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Qualities / Grades / Purities in Chemistry

In addition to the actual substance (clearly defined by the CAS number, see Newsletter dated 30.10.2018), quality also plays a role in the selection of the chemical. There is no fixed or systematic nomenclature for the different quality names. Ultimately, each manufacturer sets the quality name itself and defines its own quality standards. These standards are shown in the specification or certificate of analysis of the chemical.

What quality is necessary for me?

The choice of quality level depends heavily on the application

Between how many quality levels is a distinction made?

There are 6 different quality levels in chemistry

Which application-related quality designations are there?

A distinction is made here between biochemistry, molecular biology and cell biology

Qualities should never be interpreted as an application limitation

If a chemical carries the suffix "for cell biology", it merely means that the specification parameters (e.g., endotoxin-free, sterility) are particularly tuned to these applications. The quality is therefore particularly well suited "for cell biology", not exclusively. It is generally a high-purity product, which can also be used in other applications without problems (example HEPES, dimethyl sulfoxide, amino acids, salts).

Parameters that are not specified in the specification may also be met

Parameters specified in the specification are tested and maintained batch-specifically. However, this does not necessarily mean that other parameters desired by the customer do not apply. Example: A chemical may well be germ-free and endotoxin-free, although this is not explicitly indicated in the AZ. Or be RNAse-free. Or have the desired pH. Or the low water content. This is best to consult with neoFroxx

How do I find the right quality?

Optimalerweise ist einer dieser Punkte erfüllt:

  • The application can be found in the quality designation again
  • The important specification parameters are fulfilled
  • I use the request form of the manufacturer -> Go to the online form

What distinguishes the most important qualities?

For laboratory chemicals (Labochem) you will find (as with many other suppliers) 6 different quality groups. The chemical purity increases with each quality level - just like the parameters stated in the Certificate of Analysis and of course the price!

quality designationmeans
technical / technical grade Chemicals with various impurities; mostly produced on an industrial scale. Use for technical purposes (cleaning agents, solvents)
for the synthesis / synthesis grade Chemicals with minor impurities. Since the product is purified anyway after the synthesis, the starting materials need not be highly pure.
pure Substances of high purity with a content of at least 95%
pharmaceutical quality; purest EP / USP / BP / ... Substances of very high purity with a content of mostly 98%. Chemicals that have been tested according to the specified pharmacopoeia are in fact identical for all suppliers!
for analysis / p.A./ pro analysis High purity chemicals with a content of at least 99%. Contained impurities (e.g., metals) are specified in analytical conditions; i.e. The permissible concentration range is precisely defined
ultrapure / for HPLC / for crystallography / for LC-MS Extremely pure chemicals with a content of typically 99.9% and the specified suitability for certain analytical methods.

In the field of life sciences (BioFroxx) numerous quality labels are added. These are generally very high purity grades (at least 99%) where, depending on the application recommendation, the specified specification parameters will vary, e.g.

quality designationtyp. specification parameters
for biochemistry / biochemical Heavy metals; Absorption values (for photometric measurements)
for molecular biology DNase, RNase and protease
for cell biology / cell culture / tissue culture endotoxins

Further information about the purities of substances

Additional information on Wikipedia.com Weblink >>