A.Trying to pick out the correct test can prove to be a challenge. There are a number of different tests available from Hach to test for Iron and you will need to select the most appropriate test for the specific form of iron you are testing for.
Iron can be present in natural and treated water. The presence of excess iron can have negative impacts for instance insoluble deposits (rust) can form giving water a reddish colour and may block industrial machinery. In drinking water, the presence of iron above a certain threshold will cause an unwanted metallic taste. Iron-oxidizing bacteria may also thrive in these conditions, feeding off the excess iron and they can give rise to slimy deposits. Iron monitoring can also form part of corrosion control in industry.
In water, iron can be present in a number of different forms– Fe2+ (Ferrous), Fe3+ (Ferric), complexed iron (such as being bound to the chelating agent EDTA) and iron oxides (rust). Total iron is comprised of all of these forms- some of which are soluble and some which are insoluble. You may also wish to measure only total soluble iron, in which case the sample would need to be filtered to remove any insoluble iron.
The following methods are used to test for each of the forms of iron:
Fe2+ Ferrous Iron
Ferrous iron is not stable when exposed to the air and will oxidize to Ferric iron. Therefore, it is important to perform analysis on your sample as soon as possible.
1,10 phenanthroline method (0.02 – 3.00mg/L)
Fe3+ Ferric Iron
This would be obtained by running a total iron and ferrous iron method in samples of the same sizes then subtract the ferrous result from the total to get the levels of Ferric present.
There are a number of different methods that can be used to measure total iron and you would select the method based on the range of iron you are testing for (the FerroZine, TPTZ and FerroVer methods differ mainly in sensitivity), plus consideration for a few other factors.
FerroVer and TPTZ methods will react with complexed iron. They will only recover most insoluble iron oxides without digestion, and therefore digestion is recommended to recover the insoluble forms. The only USEPA- accepted method would be FerroVer with digestion. FerroZine is the most sensitive method and also requires digestion/boiling to dissolve rust. Iron complexed with EDTA would be an interference with this method, so you would need to select FerroVer or TPTZ if present.
FerroZine method (0.009 -1.400mg/L) – all Hach instruments except the DR850, DR820
TPTZ method (0.012 – 1.800mg/L) – all Hach Instruments except DR3000, DR2000, DR820
FerroVer method (0.02 – 3.00 mg/L) – all Hach Instruments except DR2000 and DR3000
TitraVer titration (10-1000mg/L) – digital titrator required
LCK321 reduce iron to Ferrous state and measure using the 1,10 phenanthroline method (0.12 – 6.00mg/L) – The LCK vials are designed to work with DR1900,DR3900 and DR6000 and older models DR2800,DR3800 and DR5000. To use LCK321 to measure insoluble iron, a digestion will also need to be performed using LCW902. If you are short on time, this digestion can be sped up using the HT200S digestor. More information can be found on this here.
Total Iron (in the presence of Molybdenum compounds)
FerroMo method (0.01-1.80mg/L) – works with all instruments except DR820
Upon selecting the most appropriate method, if you take a look at the Hach instruction sheets, they will list any extra equipment you may require to perform the test.
All of the tests mentioned are available to purchase through Camlab.co.uk. If you need any help selecting a test, please feel free to contact the Camlab Tech Team using for the contact form below or email us at firstname.lastname@example.org.