Hardness, Total
Hardness, Total
Hardness_MP_ULow_CPZ_Eng_2400.fm Page 3 of 6
Interferences
Interference studies were conducted at various hardness levels between 0 and
500 µg/L as CaCO
3
. Various cations and anions were evaluated at levels in the
range appropriate to ultra pure water applications. An ion is said to interfere
when the resulting concentration is changed by ±10%.
Treating Analysis Labware
Thoroughly clean all containers used in this test to remove any traces of calcium
or magnesium. If possible, use plastic containers for all analysis and storage.
Clean containers by normal means, then rinse with ultra-pure (aldehyde-free)
water. Fill and soak for 10 minutes with a 1:25 dilution of Chlorophosphonazo
Reagent in ultra-pure water. Rinse well with ultra-pure water. Keep containers
tightly closed and dedicate them for ULR Hardness only. If containers are rinsed
and capped after each use, only occasional soaking is necessary.
Sampling and Storage
Do not use glass containers. Collect samples in clean plastic containers,
preferably with screw-type closures. Rinse containers several times with the
water to be analyzed before capturing the final sample. Seal to avoid
contamination during transport. Analyze as soon as possible.
Table 1 Negative Interference
Ion Level above which the ion interferes (µg/L)
Aluminum 150
Sodium 79,000
Table 2 Positive Interference
Ion Level above which the ion interferes (µg/L)
Copper 250
Silicon 1000
Table 3 No Interference
Ion Highest Concentration Tested (µg/L)
Potassium 1000
Ammonium 1000
Formaldehyde 47,000
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