Chemists have worked with buffering agents for generations, hunting for better control in both biochemistry and chemical production. The search hasn’t been all theory and text. At conferences and in cold early-morning labs, folks swapped stories about buffer failure or triumph. Researchers needed something reliable, with low reactivity and precise buffering range. In this search, 2,2'-(Piperazine-1,4-Diyl)Bis(Ethanesulphonic) Acid (commonly called PIPES) came along in the 1960s—a creation aimed at filling the holes left by unstable or problematic alternatives. PIPES entered the benchwork scene at a time when solid pH control meant the difference between failed and breakthrough experiments, especially at the frontier of cell biology and enzymology. It wasn’t invented on a whim; it grew out of practical needs and close observation. Early papers—tucked away in library archives—carried simple hand-sketched chemical structures and pH titration curves. Academic teams described its sharp buffering action, especially in the pH range near neutrality. The rise of PIPES came alongside changes in protein chemistry and cell culture research. Laboratory manuals and biotech companies soon listed it as a reliable workhorse, and demand kept rising as researchers trusted its stability and reproducibility over endless reruns and multi-day bench setups.
PIPES doesn’t grab headlines, but it sits in refrigerators, storerooms, and beakers around the globe. Chemically, it looks simple but gives researchers exactly what they expect. Its formula—C8H18N2O6S2—puts it in the family of zwitterionic buffering agents, which don’t mess with cell membranes or stray into the world of unwanted side reactions. Bottles arrive as solid, white to off-white powders, usually supplied in tight double-bagged packages to keep moisture out. Standard labeling offers clear product names and batch-specific information. Sometimes labs circle or underline “PIPES” on their inventory sheets, shorthand for a staple they’d run out of only with great regret. Suppliers have caught onto the routine requests, usually selling it in amounts from a few grams up to kilogram-scale, each with a certificate of analysis and purity often above 99%. The world’s leading producers print out technical datasheets, typically in half a dozen languages, because this product travels from academic biochemistry departments to commercial-scale fermenters and vaccine development suites.
PIPES has some habits that make it a favorite. It dissolves well in water, yielding a clear solution without fuss. Its melting point sits well above a hundred degrees Celsius, so nobody worries about it degrading in standard lab conditions. Chemists love its stability, both as a free solid and in solution, because it shrugs off minor heating and repeated freeze-thaw cycles. The acid shows almost no tendency to form volatile or explosive species. Its strong sulfonic acid groups create a gentle but effective buffer action, hitting a sweet spot for pH control between 6.1 and 7.5. The chemical formula gives it a weight of around 302.4 grams per mole. Every container shows molecular structure on the label. No funny odors, no color changes, and no need for exotic solvents—just dependable performance in water.
Suppliers cater to demanding customers—so purity levels must stay high, with minimal presence of heavy metals or organic contaminants. Reputable vendors provide batch numbers, expiration dates, and detailed assay results. Labels often list not just the chemical name, but a string of alternative names: PIPES, 1,4-Piperazinediethanesulfonic acid, and even its less-catchy IUPAC versions. Most containers also mark recommended storage conditions, reminding users to keep the powder cool, dry, and sealed. Some suppliers add application notes, tailored for users who prepare buffer concentrates, stock solutions, or sterile filters for tissue culture. Alongside the basics—chemical structure, formula, weight—labels will warn about eye and skin contact risk because labs keep safety at the front, not as an afterthought.
Turning raw materials into PIPES demands a batch approach rooted in reliable reactions between piperazine and ethane sulfonic acid derivatives. It isn’t alchemy; the steps build on decades-old amination chemistry. In some plants, workers charge glass-lined reactors with dry piperazine, then they introduce sulfonic acid components dropwise under inert atmosphere. Careful temperature control keeps things moving without runaway heat. After the main reaction, plant technicians use filtration, washing, and vacuum drying to isolate the acid in pure form. Analytical chemists check for side products using HPLC and NMR—no expansion beyond the ordinary unless strict pharmaceutical or diagnostic standards apply.
