HJ/T 345-2007 Water quality - Determination of iron - Phenanthroline spectrophotometry
1 Scope of application
This standard is applicable to the determination of iron in surface water, groundwater, and wastewater. The minimum detectable mass concentration of this method is 0.03mg/L, with a lower limit of determination of 0.12mg/L and an upper limit of determination of 5.00mg/L. For water samples with iron ion concentrations greater than 5.00mg/L, they may be appropriately diluted before determination using this method.
2 Principle
Ferrous ions may form stable orange-red complex with phenanthroline in solutions with a pH between 3 and 9. The reaction may be represented as:
This complex may be stably stored for up to six months when protected from light. The measurement wavelength is 510nm, with a molar absorption coefficient of 1.1×104L/(mol·cm). If a reducing agent (such as hydroxylamine hydrochloride) is used to reduce ferric ions, this method may be used to determine both the content of ferric ion and the total iron content.
3 Reagents
Unless otherwise specified, all reagents used in this standard are analytical grade chemical reagents conforming to national standards; the experimental water is freshly prepared deionized water.
3.1 Hydrochloric acid: ρ(HCl)20=1.18g/ml, of guaranteed reagent grade.
3.2 (1+3) hydrochloric acid.
3.3 10% hydroxylamine hydrochloride solution.
Foreword III
1 Scope of application
2 Principle
3 Reagents
4 Apparatus
5 Elimination of interferences
6 Procedure
7 Result calculation
8 Precision and accuracy
