Let's say I am testing for fluoride in a water sample. I diluted the sample 10 times by making 10ml of sample into 100ml. I take absorbance of this diluted sample using UV-Vis. So, my doubt is, Should I multiply the absorbance value by 10 first and calculate the concentration or calculate the concentration first and then multiply it by 10? Where should I incorporate this dilution factor?
Thanks in advance!
You may use the equation:
In a serial dilution the total dilution factor at any point is the product of the individual dilution factors in each step leading up to it. Final dilution factor (DF) = DF1 * DF2 * DF3 etc.
First calculate the concentration then multiply by the dilution factor.
First, the calculation is made on the diluted sample. It is then multiplied by the dilution coefficient.
Thank you, Duried Alwazeer and Yasin Yakar for the response. But my doubt remains the same. Why have we calculated the concentration first? Why not multiply the DF with the absorbance directly and then calculate the concentration?
Hi Auchitya Verma , when you calculate the concentration of any substrate in the initial sample, you need first to know its concentration in the diluted sample (instrument value).
According to the formula C1*V1=C2*V2, the dilution factor equals DF=C1/C2=V2/V1
where C1 is the starting concentration (of the initial sample), V1 is the starting volume (of the initial sample), C2 is the final concentration (instrument value), and V2 is the final volume.
For calculating C1 according to the above-cited formula, we can write:
C1=C2*V2/V1
or
C1=C2*DF
So, you can see that to calculate C1 we need first to know the instrument value C2 then multiply it by DF value.
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