Chemical products for industrial use - General method for determination of iron content - 1, 10-Phenanthroline spectrophotometric method
1 Scope
This standard specifies a general 1, 10-phenanthroline spectrophotometric method for the determination of the iron content of chemical products for industrial use.
It describes a technique for the determination of the content of iron in a solution. Reference shall be made, for the preparation of the test solution, to the standards relating to the product to be analysed, which shall indicate the modifications necessary to make the method applicable to that product.
2 Field of application
The method is applicable to test solutions from which an aliquot portion can be taken containing between 10 and 500 μg of Fe in a volume of not more than 60mL.
Large amounts of alkali metals, calcium, strontium, barium, magnesium, manganese (II), arsenic (III), arsenic(V), uranium(VI), lead, chloride, bromide, iodide, thiocyanate, acetate, chlorate, nitrate, sulphate, sulphide, metaborate, selenate, citrate, tartrate, phosphate and up to 100 mg of germanium(IV), in the test solution, do not interfere. In the presence of tartrate, citrate, arsenate or more than 100 mg of phosphate, colour development is, however, liable to be slower.
Details of certain interferences and means by which they can be overcome are given in Annex A.
3 Principle
Reduction of all the Fe3+ present in the test solution to Fe2+ with ascorbic acid. Formation of the orange-red complex between iron and l,l0-phenanthroline at a pH between 2 and 9, and spectrophotometric measurement of the absorbance of the complex at the wavelength of maximum absorption (510nm).
Under the specified conditions, the complex is measured at a pH between 4 and 6.
