DISCRETE ANALYZER CHEMISTRY Total Hardness Method
Methods Referenced • SEAL Analytical AQ400 Method EPA-106-C Rev 1 • EPA Method 130.1 — (Colorimetric, Automated EDTA) • Standard Methods 2340 C — “EDTA Titrimetric Method” This method covers the determination of Total Hardness in drinking, surface, and saline waters.
Method Range 25 – 400 mg CaCO3/mL
Reagent Composition Two Reagents are used for the Total Hardness method: Reagent 1: SEALAnalyticalAQ Hard-Buffer — Mg-EDTA Buffer in DI water: 5 g/L EDTA disodium magnesium salt hydrate 67.6 g/L Ammonium chloride 572 mL/L Ammonium hydroxide Reagent 2: SEALAnalyticalAQ Hard-Calmagite — Calmagite Reagent in DI Water: 0.5 g/L Calmagite We recommend ICCA1 to make your standard for this method. This solution is made from CaCO3 starting material and is compatible with this method. A simple conversion from Ca to CaCO3 is all that is needed — divide the standard concentration by the weight fraction of Ca/CaCO3 (0.4004) — then you can dilute this standard to your required working concentrations. Note: When using the SEAL Method, manual construction of the calibration curve is required, as the small sample volume is insufficient for the instrument to generate this curve automatically.
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