| HS Code | 373288 |
| Chemical Composition | Aqueous compound solution of formaldehyde (CH2O) stabilized with methanol |
| Cas Registry Number | 50-00-0 for formaldehyde active moiety |
| Molecular Weight | 30.03 g/mol for formaldehyde |
| Appearance | Clear, colorless liquid with a pungent odor |
| Assay Content | Formaldehyde 34.0-38.0% w/w; methanol 8.0-15.0% w/w as compound grade |
| Solubility | Miscible with water, ethanol, isopropanol, and acetone |
| Ph | 2.8 to 4.0 as supplied |
| Density | Approximately 1.08 g/mL at 20°C |
| Boiling Point | Approximately 96°C |
| Flash Point | Approximately 60°C (closed cup) |
| Veterinary Grade Purity | Meets veterinary API specifications with residue on ignition ≤0.1% and heavy metals ≤20 ppm |
As an accredited Compound Formaldehyde Solution Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 25 kg HDPE drums with tamper-proof seals, labeled veterinary grade, ensuring safe, stable delivery of Compound Formaldehyde Solution API. |
| Container Loading (20′ FCL) | 20′ FCL container loading: veterinary-grade compound formaldehyde solution API in drums, suitable for tablets, injections, capsules, powders, granules, premix, and solutions. |
| Shipping | Shipping of Compound Formaldehyde Solution (Veterinary Grade API) requires strict compliance with hazardous materials regulations. Use UN-approved, leak-proof containers, clearly labeled. Transport in ventilated, temperature-controlled vehicles away from incompatible substances. Secure upright; provide spill containment. Ensure documentation includes Safety Data Sheets and proper hazard declarations for air, sea, or road freight. |
| Storage | Store in tightly closed, corrosion-resistant containers in a cool, dry, well-ventilated area away from direct sunlight and incompatible substances. Maintain temperature between 15–25°C; avoid freezing, which causes polymerization. Keep containers upright and clearly labeled. Protect from contamination and moisture, and use first-in, first-out rotation to ensure stability. |
| Shelf Life | Shelf Life: 24 months when stored in tightly closed containers, protected from light, at controlled room temperature. |
During manufacture of killed virus vaccines for poultry and swine, the compound formaldehyde solution is metered as a process reactant rather than a direct injectable ingredient. The stock solution, typically 37% (w/w) formaldehyde stabilized with 10–15% methanol, is diluted into clarified virus harvest fluid to a final free formaldehyde concentration of 0.05–0.2% v/v. The incoming material must meet Ph. Eur. 0826 for formaldehyde solution (35%) unless the national control authority accepts an equivalent compendial standard. Inactivation is carried out in a jacketed stainless steel vessel with temperature held at 37°C ±1°C. The reaction follows first-order kinetics under continuous mixing. Sampling intervals are fixed at time zero and at three additional points during inactivation to establish a kill curve for each master seed lot. Complete inactivation is confirmed by serial passage in embryonated chicken eggs or susceptible cell culture for at least three blind passages.
The principal process conflict is between complete viral inactivation and retention of protective epitopes. Overexposure to formaldehyde crosslinks capsid and membrane proteins, reducing hemagglutination-inhibition titers and ELISA reactivity. Published data for specific antigenic strains is limited. Manufacturers therefore establish strain-specific inactivation windows rather than relying on a fixed single time point. After inactivation, residual free formaldehyde is neutralized with sodium metabisulfite at a molar ratio of 1.05:1 relative to measured free formaldehyde. Residual free formaldehyde is then determined according to Ph. Eur. 2.4.18 or an equivalent validated spectrophotometric method. For US-regulated products, serial inactivation and safety data are reviewed under 9 CFR Part 113.200 for killed virus vaccines. The terminal product is an inactivated monovalent or multivalent viral antigen concentrate that is formulated with adjuvants into injectable emulsions for poultry, swine, and ruminants.
