| HS Code | 831812 |
| Chemical Name | O,O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate |
| Cas Number | 2921-88-2 |
| Molecular Formula | C9H11Cl3NO3PS |
| Molecular Weight | 350.59 g/mol |
| Appearance | White to off-white crystalline powder |
| Solubility | Slightly soluble in water; soluble in acetone, methanol, ethyl acetate and other organic solvents |
| Melting Point | 41-43°C |
| Boiling Point | Approximately 160°C at 0.1 mmHg (decomposes) |
| Therapeutic Category | Organophosphate antiparasitic and insecticidal agent |
| Mechanism Of Action | Irreversibly inhibits acetylcholinesterase, causing acetylcholine accumulation and disruption of nerve function |
| Indications | Treatment of susceptible ectoparasitic and endoparasitic infestations (as per approved veterinary/pharmaceutical formulations) |
| Dosage Forms | Tablet, capsule, granule, and injection |
| Route Of Administration | Oral and injectable |
| Purity | 98.0% to 102.0% on dried basis |
| Storage Conditions | Store in tightly sealed containers in a cool, dry, well-ventilated area, protected from light and moisture |
| Shelf Life | 24 months when stored under recommended conditions |
As an accredited Chlorpyrifos Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Pharma Grade Chlorpyrifos API is packed in 25 kg HDPE drums with double polythene liners and tamper-evident seals for oral and injectable use. |
| Container Loading (20′ FCL) | 20′ FCL: palletized drums of Chlorpyrifos Pharma Grade API, secured for oral/injectable formulations, with proper segregation and ventilation. |
| Shipping | Ship as a hazardous, moisture-sensitive pharmaceutical API. Use sealed, light-protected, temperature-controlled containers (15–25°C). Comply with IATA/IMDG for air/sea. Label as Toxic (Class 6.1). Include MSDS, COA, and traceability docs. Handle with gloves and goggles; prevent leaks. Ensure secure, upright storage. |
| Storage | Store Chlorpyrifos Pharma Grade API in tightly sealed, original containers under cool, dry, well-ventilated conditions, ideally at controlled room temperature (20–25°C). Protect from moisture, direct sunlight, heat, and incompatible substances like strong oxidizers or alkalis. Ensure proper labeling, segregation, and secure handling to prevent contamination, degradation, or accidental exposure. |
| Shelf Life | Shelf Life: 24 months from manufacture date when stored in original tightly closed container, protected from light, heat, and moisture. |
Chlorpyrifos pharmaceutical-grade active ingredient (CAS 2921-88-2, Mw 350.59 g/mol) has no recognized human pharmacopoeial monograph in USP, Ph. Eur., or BP, and no authorized human oral tablet, capsule, granule, or injectable product has been registered under 21 CFR 314 or Directive 2001/83/EC. Its acetylcholinesterase inhibition lacks the selectivity margin required for systemic human therapy, and the high log Kow of 4.96 indicates rapid sequestration in lipid-rich tissues following systemic exposure. Accordingly, the downstream sectors described below are restricted to registered veterinary ectoparasiticide devices, non-food animal premises, and professional non-food pest-control matrices in jurisdictions where chlorpyrifos remains authorized. Each scenario includes the applicable compliance anchor, formulation addition ratio, downstream production process, and terminal finished product type.
