Microwave sulfated ashing procedure for pharmaceuticals

The USP chapter <281> describes the methodology for measurement of inorganic contaminants in pharmaceutical samples, where the adopted technique is the Sulfated Ashing. Milestone's PYRO is an advanced sulfated ashing system, that allows to run this particular application in one step only, thus assuring operators’ safety and reproducibility of results.

The reason for doing sulphated ash is to prevent volatilization of some important elements to be determined. When phosphorus is absent, barium, calcium, magnesium, sodium and potassium are converted to their sulphates. Tin and zinc are converted to their oxides.

Determination of such elements is important since some minerals are essential to a healthy diet (e.g., calcium, phosphorous, potassium and sodium), whereas others can be toxic (e.g., lead, mercury, cadmium and aluminum).

The conventional method requires to evaporate the H₂SO₄ 98% acid using a hotplate or flame under a fume-hood. This operation is very dangerous for the operator since he has to manage very hot crucibles and he could be exposed to the highly toxics sulphuric acid fumes. These fumes are also very corrosive and can easily damage all instruments and tools placed under the fume hood and the hood itself. In addition by the nature of this procedure it leads to poor reproducibility.

The following application report has the intent to show the performances of PYRO microwave sulfate ashing system on two different pharmaceutical samples.

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