This is the way.....praphrased......that Steve Hampton explains it on another site:
For those who want to know and like to monitor nitrate levels accurately and with some precision you can't beat the LaMotte NO3-N test kit. The big advantage is not having to depend on the color cards. Instead the test vial is compared to colored fluid samples
Also this test is a NO3-N test kit. Meaning the result is Nitrate as Nitrogen, so the actually test result must be multiplied by 4.4 times. So if your tank water tests matched the fluid in 1.0 sample of NO3-N then you would multiply 1.0x4.4 for a nitrate reading of 4.4 ppm. Note that NO3-N of 1.0 ppm is equal to NO3 of 4.4 ppm.
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I have not used a LaMotte kit, but would be very interested to hear how this kit works out for you, as I'm seriously considering one in the near future.
I hope this helps.
Len
I was just pointing out what you forgot to mention. I've never used that kit, so I can't help. I know there are a few people who have used it and will probably come to your aid soon.