Compound formaldehyde solution is used as a reactant in the synthesis of methenamine, the active moiety in urinary antiseptic tablets and capsules for companion animals. The condensation of formaldehyde with ammonia proceeds according to 6 HCHO + 4 NH3 → C6H12N4 + 6 H2O. A molar formaldehyde-to-ammonia ratio of 1.5:1 is maintained by controlled addition of 25% (w/w) aqueous ammonia to the 37% (w/w) formaldehyde solution. The reaction is exothermic, and the cooling system maintains the glass-lined reactor at 25–35°C. Temperatures above 40°C increase ammonia volatilization and darken the crystalline mass. Methenamine crystals are recovered by filtration, washed with cold deionized water, and dried in a vacuum tray dryer at 60°C with a maximum product layer depth of 5 cm. Residual moisture is controlled to 0.5% w/w or less before salt formation.
The methenamine base is converted to hippurate or mandelate salts and formulated into 500 mg and 1 g tablets or capsules. Because methenamine salts require acidic urine for hydrolysis to formaldehyde in the urinary bladder, dissolution testing is performed across a pH range from 1.2 to 6.8. Tablet hardness is monitored during compression to avoid capping of high-dose methenamine hippurate tablets. Compendial quality is checked against USP Methenamine Hippurate Tablets and USP Methenamine Mandelate monographs where applicable. Free formaldehyde in the methenamine intermediate is assayed before salt formation to ensure that the condensation reaction has consumed the formaldehyde feed. The terminal products are veterinary methenamine hippurate tablets, methenamine mandelate capsules, and bulk granules for repackaging. The final dosage form does not contain the original formaldehyde solution as a solvent; instead, formaldehyde is released from the methenamine molecule after oral administration under acidic urinary conditions.
Aquaculture facilities diluting the 37% (w/w) compound solution for salmonid egg disinfection target a final bath concentration of 1,000–2,000 ppm formaldehyde. This is equivalent to 2.7–5.4 L of the stock solution per 1,000 L of hatchery water. The bath is prepared by metering the stock solution into a side stream of 10–12°C water, then distributing the diluted product into a flow-through egg stack or a static raceway. Diffused aeration is run continuously because formaldehyde oxidizes and increases biological oxygen demand in the water column. Exposure is limited to 15–30 min. Dissolved oxygen is maintained above 6 mg/L before eggs are returned to normal incubation flow. Water pH below 6.5 increases formaldehyde toxicity to fish eggs and requires immediate pH correction or bath termination.
In the United States, the use is regulated as a new animal drug under 21 CFR Part 514. Approved formalin products carry label instructions for egg disinfection, and use on food fish without an approved label is not permitted. Published data for this specific configuration is limited because efficacy varies with water temperature, organic load, and egg species. The terminal product is an extemporaneous immersion bath that is discarded through controlled effluent treatment or chemical neutralization. Sodium metabisulfite is not added directly to the hatchery bath because the resulting neutralization reaction can produce heat and sulfur dioxide in confined raceways. Instead, spent bath water is collected and treated in a separate neutralization basin before discharge.
Compound formaldehyde solution is applied as a spray to finished mash or pellets in a horizontal batch mixer or screw conveyor. The 37% (w/w) stock solution is metered at 2.5–4.0 kg per tonne of feed, equivalent to 0.25–0.4% w/w of the stock solution. Direct spray application is preferred over low-pressure nozzle application because it produces finer droplets and increases contact with particle surfaces. The spray cycle is set at 120–180 s in a double-shaft paddle mixer operating at 25–35 rpm. After mixing, the batch is transferred to a ventilated bin for 24–48 h to allow moisture equilibration and off-gassing. Exhaust air is maintained at 6 air changes/hour to reduce worker exposure and prevent formaldehyde vapor accumulation. The terminal products are broiler mash, pelleted feed, and granular premixes with reduced surface microbial loading.
The US feed additive clearance is covered by 21 CFR 573.460. Occupational exposure must be controlled under 29 CFR 1910.1048, which sets an 8-hour time-weighted average of 0.75 ppm and a short-term exposure limit of 2 ppm. Formaldehyde solution is not combined with sodium metabisulfite in the same batch because neutralization reduces antimicrobial activity. The process is incompatible with high-moisture feed matrices above 15% w/w because excessive moisture can slow off-gassing and create condensation in storage bins. Published data for this specific configuration is limited; effectiveness depends on initial microbial load, feed matrix moisture, and dwell time after spray application.
