Long before 4-Morpholinopropanesulphonic acid made its way into every biochemist’s tool kit, researchers were struggling with buffers that didn’t always behave under pressure. Work in the mid-20th century, much of it in pursuit of reliable pH control in ever-expanding biochemical experiments, sent scientists down the path to develop a range of so-called “Good’s buffers.” These molecules, named after Norman Good, were crafted to be non-toxic, water soluble, minimally interactive with biological systems, and, above all, stable. 4-Morpholinopropanesulphonic acid entered the scene as one of these tailored compounds, providing researchers with a buffer that stood up well in many demanding contexts—especially enzymatic work and cell culture. The adoption didn’t happen overnight, but as experience accumulated, so did confidence.
Many laboratories rely on 4-Morpholinopropanesulphonic acid, commonly called MOPS, for a consistent and reliable buffer. MOPS fills a niche for experiments that operate near neutral pH, particularly in range from 6.5 to 7.9. This range covers essential ground for proteins and nucleic acids, both of which react poorly to wrong pH conditions. Scientists appreciate its solubility in water and the fact that it doesn’t form troublesome complexes with metal ions—a real concern when working with sensitive enzymes or trying to avoid contamination. I have seen protocols updated to swap in MOPS for other buffers simply because it delivers cleaner results, with fewer unexplained variables cropping up.
4-Morpholinopropanesulphonic acid shows up most often as a white or off-white powder. The water solubility is a real boon, dissolving smoothly and making it easy to prepare stock solutions at high concentrations. Take a scoop on the scale and it behaves predictably—no hydroscopic weirdness, not clumping up from air moisture. The structure features a sulfonic acid group, a three-carbon propyl chain, and a morpholine ring. The pKa sits at about 7.2 at 25°C. I’ve found that pH measurements stay stable for hours, critical for long cell culture experiments or chromatography runs. The melting point runs upwards of 180°C, and you don’t get much volatility, even when working at the edge of temperature-controlled processes.
Nobody wants to risk pipetting something unidentified or impure. For that reason, technical specs matter. High-quality MOPS typically comes with purity logged at 99% or better, and vendors supply batch-specific certificates of analysis that detail residual moisture (often under 0.5%), levels of common contaminants like heavy metals, and precise pKa at several temperatures. Labels spell out everything from CAS number (1132-61-2), formula (C7H15NO4S), to hazard statements and recommended storage conditions. For storage, dry and cool does the trick—room temperature in a sealed bottle keeps the powder from caking or degrading.
Manufacturers synthesize MOPS by reacting morpholine with 1,3-propane sultone. The chemistry is reasonably straightforward: morpholine nucleophilically attacks the sultone ring, opening it to produce the sulfonic acid. Careful control of reaction temperature and timing leads to high yields, with minimal by-products. Thorough purification, often via crystallization and washing, produces the high-purity product required for biological applications. I’ve watched the recrystallization process weed out colored impurities that could interfere with sensitive protein assays. The method, robust and scalable, brings down costs and keeps supply steady.
While MOPS does its main job as a buffer, its chemical structure offers some flexibility for further modifications if a niche application requests it. For example, derivatization of the morpholine ring can tweak solubility or alter its buffering capacity. The sulfonic acid group can take part in ionic interactions, making it possible to immobilize MOPS on solid supports for certain chromatographic setups. In my own work, using MOPS as a base to build more complex buffering cocktails improved performance for some tricky protein purifications, especially under non-standard salt conditions.
MOPS may crop up under several names, especially on product catalogs and chemical safety sheets. “4-Morpholinopropanesulphonic acid” remains the formal IUPAC term. Common shorthand includes “MOPS buffer,” and vendors may list “3-(N-Morpholino)propanesulfonic acid.” Internationally, the CAS number keeps confusion at bay. Some companies blend MOPS with sodium to make “MOPS sodium salt,” frequently seen in pre-mixed buffer packs, allowing users to dial in concentrations without tricky calculations.
Bench chemists and biologists work with MOPS safely, though it’s not edible or entirely free of risk. Safety data sheets advise against breathing dust, eating, or getting it in the eyes or mouth. In practice, simple measures—gloves, protective eyewear, dust masks in large-scale prep—suffice for daily handling. On the operational side, labs lean on standard operating procedures for solution preparation, labeling, and waste. Local regulations treat MOPS waste as non-hazardous, except where large quantities or contaminated solutions (like mixed with heavy metals or biological agents) push it to regulated disposal. Training plays a big role; staff who understand what they’re measuring are less likely to run into trouble.
