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Re: Re: Test Kits

There are several key points to consider in purchasing and 
using any test kits (including pH, nitrate, nitrite, ammonia,
iron, phosphate, hardness, etc):

1) Does the kit test what you want?  For example: not all
iron test kits can measure chelated iron even if the kit
is labelled "total iron."  Total iron may only mean ferrous and
ferric dissolved and suspended iron, but not chelated.  To test
chelated iron requires chemical digestion of the chelating agent
such as EDTA.  To ensure that your test kit is going to measure
what you want do not hesitate to contact the technical support
staff at LaMotte, Hach, SeaChem etc, they are all very helpful.

2) Are the chemicals in the kit still functional?  Most 
chemical test kits have a life-time of no more than 1 year, 
although admitedly I have used the same chemical pH test 
for several years but the results may not be reliable.  The 
age of the test kit does not necessarily start when you 
purchase it.  I bought a phosphate test kit and it didn't
measure correcly and the standard did not measure at all.  
The test kit company was very helpful and they said the
serial number on the box indicated it was an "old" kit.  
Therefore, the kit had been siting at the distributer 
for sometime.  The test kit company offered to replace the
entire kit!  Regarding pH chemical kits bromothymol
blue can change and give bad readings.  My experience has found
that pH tends to read high by as much as 0.5 pH units when the
bromothymol blue has degraded.

I still use many chemical tests as a quick source of info, 
but use a pH meter and a spectrophotomter for detailed
analysis.  Comparisons of test kits with that equipment has
generally shown  test kits to work well if the kits are
testing the same set of paramaters and the chemicals aren't 
too old.

The bottom line is replace test kits annually, and check with
the manufacturer to be sure that it will test all the 
parameters you want.

Niall McCarten