In dairy cattle housing, the 37% (w/w) compound solution is diluted with water to a working concentration of 4–5% w/w formaldehyde. A 5% w/w bath is prepared by adding 6.4 L of water to 1 L of stock solution. A 4% w/w bath uses 8.25 L of water per 1 L of stock solution. Footbath volume is typically 150–200 L in a walk-through channel with side walls high enough to prevent splash. The bath is replaced after 200 cow passages or when visible turbidity from manure loading appears. Cows are walked through the bath twice daily on concrete walkways with no alternative bypass route for at least three consecutive days. The terminal product is a medicated hoof bath solution for the control of digital dermatitis-associated bacteria.
Ammonia from urine and manure consumes formaldehyde by forming hexamethylenetetramine, reducing active concentration. Baths are shielded from rain and direct sunlight to slow volatilization and maintain concentration. Worker exposure must remain below the 8-hour time-weighted average of 0.75 ppm and the 15-minute short-term exposure limit of 2 ppm specified in 29 CFR 1910.1048. Where the solution is used as an animal health product rather than a strictly industrial biocide, the label and national veterinary drug authority determine dilution, use frequency, and disposal limits.
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Compound Formaldehyde Solution Veterinary Grade API, product designation CFS-VET 37/12 and low-methanol variant CFS-VET 37/6, is a clear, colorless to faintly opalescent aqueous mixture intended for use as an active pharmaceutical ingredient in veterinary tablets, injections, capsules, powders, granules, premixes, and diluted solutions. In this system, formaldehyde is not present solely as free carbonyl but predominantly as methylene glycol and short-chain poly(oxymethylene) glycols; methanol at 10–12% w/w suppresses paraformaldehyde nucleation during storage and transport below 15°C. The nominal formaldehyde mass fraction is 37.0–37.4% w/w, with water constituting the remainder and acidity controlled to ≤0.1% w/w as formic acid. The product is released according to the current European Pharmacopoeia formaldehyde solution monograph Ph. Eur. 0826 and the residual solvent criteria of VICH GL18. Because this material is an API starting component, it is not a terminally sterilized or depyrogenated finished dosage form; each downstream process must establish its own sterility and endotoxin control. The principal technical difference from industrial formalin, disinfectant grade formaldehyde, and embalming fluids is the control of methanol ratio, oxidation acidity, particulate matter, bacterial endotoxins, and trace metal content required for parenteral, oral, and premix applications.
In wet granulation, the product is pre-diluted with purified water to a working formaldehyde concentration of 2.5–5.0% w/w and sprayed into a top-spray fluid-bed granulator at 0.5–1.0 L/min per 100 kg dry powder with inlet air at 40–45°C. Granule moisture measured by Karl Fischer titration according to ASTM E203 is held at 1.8–2.4% w/w; drying above 55°C is avoided because methanol and formaldehyde evaporate at different rates and cause assay nonuniformity. For tablets, granules with at least 65% w/w retention between 125 µm and 710 µm are compressed on a rotary tablet press at 15–25 kN main compression force. For capsules, hard gelatin shells are not placed in continuous contact with concentrated formaldehyde-containing liquids because formaldehyde cross-links gelatin at amine sites, increasing disintegration time in 0.1 N HCl from 8 min to more than 45 min. Hydroxypropyl methylcellulose capsules or sealed gelatin shells are used for liquid-filled or semi-solid formulations containing free formaldehyde.
