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Biochemicals & Reagents

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Buffers, substrates and the general biochemicals a laboratory consumes rather than studies. Purity here is necessary but rarely sufficient: the specifications that decide whether a lot is usable — endotoxin, nuclease activity, the pH at your working temperature — are separate tests that a chemical certificate of analysis does not report.

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In this range

Listed on the TSS storefront and searchable there by name or CAS number. Every enquiry is contracted and invoiced by Taitil Global Inc. in the United States or Europe.

Specifying it

What decides the purchase

The compound is usually fixed by the route. These are the things that vary between suppliers and between lots.

  1. Buffering range, and the pKa you are actually working at

    A buffer controls pH usefully within roughly one unit either side of its pKa and does very little outside that window. Choosing by familiarity rather than by range is how a system ends up nominally buffered and actually drifting. Match the buffer to the pH the assay runs at, not to what the last protocol happened to use.

  2. Tris moves with temperature, and by a lot

    Tris has a temperature coefficient near −0.03 pH units per degree, so a buffer adjusted to pH 8.0 at room temperature is closer to 8.6 in a cold room and below 7.7 at 37 °C. If a buffer is prepared at one temperature and used at another, state the temperature at which the pH must hold — otherwise the certificate and the experiment refer to different conditions.

  3. Endotoxin and nuclease are separate specifications

    A biochemical can be chemically pure and still carry bacterial endotoxin or residual nuclease activity that ruins a cell assay or degrades RNA. These are tested for and certified separately. If the application is biological, the requirement belongs on the enquiry explicitly — assuming a high chemical purity implies either is a common and expensive mistake.

  4. Hygroscopicity changes what you weigh

    Many buffer salts and biochemicals take up water rapidly on opening. A hygroscopic solid weighed from a jar that has been open on a bench is not the mass of compound you intended, and molarity calculated from it is out. Buy in unit sizes matched to consumption, and store desiccated where the material calls for it.

Questions

Does high chemical purity mean a reagent is endotoxin-free?
No. Endotoxin is a bacterial lipopolysaccharide that survives autoclaving and is not detected by the assays behind a chemical purity figure. A 99.9% pure buffer salt can carry enough endotoxin to affect a cell-based assay. If it matters, it has to be specified and certified separately — usually by LAL test, with a limit in endotoxin units per gram or per millilitre.
Why does my buffer read a different pH than when I made it?
Most often temperature. Tris is the notorious case, shifting roughly 0.03 pH units per degree, so a buffer adjusted at the bench reads differently in a cold room or an incubator. Dilution also shifts pH for some systems. Adjust at the temperature of use, and state that temperature when specifying a buffer whose pH must be certified.
What grade should I order for cell culture?
One certified for the specifications cell culture actually depends on — endotoxin, and often sterility and osmolality — rather than simply the highest chemical purity available. Cell culture tested grades exist and carry that testing on the certificate. An ACS-grade salt may be chemically cleaner and still unsuitable, because nothing has established it is endotoxin-free.