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Phone: 631-242-4249 | Toll-Free: 888-686-3454
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With 6.2 %, iron is the 4th most abundant element in the earth’s crust and, after aluminum, the second most abundant metal. In water, it is present in various forms. Groundwaters with low oxygen levels and reducing medium often have iron contents of above 0.1 mg/L. The divalent iron(II) Fe2+ is particularly sensitive to air. It is oxidized by atmospheric oxygen to form trivalent iron(III) Fe3+, which precipitates as a brown, fuzzy-amorphous iron oxide hydrate due to its low solubility. Furthermore, the presence of iron is also pH-dependent. At pH values above 8, iron(II) ions Fe2+ are converted to poorly soluble iron(II) hydroxides.
Dissolved iron can limit the use of the water for consumers because precipitation can occur upon use of the water, for example in laundering. Iron in drinking water is undesirable because it leads to brown color and foul odor.
At the usually present concentrations, iron (and manganese) poses no direct health risk to humans. However, in drinking water these compounds are undesirable because they can form deposits in the pipe network that increase the flow resistance to a considerable extent. Consequences of this are firstly unwanted discolorations, on the other hand so-called secondary microbial contaminations due to corresponding iron and manganese bacteria.
The main application of iron is in the steel and metal industry. Due to its easy availability, strength and toughness, iron is one of the most important base materials. Iron is also used, amongst other things, as a flocculating agent. Determination of dissolved iron is an important indicator of the extent of corrosion.
All test kits are based on one of two different reaction principles:
(a) Triazine method:
Iron(II) ions react with a triazine derivative to form an intensely colored purple complex.
Triazine derivatives are highly miscible with thioglycolic acid. Thioglycolic acid is used for the
reduction of iron(III) to iron(II), and for pH adjustment. Thus only one reagent is required for analysis.
Test kits VISOCOLOR ECO Iron 1, VISOCOLOR ECO Iron 2, VISOCOLOR HE Iron, NANOCOLOR Iron 3, and NANOCOLOR Iron LR are based on this method.
R = H, SO3H
(b) DIN method analogous to APHA 3500-Fe D, DIN 38406-E1-1, ISO 633:
Iron(II) ions form an orange-colored complex compound with 1,10-phenanthroline. Iron(III) is reduced by a
suitable reducing agent to iron(II) and is also detected. A buffer adjusts the pH. This orange-red
phenanthroline complex is stable in the pH range of 2.5–9.
The described method detects dissolved iron and easily soluble iron compounds.
Following test kits are based on this method: VISOCOLOR Powder Pillows Iron, NANOCOLOR Iron, NANOCOLOR ECO Iron.
Dissolved iron comprises only the iron compounds present in the sample in completely dissolved form. Prior to analysis, filtration of the sample with the membrane filtration kit 0.45 µm is recommended.
For determination of total iron, decomposition with the reagent NANOCOLOR NanOx Metal or with the decomposition kit is required.
It is possible to distinguish between the two different oxidation states of iron in two tests: VISOCOLOR ECO Iron 2 and the standard test NANOCOLOR Iron.