Technical formalin and disinfectant grades are usually sold on the basis of total aldehyde content alone, with methanol concentration varying widely between 6% w/w and 15% w/w depending on transport and winter storage requirements. They may contain iron leached from carbon steel storage, formic acid from aerial oxidation, and insoluble paraformaldehyde formed during temperature cycling. Disinfectant grades may also include surfactants, dyes, or quaternary ammonium additives that are incompatible with veterinary active-ingredient use. CFS-VET 37/12 excludes non-declared additives; the only specified stabilizer is methanol, and the residual formaldehyde-methanol equilibrium is validated by GC headspace analysis according to Ph. Eur. 2.2.28. The parenteral-grade material is further controlled for bacterial endotoxins at ≤0.50 EU/mg by Ph. Eur. 2.6.14, whereas technical grades are not tested. For oral and premix applications, iron is limited to ≤3 ppm because redox-active iron accelerates formic acid formation during high-shear granulation and may discolor finished tablets over storage. These controls do not make the API sterile; they reduce pyrogenic and particulate burden before subsequent filtration or dry heat treatment.
| Parameter | CFS-VET 37/12 Veterinary API | Technical Formalin | Disinfectant Grade |
|---|---|---|---|
| Formaldehyde mass fraction | 37.0–37.4% w/w | 30–40% w/w variable | 30–40% w/w variable |
| Methanol mass fraction | 10.0–12.0% w/w | 6–15% w/w uncontrolled | 0–15% w/w |
| Acidity as formic acid | ≤0.1% w/w | ≤0.3% w/w typical | not controlled |
| Iron | ≤3 ppm | ≤10 ppm possible | not controlled |
| Bacterial endotoxins | ≤0.50 EU/mg parenteral grade | not tested | not tested |
| Declared additives | none beyond methanol | none declared | surfactants, dyes, quaternary ammonium possible |
| Particulate matter | per Ph. Eur. 2.9.19 | not controlled | not controlled |
Analytical verification of formaldehyde in finished veterinary dosage forms requires liberation of bound aldehyde. Free formaldehyde is determined by derivatization with 2,4-dinitrophenylhydrazine followed by HPLC with UV detection at 360 nm; total available aldehyde is determined by acid hydrolysis of methylene glycol and poly(oxymethylene) glycols before derivatization. The difference between free and total aldehyde is particularly relevant in premixes and aqueous solutions because formaldehyde binds weakly to lactose, starch, and some proteins; assay methods based only on free aldehyde under-report total active content by 5–20% in such matrices. A method-specific validation should determine extraction recovery using the actual finished matrix; published data for compound formaldehyde solution in every veterinary formulation is limited, so matrix-specific validation is required under good manufacturing practice.
Batch-to-batch variance in large-volume manufacturing is influenced by the location of the formaldehyde feed point. In one configuration used for granulated premixes, addition of the diluted active at the top of a top-spray granulator results in assay RSD below 3%, whereas bottom-spray addition of the same dilute solution under identical air flow produces localized enrichment and assay RSD above 8%. Therefore, equipment qualification should include active dispersion studies at the intended spray rate, not only bulk blend uniformity after the final mixing step. For tablet compositions, blending time studies using ASTM E2810 or equivalent demonstrate that over-mixing beyond 20 min after granule drying can increase fines and alter compressibility, but published data for formaldehyde-containing veterinary granulations is limited to specific matrices and should not be extrapolated across formulations.
Premix and powder applications require a different stabilizer profile because methanol residues are regulated in feed materials and may exceed the permitted daily exposure for young animals under VICH GL18. The low-methanol variant CFS-VET 37/6 contains 6–8% w/w methanol while maintaining formaldehyde at 36.5–37.5% w/w. It is sprayed, after 1:10 dilution with purified water, onto carriers such as fumed silica, lactose monohydrate, or corncob granules using a ploughshare mixer with centrifugal atomizer speed 2500–3500 rpm. Blending in a ribbon blender for 12–15 min after addition of the active pre-blend yields assay relative standard deviation ≤5.0% at a final formaldehyde concentration of 0.5–2.0 g/kg. Vacuum drying at 35°C and 40–60 mbar reduces residual methanol in the finished premix to ≤0.1% w/w; sieve retention between 150 µm and 850 µm according to ASTM E11 is monitored to prevent segregation during bagging and farm mixing. The lower methanol content narrows cold-storage stability; therefore, CFS-VET 37/6 should be stored above 15°C and protected from temperature cycling to avoid paraformaldehyde haze. Published data for silo storage of this exact low-methanol grade in tropical feed mills is limited, so shippers should validate pack-level clarity after 72 h at 5°C for each new supply chain.
