Introduction to Buffers
A buffer is a solution that can resist pH change upon the addition of an acidic or basic components. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable. This is important for processes and/or reactions which require specific and stable pH ranges. Buffer solutions have a working pH range and capacity which dictate how much acid/base can be neutralized before pH changes, and the amount by which it will change.
What is a buffer composed of?
To effectively maintain a pH range, a buffer must consist of a weak conjugate acid-base pair, meaning either a. a weak acid and its conjugate base, or b. a weak base and its conjugate acid. The use of one or the other will simply depend upon the desired pH when preparing the buffer. For example, the following could function as buffers when together in solution:
Acetic acid (weak organic acid w/ formula CH3COOH) and a salt containing its conjugate base, the acetate anion (CH3COO-), such as sodium acetate (CH3COONa)
Pyridine (weak base w/ formula C5H5N) and a salt containing its conjugate acid, the pyridinium cation (C5H5NH+), such as Pyridinium Chloride.
Ammonia (weak base w/ formula NH3) and a salt containing its conjugate acid, the ammonium cation, such as Ammonium Hydroxide (NH4OH)
Buffers are a class of solution-stabilizing molecules which existed long before contemporary lab technology. Natural buffer substances like bicarbonate and carbonic acid are manufactured by organisms and molecular interactions, functioning to maintain pH equilibrium.
After natural buffer systems were discovered, their balancing effects became indispensable in scientific exploration. Synthetic buffers were developed over decades to produce reliable reactions in experimental models, enhancing biochemical reactions and medicinal products.
New buffers are introduced every year, built from the fundamentals developed over a century ago. This article explores buffers beginning with the foundation which made them inseparable from biochemistry. We'll then follow the construction and replacement of buffering systems among individual studies as procedures are continually refined.
Basic reagents are used in combination to produce the most potent buffer solutions. Once buffers transitioned into biochemistry, researchers began to establish what chemical mixtures were most productive for equalizing the pH of certain reactions.
Between the 1960s and 80s, a project for determining the best buffers resulted in a list that remains crucial in modern laboratories. "Good's buffers" were produced or collected by Norman Good and his colleagues, and selected on a number of criteria that qualified application to research in the biological field. Some of the requirements were pKa between 6 and 8, high water solubility, stability and a lack of exchange with membranes or biochemical reactions. Good also prioritized substances that could be prepared easily and safely.
One of the lab world's most valuable buffer agents, Tris – was first recognized by Good in the early 1960s. Known in therapeutics as THAM, Tris quickly adopted scientific roles. Tris and other reagents identified by Good continue to act as the equalizing agents within buffer mixtures by adjusting pH to a specified range.
How are Goggles Made
Goggles are a form of eye protection that is designed to shield the wearer from injuries to the eye due to hazardous conditions in the workplace, home, or other venues such as while playing sports. According to the National Institute for Occupational Safety and Health (NIOSH), approximately 2,000 work-related eye injuries requiring medical treatment are reported in the U.S. every day, the majority of which could have been prevented or been less severe had the proper eye protection been worn. Furthermore, the Department of Labor reports that eye injuries result in an estimated $300 million annually in lost production time, medical expenses, and workers' compensation.
This article will describe how goggles are made and will discuss the common types of safety eyewear used as Personal Protection Equipment (PPE). You can learn more about other types of PPE in our related guides and articles, a list of which may be found at the end of this article.
When her Danish colleagues first suggested distributing protective cloth face masks to people in Guinea-Bissau to stem the spread of the coronavirus, Christine Benn wasn't so sure.
"I said, 'Yeah, that might be good, but there's limited data on whether face masks are actually effective,'" says Benn, a global-health researcher at the University of Southern Denmark in Copenhagen, who for decades has co-led public-health campaigns in the West African country, one of the world's poorest.
That was in March. But by July, Benn and her team had worked out how to possibly provide some needed data on masks, and hopefully help people in Guinea-Bissau. They distributed thousands of locally produced cloth face coverings to people as part of a randomized controlled trial that might be the world's largest test of masks' effectiveness against the spread of COVID-19.
