Can someone please help me with this question about atomic absorption spectroscopy

[shenzys]

The BP sets a limit of 3ppm for the cadmium content of calcium stearate. Use the data below to calcualte if the sample compies with this BP rwequirement.
0.3162g of sample was heated with nitric and hydrochloric acid and then made up to 25 ml with water. 5 ml aliquots of this solution plus various volumes of a 0.1 microgram per mil Cd(iii) solution were made up to 10 ml and then aspirated into an atomic absorption spectrophotometer set up for Cd. The following results were obtained:

Vol of Cd Soln: 0.0 1.0 2.0 3.0
Absorbance: 23 35 45 57

Any help would be appreciated. Thank you.

[Fleegle]

Please post your proposed answer, including all working, so I can have a look at it.

Fleeg.

[johnep]

Well said fleeg, let them approach us properly for help after they have at least tried. Not do their homework for them.
johnep

[shenzys]

Please post your proposed answer, including all working, so I can have a look at it.

Fleeg.

The BP sets a limit of 3ppm for the cadmium content of calcium stearate. Use the data below to calcualte if the sample compies with this BP rwequirement.
0.3162g of sample was heated with nitric and hydrochloric acid and then made up to 25 ml with water. 5 ml aliquots of this solution plus various volumes of a 0.1 microgram per mil Cd(iii) solution were made up to 10 ml and then aspirated into an atomic absorption spectrophotometer set up for Cd. The following results were obtained:

Vol of Cd Soln: 0.0 1.0 2.0 3.0
Absorbance: 23 35 45 57

Any help would be appreciated. Thank you.

I actually can't get very far at all, since I am very confused but here is what I have done so far, which is basically nothing:
0.3216----------->25ml (Soln A)
-------------------5ml-------------->10ml (Soln B)

So, this is where I get confused, what do I do next? I did a similar question to this and could do it but that question gave me a graph telling me the volume required to give 0 absorbance. This question does not tell me that... I know you shouldn't give me the answer but I just need a bit of guidance as to what to do next or textbooks that can help me since I have raided my library and found nothing that can help me with working these things out.
Thank you.

[johnep]

Well it is over 50 years since I did any of this, but it has been my experience that simple arithmetic and proportion will solve most problems.

Vol of cd soln added 0.0, 1.0, 2.0, and 3.0

absorbances were 23, 35, 45, and 57

Thus adding 1ml increased absorbancy by 10, 2ml by 25, and 3ml by 34

Almost a linear response in my view and thus you need to draw a graph and extrapolate line to 0.

That's about enough for my poor old brain. Calculate ppm of the various amounts of Cd in above vols.

johnep

[Nik]

Presumably I think this is how you should approach it:

First, taking into account dilution factors, work out original conc.
Then, using the vol of Cd soln given, you can work out conc values to plot against absorption. You prob will end up with a straight line or thereabouts. You should also have been given an atomic absorption reading for cadmium, which you then use - look at the calibration graph and read off for the appropriate conc. Convert conc in mg/ml or whatever to ppm.
This prob might not be the exact answer but it would be how i would approach it anyway.

[Nik]

Check out Pharmaceutical Analysis by D G Watson.

[shenzys]

Thank you both so much!

[Fleegle]

Good posting there Nik...keeping it to guidance only.

Fleeg.

[Nik]

It is becoming more tedious to do calculations for other people, whether i know it or not. It's a waste of my time and I'm sure other students don't learn - except how to transfer my post onto a piece of paper. I will help guide other students on answering a question but I am not an answerbank.