Study of Ascorbic Acid as Iron(III) Reducing Agent for Spectrophotometric Iron Speciation

Abstract

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.

A Novel and Facile Method to Characterize the Suitability of Metallic Iron for Water Treatment

“…It should be recalled that (Fe-EDTA) 3+ is not destabilized by many inorganic reducing agents, including hydroxylamine. Hydroxylamine is used in the standard spectrophotometric method to reduce Fe 3 species prior to the formation of the characteristic orange complex of Fe 2 -Phen [59]. Lastly, amorphous Fe 3 corrosion products are (at least partly) dissolved in EDTA (Equation (6)).…”

“…In this study ascorbic acid was used because of parallel experiments with EDTA [21]. In routine Phen tests, all other reducing agents (e.g., hydroxylamine) can be used, but the authors recommend ascorbic acid for its less toxicity and even its better affordability [59]. Figure 3a depicts a large variability of the standard deviation (results not shown) which results from various amounts of atmospheric corrosion products initially available on the SW specimens and the evidence that dissolved O 2 accelerates iron dissolution.…”

Aqueous solution–gel precursors for LiFePO 4 lithium ion battery cathodes, their decomposition and phase formation

“…of CA by 4 eq. of ascorbic acid, as ascorbic acid is known for its ability to reduce Fe(III) to Fe(II) in solution [28]. This hypothesis was also verified by adding a small amount of a solution of KSCN to the precursor solution.…”

Flow Injection Analysis of Iron in Presence of Uranium

“…Orthophenanthroline was tried initially. It is well known that orthophenanthroline is used for the determination of iron in its + 2 state [13]. However, in the present study, iron being in its + 3 state had to be reduced prior to its determination with orthophenanthroline.…”