ICP or Test Kit Issue? (1 Viewer)

[RobertP]

Got the results back from an ICP-Analysis and was not happy with a couple readings. ICP says the calcium is 371 but before it was sent out I tested it with a Hanna checker which said 433 and a Red Sea kit that said 500. Also the Magnesium on my Red Sea kit has read over 1600 for a couple months but ICP says it is 1345.8! All my test kits are within dates and I realize it is a hobby grade test kit but I should at least be closer than this! I would think I should trust ICP more but how in the world would I dose for something I cannot test accurately.

Is it possible that the water values changed while in transit? Seems hard to believe that is the case though. I mailed is within a couple days and it want inside until it got to the shipper.
Not sure what to think at this point.

Arsenic, Strontium, and Iodine were all low. I have planned to dose Iodine but sounds like a water change is in order first.

 

[webster1234]

I would have initially pointed to your ICP test if you didn't have two kits that were that different, but 3 tests with a 15% difference is a lot. I would rerun your hanna and red sea tests again.

I have always been a little suspicious of the ICP tests since they are normally expensive and time consuming to run. I ran them in chemistry in college and between each test, the instrument was supposed to be purged with nitrogen which took almost 2 hrs to purge, plus the expense of the gas.

I'm sure they have improved on the process in recent years but I have to wonder if while running samples back to back, given time constraints and trying to keep costs low, that some of another hobbyists sample doesn't contaminate my sample if the instrument wasn't purged sufficiently.

I have spoken ICP-analysis and they assure me that the instrument is sufficiently purged between samples but who knows. We have to go with something right? Hobby kits don't accurately test for some things that shows up on the ICP. Personally, I try to get an ICP test every quarter or so and watch for a general trend vs a hard and fast accurate reading. And I also understand that my readings could be off some so I watch for differences between current and past tests.

 

[blfuller123]

My Hanna Calcium is usually pretty close to ICP results. I gave up on Red Sea for Magnesium, as it always reads extremely high.

 

[RobertP]

I am starting to see why Triton ICP tests are double the price. The last couple times I used them there was never a discrepancy between them and my home grade test kits.