PIPES stays quietly stable in most biological settings. It resists oxidation and only reacts under harsh chemical conditions—like concentrated alkali or strong acids. In research, some biochemists modify it by adding isotopic labels or fluorescent tags for niche experiments in proteomics or cell imaging. A few material chemists graft its backbone to polymers for specialized sensors. The main feature—those two sulfonic acid groups—remains stubbornly unchanged unless someone goes out of their way to break them apart. Free amine groups allow it to act as a linking handle for advanced chemical reactions, though most users want it as pure buffer, not a complicated reagent.
Look through older journal articles or online catalogs and the variety of names for this buffer immediately stands out. Some listings say “PIPES,” others get formal: “Piperazine-N,N′-bis(2-ethanesulfonic acid)” or “1,4-Piperazinediethanesulfonic acid.” European sources sometimes spell it differently, while on the other side of the world, labels appear in Mandarin, Hindi, or Russian, though the molecular structure never changes. Vendors tend to unify most synonyms under one entry, with standardized product codes, so researchers from across borders face fewer mix-ups in ordering and quality control. Common abbreviations (like PIPES) win out in fast-paced labs where communication stays crisp and technicians work by habit as much as by protocol.
Workers mixing or weighing PIPES always put on gloves and goggles—basic protocols shaped by experience with all laboratory powders. Labeled as a low-toxicity compound, it still gets classified as an irritant, so nobody pours it bare-handed. Material safety data sheets (MSDS) recommend handling in ventilated spaces and keeping dry powder out of eyes and lungs. Some years ago, anecdotes circulated of careless users coughing after tipping open a new jar and getting a faceful of dust. Standard cleanup for spills involves nothing special—just sweep and dispose as non-hazardous laboratory waste, but safety audits want everything logged and checked. Long-term studies haven’t found evidence of cancer risk or cumulative toxicity at common lab doses, though regulatory authorities ask for careful disposal, especially in schools or shared research facilities.
Research scientists pick PIPES for its steady buffering action in animal cell culture, enzyme kinetics, and protein purification. Anyone running electrophoresis gels or stabilizing samples for microscopy likely has prepared a PIPES solution by rote. The compound barely interferes with most biochemical assays, letting other variables take the spotlight. Down the corridor from the academic labs, biopharma companies use it in the manufacture of diagnostic reagents and as a standard buffer in quality control checks. Environmental scientists have tested water quality and aquatic toxicity with PIPES-buffered samples, appreciating its clarity and lack of unwanted side reactions. In recent years, high-throughput screening labs, as well as point-of-care device manufacturers, rely on its consistent performance for thousands of small-volume tests, supporting early diagnostics and precision medicine.
Teams across the globe keep studying new ways to tweak PIPES and other Good’s buffers for tighter pH range, better compatibility with membranes, or faster dissolution. Several journal articles chase after minor modifications—altering side chains to fix specific quirks in protein crystallization or enzyme assays. Sometimes instrument manufacturers adjust the formulation for proprietary diagnostic platforms, demanding purity down to parts per billion and complete documentation. In my own research, I’ve watched undergraduate students prepare brand new buffers, then compare them head-to-head with PIPES controls; over and over, its reliability keeps it as the benchmark. Funding agencies still support efforts to develop greener production methods for PIPES, with chemists aiming to cut down on waste and water consumption. Regulatory bodies and universities maintain a steady watch for any emerging toxicity or contamination findings.
The story of PIPES and toxicity follows a reassuring narrative. Standard animal testing puts PIPES in a low-risk group compared to many other buffering agents. Acute toxicity studies on mammals and invertebrates show few adverse effects, even at concentrations higher than used in typical laboratory practice. Cell line research consistently finds minimal impact on viability or gene expression, provided concentrations stay within the bounds of established protocols. Environmental toxicity gets more attention these days, prompted by increased volumes used in industrial bioprocessing and academic labs. Some wastewater studies indicate PIPES breaks down slowly, which nudges municipalities and research centers to improve treatment and disposal practices. Researchers recommend caution before dumping any buffer directly into groundwater or streams, especially in sensitive habitats. Detailed epidemiological surveys still haven’t flagged any chronic risks to either workers or nearby communities under current norms, but worldwide regulations ask suppliers to keep running these assessments, just in case.
