For my research on the detection of Cr (VI), I must dilute my solution 3 times using 2 fold serial dilution to be able to analyze it with a UV spectrophotometer. So, I can calculate the 3 times diluted solution concentration by the standard curve which I had plotted before. My question is, how can I calculate the concentration of the undiluted solution?
If you use the same dilutions (preferably not serial) for the standards and the samples then no calculation is required
Build a calibration curve with standards where the absorbance of your diluted sample falls within, ideally in the center. ideally prepares the solutions in a blank sample, that is, a matrix-fortified curve. Plot absorbance vs. concentration and calculate the slope and intercept of the line. The sample concentration is calculated as: c = dilution factor*(abs sample - intercept)/slope. If you do not have the standard, you can find out the extinction coefficient and calculate it with the beer-lambert equation. Check any analytical chemistry textbook
As you have already find out the concentration of diluted samples, you need to multiply the results by dilution factor. For example, if you have diluted it with adition of 100ml solvent, now multiply the results of diluted sample by 100, you will get the concentration of the original undiluted sample.
The reference basis of your relationship is non-linear, so it becomes complex to analyze the absorbance versus concentration in multi solute mixtures. A pre-linearizing initial step is required using the Beer Lambert law. This quantifies a linear relationship between the absorbance and the concentration, molar absorption and the optical path length of the sample as follows.
A = ecl
Where: A is Absorbance
e is Molar absorption coefficient
c Molar concentration
l Optical path length.
Hi Saesha,
You may use the web tool to calculate
https://www.alfa-chemistry.com/solution-dilution-calculator.htm
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