DISCRETE ANALYZER CHEMISTRY Silica (SiO 2 ) Method
Reagent Composition Two Reagents are used for the SiO 2 method: Reagent 1: SEALAnalyticalAQ SiO2-Molybdate — Ammonium Molybdate Reagent in DI Water: 100 g/L Ammonium molybdate (VI) tetrahydrate Trace Ammonium hydroxide for pH adjustment Reagent 2: SEALAnalyticalAQ SiO2-OxalicAcd – Oxalic Acid Reagent in DI Water: 100 g/L Oxalic acid dihydrate Reagent 3: 10% v/v HCl Methods Referenced • SEAL Analytical AQ400 Method EPA-121-C Rev. 2A • EPA Method 370.1 — (Colorimetric) • Standard Methods 4500-SiO2 C — “Molybdosilicate Method” This method covers the determination of Silica in drinking, surface, and saline waters, and domestic and industrial wastes. Method Range: 0.25 – 25 mg Silica (SiO2)/L We recommend CGSIO1 or CGSIONA1 to make your standard for this method! Both solutions are made from a Silica starting material. The only difference is the matrix. CGSIO1 has a matrix of 1% v/v Nitric Acid /tr Hydrofluoric Acid, while CGSIONA1 has a matrix of 0.2% wt/v Sodium Hydroxide. Diluting either of these standards in DI H2O to achieve your working concentrations for this method will result in either of the matrix options being less than 0.03% of your final solution.
Note: Inorganic Ventures and Seal Analytical don’t offer a 10% HCl reagent for the 25 ppm Silica method because it’s much more cost-effective for you to prepare it in-house. Making this reagent is simple (combine acid and water in the appropriate amounts), and there will be little room for error when following the standard procedure. Plus, it doesn’t have any stability concerns, so you can be confident in its performance. By mixing it yourself, you save on costs, make volumes that make sense for your lab, and still get accurate and reliable results, when used in combination with the pre-made reagents above. Maintenance Tip: After Silica analyses are complete for the day it is recommended to run an alkaline EDTA solution through the instrumentation to remove any reagent deposits and prevent contamination of subsequent samples. Prepare this solution by dissolving 5g of disodium EDTA dihydrate and 10g of Sodium Hydroxide pellets in 500 mL DI H2O.
For more information, contact EMAIL: inform@seal-us.com PHONE: (262) 241-7900 WEBSITE: seal-analytical.com
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