Looking ahead, PIPES will likely hold its position in the research landscape as both established buffer and subject of incremental improvement. The rise of single-cell genomics, high-throughput biological screening, and custom diagnostics keeps pushing demand for ever-purer, even more inert chemical environments. Startups and manufacturing giants see rising opportunity in greener, safer production methods for legacy reagents, and PIPES fits neatly into those goals—a known performer in a world that expects lower energy use and strict sustainability targets. Environmental questions about buffer disposal will spark new research into biodegradable alternatives or advanced waste treatment. In academic poster sessions and industrial production meetings, PIPES continues to draw respect—holding firm as an everyday solution for the small but critical challenge of precise pH control. If innovation in chemical synthesis or bio-combatibility opens up a new era for laboratory buffers, it will owe much to the foundation laid by everyday compounds like PIPES, familiar to generations and still quietly vital.
Every time I step into a lab, the importance of stability in experiments jumps out at me. 2,2'-(Piperazine-1,4-diyl)bis(ethanesulphonic) acid, usually called PIPES, makes that possible—especially in biology labs. Think of growing cells, running a DNA test, or preparing any protein research. pH stability matters, since even tiny shifts can destroy results. PIPES stands out because it holds the solution at the right acidity or alkalinity. Biologists trust it for work inside the pH 6-7.5 range, supporting delicate experiments from start to finish. Without this help, decades of cell biology and molecular research would have run into dead ends.
Take protein purification—a step-by-step process where you coax one protein out of a soup of chemicals. The wrong buffer means ruined samples, wasted budgets, and weeks of lost time. PIPES steps up here for its consistency. I’ve seen many researchers avoid familiar solutions like phosphate buffers because they get in the way of key reactions. PIPES sidesteps this issue, staying out of the way chemically and supporting enzymes and proteins. Academic papers highlight its low affinity for metal ions, meaning less unwanted reaction. In labs focused on enzyme reactions, neuroscientists and microbiologists use it to keep samples healthy and viable.
Clinical labs depend on diagnostic tests that need buffers with near-perfect reliability. Hospitals hunt for accuracy before anything else, since patient treatment rests on test results. PIPES gives them that edge in tests that track electrolytes, proteins, or genetic markers. Some modern blood analyzers use it internally to manage the mix of chemicals while avoiding reactions that would throw off patient data. Its chemical background means less interference and less need for repeated tests—this reduces cost and time for both labs and patients.
Science in industry faces issues that don’t always show up in a lab notebook. Chemical manufacturing, food testing, and even water treatment look for additives that support processes without causing unwanted side effects. PIPES helps hold pH stable in fermentation tanks and bioreactors, giving companies a tool that matches the demands of living systems. Minimized chemical waste matters, especially as regulations lock down what industries can pour down the drain or emit to the air. Its stability protects both the product and the environment.
Although it helps labs and industries, access to quality PIPES isn’t equal everywhere. Some regions deal with shortages or high prices. Researchers in developing countries have told me that sometimes, lack of a simple buffer halts their work entirely. Companies can help by supporting open-access distribution or partnering with local suppliers, making sure bright minds everywhere can take part in scientific progress. Strengthening international supply chains guarantees science moves forward, no matter where it starts.
Most people won’t ever measure out PIPES themselves, but its work happens behind the scenes. Accurate medical tests, new drugs, vaccines, and food safety checks all lean on the kind of stability PIPES delivers. If you or a family member ever received quick medical results, or if cleaner food landed on your table, solid lab materials are part of the reason. That reliability travels further than the lab bench—it affects daily lives in real but quiet ways.
Standing in a lab, one lesson gets hammered into your head fast: never ignore the basics. The formula and molecular weight of a compound look like boring details, but they control where an experiment starts and whether it ends with success or a mess. Nobody wants to scramble for a calculator mid-reaction. Finding the right numbers on a compound label can spare you from hours of wasted effort or a costly batch gone wrong.
A compound’s formula lists every element inside. Each letter and tiny number tells you what's present and how many atoms of each do the heavy lifting in every gram. Make a mistake reading this, and the rest of your day will head downhill quickly. Look at glucose: C6H12O6. Each C, H, and O stands for carbon, hydrogen, and oxygen. Miss one digit, the entire world of metabolism drops apart.
Those who work with medications or food additives study these letters the way a chef knows ingredients—because people depend on that accuracy. A single missing atom or an extra branch in a molecule has tossed whole batches, and sometimes, whole product lines, into regulatory limbo. Chemistry doesn’t accept “close enough.”