Face masks are the ubiquitous symbol of a pandemic that has sickened 35 million people and killed more than 1 million. In hospitals and other health-care facilities, the use of medical-grade masks clearly cuts down transmission of the SARS-CoV-2 virus. But for the variety of masks in use by the public, the data are messy, disparate and often hastily assembled. Add to that a divisive political discourse that included a US president disparaging their use, just days before being diagnosed with COVID-19 himself. "People looking at the evidence are understanding it differently," says Baruch Fischhoff, a psychologist at Carnegie Mellon University in Pittsburgh, Pennsylvania, who specializes in public policy. "It's legitimately confusing."
Endotoxin Removal from Bench to Process Scale
Endotoxin or lipopolysaccharides (LPS) are highly toxic components of the cell wall of Gram-negative bacteria and are often present in significant amounts in bacterial cell expression systems such as E.coli.
A number of methods have been adopted for the removal of endotoxin based on adsorption, in particular ion exchange chromatography. Although downstream processing can significantly reduce endotoxin levels in the product, efficient and cost effective removal of residual endotoxin from biopharmaceutical preparations remains a challenge.
Astrea Bioseparations Ltd. ('Astrea') has developed a novel affinity chromatography adsorbent, EtoxiClear, that is highly stable, robust and non-toxic, with a high affinity for bacterial endotoxin and low protein binding. EtoxiClear is a cost effective and scalable technology designed for use in endotoxin removal applications including process development, sample/buffer preparation and product polishing steps used during cGMP manufacture of biological molecules.
This application note describes the use of EtoxiClear? to effectively remove endotoxin from a purified immunoglobulin protein solution at both bench scale and process scale; utilising Astrea's new 100 mm diameter Evolve? Process Column.
A Basic Tool for the Small Clinical Lab
No matter how elementary or advanced, every clinical laboratory has one essential device—a centrifuge. Whether it stands on the benchtop or floor and is refrigerated or not, a laboratory centrifuge fractionates liquid specimens by creating spin-induced high g-forces, and has long been a standard tool for both clinical and research applications. With broad utility, laboratory centrifuges are true workhorses, usually providing trouble-free service for many thousands of cycles over many years of steady use.
Benchtop centrifuge, also known as tabletop, centrifuges have smaller throughputs and cannot provide high-end g-forces compared with floor models, but can accommodate most applications. Tabletop models include low-speed clinical centrifuges used for diagnostics; high-speed instruments for whole-cell harvesting and some nucleic acid applications; multipurpose centrifuges that accept either fixed-arm or swinging bucket rotors; and cell washers, which are highly specialized for washing red blood cells. For those considering a replacement or initial purchase, here is a brief overview of several of the most popular benchtop models used in the small laboratory. All are manufactured by laboratory equipment companies with long-standing reputations for quality and reliability.
Low-Speed, Fixed-Angle Clinical Centrifuge Options
At the entry point of its centrifuge line, the Drucker Company (Philipsburg, PA) produces the Model 614B as its most affordable basic centrifuge. The device is designed for the small lab or doctor's office and is a single-speed centrifuge (up to 3150 rpm) used for blood separations. The 45o rotor will hold six test tubes of up to 15 mL (17 mm × 125 mm). The unit has a lid safety switch and is UL/CSA compliant. It includes a 30-minute timer, a double-encased, brushless motor, and a clear lid with a safety switch. The motor housing and rotation chamber are designed to allow for cool operation. Standard accessories include three sets of tube holders to fit tubes of varying lengths.
Thermo Fisher Scientific, Inc. (Waltham, MA) characterizes its Medilite centrifuge as ideal for routine low-speed centrifugation of blood and urine samples. Each Medilite centrifuge includes a 6- or 12-place 45o rotor and standard shields for aerosol containment. The device is designed with an integral 30-minute timer and accepts a variety of tube sizes up to 10 or 15 mL, depending on the rotor. This centrifuge also features a maintenance-free brushless motor, incorporates a power interrupter for user safety, and provides fixed speeds of 3100 or 2700 rpm.
- أنشئت: Fri 15-Oct-2021 5-31 AM
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