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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.

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.

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