Many of the biggest advances in molecular biology depended on reliable buffers. In my own molecular cloning days, running agarose gels with MOPS-buffered systems gave sharp, clear RNA bands. Biochemical enzyme assays rely on MOPS because the buffer stays stable even with swings in ionic strength or temperature—essentials in enzymology where reactions often run for hours. Cell culture media often include MOPS to keep pH steady during cell growth or drug testing. Beyond bench science, diagnostic firms build it into testing kits, and some industrial fermentation operations spike MOPS into growth media for delicate microbial cultures, where pH drift hampers productivity.
Researchers continue to probe ways to make buffering more precise and less invasive, and here MOPS holds its ground. Recent studies dive into how buffer choice can influence outcomes in protein crystallization or affect the activity of new enzyme variants designed through protein engineering. Some labs explore how to pair MOPS with other buffering agents to widen pH stability, providing options in applications that would otherwise burn through single buffers. I’ve seen new variants of MOPS emerge from these efforts, offering tweaks for use in high-throughput assay formats or compatibility with automation.
Toxicological data points to MOPS being of low acute toxicity. It doesn’t readily absorb through the skin, doesn’t build up in tissues, and environmental studies show little risk to aquatic life at concentrations typical of lab waste. Ingestion in significant amounts can irritate the digestive tract. Lab animal tests—done decades back—outline mild irritant effects at high doses. Nobody should treat any chemical buffer as risk-free, so the onus lands on the user to follow common-sense safety. Many leading labs now require buffer use logs and routine reviews of safety data, no matter how long a chemical has been in use.
As biomedical research keeps pushing boundaries—synthetic biology, advanced protein therapeutics, and next-generation diagnostics—the need for dependable pH control grows. Companies invest in making MOPS even purer, lowering trace metal content for applications like CRISPR gene editing, where minute impurities derail results. Opportunities abound in creating single-use, pre-mixed MOPS buffer packs to cut down on preparation mistakes, speed up workflows, and ensure traceability. In green chemistry, efforts target synthesis routes that use less energy and reduce waste. As regulatory scrutiny on laboratory waste tightens, biodegradable or recyclable buffer systems could build off a base like MOPS. Whether in academia or industry, few can afford to gamble with buffer stability, so MOPS looks set to stay in the mix, supporting the many hands and eyes working at the intersection of chemistry and life science.
Walk into any biochemistry lab and you’ll spot bottles and containers labeled with things like “MOPS.” That’s not a cleaning solution – it’s 4-Morpholinopropanesulphonic Acid. Its main claim to fame comes from scientists who rely on it to keep experiments running smoothly. MOPS acts as a buffer, which means it keeps the environment from swinging wild between acidic and basic. This keeps everything stable, especially important when you’re tracking how enzymes, proteins, or microorganisms behave.
A stable pH may sound trivial until you realize how finicky enzymes and proteins can be. One slight shift, and the data can turn useless. Using MOPS, experiments stick to pH 7.2–7.4, which happens to be very close to what you’ll find in the human body. So, anything designed to mimic what happens in cells or tissues needs that consistency. Try to clone a gene or run protein purification without the right buffer, and things break down quickly. What I find interesting is how often I see research teams skip cheaper alternatives and go for MOPS without hesitation, even on a tight budget.
The broader impact isn’t limited to research. Health professionals rely on data from lab tests run under controlled conditions. With MOPS in the mix, labs produce results that actually make sense outside the test tube. Reliable buffer systems like this one let researchers create cell culture media where everything from antibiotics to cancer drugs can be screened. When a new drug gets to clinical trials, the early data often comes from work done in environments where MOPS set the tone for accuracy.
Beyond research, diagnostic companies count on MOPS. Every time labs analyze blood proteins or test for viruses, buffered environments prevent false readings. Nobody wants a misdiagnosis because a test’s environment drifted out of control. Many years ago, I worked with a biotech startup that compared cheap, unstable buffers with more reliable options. Early on, inconsistent results nearly sank an entire project, and switching to MOPS made all the difference. Anything at stake—even a hospital patient’s well-being—shows the value of something as tiny and overlooked as a good buffer.
No chemical is perfect. MOPS isn’t always suitable for every assay or living system. Some reactions react poorly to sulfonic acids, and scientists always watch for contamination if the buffer breaks down. On top of this, stockpiling specialty chemicals raises costs, which can hit small labs or low-resource regions hard.
Thinking forward, manufacturers need to focus on sustainable production and lower environmental impact. Labs should track buffer disposal, since large volumes add to chemical waste. Green alternatives often lack the stability or reliability of MOPS, but collaboration across academia and industry could shift this over time. Reliable, safe, and affordable buffers will be key as medicine and diagnostics keep evolving.
