Determination of iron in water
Iron in water comes in several forms:
- dissolved iron - divalent cations Fe2 +;
- not dissolved iron - trivalent cations Fe3 +; gives water brown-yellow color, precipitates;
- organic compounds with iron;
- iron oxides - iron oxide-oxide, rust, ferrites (Fe2O3).
Ferrous iron is water soluble and usually found in groundwater. On contact with air, ferrous iron is rapidly oxidized to ferric iron. To control the quality of water, it is of interest to determine ferrous and ferric iron, as well as their sum - total iron. The maximum permissible concentration of iron in drinking water is 0.3 mg/L.
How to determine iron concentration in water
Iron in water in accordance with most common standards is determined by the colorimetric method. The reagents are diluted, the necessary reagents are added to the water sample, and the optical density of the colored solutions is measured according to the color intensity of the solution, calibration graphs are built, and only then the mass concentration of iron is calculated. The process takes several hours. This procedure requires a background in chemistry, experience with handling chemical reagents, and skills in setting up a spectrophotometer.
Colorimetric method
Hach has developed turnkey solutions for measuring iron in water samples and simplified the process as much as possible so that the untrained user can measure samples with high accuracy in a few minutes.
For example, to measure the iron content with the LCK test (part number LCK321), you need to add the sample to the cuvette with ready-made reagents and set the cuvette in the spectrophotometer. The device itself reads the barcode on the cuvette, determines the required measurement method and gives a ready-made result of the sum of ferrous and ferric iron in mg/L. Measurement time will take not more than 15 - 20 minutes. If it is necessary to measure the content of undissolved iron and iron contained in the complexes, it is necessary to additionally use the Crack Set for digeastion (p/n LCW902).
You can also measure iron with powdered reagents, such as 2105769, or with ready-made AccuVac ampoules (item no. 2507025). The method complies with ISO 6332: 1988 (en) Water quality - Determination of iron - Spectrometric method using 1,10-phenanthroline (orthophenanthroline).
These powdered reagents and ampoules can be used to determine the concentration of iron in water using all Hach colorimeters and spectrophotometers:
- multiparameter handheld colorimeter DR900
- pocket iron colorimeter DR300
- handheld spectrophotometer DR1900
- laboratory spectrophotometers DR3900 and DR6000, for more details follow the link ->
Visual comparison method
If the accuracy of the determination is not too important, you can use the visual method of monitoring the content of dissolved iron in water. A comparator with a color disc and a Hach reagent kit (test kit part number 146400) are suitable for this method.
The advantage of the method will be the absence of the need for additional devices and the ability to perform analysis in the field without power connection, and the disadvantage is the approximate result due to the large measurement error.
In order to choose the correct reagent and measurement method, first you need to decide with what accuracy you want to determine the iron content in the sample. The engineers of AquaAnalytics® can help with the selection of equipment and reagents for measuring the concentration of iron. Contact us in a way convenient for you.
Representative office in Russia: +7 (495) 201-53-02 info@aquaanalytics.ru
Representative office in Uzbekistan: +998 (90) 174-57-84 info@aquaanalytics-tekhnika.ru