Look up sodium chloride: NaCl. Add up sodium (about 23) and chlorine (about 35.5), and you get roughly 58.5 g/mol. Each “g/mol” translates from molecular language to usable lab grams, a bridge between what’s in the bottle and what’s on the scale. Dosing medicine works on this same math, whether preparing an IV or figuring out how much salt to add to a cell buffer.
Professionals who cut corners end up fighting with inconsistent results. The worst moments happen not from one big mistake but from nagging errors that sit unchecked: botched measurements in food processing, wonky yields in chemical plants, dosages drifting dangerously in pharmaceuticals. All preventable by checking these two quiet facts—molecular formula and weight—before heading to the bench.
Reliable data stops risky improvisation. I learned this lesson in a university lab, prepping a routine solution. A friend saved me from adding far too much acid after I mixed up sulfuric acid with sulfurous acid. The labels looked similar— the formulas were not. Marine chemists face worse in water analysis, chasing compounds that show up in tiniest traces. Mistakes in formula or weight trickle through calculations until big decisions get made on faulty data.
The solution? Stick to validated databases and double-check numbers at every step. Cross-reference chemical registries, drug formularies, or peer-reviewed publications that offer clear, current, and accurate measurements. Digital lab notebooks help, especially with built-in calculators. Still, the most powerful tool is the habit of questioning every piece of data before acting on it.
Every career in science starts with rote memorization, but real judgment comes from those who ask for the source behind every number. Following this habit—whether mixing fertilizer, developing new materials, or preparing a teaching demo—keeps experiments honest and safer. Nothing beats the confidence of knowing the formula matches the flask and the grams lined up with the plan.
Anybody handling chemicals in a lab knows the drill: how you store what you use can make all the difference. There’s no fancy workaround for 2,2'-(Piperazine-1,4-Diyl)Bis(Ethanesulphonic) Acid. I’ve worked in small academic prep rooms and bigger industrial spaces, and the same storage rules always hold up—keep things simple, reliable, and safe. This compound turns up a lot in biochemistry labs and buffers, known for being dependable during protein purification work and electrophoresis.
Humidity might seem harmless, but some of the worst contamination problems I’ve seen have started with a careless storage area. Leave this acid in a damp place, and you’re looking at clumping, lost purity, and a real headache if you’re chasing reliable assay results. Shelves inside a temperature-controlled room—ideally 2–8°C—work best. None of those hot, drafty spots near radiators or under air vents. Stability over time means everything, especially if you want to avoid replacing reagents every few weeks.
Direct sunlight can hammer away at chemical stability before anyone realizes what’s going on. Lab instructors taught me early on to reach for amber glass bottles for nearly anything that could break down in full light. Even if your reagent isn’t highly photosensitive, a solid habit in chemical management is choosing containers that fight degradation—dark glass, tight lids, zero exposure to the open air. Screw caps seal in both quality and shelf life. Forgetting to close a jar tight after use often turns fresh-for-months powders into spoiled, unreliable piles of wasted money.
Misplacing a label or mixing containers happens in busy labs, but that small error can spiral into wasted time and compromised work. Every bottle I’ve seen in a well-run facility lists the full chemical name, concentration, and the date received. You save future-you from playing a guessing game. Hazard symbols prevent cross-contamination, especially with reactive acids and bases in the same fridge or on the same rack.
Access control never lost its importance for any chemical. I’ve seen cleaners and lost undergrads pop the lids off mystery containers more than once. That’s why cabinets with restricted access mean fewer safety scares and no accidental spills. Just because something isn’t explosive does not mean it’s safe to leave unattended.
Studies suggest contamination costs labs millions yearly—not just in ruined experiments, but in burned time and resources. The ACS and CDC recommend humidity control and proper segregation for acids like this one. It’s not just bean-counting; it’s about hitting published research targets and making sure efforts pay off.
Daily checks go farther than any written protocol. If you think the powder looks strange or the container’s warm or sticky, swapping it out beats risking a failed test. Rotating stock—first-in, first-out—saves a lot of trouble down the line. Speaking from long days on the bench, sticking to these habits guards both results and budgets, especially with price tags on specialty chemicals climbing every year.
