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Maleic acid has a history that links back to industrial chemistry's relentless push for reliable intermediates. As old chemical processes got fine-tuned and the demands of human health grew, scientists realized that maleic acid fits the bill for many jobs in pharmaceuticals. Its roots start in the centuries-old study of plant gums, but the real leap happened once the petrochemical boom provided a clean pathway from benzene to maleic anhydride, and with a bit of water, to maleic acid. This material soon gained a reputation for reliability, thanks to how readily it steps in as a pH corrector, coupling agent, and intermediate for other critical actives. Pharmacopoeial standards (BP, EP, USP) soon took note, giving it a seat among the pharma-grade substances that underpin modern formulations.
Pharma-grade maleic acid carries a stamp of purity that regular tech-grade products just don’t reach. Each batch measures up to monograph specifications, holding tight to limits on heavy metals, residual solvents, and other contaminants. When holding a sample in hand, it takes form as colorless crystals—slightly bitter, unmistakably sour on the tongue. With chemical formula C4H4O4 and a molar mass of 116.07 g/mol, few other dicarboxylic acids match its performance for controlled reactivity and safety in pharma settings. Its hydrophilic nature and rapid dissolution make it a familiar face in labs, especially for those who tackle tough formulation challenges.
A closer look at maleic acid tells plenty about how it behaves in the real world. It melts at a modest 135–139°C, with a boiling point that causes it to decompose long before turning fully to vapor. This matters in scaling up processes, limiting some routes but opening others. In water, maleic acid dissolves with ease, releasing hydrogen ions in solution, thus dropping the pH quickly. That level of acidity sets it apart from similar acids, giving it an edge in titration and buffering roles. It resists oxidation under normal conditions, standing up to the kind of storage environments often seen in pharma warehouses.
Meeting BP, EP, and USP grade standards requires more than simple crystallization. Manufacturers run repeated purity checks for assay (usually >99% C4H4O4 content), low sulfate and chloride, and undetectable lead or arsenic. Bulk labels on drums or inner containers quote precise batch numbers, expiry dates, and traceability codes. Each container holds documentation for transportation, including GHS hazard pictograms and instructions for safe handling. Temperature control during transit and storage features heavily in standard operating procedures—exposure to extreme humidity can clump and degrade the purity.
Modern chemical plants typically prepare maleic acid by hydrolyzing maleic anhydride, giving an energy-efficient way to produce high-purity crystals with minimal waste. This process cuts down on environmental impact, especially compared to legacy routes that used less selective oxidations. Water gets added to maleic anhydride under tightly controlled conditions, triggering conversion without byproducts that would taint pharma-grade lots. The product undergoes rigorous filtration, evaporation, and recrystallization steps, drawing on decades of process chemistry experience from operators who know the cost of impurity or batch loss.
Maleic acid’s two carboxylic acid groups make it one of the most versatile intermediates in the lab or plant. With bases, it neutralizes to form maleates—salts often used in extended-release formulations or for improved active ingredient solubility. Further, it undergoes addition reactions with alkenes through Diels-Alder chemistry, or forms copolymers for sustained drug release films. Modification of its structure opens doors to biodegradable materials, specialty excipients, and even diagnostic probes. Any process that tweaks its backbone stands on the foundation of strict control over temperature, reagent ratio, and pH, where even small changes ripple into final product consistency.
Across industries, maleic acid sometimes travels under different names. Its IUPAC calling card is cis-butenedioic acid, while synonyms like toxilic acid, maleinic acid, or E297 crop up in old technical documents and food chemistry. In regulatory filings and catalogs, the simplicity of “maleic acid BP/EP/USP” takes precedence, ensuring clear communication among procurement, R&D, and regulatory specialists. Search for its CAS number—110-16-7—and global trade partners know precisely what is being discussed, avoiding confusion that can stall critical projects.
Handling maleic acid, especially at pharma purity, calls for respect but not fear. Contact with skin or ingestion can irritate, and its dust can affect breathing, pushing labs and plants to maintain diligent PPE standards. Ventilated workspaces, splash-proof goggles, and gloves sit atop the safety checklist, while storage in covered, cool, well-ventilated places prevents spoilage or accidental releases. Material safety data sheets spell out care for spills or accidental exposure, minimizing downtime and protecting teams. Strict adherence to waste protocols guarantees nothing hazardous winds up in the water or landfill stream.