You might not find 4-Morpholinopropanesulphonic acid, commonly called MOPS, stocked in household cabinets, but plenty of biochemists know it by heart. Its structure looks pretty simple on paper—C7H15NO4S. The backbone starts with a morpholine ring, which is a six-membered ring made up of oxygen and nitrogen, surrounded by four carbon atoms. A propanesulfonic acid group attaches itself to the nitrogen, stretching out like a tail. This combination gives the molecule the ability to serve as a buffer, regulating pH in a way that keeps laboratory reactions on track.
With my early experience in a research lab, the structure of MOPS felt as familiar as the smell of agar plates. On the morpholine ring, two heteroatoms—oxygen and nitrogen—sit opposite each other. That nitrogen becomes the anchor point for a three-carbon chain, which ends with a sulfonic acid group (–SO3H). The entire shape puts water solubility front and center, and it resists breakdown, which is exactly what researchers want. Visualizing the connectivity:
Years ago, I watched a colleague waste dozens of precious samples due to wild pH swings. That’s not just a headache—it means stalled results, lost money, and dashed hopes. MOPS steps in by resisting shifts in pH between 6.5 and 7.9, keeping reactions stable and proteins happy. Its structure avoids breaking down under most experimental conditions, so researchers don’t have to clean up after messy side reactions or chase disappearing buffer capacity.
The design behind MOPS didn’t happen by accident. Scientists looked for a buffer that wouldn’t soak up metals, wouldn’t react with common enzymes, and wouldn’t sway results. With this structure, MOPS covers those needs, holding firm even as temperature or salt concentration changes. Its utility shows up in protein purification, electrophoresis work, and cell culture experiments.
Reliable safety data and studies back up the claims about MOPS. Researchers point to its low toxicity and predictability. The American Chemical Society and IUPAC support its use, and you can spot the references to its structure in peer-reviewed literature. Handling any chemical in the lab demands constant vigilance: wear gloves, avoid inhalation, don’t let it sit uncovered. Strong protocols and a working knowledge of the structure keep surprises out of the workflow.
The field marches on. As scientists search for new buffering agents, they still want molecules stable enough to trust, simple enough to make, and gentle enough for complex systems. Sharing accurate, clear information about MOPS’s structure helps keep mistakes low and keeps conversations honest. It all starts with understanding those rings and chains—the small unseen shapes that keep cells alive and research running.
4-Morpholinopropanesulphonic Acid—or MOPS, as most in the lab world call it—often helps researchers keep solutions steady with its buffering action. Its main job: keep pH levels from swinging around during experiments. You’ll see MOPS in biology and biochemistry work, from protein studies to electrophoresis. It doesn’t usually jump off the page as a red-flag chemical, but safety in chemistry relies on real knowledge, not just comfort with a name.
Diving into the data, the usual sources—like Sigma Aldrich and the NIOSH registry—describe MOPS as a low-to-moderate hazard. Swallowing or inhaling large amounts can irritate the body. It’s not considered carcinogenic. Skin or eye contact brings a risk of local irritation, especially if someone skips gloves or goggles. I remember spilling a buffer on my own hands in college; nothing happened at first, but a few hours later, my skin felt itchy and dry. It is easy to get careless, thinking a mild acid can’t hurt, but these small exposures add up over long hours at the bench.
It’s important to think about who handles these substances and where they end up. Lab techs and students pour out thousands of liters each year, and universities build up waste drums full of buffer solutions. If labs wash them down the drain, local wastewater plants have to process trace chemicals they may not expect.
People often want to know if MOPS is going to cause environmental trouble. Studies show that it breaks down slowly in nature, doesn't build up rapidly in living organisms, and isn’t especially toxic to fish or algae. Still, “not especially toxic” doesn’t mean “harmless.” Small doses to a goldfish tank won’t cause a die-off, but repeated exposures over time, mixed in with other chemicals, stack up in unpredictable ways.
Wastewater full of synthetic chemicals winds its way into rivers, lakes, groundwater supplies. Most chemicals dilute and degrade through sunlight, microbes, or time, but substances like MOPS linger. Over my years in research, I saw chemical safety officers flag the same concern: it’s usually not one chemical that surprises us, but the cocktail effect of dozens poured out daily.