| Sector | Primary compliance anchor | Load or dilution | Terminal form |
|---|---|---|---|
| Cattle ear tag polymer matrix | EPA FIFRA 40 CFR 156.10; OECD 505 | 2.0–8.0% w/w finished tag | 8–15 g single-season ear tag |
| Sheep ectoparasiticide emulsifiable concentrate | FAO/WHO JMPS; CIPAC MT 36.3; Directive 91/412/EEC | 240–480 g/L concentrate; final dip 0.25–1.0 g/L a.i. | 1–20 L HDPE concentrate |
| Poultry house premise spray | EPA FIFRA Section 3; 40 CFR 156.10 | Final spray 0.25–0.50% a.i. (2,500–5,000 ppm) | 5 L / 20 L concentrate |
| Granular non-food soil insecticide | FAO/WHO JMPS; CIPAC MT 59 | 0.5–10.0% w/w active on dry carrier | 25 kg bag / 454 g container |
The slow-release polymer-matrix ear tag sector for non-food cattle is a melt-processed dispersion system in which the limiting threshold is thermal degradation of the phosphorothioate ester rather than hydrolytic stability in aqueous media. Formulation loading is held between 2.0% w/w and 8.0% w/w of the finished tag mass; below 2.0% w/w equivalence with registration data for Haematobia irritans and Stomoxys calcitrans cannot be maintained over a 12–16 week season, while above 8.0% w/w surface exudation and low-temperature embrittlement at −10°C become measurable. The production system uses PVC plastisol with 35–45 phr of DINP or citrate plasticizer and 5–10 phr epoxidized soybean oil co-stabilizer; chlorpyrifos is pre-milled to <50 μm and dispersed under high shear at 20–25°C, then the paste is degassed at −0.08 MPa for 20–30 min before injection molding on presses with 100–200 t clamp force. Molding is performed at 160–175°C with a dwell of 4–8 min, and residence above 180°C is capped at 10 min; batch records show that longer residence increases 3,5,6-trichloro-2-pyridinol content and reduces active content by more than 1.5%. Compliance is anchored to EPA FIFRA 40 CFR 156.10 and OECD 505 accelerated storage at 54±2°C for 14 days. Terminal finished product types are single-season cattle ear tags of 8–15 g per unit.
Chlorpyrifos emulsifiable concentrate for sheep ectoparasite control is formulated at 240 g/L or 480 g/L active ingredient, equivalent to 21.8% w/v and 43.6% w/v. The formulation addition ratio for solvent is 50–70% w/w aromatic hydrocarbon and 5–10% w/w of an anionic/nonionic emulsifier pair. The downstream production process charges the solvent and emulsifier first, adds chlorpyrifos at 20–30°C, and then applies rotor-stator shear at 2000–3000 rpm; the batch passes through a 10 μm filter before filling. Emulsion stability is controlled by CIPAC MT 36.3 in 342 ppm hard water, with an acceptance limit of <2 mL oil separation after 24 h at 30°C. The aqueous dilution pH is maintained at 4.0–6.0 because alkaline hydrolysis of chlorpyrifos accelerates above pH 7.0; the half-life shifts from weeks to days at pH 8.5. Because chlorpyrifos concentrates can precipitate when stored below 5°C, low-temperature stability is assessed before release, as crystal formation in the concentrate changes the dispersed-phase droplet size distribution and complicates accurate dilution into the final dip bath. The final manufacturer-recommended dip addition is 0.25–1.0 g/L active ingredient, depending on target ectoparasite and label registration. In the United Kingdom, this sector falls under VMD veterinary medicinal product authorization and the applicable veterinary GMP framework, formerly Directive 91/412/EEC; in non-EU pesticide jurisdictions, it is registered under national FIFRA-equivalent frameworks. Terminal finished product types are 1 L, 5 L, and 20 L HDPE containers of sheep dip concentrate.
The non-food animal facility premise-spray sector, particularly for poultry house Alphitobius diaperinus and Musca domestica control, uses the same 480 g/L emulsifiable concentrate intermediate but shifts process control from storage to low-pressure hydraulic application. The formulation addition ratio in the end-use mixture is 0.25%–0.50% active ingredient (2,500–5,000 ppm), prepared by diluting the concentrate at 1:100 to 1:200 with water. Downstream application is performed only when birds are removed, using backpack or cart-mounted sprayers at 2–3 bar with 80° flat-fan nozzles; the liquid is directed to wall voids, litter bands, and cage frame interiors at 1 L final spray per 20 m². Re-entry is restricted until treated surfaces are dry. Compliance for this sector is governed by EPA FIFRA Section 3 and 40 CFR 156.10 label directions; in the European Union, non-food animal premises use is not available where chlorpyrifos is non-approved under Regulation (EC) No 1107/2009. Terminal finished product types are 5 L and 20 L professional concentrate containers, not tablet, capsule, granule, or injectable presentations.
