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Polyethylene Glycol 400 BP EP USP, usually recognized as PEG 400, stands among the most trusted excipients pharmacists, chemists, and manufacturers keep on hand. Its formula, C2nH4n+2On+1, reflects a chain of repeating ethylene glycol units. Many industries call on its versatility, but in pharmaceuticals, it supports both liquid and solid dosage forms. PEG 400’s purity meets standards set by BP (British Pharmacopoeia), EP (European Pharmacopoeia), and USP (United States Pharmacopeia), showing it as reliable no matter where the work happens. Makers value it because it blends easily with water and many organic solvents, holds moisture, and stays stable even after repeated use.
PEG 400 appears primarily as a clear, colorless, almost odorless, slightly viscous liquid at room temperature. Sometimes people expect flakes or beads with higher molecular weights, but PEG 400 flows freely and pours without clumping. With a molecular weight averaging around 400 daltons, its density typically measures about 1.125 g/cm³. It remains completely soluble in water and mixes with acetone, methanol, and other alcohols. The liquidity allows it to act as a base in topical gels or as a vehicle in oral syrups. Anyone handling it will notice the gentle, clean sensation on skin—no oily residue, just a faint cooling effect.
For pharmacies and labs, having reliable specifications matters more than marketing promises. PEG 400 runs at a pH near neutral—usually between 4.5 and 7.5. Viscosity ranges from 70 to 90 centistokes at 20°C, which translates to an easy pour and simple mixing. Boiling point extends past 250°C, and even under freezing conditions, the liquid doesn’t solidify easily. Manufacturers assign it the HS Code 29053100, marking it as a standard chemical export. In routine applications, you see PEG 400 described by its physical state—always liquid, unlike its higher-weight cousins that stack as flakes or solid powders.
PEG 400 emerges from the reaction of ethylene oxide with water, producing a linear polyether chain. This chain length brings a blend of low viscosity, good solubility, and flexibility in use. The raw materials, mainly ethylene glycol and catalysts, follow strict pharma-grade production lines, making sure contamination risks stay low. During synthesis, every batch faces quality testing to validate molecular consistency, density, and toxicity levels far below thresholds of concern for pharmaceuticals.
People handling PEG 400 daily appreciate its generally recognized safety. It doesn’t carry a strong risk in approved concentrations. Studies and long clinical tradition push PEG 400 as one of the least reactive substances in topical or ingestible applications—rarely triggering an allergic response. Entry through the skin, inhalation, or digestion doesn’t build up harm under normal use. Still, like any chemical, improper storage or large-scale spillage brings irritant potential, especially in eyes or on mucous membranes. Guidance suggests storing PEG 400 in tightly sealed containers, away from strong acids, oxidizers, or heat sources to avoid breakdown or degradation. Industrial accidents involving PEG 400 cause minor short-term symptoms—mainly mild irritation—and emergency response documentation agrees it poses very low hazardous risk relative to many other raw materials in the pharma supply chain.
PEG 400 supports daily life more than most realize. It works as a solvent and carrier for active pharmaceutical ingredients, aiding with the solubility of otherwise stubborn compounds. In topical creams, it stops separation and keeps products consistent through months of use and storage. Dental solutions use PEG 400 to provide moisture and hold flavoring agents, while eye drops rely on it for lubrication without blurring. Vaccine and drug formulation teams turn to it because the product’s consistency doesn’t change in regular environmental shifts. As a result, patients experience fewer side effects, doctors rely on uniform dosages, and industrial lines run smoothly without gunking up complex machinery.
The repeating ethylene glycol units in the PEG 400 molecule let it wrap around both hydrophilic and some hydrophobic molecules, which improves solubilization in multi-phase solutions. That’s directly tied to the C2nH4n+2On+1 formula, where the n-value determines the average chain length. Longer chains thicken the mix, but PEG 400 lands just right for many syrup and clear gel formulations. Chemists trust the predictability of PEG 400’s performance in mixtures; each batch delivers consistent outcomes in both research and commercial manufacturing. This predictability allows precise calibration—dose after dose, application after application.
Organizations like the US Pharmacopeia, European Pharmacopeia, and British Pharmacopeia update monographs to demand purity, low toxicity, and identifiable physical parameters. Regular lab testing checks for aldehydes, ethylene oxide residues, and heavy metals, keeping levels far below thresholds. Only lots meeting these publications’ requirements qualify to receive the BP, EP, and USP tags. I’ve seen manufacturers lose valuable contracts after failing a round of tests—without precisely matching these standards, there’s no access to regulated markets or pharmacies.
People working with PEG 400 store it in secure, opaque containers to keep out sunlight or moisture, which might degrade quality over time. Some facilities move thousands of liters monthly; bulk drums keep the liquid manageable, and smaller labs portion it out as needed. Suppliers track every drum’s origins back to the raw ethylene glycol manufacture, maintaining clean paperwork trails for regulators and auditors. Any material delivered needs full traceability, safety data sheets, analysis certificates, and testing reports, confirming PEG 400 hasn’t picked up unwanted contaminants.
Compared to more aggressive chemicals, PEG 400 places little stress on waste management systems. After use, most waste streams dilute the compound enough to avoid environmental regulations. Responsible labs dilute or collect spent solutions for chemical recycling rather than washing everything down the drain. Because the molecule resists easy breakdown but does not bioaccumulate, local guidelines call for careful disposal at high concentrations. Environmental experts continue to review guidance on PEG waste streams to limit aquatic buildup, but evidence suggests little long-term accumulation in most conditions.
Quality issues rarely dog PEG 400 use, but mistakes in storage or sourcing can introduce trouble. If a batch sits exposed to open air for too long, it may absorb water or develop unwanted odors. Occasionally, unscrupulous traders blend down PEG 400 with lower-grade glycol, risking serious contamination threats. Responsible companies test input material and keep audit trails. Staff training on safe, careful handling pays off in better stability and fewer recalls. In my experience, regular review of supplier credentials and double-checking incoming shipments with in-house testing saves a lot of repair work later. Future improvements may include onsite recycling stations and tighter global sourcing networks, reducing waste and streamlining chemical logistics further for the industry.
Chengguan District, Lanzhou, Gansu, China
