I don't know whether the comparator is the same as mine BUT
I got better matches putting very little cotton wool on the top
of plain water tubes...

Perhaps you should try several SMALL cotton wool amounts ?

For now I have problems with my last Sera NO3 kit that sees
far more than the previous one and than my too old LaMotte kit...

Philippe


"Dan Drake" wrote in message
news:vhIsdqY67dTD-pn2-hdN803ZdU5Wx@localhost...
On Thu, 9 Oct 2003 23:34:33 UTC,
(nikolay_kraltchev) wrote:

Hach Nitrate is great and very precise. I wish their Phosphate test
was not $134...

...

Will check out for Lamotte Phosphate now...

The trouble with the Lamotte low-level phosphate test is that the color
comparator has colors that are quite different from those that the test
produces. The instructions insist that you should read the test in
natural sunlight, which helps a little, but the comparison is still
unconscionably bad for something that costs this much.

YMMV. Maybe we have weird sunlight in California. (Insert joke here)

Currently I'm running double tests: I make up a standard at 1 ppm or
whatever I expect the result to be, and run the analysis on it and on the
test sample. I keep a stock at 10 ppm and dilute with really pure water
for use. By carefully extracting solution in measured amounts from the
darker of the two tests, trying to get about the same color density when
looking down the length of the tubes, you can get something that's
probably a lot better than just "Yup, this is less than 1 ppm, all right."

This uses twice as much of the reagents for every test, of course.

Did I say something about unconcsionable?


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