This acid has a long-standing reputation as a pH adjuster and flavor modifier in oral pharma formulas—improving taste by balancing the sharpness of active ingredients. Some drug developers use it in salt forms to stabilize or transport delicate APIs, extending shelf life. Other uses include coating agents for controlled-release tablets, and as links in polymer networks for slow-release nutrition or antibiotic formulations. This industrial favorite also finds a place in research labs looking for a model acidic compound to probe membrane transport, absorption, or catalysis in physiological conditions. Its highly predictable behavior in analytic chemistry means QC labs can rely on it day in, day out.
Current drug formulation work stretches maleic acid’s toolkit to meet regulatory expectations for new excipients while also tapping its green chemistry potential. Researchers investigate ways to pair maleic acid derivatives with novel drug candidates to boost solubility profiles or to slow their release for once-daily tablets. Teams in polymer chemistry fields synthesize hydrogels or biodegradable scaffolds using its backbone, helping tissue engineering and wound care devices. Industry labs invest heavily in process improvements to cut waste, energy use, and improve the atom economy of each batch—efforts that tie closely to sustainability goals and cost management. In my own work, switching from outdated neutralizers to pharma-grade maleic acid immediately slashed the cost of GMP documentation because of regulatory familiarity.
Toxicological studies over decades find that, in small, controlled doses, maleic acid doesn’t accumulate in tissues or act as a persistent toxin. Even so, regulators ask for strict limits on residual levels in finished pharmaceuticals. Chronic exposure or ingestion carries the risk of kidney impacts, pushing formulators to carefully set acceptable daily intake values and monitor cumulative product exposure. Animal studies drive ongoing debate on how breakdown products may interact in sensitive patient populations such as infants or those with kidney disease. Ongoing research in the public domain tracks metabolic pathways, looking for biomarkers that signal overexposure. Safety profiles updated with each monograph revision channel data straight into daily practice, so no one loses sight of emerging risks.
Interest in maleic acid isn’t fading—it shifts to fit new medical needs. Green chemistry efforts see it as a cornerstone in synthesizing cleaner excipients, while manufacturers seek out new grades compatible with high-speed continuous processing equipment. The food-drug boundary blurs, and research explores microencapsulation techniques to protect unstable actives in infant and geriatric nutrition—often improving performance with maleic acid-based carriers. As new drug delivery platforms demand excipients with tighter specifications, chemists worldwide update preparation and testing methods. Not a year passes without another investigation into its potential to serve as a stabilizer, release modifier, or taste-masking agent for the booming generic medicine market. New regulatory guidance comes out regularly, keeping everyone on their toes and driving even higher standards.
Pharmaceutical manufacturers put a lot of thought into keeping drugs both stable and safe during their shelf life. Maleic acid comes into play as a trusted acidifying agent, adjusting pH in everything from injectables to oral medicines. Too high or too low, and the active ingredients break down or stop working altogether. With maleic acid, chemists gain precise control over this delicate balance, making sure medicine remains as effective on day 500 as it was on day one. In my early days working at a compounding pharmacy, every powder or tablet with unpredictable pH became a headache. Maleic acid helped level the playing field, especially in products that didn’t cooperate with more mainstream acids like citric.
Raw materials in pharma aren’t just ingredients – they’re puzzle pieces. Maleic acid steps in as an intermediate in the synthesis of several active pharmaceutical ingredients, including antihistamines and some antivirals. Process chemists like predictability, and maleic acid delivers because its reactions tend to follow clear, reproducible patterns. In a time where drug recalls and supply chain shocks make headlines, having a reliable base chemical makes a huge difference. If one link in the chain doesn’t pull its weight, the domino effect can scramble a whole batch, costing both money and trust.
Tablets need to dissolve at the right speed and place in the body. Add a small amount of maleic acid, and those tablets break down in a way that ensures predictable absorption. There’s a learning curve when getting a tablet to release its contents exactly where it should. With maleic acid, it became easier for our team to fine-tune that process, especially for products that felt stubborn during development. There’s personal satisfaction in watching a formulation go from theoretical to real-world reliable because of one well-chosen ingredient.
