From API customer service:
Each reagent bottle has a Lot # printed on the bottle. The last four digits are the month and year of manufacture. Example: Lot # 28A0102. This is a pH
reagent manufactured in January of 2002.
Pond Care Wide Range pH, ammonia
, High Range pH, Nitrate, phosphate
, Copper, calcium
all last for three years. nitrite
will last for four years. Freshwater pH(low range) and Pond Care Salt Level will last for five years.
Liquid Nitrate Test Kits from any manufacturer can have a common problem with their last test solution. For us it is bottle number 2. One of the ingredients wants to solidify out of liquid solution. If the test bottle sits for any period of time, this can happen. If this does happen and the test is performed without Bottle # 2 mixed properly, then you can get a falsely low reading. I have never heard of falsely high readings with Nitrate Kits.
I would try tapping your Bottle # 2 a few times on a table or counter top. This should loosen-up anything that has solidified. Then I would shake this bottle for about 2-3 minutes, to really mix it up. Try the test again and hopefully this will fix your problem. With regular weekly usage, this bottle should only need to be shaken for 30-60 seconds.
Always check results at the recommended duration of time. Letting the tubes sit longer can result in falsely high levels."
Hope this helps!
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