Adv. Chem Investigation on Aspirin.....HELP!

[sara7000]

Hi,
I am doing my chemistry investigation on the effect of aspirin on copper metal and iron metal ions. I initially set up a visking tube with copper nitrate solution to demonstrate the transport of copper ions across the membrane. And the readings I got at 3 minute intervals with the colorimeter were low to high then low again and then fairly constant but only for 15 minutes. After that it again went high, low, constant. I believe this is due to diffusion. But I don't understand why the concentration of copper ions would be constant but then go high again and repeat the trend?

Now, my next step is to use aspirin and see how it affects the transport of copper ions across the membrane. I am expecting the same trend but relatively higher concentrations of copper ions at those particular intervals. However, my technique seems so SIMPLE. I only have three weeks left, 4 hours/week, and still have to do iron metal aswell. Are there any other ways I can measure concentration of metal ions at regular intervals besides using a calibration curve? I am going to do some research on beer-lambert law to tie up absorbance and concentration, but I am not really clear if I can use the equation to find the concentraions, or do I just read them off the calibration curve?

Also, I did a simple test with aspirin and copper nitrate solution, and there was no colour change. This means either the aspirin forms no complex or is forming a complex that is of the same colour. Somehow I have to link in ligands. Is there a way I can prove it is a ligand forming if there is one? Thanks

I really need help, I am so confused and I feel like crying, with all the uni stuff on top of this and a bio investigation

I will acknowledge all the people that help me, so please do not think I will steal your ideas

Sara xxx

Edit: I now understand how to use my calibration curve and beer-lambert law. Only problem left: How do I test whether a complex is formed? And why did my results for copper ion transportation go UP, DOWN, CONSTANT, UP, DOWN, CONSTANT? Thanks again

EDIT AGAIN: INVESTIGATION CANCELLED...........NO FURTHER INFO. REQ.