Children and elderly people struggle the most with bitter or sour medicines. Maleic acid’s inclusion as a flavoring agent preserves a product’s safety profile without making it intolerable. I’ve seen parents beg pharmacists for syrups their kids won’t spit out. Better-tasting options mean fewer skipped doses, fewer treatment failures, and less frustration all around. It sounds trivial until you’re the one at the counter or the parent desperate for a solution.
Not all maleic acid is equal. Pharma grade material, classified as BP, EP, or USP, undergoes tighter scrutiny and frequent batch testing. Contaminants that might slip through in lower grades get filtered out. This matters when patient health is on the line. Regulatory authorities expect transparency; doctors and patients bank on that same promise. Years in quality assurance drilled into me that cutting corners on ingredient quality always comes back to haunt you, sometimes in ways you’d never predict.
Better oversight, broader access to high-purity maleic acid, and more open data sharing could streamline manufacturing and improve patient safety. Drug shortages often trace back to overlooked fine-print details, like sourcing problems with a basic acidifier. Building resilient supply chains for pharma grade chemicals is no longer just smart – it’s a necessity.
Doctors and pharmacists want one thing above all: safety for patients and predictability from every tablet, capsule, or solution. The tiniest variation in a pharmaceutical ingredient can lead to big questions about trust and quality. Maleic acid works as a common acidulant, pH adjuster, and sometimes a precursor for drug substances. For those reasons, what goes into a “pharma grade” batch isn’t just some fussy paperwork. It is a guarantee that the chemical will not throw off a formulation or worry a regulatory inspector.
International pharmacopoeias set quality hurdles that manufacturers must clear. The British Pharmacopoeia (BP), European Pharmacopoeia (EP), and United States Pharmacopeia (USP) each spell out what “pharmaceutical grade” means. For maleic acid, the specifications aren’t just streaks on a page. Each test number stands guard between people and chemical roughness.
Pharma grade maleic acid should deliver a high minimum purity — often not less than 99.0% to 100.5% when dried, calculated on the anhydrous basis. A batch containing heavy metals or organic impurities is not fit for pills or syrups. Lead, arsenic, and mercury levels must stay below strict cut-offs. Chloride and sulfate impurities also stay very low; typical maximums are 0.01% for chlorides and 0.02% for sulfates. Loss on drying (moisture content) has to be less than 0.5%, since too much water means potential instability in storage or unpredictable weight in formulations. Read a certificate of analysis, and you’ll spot limits for fumaric acid (often under 1.0%) since maleic acid can isomerize during processing.
Pharmacopoeia methods don’t just look for chemical content. Color, solubility, and pH get checked too. Maleic acid should dissolve easily in water and alcohol, appearing white to off-white and crystalline. Any hint of odd color or particles will raise a red flag. You can’t fudge a chemical’s appearance, and in my view as someone who’s handled raw ingredients, a pure white powder speaks volumes.
Not every batch of a chemical looks the same, even with the same starting recipe. This is why suppliers take seriously those pharmacopoeial tests. High purity matters for stability, taste, reaction yields in synthesis, and — honestly — making sure no one has to recall a bad batch. Anything labeled “pharma grade” must clear these hurdles so that no doctor loses sleep, no patient ends up with an unexpected side effect from a contaminant.
Having spent time in labs weighing out acids for buffer solutions, it’s easy to take batch consistency for granted. All it takes is one slip to ruin a result. Patients and drugmakers expect zero drama: those numbers on a specification sheet tell you if a warehouse shipment is safe for a blood-pressure tablet or a cough syrup.
How do we keep quality high? It starts with careful choice of sourcing partners — reputable manufacturers who can produce a complete analytical report for every batch. Strong handling, storage, and transport habits also avoid water uptake or impurity ingress. All major suppliers provide certificates aligned with BP, EP, and USP requirements, and their laboratories must follow validated methods to keep everyone safe.
Pharmacists, buyers, and R&D teams do well to always check for these reports. Scrutiny is the best answer to “Is it really pure enough?” Over time, this isn’t just about meeting a checklist. It has become the culture of trust and safety that the world expects for every medicine that reaches the shelf.
