DISCRETE ANALYZER CHEMISTRY Total Hardness Method
Method Description Total Hardness quantifies the concentration of magnesium and calcium ions, and other dissolved minerals in a sample. This method utilizes Mg-EDTA from SEALAnalyticalAQ Hard-Buffer to exchange free calcium ions for magnesium, thereby forming a more stable EDTA chelate. The remaining free magnesium reacts with calmagite in SEALAnalyticalAQ Hard- Calmagite at a pH of 10, producing a wine-red color that is measured photometrically at 520 nm. This method is largely unaffected by most interferences, with the exception of color and turbidity, which can be removed via filtration or corrected for in the analysis. Historically, the Calmagite reagent also contained the buffer, with the EDTA solution being separate. The Calmagite & Buffer reagent also included SDS. To improve the long-term stability of the reagents without compromising method performance, the EDTA reagent was combined with the buffer, while the Calmagite was kept separate in deionized water. Additionally, SDS was removed, as it was suspected to contribute to reagent degradation. Tip: Due to the absence of SDS, it is recommended that technicians run a thorough cleaning solution through the system following Total Hardness analysis to prevent reagent buildup and ensure the continued accuracy and longevity of the instrumentation. Ca 2+ +Mg-EDTA Ca-EDTA+Mg 2+ Mg 2+ +Calmagite Mg-Calmagite Complex (wine-red)
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