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# Assay calculation on as is or anhydrous or dried basis

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San3456
India

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 Topic Started by San3456 on 11/23/2009 3:26 AM

Dear dr. Analytical,

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

Thanks,
Sanjay

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Dr. Analytical
United States

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 Posted By Dr. Analytical on 11/24/2009 9:07 AM
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.

gpronger
United States

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 Posted By gpronger on 11/24/2009 9:26 AM

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
India

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 Posted By amolrjedhe on 7/13/2011 7:30 AM

Dear sir ,

Please give Anhydrous and as such calculation for HPLC analysis.

Thanks

Amol Jedhe

Annasaheb
India

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 Posted By Annasaheb on 10/1/2011 5:20 AM

Dear Sir

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

Thanks

Annasaheb

Dr. Analytical
United States

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 Posted By Dr. Analytical on 11/22/2011 8:31 AM

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
India

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 Posted By bujjikanchi on 4/4/2012 21:19 PM

(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
United States

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 Posted By chukwuemeka on 1/17/2013 10:14 AM

chukwuemeka
United States

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 Posted By chukwuemeka on 1/17/2013 10:17 AM

I will you to me a detail responcse of my questions

momo@ss
Singapore

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 Posted By momo@ss on 5/27/2013 16:24 PM

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

Dr. Analytical
United States

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 Posted By Dr. Analytical on 5/28/2013 7:12 AM

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)

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 Posted By Christine Bian on 7/6/2014 6:08 AM

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

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

I want to know the difference between &quot;to be taken&quot; and &quot;taken&quot; in the above formula. Looking forward to your answers!&nbsp;

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 Posted By Christine Bian on 7/6/2014 6:15 AM

&nbsp;I want to know the difference between &quot;to be taken&quot; and &quot;taken&quot; in the following formula.&nbsp;

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

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