New test kit, can't find expiration date

[BPags52]

I just got my API master freshwater test kit in the mail yesterday. My Ammonia and nitrite levels showed as 0. pH showed 8.0 (my tap water is naturally high ph/hard).

What i'm confused about is the nitrate test though. On my first test it showed 40ppm (which baffled me because I've been doing multiple water changes a week lately). So I tested again right after that 40ppm reading, and got a 20ppm reading, which seemed more accurate to me, and I left it at that. I just got home from work today and tested the nitrate again, and now it shows as 10ppm.

Haven't done a water change inbetween readings so I'm not sure why nitrate levels seem to be going down. I've seen people here saying to check the expiration date on your API kits, but I can't find one. Where is the expiration date shown? I ordered the kit from walmart (someone gave me a gift certificate...). It came in a clear plastic case with the testing equipment inside (as opposed to a box with an expiration date clearly printed on the exterior).

edit: I'm wondering if wal-mart re-packaged an expired test kit.

Taking a closer look at each bottle, the High Range pH bottle says "copyright 2006" on it, the nitrite bottle says copyright 2008, and the pH test copyright 2007. Is this normal?

I do now see printed numbers near the top of the bottles. Example: LOT 84A0209, or LOT 26A0209. Does this mean it expired 02/09?

I don't have any de-nitrate media or anything like that. Its a 125g freshwater tank with 2 emperor 400s for filtration. I have some biomax media in one of the 4 secondary slots (ordering more biomedia this week to fill 2 more slots, saving 4th slot for carbon if/when needed).

 

[BPags52]

Found my answer on a different forum after a google search. Posting it in case it might help someone else.

Quoted from an email response from API to some other guy with a similar problem/question:

"Thank you very much for contacting us regarding our products. All of
your comments and questions are valuable. We use your feedback to
create the most effective line of aquarium and pond products available.

Your solutions are not expired. 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 and GH all last for three years.
nitrite and KH will last for four years. Freshwater pH(low range) and
Pond Care Salt Level will last for five years. I would not trust these
kits after they have expired.

Liquid Nitrate Test Kits from any manufacturer can have a common problem
with their last test solution. For some companies, it is bottle number
3, but 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."