Standing in the store aisle, turning a product over in your hands, the fine print can feel like reading a new language. “Hazardous,” “toxic,” “eco-friendly” — these words get tossed around, but what do they really mean for everyday safety? I learned to look past the marketing and dig into the science after a friend landed in the ER because of a cleaning product mishap. It’s not enough to trust the bold labels or splashy green logos.
Hazardous and toxic don’t mean the same thing. Hazardous means you could get harmed through normal use — maybe a corrosive that burns skin, a flammable liquid, or something that messes with your breathing. Toxic refers to something that can poison your body, either over time or after a single exposure. Common household stuff clocks in on both lists. Take bleach. Most folks have it under the sink. It can burn eyes, skin, or lungs if you use it carelessly. Mixing bleach with ammonia — whether on purpose or by accident — creates toxic chloramine gas. It’s a hidden threat in ordinary moments.
Companies must list ingredients, but loopholes remain. “Fragrance” can cover up a mix of chemicals, some of which may disrupt hormones or trigger allergies, according to research documented by the Environmental Working Group. This makes it tough for shoppers who want clarity about potential risks. I’ve stood in front of shelves, scanning for real information, and left just as baffled. Transparency improves safety — the more straightforward the label, the easier it is to protect your family.
Children, pets, and seniors react differently to chemicals. A dose that barely affects a healthy adult might seriously harm a small child or a curious dog. In my own home, I locked away cleaners after my toddler grabbed a bottle from under the sink. It only takes a second of distraction for disaster to strike.
Product websites and government databases offer another layer of checking. The U.S. Environmental Protection Agency (EPA) keeps lists of ingredients classified as hazardous or toxic. The National Institutes of Health runs the Household Products Database, letting you search actual brands for known risks. Digging into these sources helps cut through marketing fog.
People also forget about personal protective equipment. How often did you clean the bathroom, breathing in fumes with nothing but a cracked window? Gloves, goggles, or a mask go a long way towards keeping chemicals off skin and out of lungs. Taking precautions doesn’t mean wrapping yourself in plastic, just respecting what’s on the label and what’s missing from it.
Not all risk can be eliminated, but habits matter. I’ve started making a few cleaners at home using vinegar and baking soda for many jobs. For heavier tasks — like unclogging a drain — I check the exact warnings, open the windows, and don’t get lazy about gloves. Teaching children to ask before touching unfamiliar bottles became part of our routine, along with explaining what the skull and crossbones symbol means.
The right to know what’s inside a product shouldn’t feel like detective work. Asking questions, reading up on independent ratings, and contacting manufacturers for more details give control back to people, not corporations. As communities push for better rules and full transparency, safer choices become more than just a privilege for those with time to spare — they become the baseline. That makes every home a little safer, one clear answer at a time.
Research and industry thrive on practical solutions. Whether running a university laboratory or managing production on a factory floor, people look for tools and processes that get results. In my years working with both academics and engineers, I’ve seen a handful of applications stand out for their impact.
Labs use advanced techniques to get answers from the smallest samples. Polymerase Chain Reaction (PCR), for example, has changed disease diagnostics and genetic research. Twenty years ago, tracking down gene expression or a viral load in a sample felt like guesswork. PCR gives researchers concrete answers fast, and high-throughput sequencing adds even more detail.
Drug discovery teams also lean on biotechnology. Automated screening systems zip through thousands of variants, checking which compounds might block a virus or jumpstart insulin production. Robots don’t care about long hours or missed coffee breaks; they just keep churning. Speeding up these processes brings breakthroughs closer.
Every smartphone, car, or bridge owes something to advances in materials science. Engineers hammer away at new metal alloys and ceramics for heat resistance and strength, aiming to make planes lighter and batteries last longer. In my previous job, I watched teams test dozens of composites each month, searching for one more hour of battery life or a more crash-resistant polymer.
Nanotechnology moves the game forward. Nanoparticles add antimicrobial punch to bandages or boost the power of solar cells. Thin films keep smartphone screens scratch-free. These changes shift how products perform, and industries notice.
Factories don’t look like they did twenty years ago. Automation guides machines along the assembly line, measuring every action, flagging every mistake. Precision machining now shapes spacecraft parts to within millionths of a meter. I remember meeting machinists who embraced computer-controlled tools not out of love for technology, but because they cut down waste and rework.