Maleic acid pops up in a few different places in pharmaceutical work. The industry uses this ingredient mainly as a pH adjuster or sometimes in salt forms that help certain drugs dissolve better. Before a chemical gets anywhere near patients, especially in tablet or injection form, manufacturers and regulators keep a close eye on it. Usually, three pharmacopeial standards are used as benchmarks: BP (British Pharmacopoeia), EP (European Pharmacopoeia), and USP (United States Pharmacopeia). Products labeled BP/EP/USP must meet strict tests for purity and trace contaminants.
Doctors and pharmacists want to know that whatever goes into the body won’t do harm. That’s not just common sense—it comes from history. Past mistakes with contaminated ingredients leave scars. So, pharma-grade maleic acid faces limits on heavy metals, organic impurities, and residual solvents. These cutoffs come from toxicology studies and reflect large safety margins. The standards don’t just serve scientific theory; they exist because, in real-world settings, poor-quality chemicals have caused disaster before.
I’ve seen plenty of pharma production audits. It surprised me, the extent of testing each batch faces. With maleic acid, there’s titration, chromatography, loss-on-drying, and more—all to prove each drum and bag delivers what’s promised. Manufacturers submit reports to regulatory agencies, and companies check vendors regularly, not just by paperwork but with site visits.
Animal testing, sometimes controversial, still supplies much of the data regulators rely on. Studies in rats and mice found that maleic acid, even at doses far higher than what would show up in a human dose, produces only mild and reversible problems, mainly at very high exposures. In small, controlled amounts, the risk profile looks low, especially compared to many common excipients. The World Health Organization and other major agencies set guidelines for exposure, all far above levels people would get from a therapeutic product.
Allergic responses or hidden toxicity can show up from unexpected corners, so reviews keep circling back to real-world use. Over years of experience, maleic acid hasn’t built any reputation as a problematic ingredient at regulated doses. Still, healthcare relies on constant vigilance, and each drug formula goes through a lengthy review before approval.
One real sticking point: even if the chemical itself proves safe, contamination in the supply chain creates unexpected danger. Counterfeit or poorly manufactured ingredients have slipped through in parts of the world suffering from weak oversight. A big company usually presses for traceability back to the raw materials, even tracking what machinery handled a batch and cleaning processes inside factories.
From pharmacy shelves to hospital IV bags, quality is never automatic. It gets built layer by layer—through skilled professionals, tough audits, and strict supply policies. Investing in qualified personnel and robust documentation keeps invisible problems from ever reaching a patient. Technology like rapid chromatography and blockchain tracking could tighten this web even more.
Medicine evolves fast. Sometimes, new delivery techniques or product formats require chemical components that haven’t seen wide use before. Each change triggers scrutiny. Maleic acid, with decades of safe pharmaceutical use behind it under pharmacopeial standards, gives regulators and practitioners some reassurance. Still, trust grows from transparency. Anyone in the industry who ever doubts a powder or liquid’s safety finds room to ask questions—and should.
In a world where shortcuts tempt and resources stretch thin, safety built on real evidence, continual testing, and open reporting keeps medicine trustworthy. As long as these foundations stay intact, ingredients like maleic acid in BP, EP, and USP grade will continue to have a place in the pharmaceutical world.
Maleic acid isn’t some obscure chemical hiding out in the back corner of labs. Plenty of pharmaceutical manufacturers rely on it daily to tweak pH levels or create important compounds. The fact is, storing this stuff right isn’t just following a checklist—it's about keeping workers safe, protecting products, and avoiding unnecessary waste. If you let maleic acid sit in the wrong environment, it can clump, degrade, or even corrode its container. It doesn’t hurt to remember that this is a solid with some bite to it, not something you want leaking onto a crowded storeroom floor.
A dry, cool room beats a hot, humid warehouse every time. Humidity has a knack for creeping into packaging, causing clumps or unwanted reactions. Even the most rugged container can sweat if the room temperature swings wildly. In my time working with chemical sourcing and storage, I saw more ruined batches from damp storerooms than from any spill or accident. Moisture really is the enemy here; it encourages the acid to pick up water, clump together, and become hard to handle. Seal it up every time one finishes a batch—those screw caps or bags aren’t just for show.
