d) You set up the following dilutions of a 1 mg per ml solution of \'compound A\

Question

d) You set up the following dilutions of a 1 mg per ml solution of 'compound A", reading the absorbance at 560 nm. Calculate the percentage of dilution of compound A for each dilution and fill in the table below. 1 mg/ml Compound A 10ml 8ml 6ml 4 mL 2 mL 1 mL 0 ml Dilution % 100% Absorbance 560 nm 1.050 1.000 0.750 0.500 0.250 Buffer solution 0 mL 2ml 4ml 6ml 8mL 9 mL 10 mL 20-7 0.125 0.010 b. Graph concentration vs absorbance of the above dilutions. Be sure to label all axes A colleague comes to you with a sample of "compound A" he says has a 560 absorbance of 0.925 and he wants you to tell him the concentration. What do you tell him?? C.

Explanation / Answer

First you will have to make a stock solution of compound A and then make the different concentration of compound A by serial dilution of stock solution and take the absorbance of all concentration. Now draw a standard curve from the data obtained (as given in the table). In this standard curve, the X axis will be concentration and Y axis will be absorbance. From this standard curve you will get an equation Y = mX + C. Here Y = absorbance of the sample and X = concentration of the sample. m and c are constant.

Now by putting the value of absorbance of unknown sample you can calculate the concentration of unknown sample.

Here from the data given in table the obtained equation is: Y = 1.11X + 0.034

Therefore 0.925 = 1.11X + 0.034

or 1.11X = 0.925 - 0.034 = 0.981

or X = 0.981/ 1.11 = 0.88

It means the concentration of unknown sample = 0.88 mg/ ml

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