Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Spleens on November 12, 2021, 06:10:30 PM
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When calculating the % of an analyte in a product, say Benzoyl Peroxide in a lotion, the raw material was found to be 79% pure, and the standard used to analyze was 75% pure. Do you take into account both purities when determining the actual % BZP? Just the purity of the standard? Just the purity of the raw material? Don't include purity in the calculation?
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Standard was 75 % pure, so its surface should cover 75 % of all peaks surface. Raw material was found to be 79 % pure, because its peak covers 79 % of all peaks surface ?
Of course - if the raw material is that what you have put in the chromatograph....
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To be correct - standard was 75 % pure, because its peak surface was 75 % in comparison to pure (100 %) benzoyl peroxide.
And raw material was found to be 79 % pure because its peak covers 79 / 75 = 105 % of standard's peak surface.
I mean - sum of the all peaks does not need to represent 100 % of the what is it in the sample (may be 50, 70 or 90 %), because we don't know what kind of detector you were using.