to identify what could break and therefore what you must verify. For example, a solvent swap may demand hazard re‑evaluation and solubility/precipitation testing; a dispersant shift may demand particle size and re‑dispersion tests; a preservative change may demand micro challenge logic in water‑based systems. Without QRM, testing plans become random, and teams over‑test the easy things while missing the failure modes that matter in the field.

6) Supplier Qualification – Co‑Formulants Live and Die by Supplier Consistency

Co‑formulant changes often originate with supply disruptions: a supplier exits, a plant relocates, a feedstock changes. That is exactly why supplier qualification and COA verification matter. For higher‑risk co‑formulants, qualification should include: composition understanding (what is actually in it), variability controls, analytical confirmation strategy, and change notification expectations. A supplier who cannot reliably tell you when they change feedstocks is not a safe supplier for a co‑formulant that controls product behavior.

7) Material Identity and Incoming Controls – Don’t Assume Labels Are Truth

Many “same co‑formulant” failures are actually identity failures: mislabeled containers, wrong grade received, or a new product line delivered under an old name. Strong incoming controls include material identity confirmation, defined sampling rules, and clear acceptance criteria beyond “COA present.” In data‑mature operations, lot identity is captured digitally and tied to usage through lot assignment and genealogy so you can link performance outcomes to the exact co‑formulant lots used.

8) Formulation Science Verification – Stability, Performance and Compatibility

Verification should match the risk. Typical evidence packages include accelerated stability screening, freeze‑thaw where relevant, viscosity and flow curves over time, phase separation checks, re‑dispersion testing for suspensions, and tank‑mix compatibility in representative water qualities. Field performance equivalence can be complex; you don’t always need full efficacy trials, but you do need scientifically justified proxies that are sensitive to the co‑formulant’s function. If the co‑formulant controls dispersion, you must test dispersion behavior; if it controls emulsification, you must test emulsion stability. Testing the wrong attribute is a common way to “approve” a change that later fails.

9) Process Impact – Manufacturing Is Where Small Differences Become Big Problems

Co‑formulant changes can change how the process behaves: mixing time to reach homogeneity, foaming behavior, pumpability, filtration loading, or heat generation. That means the change process must assess manufacturing impact and, where needed, update parameters under recipe and parameter enforcement. If a batch needs different shear or order of addition with a new surfactant, that is not “no impact.” It is a process change that must be documented, trained, and controlled like any other critical change.

10) Packaging Compatibility – Co‑Formulants Can Attack Plastics and Liners

Packaging interaction is an underappreciated failure mode. Certain solvents, surfactants and additives can extract plasticisers, stress‑crack HDPE, soften gaskets, or change permeation behavior. A co‑formulant swap that improves formulation stability but degrades container integrity is still a failure. Practical controls include compatibility screening with representative packaging, inspection of seals/liners, and stability checks in the final pack – not just in glass jars in the lab. Packaging problems tend to appear late and expensively: leaks in distribution and customer returns.

11) Master Data and Recipe Governance – BOMs, Specs and Versioning

Once a change is approved, governance must make it real. That means updating BOM, raw‑material specifications, allowable alternates (if you use them), and recipe definitions under recipe versioning. If the old co‑formulant remains selectable in the system without constraints, operators will keep using it. If purchasing can buy either version without clear controls, warehouses will mix inventory. Master data is where change control either becomes enforceable or becomes a document nobody follows.

12) Digital Execution – Hard Gating in MES/WMS/ERP

In modern operations, co‑formulant change control should be enforced digitally. MES should prevent selection of unapproved materials for a given recipe version. WMS should control inventory status and prevent issue of quarantined or obsolete co‑formulant lots. ERP should reflect allowed alternates and block purchasing of withdrawn grades when required. This is where hard gating changes the game: it turns policy into enforcement.

13) Disposition of In-Flight Inventory – What Happens to Old Co‑Formulant Stock

Every change creates inventory questions: do you consume existing stock, segregate it by recipe version, return it to the supplier, or scrap it? Your answer must be documented and consistent. For some changes, you may allow a controlled transition period; for others, you may require immediate cutover due to hazard or performance risk. Either way, you need clean traceability (see end‑to‑end genealogy) so you can identify which finished lots used which co‑formulant version. Transition ambiguity is how recall scope balloons later.

14) Trending and CAPA – Repeated Co‑Formulant Changes Are a Risk Signal

Frequent co‑formulant substitutions often indicate systemic issues: unstable suppliers, over‑tight purchasing targets that force opportunistic buying, or formulations that are not robust to normal variability. Trending change frequency, reasons, and post‑change performance indicators provides a reality check. If changes correlate with increased complaints, batch variability or repeated variance investigations, you need corrective action, not better paperwork. Where appropriate, the response should follow normal quality system logic: investigation, RCA, CAPA and effectiveness checks.

15) FAQ

Q1. Are co‑formulant changes always “minor” because they are not the active ingredient?
No. Co‑formulants often control physical stability, usability and even hazard profile. A surfactant or solvent change can materially change product behavior without changing assay. Treat co‑formulant changes as real formulation changes unless you have evidence they are functionally equivalent.

Q2. Can we approve co‑formulant substitutions with only COA review?
Usually not. COAs rarely capture the properties that drive performance (distribution, impurities, interfacial behavior, variability). COA review is necessary, but higher‑risk co‑formulants typically require functional testing and a defined risk‑based evidence package.

Q3. What’s the biggest failure mode in co‑formulant change control?
Approving on paper and assuming equivalence. The second biggest is allowing “temporary” substitutions that become permanent without proper governance. Both create silent drift that shows up later as complaints and unstable batches.

Q4. When do we need additional labeling or regulatory assessment?
When the change could affect hazard communication, product composition commitments, or jurisdictional formulation constraints. Your change process should force a Regulatory checkpoint so this isn’t decided ad‑hoc on the shop floor.

Q5. What is a practical first step to improve co‑formulant change control in a legacy plant?
Start by defining co‑formulant criticality tiers (what can change easily vs what demands deep review), then standardise triggers, risk assessment templates and required tests per tier. Lock recipe versioning and block unapproved substitutions operationally so the process doesn’t rely on memory.

Related Reading
• Governance: Change Control | Management of Change (MOC) | QRM | Recipe Versioning | BOM
• Suppliers & Inputs: Supplier Qualification | COA Verification | Material Identity Confirmation | Lot Assignment
• Execution & Outcomes: MES | WMS | Lot Traceability | Variance Investigation | CAPA
• Integrity: Data Integrity | Audit Trail | Hard Gating | QMS