Additive manufacturing, or 3D printing, turns digital designs straight into parts without molds or lots of downtime. On the research side, 3D printing lets inventors try out dozens of shapes before settling on the right one. In industry, workers rely on these machines to create custom replacements and speed up repairs.
The modern research paper often draws from mountains of data. Machine learning crunches information on everything from buying habits to protein folding. Medical institutions, for example, turn mammograms or scans into health predictions that save lives. Retailers adjust supply chains by watching demand trends through algorithms.
Most companies still face challenges in managing and protecting data. Cybersecurity gaps, inconsistent data formats, and skills shortages slow adoption. Smart teams focus on regular training and basic digital hygiene—simple passwords, strong backups, and practical rules for sharing sensitive information.
The best applications add value, not complexity. I’ve seen that success depends on matching the right tool with a real-world need—avoiding gadgets for their own sake. Open conversation between researchers and frontline workers always brings out new ways to improve, often by building on ideas from both sides.
| Names | |
| Preferred IUPAC name | 2,2'-[(piperazine-1,4-diyl)bis(ethane-2,1-diyl)]bis(sulfonic acid) |
| Other names |
PIPES Piperazine-N,N′-bis(2-ethanesulfonic acid) |
| Pronunciation | /ˌpaɪpəˌreɪziːn wʌn fɔːr daɪil bɪs ˌɛθ.eɪnˈsʌlfɒnɪk ˈæsɪd/ |
| Identifiers | |
| CAS Number | 6960-47-4 |
| 3D model (JSmol) | `3D structure; JSmol-model string for 2,2'-(Piperazine-1,4-diyl)bis(ethanesulphonic acid)`: ``` CCS(=O)(=O)N1CCN(CCS(=O)(=O)O)CC1 ``` *This is the SMILES string representation, which is commonly used to generate 3D models in JSmol and similar viewers.* |
| Beilstein Reference | Beilstein Reference: 3684784 |
| ChEBI | CHEBI:91273 |
| ChEMBL | CHEMBL3342100 |
| ChemSpider | 19782041 |
| DrugBank | DB01626 |
| ECHA InfoCard | 06c5c9b0-4b44-4841-93bb-4a99ed6b7c50 |
| EC Number | 2261-96-9 |
| Gmelin Reference | 84859 |
| KEGG | C07248 |
| MeSH | D017209 |
| PubChem CID | 71345 |
| RTECS number | GS8575000 |
| UNII | Q16FFQ53H9 |
| UN number | Not regulated |
| CompTox Dashboard (EPA) | DTXSID3049381 |
| Properties | |
| Chemical formula | C8H20N2O6S2 |
| Molar mass | 390.48 g/mol |
| Appearance | White solid |
| Odor | Odorless |
| Density | 1.228 g/cm³ |
| Solubility in water | soluble in water |
| log P | -2.5 |
| Vapor pressure | Vapor pressure: <0.01 hPa (20°C) |
| Acidity (pKa) | 1.8 |
| Basicity (pKb) | pKb 4.8 |
| Magnetic susceptibility (χ) | -0.8E-6 cm³/mol |
| Refractive index (nD) | 1.546 |
| Viscosity | 45 cP (25°C, 20% in H2O) |
| Dipole moment | 6.24 Debye |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 311.6 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -1564.9 kJ mol-1 |
| Std enthalpy of combustion (ΔcH⦵298) | -2062.8 kJ/mol |
| Pharmacology | |
| ATC code | A06AD21 |
| Hazards | |
| Main hazards | Causes serious eye irritation. Causes skin irritation. May cause respiratory irritation. |
| GHS labelling | GHS07 |
| Pictograms | GHS07 |
| Signal word | Warning |
| Hazard statements | H315, H319, H335 |
| Precautionary statements | P280, P305+P351+P338, P337+P313 |
| NFPA 704 (fire diamond) | 1-0-0 |
| Flash point | > 255.2 °C |
| LD50 (median dose) | LD50 (median dose): Mouse intravenous 900 mg/kg |
| NIOSH | 'WF4740000' |
| PEL (Permissible) | Not established |
| REL (Recommended) | 50 mg |
| Related compounds | |
| Related compounds |
Piperazine Ethylenesulfonic acid Piperazine sulfonic acid TES (N-Tris(hydroxyethyl)methyl-2-aminoethanesulfonic acid) HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) |