Containers made from plastic or glass do best here. Metal corrodes quickly in maleic acid’s company. A colleague once thought steel drums would ‘keep things secure’; weeks later, pitting showed up along the inside walls. Regular checks on storage spaces matter. One glance at irregular temperatures on a thermometer signals it’s time to fix things before the acid degrades.
Pharmaceutical grade means it’s pure, but purity shouldn’t fool anyone into thinking it’s harmless. Always gear up—gloves, goggles, methodical movements. In labs I’ve visited, attention dropped fastest when handling ‘routine’ chemicals, like maleic acid. Trusting the ‘pharma grade’ label lulled teams into skipping gloves or goggles “just this once.” Before long, skin irritation and eye discomfort became regular complaints. The acid that helps balance formulations can just as easily throw off a good day, so personal protection isn’t negotiable.
Spills and powder dust still happen. Keeping a vacuum rated for fine particles handy helps pick up small messes before they turn into big ones. No need for a full hazmat suit, but understanding the Material Safety Data Sheet really helps. I once watched someone ignore a mild spill, only to have it harden and stick to equipment days later, doubling cleanup time.
Moving maleic acid from supplier to storage to lab isn’t glamorous, but mistakes here can cost. Proper labeling, with hazard warnings and handling notes, makes sure no one guesses what’s inside. A supplier once sent a plain bag—no lot number, hazard symbols, nothing. Sorting out the confusion took hours, and left a sour taste with the shipper and our team.
International regulations expect the same level of caution everywhere. Regulatory inspections never overlook the acid’s paperwork, proper labeling, and condition of the storage area. It’s not bureaucracy for the sake of it. Precise records stop mix-ups and can trace any quality issues fast. Some teams use barcodes, others simple logs. The key remains accountability.
No mystery surrounds safe storage and handling of maleic acid. Trained staff, reliable gear, routine checks, and a prioritized safety culture get the job done. Solving problems before they grow—temperature swings, leaks, missing gloves—means both the acid and the people around it stay protected. That’s not just good business sense—it’s basic respect for colleagues and for the products heading to pharmacies and hospitals. And that’s why I take storage and handling seriously, every single time.
You can’t overstate the importance of pharmaceutical grade chemicals lining up with strict regulations. Many of us take medicine on a regular basis, trusting that every ingredient inside meets demanding quality rules. Maleic acid, used for different purposes—from adjusting pH to acting as a reactant—needs to fit within tough boundaries set by organizations like the British Pharmacopoeia (BP), European Pharmacopoeia (EP), and US Pharmacopeia (USP).
Working in manufacturing, I’ve seen firsthand how strict these expectations get. Inspection teams arrive, paperwork gets reviewed, and lab tests run on every batch. When a label claims BP, EP, or USP grade, it signals more than just purity; it means consistent safety and reliable performance in the finished product.
Each pharmacopeial standard sets its limits for trace elements, contaminants, pH ranges, and even color. If a supplier says maleic acid meets BP, EP, or USP, they’re stating the product has passed a series of specific requirements. For maleic acid, this could include heavy metal thresholds, clarity in solution, defined melting points, and absence of certain impurities—checked not just once, but lot after lot.
In my experience coordinating lab analysis, a lot of paperwork and lab hours go into making sure each drum matches what the pharmacopoeias require. Sometimes a test flags a small deviation—maybe an impurity hovers near the borderline. That’s cause for immediate review, because out-of-spec ingredients don’t get used. Regulatory agencies love documentation, especially certificates of analysis and traceability. They want to see a chain of evidence for every batch.
There’s real risk when raw ingredients don’t meet set standards. Sub-optimal chemicals can react differently in manufacturing or deliver unexpected results in finished tablets or capsules. Imagine a blood pressure pill with extra contaminants: even low-level impurities can trigger side effects or mirror other compounds, muddying clinical outcomes. Recognized standards like BP, EP, and USP act as the firewall keeping these risks out of the supply chain.
History shows how failures in ingredient quality caused recalls and scandals. In 2007 and 2008, tainted heparin caused dozens of deaths—the cause traced back to sub-par raw materials with impurities. Stringent standards prevent those tragedies and reinforce public trust.
Regular, independent testing of incoming maleic acid avoids surprises down the line. I’ve seen companies run spot-checks on top of standard supplier paperwork. Some hire third-party auditors or use outside labs for a second opinion. These actions cost money but give peace of mind that goes far beyond what a certificate on paper provides.