Most researchers do not suffer acute poisoning from buffer chemicals. Problems show up as chronic skin irritation, unpredictable allergies, or, rarely, accidental ingestion. The best fix is to treat every chemical in the lab with respect: gloves, goggles, fume hood, and tidy labeling. Mistakes come from rushing or skipping checks. MOPS powder drifts into the air easily; wetting it down immediately reduces airborne dust.
Disposal deserves respect as well. Don't assume a drain can handle everything. Ask a local waste company or university EHS team for guidance, and try to use the smallest amount possible. Many labs now try greener buffers or digital testing methods to replace old routines—tech keeps moving forward, cutting risks where it can.
It all boils down to honest information and everyday habits. No chemical in the lab deserves blind trust. MOPS won’t send you running for the emergency shower, but a slack approach breeds bigger problems for the next person, or for your own future self. Risks hide in ordinary things, and everyone—from the lab rookie to the seasoned scientist—benefits from careful routines and a little extra respect for what goes down the drain.
Laboratories keep all sorts of busy and sometimes dangerous chemicals on their shelves, and 4-Morpholinopropanesulphonic acid—or MOPS, as most chemists call it—happens to be one of those that rarely leaves the research bench. Kind of like flour in a baker’s kitchen, it shows up in buffers and cell work. The white powder doesn’t look threatening, but—like most chemicals—improper storage can turn routine into risk.
Folks who work with reagents like MOPS know how easy it is to get careless after a hundred successful uses. Without warning, an unlabeled bottle or an absent lid could throw a day’s work in the garbage or, worse, send someone to the hospital. The lessons always come after the mistake. But in research, we don’t get many second chances.
MOPS wants a dry, cool home. Water turns it into a sticky mess; heat makes it break down. That’s the ugly truth about stability. I remember a graduate student who left a sample on the heater overnight—lost half his experiment and learned the hard way that refrigerators exist for a reason. Industry handbooks put 2-8°C as the sweet spot, away from sunlight and out of the way of lab traffic.
Air exposure raises red flags too, and not just because of moisture. Dust, contamination, and even the gentle breeze from a vent can change the balance. Most accidents I’ve seen come from lazy sealing. A simple airtight glass bottle, tucked out of light, keeps the powder safer than everything else.
Messy shelves breed confusion. I walk into some labs and see open jars, unmarked containers, and it takes me back to the panic after a hazardous spill. All it takes is one distracted moment. MOPS needs clear labels, hazard stickers, and its own slot away from incompatible substances—think strong acids, bases, oxidizers.
High-traffic bench space tempts people to cut corners, but the safe bet is storage in a chemical cabinet with a secure latch. It costs less to put chemicals in order than to clean up a spill. The time spent now saves money and stress later.
Weathered chemists talk up the basics for good reason. Standard operating procedures only work if followed. I’ve seen productivity jump in labs with routine safety meetings and checklists because everyone knows what’s expected and where to report trouble. People may poke fun at checklists, but all it takes is reading an MSDS (Material Safety Data Sheet) once to see that MOPS, inhaled or spilled, brings real harm.
Building a culture where everyone feels responsible for their own safety—and cares about their coworkers—does more than rules on a wall ever could. Trust gets earned, and from there, everyone works just a bit smarter. Every person storing or handling MOPS needs to pay attention and follow the house rules: keep it sealed, keep it cool, keep it dry, and don’t let convenience dull your caution.
Lab work often feels like a balancing act. Relying on quality chemicals isn’t just about ticking a box; it’s about getting consistent, trustworthy results. 4-Morpholinopropanesulphonic acid—better known as MOPS—takes on a serious role in biochemical research, especially when folks need a buffer with predictable behavior at physiological pH ranges. I’ve spent enough time prepping buffer solutions to know how much chasing purity, even at what seems like tiny decimal points, can avoid a lot of dead ends.
Reputable suppliers set the standard for MOPS with a purity specification that usually sits at or above 99%. This spec goes beyond just the content claimed on the label. Analytical labs check for the main compound via HPLC, and any hint of water content shows up through Karl Fischer titration. Ash content and residue on ignition also must stay minimal—less than 0.1% by weight pops up on most datasheets, since leftover metals or inorganic impurities stick around in the final sample and can mess with sensitive experiments.
Endotoxin limits get some attention too: biochemistry leaves little room for things like pyrogens, which can spark false signals or outright ruin cell cultures. Most top-grade MOPS available on the market promises endotoxin levels below 1 EU/mg. UV absorbance also gets checked at specific wavelengths, usually 260 and 280 nm, offering clues about possible contamination by nucleic acids or proteins. If there’s a yellowish tint or any bump in the baseline, something’s off.
