trouble testing magnesium

[Dingodan]

im using an elos magnesium test kit and have lately been confused with my inconsistent results. so i just did 3 back to back tests and my readings were 1350, 1200, 1250... anyone else had issues with inconsistency? could my reagents have expired? i purchased them a little over a year ago

 

[dmolavi]

See the 3rd message here:
Elos test kit expiry date? - Reef Central Online Community

The expiration dates are 18 months after the time of production.

(from an Elos employee)

 

[Gregcoyote]

Titration type tests have a fairly large error range, but it shouldn't be that extreme. I would tend to believe any two readings out of the three that are the closest. Probably 1250 which is close enough to not need dosing.