Partnerships matter too. Building long-term relationships with proven suppliers usually pays off better than chasing the lowest price for every lot. When a supplier knows they’ll be scrutinized, and trusts the business relationship, they work harder to keep quality high. Audits, shared standards, and real communication build confidence into the entire system.
Most patients never see these details—they just collect a prescription from the pharmacy. But every dose starts with reliable ingredients, checked and rechecked against tough benchmarks. Regulatory standards like BP, EP, and USP form the backbone of patient safety, and keeping maleic acid up to mark shows respect for that responsibility. Genuine compliance delivers more than paperwork—it delivers public trust, clinical success, and fewer recalls or health scares. From production floor to medicine cabinet, sticking to these standards keeps everyone safer.
| Names | |
| Preferred IUPAC name | (E)-but-2-enedioic acid |
| Other names |
Cis-Butenedioic acid Toxilic acid Maleinic acid Malenic acid |
| Pronunciation | /meɪˈliːɪk ˈæsɪd biː piː iː piː juː ɛs piː ˈfɑːrmə ˈɡreɪd/ |
| Identifiers | |
| CAS Number | 110-16-7 |
| 3D model (JSmol) | `"3D model (JSmol)" string for Maleic Acid:` `C\C(=O)C(=O)O` This is the SMILES (Simplified Molecular Input Line Entry System) string representing the structure of maleic acid used in JSmol. |
| Beilstein Reference | Beilstein Reference: 1204107 |
| ChEBI | CHEBI:28866 |
| ChEMBL | CHEMBL1406 |
| ChemSpider | 637 |
| DrugBank | DB04520 |
| ECHA InfoCard | The ECHA InfoCard for **Maleic Acid** is: **03a1b8e4-70b9-4ab1-9992-f631b437e7d0** |
| EC Number | 203-742-5 |
| Gmelin Reference | 82122 |
| KEGG | C00183 |
| MeSH | D008288 |
| PubChem CID | 960 |
| RTECS number | 'OM9625000' |
| UNII | K8AXY6Q215 |
| UN number | UN 3265 |
| CompTox Dashboard (EPA) | CompTox Dashboard (EPA) of product 'Maleic Acid BP EP USP Pharma Grade' is **"DTXSID5020636"** |
| Properties | |
| Chemical formula | C4H4O4 |
| Molar mass | 116.07 g/mol |
| Appearance | White or almost white crystalline powder |
| Odor | Odorless |
| Density | 1.59 g/cm³ |
| Solubility in water | Soluble in water |
| log P | -1.3 |
| Vapor pressure | 0.00004 mmHg (25°C) |
| Acidity (pKa) | 1.9, 6.1 |
| Basicity (pKb) | 1.76 |
| Magnetic susceptibility (χ) | -9.72×10⁻⁶ |
| Refractive index (nD) | 1.554 |
| Viscosity | 2.45 mPa·s (25 °C) |
| Dipole moment | 1.38 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 130.4 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -769.4 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | −1355 kJ/mol |
| Pharmacology | |
| ATC code | A09AB16 |
| Hazards | |
| Main hazards | Harmful if swallowed. Causes severe skin burns and eye damage. |
| GHS labelling | GHS07, GHS05 |
| Pictograms | GHS07, GHS05 |
| Signal word | Danger |
| Hazard statements | H302, H315, H319, H335 |
| Precautionary statements | P264, P270, P280, P301+P312, P330, P305+P351+P338, P310, P501 |
| NFPA 704 (fire diamond) | NFPA 704: 2-1-0 |
| Flash point | 130°C |
| Autoignition temperature | 470°C |
| Lethal dose or concentration | LD50 oral rat 2,400 mg/kg |
| LD50 (median dose) | LD50 (median dose): 2400 mg/kg (oral, rat) |
| NIOSH | UN1237 |
| PEL (Permissible) | PEL: 10 mg/m³ |
| REL (Recommended) | Pharma / Laboratory Chemicals |
| IDLH (Immediate danger) | 250 mg/m3 |
| Related compounds | |
| Related compounds |
Fumaric acid Malic acid Succinic acid Phthalic acid Tartaric acid |
Chengguan District, Lanzhou, Gansu, China
