Originally Posted by m.lemay
Well Kevin, I think the first order of business would be to determine the validity of hobby test kits versus the high tech testing methods you have access to. What kinda of costs are we talking about here? Do you have any specific knowledge of chelates vs free iron. Do they measure up equally? For instance, My experience with chelated iron has been 2-3 hours of waiting time for results rather than 45 minutes reccomended on the Seachem kit.
Please forgive my limited chemistry knowledge.
I believe the kits are good for what they are - extremely cheap ways to find an approximate answer. In the case of the atomic absorption (AA) instrument, the instrument alone costs $15000. Add in standard solutions and appropriate element-specific lamps, and on a per-test basis it will never compare in terms of cost. However, it is possible to measure in the parts per Billion range for many elements!
Before you posted I had been playing around with a pricing schedule to offer - something like $25 for the first element test with one water sample. $5 per additional sample and $10 per additional element. So a test for potassium and iron on both a tank and a tapwater sample would cost $45. If you are more interested in a long-term study of some sort, I can be very flexible. If there is a possibility of publication in a peer-reviewed journal, I might do it for free.
In terms of chelated iron vs. free iron, it makes sense that the test kit would take a lot longer - when the iron is chelated, it is in a way protected from reactions with other things. In the AA, the sample is aspirated into a flame, so the iron is quickly separated from the chelate and the test result would be the same as for free iron.
A related question I have: Calcium, magnesium, AND iron can be chelated. If you add chelated iron to your tank, can the calcium displace the iron (since there is a lot more calcium in the water), resulting in free iron and chelated calcium (and leaving the iron free to be oxidized)? If this is the case, then there is no point in using chelated iron - it would be a waste of money. I can partly answer this question by looking up the stability constants for iron and calcium chelates, but the concentration difference adds another dimension.
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