The study of ascorbic acid as a reducing agent for iron(III) has been investigated in order to obtain an alternative carcinogenic reducing agent, hydroxylamine, used in spectrophotometric standard method based on the formation of a red-orange complex of Fe(II)-o-phenanthroline. The study was optimised with regards to ascorbic acid concentration as well as pH solution. The results showed that ascorbic acid showed maximum capacity as reducing agent of iron(III) under concentration of 4.46.10 -4 M and pH solution of 1-4.Under these conditions, ascorbic acid reduced iron(III) proportionally and performed similarly to that of hydroxylamine. The method gave result to linear calibration over the range of 0.2-2 mg/L withhigh accuracy of 97 % and relative standard deviation of less than 2 %. This method was successfully applied to assay iron speciation in water samples.Keyword: Iron, speciation, ascorbic acid, o-phenanthroline, spectrophotometry
INTRODUCTIONIron is the second most abundant metallic element in the earth's crust and is essential in the metabolism of plants and animals. If presented in excessive amounts; however, it forms oxyhydroxide precipitate that stains laundry and porcelain. As a result, the recommended limit for iron in domestic water supplies is 0.3 mg/L. 1 Determination of Fe(II) and Fe(III) is important in many natural sciences like geology, agriculture, biology or environmental protection, mainly on account of different bioavailability and metabolism of iron on its two oxidation states. Iron(II) is essential for good health, as it helps transport oxygen in the blood and storage of oxygen by means of haemoglobine and myoglobine.2 Iron deficiency may lead to low immunity and infectious diseases. If the human body takes in too much iron will cause excretory functional disturbance and likely have greater carcinogenic potential. Both Fe (II) and Fe(III) are important in the biosphere, serving as an active centre of a wide range of proteins such as oxidases, reduces and dehydrates.3 However the plants need a certain amount of iron(II) to survive. Iron helps them create chlorophyll and aids in several other chemical processes plants perform. However, too much iron can have a toxic effect on the plant, weakening and eventually killing it. It should be noted that plants only absorb ferrous iron particles from the soil, and that other forms of iron will not affect plants.