Granular carriers for professional turf, ornamental, and industrial non-food soil applications are produced by impregnating a pre-sized 24/48 mesh attapulgite or montmorillonite carrier with chlorpyrifos dissolved in a low-volatility carrier. The formulation addition ratio spans 0.5% w/w to 10.0% w/w active on a dry-weight basis, with commercial products most frequently specified at 5.0% w/w. The downstream production process uses a rotary drum impregnator at 40–50°C, followed by fluid-bed drying with an exhaust temperature capped at 50°C; published data for this specific configuration is limited, but batch records show that higher exhaust temperatures reduce active recovery without improving granule hardness. The carrier is selected with a surface pH of 6.5–7.5 because alkaline carriers accelerate degradation to 3,5,6-trichloro-2-pyridinol during storage. Granule attrition is evaluated by CIPAC MT 59 with an acceptance limit of <5% fines, and dust content is kept below 2%. Compliance for the granular sector is anchored to FAO/WHO JMPS granular specifications and national pesticide registration under EPA FIFRA or equivalent. Terminal finished product types are 25 kg low-dust bags or 454 g professional containers for rotary-spreader application.
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Chlorpyrifos Pharma Grade API is supplied as a non-compendial organothiophosphate active designated CPS-PG-99 for Tablet / Capsule / Granule / Injection, Oral & Injectable evaluation. The compound is O,O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate, CAS 2921-88-2, with molecular formula C9H11Cl3NO3PS and molecular weight 350.59 g/mol. Physical constants include a melting range of 41.5–42.5 °C, water solubility 1.4 mg/L at 25 °C, log Kow 4.96, and vapour pressure 2.7 mPa at 25 °C. The designation “Pharma Grade API” is a commercial purity descriptor, not a current USP, Ph.Eur., BP or JP monograph designation. No 21 CFR 520 or 522 approval exists for chlorpyrifos as an oral or injectable animal drug, and the material is therefore restricted to non-clinical or approved veterinary experimental formulation only.
Release testing is performed against a manufacturer-defined specification because no pharmacopoeial monograph exists for chlorpyrifos as a pharmaceutical active. The material is supplied as a white to off-white crystalline powder with residual control of water, heavy metals, residual solvents, and particle size. Table 1 lists representative release parameters for the CPS-PG-99 grade.
| Parameter | Method | Release limit |
|---|---|---|
| Appearance | Visual inspection | White to off-white crystalline powder |
| Assay | HPLC-UV, external standard | ≥ 99.0% area |
| Melting range | Ph.Eur. 2.2.14 | 41.5–42.5 °C |
| Water content | Ph.Eur. 2.5.12 | ≤ 0.1% w/w |
| Particle size D90 | Ph.Eur. 2.9.31 | ≤ 75 µm solid oral; ≤ 20 µm injectable evaluation |
| Residual solvents | Ph.Eur. 5.4 / ICH Q3C | Conforms to ICH Q3C limits |
| Heavy metals | Ph.Eur. 2.4.8 | ≤ 10 mg/kg |
| Storage | — | 2–8 °C, argon headspace, light-resistant container |
Storage and handling of the API require sealed, light-resistant containers under argon at 2–8 °C. Moisture uptake occurs at relative humidity above 60% RH, and water content can rise above 0.2% w/w with repeated opening. Pre-drying is required under these conditions; vacuum drying at 30 °C for 12 h restores water content to ≤ 0.1% w/w. The material should not be exposed to temperatures above 35 °C because the melting onset is 41.5 °C and local overheating can create fused particles that shift the particle size distribution.
Particle engineering is used for solid oral and injectable evaluation. Micronised lots are produced by air-jet milling with compressed nitrogen at feed pressure 6–8 bar and venturi pressure 2–3 bar. Particle size is controlled to D90 ≤ 75 µm for tablet and capsule work, while injectable solubility screening uses D90 ≤ 20 µm. Laser diffraction according to Ph.Eur. 2.9.31 is used with dry dispersion at 2 bar. Increased specific surface area raises dissolution rate in surfactant-containing media, consistent with the Noyes-Whitney relationship.
Solid oral formulation of chlorpyrifos follows BCS Class II behaviour: low aqueous solubility and high log Kow 4.96 suggest that dissolution rather than permeability is the limiting factor. Tablets are produced from roller-compacted granules rather than direct compression because the unmilled active exhibits punch filming and sticking above 12 kN on a rotary press. A dry granulation blend contains active, lactose monohydrate, pregelatinized starch 2.5% w/w, and sodium stearyl fumarate 0.5% w/w. Roller compaction is run at roll pressure 40–60 bar and screen size 1.0 mm. Content uniformity is assessed by Ph.Eur. 2.9.40 with acceptance value ≤ 15 for single-dose solid oral forms. Tablets are film-coated with a moisture-barrier coating; coating pan product temperature is maintained below 30 °C.
