I have had very good results with the Hanna Checkers. I use the Alk, Phosphorous and Calcium. On occasion I have used the Nitrite checker. I found the key is good lab practices and I can get repeatable and accurate results when compared to outside testing services
Just a note on the Hanna Calcium Checker. I have had very good success with this checker and have been using it for over 2 years. I made three changes that brought my Gage repeatability and reproducibility to less than 10% of the target range (100...350-450)
1) Purchased .3mL syringe...very accurate...You can find these from multiple suppliers
2) Use Hanna Deionized water (HI70436) and not my RODI water which has a small amount of calcium in it and is variable from batch to batch.
With the dilution ratio being so high and the water sample amount being so small these two changes took my R&R (repeatability and reproducibility) from between 30-40% (not good! almost random results) to less than 10% a very acceptable range for this test. My results have been validated by external testing sources so I feel confident in the measurement.
3) After the test is complete I rinse the vial and cap with the Hanna deionized water then fill the vial to the top with this water and store it this way until next use. Then on the next use I empty the vial do a quick rinse with the deionized water and proceed with the test.
IMO with good laboratory practices these checkers are great tools and do not rely on color change interpretation to make the measurement which in itself is a variable
Just a note on the Hanna Calcium Checker. I have had very good success with this checker and have been using it for over 2 years. I made three changes that brought my Gage repeatability and reproducibility to less than 10% of the target range (100...350-450)
1) Purchased .3mL syringe...very accurate...You can find these from multiple suppliers
2) Use Hanna Deionized water (HI70436) and not my RODI water which has a small amount of calcium in it and is variable from batch to batch.
With the dilution ratio being so high and the water sample amount being so small these two changes took my R&R (repeatability and reproducibility) from between 30-40% (not good! almost random results) to less than 10% a very acceptable range for this test. My results have been validated by external testing sources so I feel confident in the measurement.
3) After the test is complete I rinse the vial and cap with the Hanna deionized water then fill the vial to the top with this water and store it this way until next use. Then on the next use I empty the vial do a quick rinse with the deionized water and proceed with the test.
IMO with good laboratory practices these checkers are great tools and do not rely on color change interpretation to make the measurement which in itself is a variable