Colorimeter Idea

[nkd5024]

So I was looking into the Hanna Colorimeters for Phosphate and Alkalinity today and I thought of an idea that I wanted to see what everyone thought.

I was thinking I could buy a colorimeter with all the regents used for the common testing of water parameters (pH, alk, ca, mg, nitrate, phosphate, etc) and also buy a few solutions with a known concentration of each parameter.
I could then add each regent to the known concentration samples of each chemical I'm testing for and run it in the colorimeter and make a graph of the absorbance vs. concentration of each water parameter.

I could then use the graphs to test my tanks water by comparing the absorbance of each sample to the graph I made for each parameter.

I have done this in chemistry class before to test for the concentration of salicylic acid and it wasn't that difficult to make the graph.

Does anyone see any issues that I am missing here?
Do you think this is a good idea,
Nick D.

 

[StandbySetting]

That's a good idea, the only problem I can see though is that the colourimeter requires calibration after every sample, and for the best readings you'd need to calibrate with RO water with a TDS of as close to 0 as possible, you'd also have to do multiple examinations of each liquid in order to find a mean value, I'd be inclined to make the solutions up myself, you can easily calculate how many moles of substance are in a liquid, this can then be used to give you a rough idea of PPM, it is rough as usually PPM is for like over like substances such as volume over volume.

As far as a graph goes it'd be pretty simple to do, just plot the value the colourimeter gives you against each value or mol/dm-[sup]3[/sup] (It'd be so much easier for everyone if test kits gave values in mol/dm-[sup]3[/sup]!)

One problem that I can see is that you're going to have to test multiple concentrations of each solution, as many as possible to give you the best results, most reliable and valid results.

 

[StandbySetting]

I'd also like to point out that there are going to be variations in every test kit, so you'd need to produce a new graph every time you buy a new test kit.