Capsule filling uses a dosator or tamping machine at 20–25 °C and ≤ 30% RH. The granulation is filled into hard gelatin or HPMC capsules, and banding is recommended for moisture-sensitive formulations. In-process controls include fill weight, disintegration time per Ph.Eur. 2.9.1, and dissolution profiling with USP Apparatus 2 paddle at 50 rpm in 0.5% w/v sodium lauryl sulfate solution at 37 °C. The surfactant concentration is selected to maintain sink conditions because aqueous solubility is only 1.4 mg/L.
Granule formulation uses a pH-controlled granulation fluid. Aqueous binder solution is prepared as povidone K30 2.0% w/w in citrate buffer pH 5.5. The granulation endpoint is determined by impeller torque rise and granule size distribution; target mean granule size is 150–300 µm for tablet compression. Fluid pH above 7.5 is not used. At pH 8.0, base-catalysed hydrolysis is substantially accelerated and 3,5,6-trichloro-2-pyridinol is detectable by HPLC within 24 h at 25 °C.
Chlorpyrifos is practically insoluble in water at 1.4 mg/L at 25 °C, so injectable evaluation requires a non-aqueous or co-solvent system. The compound dissolves in medium-chain triglycerides, propylene glycol, benzyl alcohol, and dimethyl sulfoxide. A vehicle based on propylene glycol and benzyl alcohol at 90:10 v/v supports target concentrations of 10–20 mg/mL at 25 °C; published data for this specific configuration is limited, and batch-specific solubility screening is required before use. The solution is filtered through 0.22 µm PVDF membrane under inert gas. Moist-heat sterilisation at 121 °C is contraindicated due to accelerated hydrolysis; aseptic filtration is the preferred manufacturing route.
Aqueous injectable systems are not used because base-catalysed degradation produces 3,5,6-trichloro-2-pyridinol and diethyl phosphorothioate. Where an aqueous phase is present, pH is maintained at 5.0–6.0 with buffer capacity below 10 mM to avoid salt-induced precipitation. Residual moisture in the non-aqueous vehicle must be ≤ 0.1% w/w to reduce hydrolysis during storage. Filter integrity testing is performed before and after filtration by bubble point measurement.
High-shear granulation is a temperature-sensitive unit operation because the melting range begins at 41.5 °C. Production-scale equipment using a 300 L jacketed bowl has shown that impeller tip speeds above 8 m/s generate frictional heat sufficient to raise local granule temperature above 35 °C. This produces surface softening and oversized agglomerates above 1,000 µm, and the resulting blend may fail Ph.Eur. 2.9.40 content uniformity. The operating window is therefore impeller tip speed 4–6 m/s, chopper speed 1,200–1,500 rpm, granulation time 60–120 s, and jacket temperature 20 °C. Drying is conducted in a fluid-bed dryer with inlet air temperature 40 °C and product temperature not exceeding 35 °C; final moisture target is ≤ 0.5% w/w. Milling through a 1.0 mm screen is performed at room temperature.
Compared with chlorpyrifos-methyl, CAS 5598-13-0, the diethyl ester in chlorpyrifos produces lower water solubility and higher log Kow, increasing the need for dry granulation and non-aqueous vehicles. Malathion, CAS 121-75-5, has water solubility 145 mg/L and log Kow 2.36; it is a liquid at room temperature and is recognised in topical pharmaceutical compendial frameworks. Solid oral formulation of chlorpyrifos is not comparable to malathion because malathion is not a crystalline solid at ambient conditions. Chlorpyrifos also differs in metabolic activation: the parent compound is a relatively weak cholinesterase inhibitor in vitro, requiring cytochrome P450-mediated desulfuration to chlorpyrifos-oxon for significant enzyme inhibition. This distinction affects in vitro pharmacological assay design and occupational hygiene assessment.
Because no USP, Ph.Eur., BP or JP monograph exists, release testing is performed against the manufacturer’s non-compendial specification and ICH Q3C for residual solvents. The material must not be represented as a human drug API. Occupational handling accounts for acetylcholinesterase inhibition; containment isolators and closed transfer systems are used for powder charging. Disposal must follow regional hazardous waste regulations for organophosphorus material.
