Assay calculation on as is or anhydrous or dried basis

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San3456
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Assay calculation on as is or anhydrous or dried basis

Dear dr. Analytical,

Please give hypothytical example  where assay is calculated on as is , anhydrous or dried basis.

Thanks,
Sanjay

Dr. Analytical
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First, calculate the moisture

First, calculate the moisture content of your sample by measuring the mass while "wet" and after drying.

The equation for determination of moisture content  is:
%Moisture = 100 (mwet - mdry)/mwet

The concentration in the sample on a dried basis is then adjusted using the following equation:
Cdry = Cwet (100)/(100 - %Moisture)
 
Note that the concentration will always increase on a dry basis.

 

Greg Pronger
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Sanjay,

Sanjay,

the reason this is often done (reporting on a dry weight), particularly for environmental soil samples is due to the changing level of hydration due to rain and seasonal changes. Once converted to a dry weight basis, overall comparability of data is improved.

amolrjedhe
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Dear sir ,

Dear sir ,

Please give Anhydrous and as such calculation for HPLC analysis.
Thanks
Amol Jedhe

Annasaheb
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Dear Sir

Dear Sir

 Please suggest me , How to apply water content of standard in assay calculation,
Thanks
Annasaheb

Dr. Analytical
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If you know the water content

If you know the water content of your standard, then you must make adjustments in your calculations.  This is the same type of correction that you use for adjusting for the purity of the standard.

If your %water is %W, then when you measure a sample (M), you must adjust for the water using the following equation:

Actual M = [(100 - %W)/100] * M

bujjikanchi
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(Area of principle peak in

(Area of principle peak in assay prep’nX wt.of W.Std. taken in Std prep’n X Wt of the test sample to be taken in assay prep’nX (100-water content of ws) X assay of ws)/

(area of principle peak in Std prep’n X weight of W.Std. to be taken in Std prep’n X wt of the test sample taken in assay prep’nX (100 – water content of test sample)

bUJJI KANCHI
9676749937

chukwuemeka
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chukwuemeka
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 I will you to me a detail

 I will you to me a detail responcse of my questions

momo@ss
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from the formula Cdry = Cwet

from the formula Cdry = Cwet (100)/(100-%moisture), where the 1st 100 came from?

Dr. Analytical
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The 100 values are used

The 100 values are used because the Moisture value is a percentage.  if the moisture value were a fraction (5% = 0.05), then the equation would be:

Cdry = Cwet (1)/(1 - Moisture)

Christine Bian
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 Hi, this is Christine Bian

 Hi, this is Christine Bian from China. I have a question about the following formula.

(Area of principle peak in assay prep’nX wt.of W.Std. taken in Std prep’n X Wt of the test sample to be taken in assay prep’nX (100-water content of ws) X assay of ws)/ (area of principle peak in Std prep’n X weight of W.Std. to be taken in Std prep’n X wt of the test sample taken in assayprep’nX (100 – water content of testsample

I want to know the difference between "to be taken" and "taken" in the above formula. Looking forward to your answers! 

Christine Bian
Christine Bian's picture
 I want to know the

 I want to know the difference between "to be taken" and "taken" in the following formula. 
Looking forward to your answers!
(Area of principle peak in assay prep’nX wt.of W.Std. taken in Std prep’n X Wt of the test sample to be taken in assay prep’nX (100-water content of ws) X assay of ws)/ (area of principle peak in Std prep’n X weight of W.Std. to be taken in Std prep’n X wt of the test sample taken in assayprep’nX (100 – water content of test sample)

Parth Raval
Parth Raval's picture
for weight to be take for analysis of hydrates drugs

 for weight to be take for analysis of hydrates drugs,  total molecular weight is with water or without water.which molecular weight to be taken in claculation wwhen we r using Purity as is basis for hydrates compound ?

Parth Raval
Parth Raval's picture
calculation for weight to be take for hydrates compound

Preparation of Azithromycin Dihydrate  1 mg/ml solutionHow much Weight to be taken for  1mg /ml solution preparation (e.g in 10 ml )  FormulaWeight taken          =      10*       total molecular Wt       *100                                                 Free Molecular WT * purityAs Per COA informationMolecular WT = 785.02Assay (On anhydrous basis)   = 98.71 %Water content = 4.64 %To convert purity ......Calculation for AS is basis  purity = (100-4.64)/100*98.71   =94.13............So...we taken weight ...... Weight taken          =      10*       785.02       *100                   =       10.57mg                                                                                               748.99   *        94.13Is it OK ???

Gaganjot Singh
Gaganjot Singh's picture
easier way

hiThe simplest way is that you dnt have to account for hydration molecule if you are preparing an aqueous solution. that volume will be compensated by volume of wahter that has to be added.