The release data include both stated stabilizer concentration and oxidation-related impurities. The following table lists representative acceptance criteria for CFS-VET 37/12 at release; the parenteral grade includes the endotoxin and particulate rows.
| Property | Limit | Reference method |
|---|---|---|
| Formaldehyde mass fraction | 37.0–37.4% w/w | Sodium sulfite titration, ASTM D2194-22 |
| Methanol mass fraction | 10.0–12.0% w/w | Headspace GC-FID, Ph. Eur. 2.2.28 |
| Acidity as formic acid | ≤0.1% w/w | Ph. Eur. 0826 acidity test |
| Iron | ≤3 ppm | ICP-MS after acid digestion |
| Sulfated ash | ≤0.1% w/w | Ph. Eur. 2.4.14 |
| Bacterial endotoxins, parenteral grade | ≤0.50 EU/mg | Ph. Eur. 2.6.14 |
| Particulate matter, parenteral grade | ≤25 particles/mL at ≥10 µm; ≤3 particles/mL at ≥25 µm | Ph. Eur. 2.9.19 |
| Density at 20°C | 1.080–1.090 g/mL | Ph. Eur. 2.2.5 |
Injectable solution preparation begins with the parenteral grade of CFS-VET 37/12, not the general oral grade. The receiving area is an ISO Class 7 cleanroom with local high-efficiency particulate air; the bulk solution is prepared in 316L stainless steel vessels with electropolished surfaces of Ra ≤0.8 µm. The concentrated formaldehyde solution is added to chilled water-for-injection at 8–12°C to reduce volatile losses. The pH is adjusted to 4.0–5.5 with sodium hydroxide; above pH 7.0, formaldehyde undergoes Cannizzaro-type disproportionation to methanol and formate, causing assay loss over 24 h. The solution is filtered through a 0.45 µm polyethersulfone prefilter and a 0.22 µm PVDF membrane at 1.0–2.5 bar; membrane integrity is tested before and after filtration by bubble point. Containers and closures are depyrogenated by dry heat at 250°C for 30 min or by validated washing with water-for-injection followed by dry heat. Terminal autoclaving of concentrated formaldehyde solutions in vented containers is not recommended because vapor pressure rises with methanol and can distort container seals; terminal sterilization of dilute injectable formulations may be possible only in sealed, pressure-rated containers with formylation compatibility. The final injectable solution should be stored in containers with low oxygen headspace because aerial oxidation generates formic acid and lowers pH; headspace oxygen below 2% v/v is typical for long-term stability.
For oral solutions, drinking-water concentrates, and topical solutions, the product is diluted with purified water to working concentrations of 0.1–2.0% w/w. The diluted solution is stable for short periods but should be protected from prolonged storage above 25°C and from exposure to air because formic acid accumulation increases acidity. In feed or water vehicles containing amines, proteins, sulfites, or ammonia, free formaldehyde forms methylol adducts, sulfite adducts, or hexamine-like products, reducing available aldehyde; therefore, such combination products require real-time assay verification rather than theoretical dilution calculation. In aqueous dilution, piping and tank materials should be 316L stainless steel, polypropylene, or high-density polyethylene; carbon steel, copper, and unlined aluminum are incompatible due to pitting, catalysis, or gas evolution. The compound should not be mixed with concentrated hydrochloric acid in closed vessels because bis(chloromethyl) ether formation is a recognized hazard; all transfers should be conducted with local exhaust ventilation at 0.5–1.0 m/s capture velocity. Personnel exposure limits for formaldehyde in air are governed by national occupational exposure legislation; engineering controls must maintain atmospheric formaldehyde below the applicable 8-hour occupational exposure limit, typically 0.3–0.5 ppm in the vapor phase depending on jurisdiction. These operational boundaries are integral to the use of this veterinary API and distinguish it from lower-cost industrial materials that lack pharmaceutical-level documentation.