Quality control isn’t always perfect, even for suppliers who talk a big game about purity. I remember ordering a batch with a “guaranteed” 99.5% purity. The buffer worked, but my results bounced all over the place every few runs. A closer look at the certificate of analysis flagged minor levels of sodium and potassium—carryover from the neutralization process. Testing new batches from other sources shut down those strange anomalies. That episode drove home how even minor contaminants generate noise in the data.
What stuck with me most was how cutting corners, even with a “high purity” label, can snowball into wasted days of troubleshooting. As a researcher, you look at unexpected readings and wonder if it’s an error in your process—many times, it’s the buffer itself kicking up the dust.
Most scientists trust a tight-knit circle of chemical suppliers for good reason. Vendors holding to ISO 9001 or cGMP standards back up their numbers better, offering more detailed COAs, and sometimes, full impurity profiles. Some labs, strapped for cash or ordering in bulk, take a risk on cheaper sources. Savings at the start can shrink once you count up the time spent hunting the source of odd results.
A safer bet means always checking the latest certificate of analysis, not just grabbing what was in stock last year. Even mixing up batches or testing a small aliquot before scaling a run helps avoid bigger headaches later. Sharing purity test results in laboratory notebooks and reporting post-purchase findings strengthens collective trust within the lab.
Keeping up standards on MOPS purity matters as life science keeps digging deeper into molecular detail. Holding everyone, from chemical companies to lab managers, to transparency cuts down on the guesswork. The baseline for MOPS shouldn’t just stay high—it needs scrutiny, whether from automated instrumentation or watchful researchers who have been burned one too many times by an “almost pure” chemical.
| Names | |
| Preferred IUPAC name | 4-morpholin-4-ylbutane-1-sulfonic acid |
| Other names |
MOPS 3-(N-Morpholino)propanesulfonic acid 4-Morpholinepropanesulfonic acid Morpholinopropanesulfonic acid |
| Pronunciation | /ˌfɔːr.mɔːrˌfəˈliː.nəˌproʊ.peɪn.sʌlˈfɒ.nɪk ˈæs.ɪd/ |
| Identifiers | |
| CAS Number | 1132-61-2 |
| 3D model (JSmol) | `3D model (JSmol)` string for **4-Morpholinopropanesulphonic Acid** (MOPS): ``` CC(CS(=O)(=O)O)N1CCOCC1 ``` *(This is the **SMILES** string commonly used for JSmol or similar 3D visualization tools.)* |
| Beilstein Reference | 1722784 |
| ChEBI | CHEBI:39050 |
| ChEMBL | CHEMBL25457 |
| ChemSpider | 14118 |
| DrugBank | DB01942 |
| ECHA InfoCard | ECHA InfoCard: 100.059.312 |
| EC Number | 1132-61-2 |
| Gmelin Reference | 82236 |
| KEGG | C02335 |
| MeSH | D018490 |
| PubChem CID | 71176 |
| RTECS number | TI3850000 |
| UNII | C32157U2H9 |
| UN number | UN3077 |
| CompTox Dashboard (EPA) | DTXSID7032183 |
| Properties | |
| Chemical formula | C7H15NO4S |
| Molar mass | 195.24 g/mol |
| Appearance | White crystalline powder |
| Odor | Odorless |
| Density | 1.096 g/cm³ |
| Solubility in water | Soluble |
| log P | -3.2 |
| Vapor pressure | Vapor pressure: 4.31E-10 mmHg at 25°C |
| Acidity (pKa) | 5.3 |
| Basicity (pKb) | 5.87 |
| Magnetic susceptibility (χ) | -6.2·10⁻⁶ |
| Refractive index (nD) | 1.510 |
| Viscosity | Viscous liquid |
| Dipole moment | 7.63 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 178.2 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -523.8 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -4631 kJ/mol |
| Hazards | |
| Main hazards | Causes serious eye irritation. |
| GHS labelling | GHS05, GHS07 |
| Pictograms | GHS05,GHS07 |
| Signal word | Warning |
| Hazard statements | H302: Harmful if swallowed. |
| Precautionary statements | P264, P280, P305+P351+P338, P337+P313 |
| NFPA 704 (fire diamond) | 1-0-0 |
| Lethal dose or concentration | LD50 Oral Rat 5200 mg/kg |
| LD50 (median dose) | LD50 (median dose): > 5000 mg/kg (Rat, oral) |
| NIOSH | Not Listed |
| PEL (Permissible) | Not established |
| REL (Recommended) | 100 mg/m³ |
| Related compounds | |
| Related compounds |
MES CHES ACES PIPES HEPES TES MOPS |
