Question

Iron-EDTA complex in food fortification: Food fortification is defined as the practice of adding vitamins and minerals to commonly consumed foods during processing to increase their nutritional value. It is a proven, safe and cost-effective strategy for improving diets and the prevention and control of micronutrient deficiencies. A food product (such as rice, wheat flour, edible oil) that is fortified through the addition of fortificants is called a “vehicle”. In African and south Asian countries, 40% of the population suffers from anaemia. Average human needs nearly 10mg of iron daily. Iron fortification may be useful in fighting iron deficiencies in humans. Reduced iron and several iron salts have been used in the past as iron fortification; however, not all are suitable for this purpose in terms of iron absorption. Recent studies have shown that beverages containing sugar fortified with either Ferrous sulphate or the Fe(III)-EDTA complex have a high rate of absorption of iron. Ferrous sulphate as well as Fe(III)-EDTA is suitable to enrich sugar, but while iron from ferrous sulphate is precipitated and poorly absorbed when fortified sugar is added to beverages such as tea, Fe(III)-EDTA reacts slowly with tea and iron is not precipitated for at least 24 hr. Fe(III)-EDTA, as iron fortification, has demonstrated so far more advantages than that observed from other iron salts, including ferrous sulphate. But EDTA is a chelating agent and its use in food technology to prevent oxidative damage to food has been restricted. Excessive consumption of EDTA can cause abdominal cramps, nausea, low blood pressure and damage to kidneys. According to the National Institute of Health, it is unsafe to consume more than 3 g of EDTA per day or continuously for more than 5 to 7 days. The amount of EDTA necessary for 10 mg of iron fortification is about 60 mg. This is within the safe limits and is comparable to the usual amount added to the diet.

Based on the information provided above, answer the following questions:

1. Why is the Fe(III)-EDTA complex stable as compared to ferrous sulphate? (1)
   OR
   What happens when hard water is titrated against Na₂EDTA?
2. You are a doctor working in Somalia. Will you recommend iron-fortified food to your patients? Support your answer with references from the passage. (1)
3. 1. What is the denticity of the ligand in the Fe(III)-EDTA complex? Name the atom(s) through which it can bind to the central metal ion.  (1)
   2. Write the structure of EDTA. (1)

Answer 1

I. EDTA is a chelating agent; it forms a ringed complex with the central metal ion and makes the complex stable.
OR
Hardness of water is estimated by simple titration with Na₂EDTA. The Ca²⁺ and Mg²⁺ ions form stable complexes with EDTA.

II. Yes. Nearly 40% of the population in Africa suffers from anaemia. Iron-fortified food provides a higher amount of absorbable iron (especially Fe(III)–EDTA), which helps reduce iron deficiency within safe consumption limits.
OR
No. Although anaemia is common, excess EDTA can cause harmful effects such as nausea, kidney damage, and high iron levels in non-anaemic patients; therefore, iron-fortified food may not be suitable for everyone.

III. (a) The denticity of the ligand in the Fe(III)-EDTA complex is 6, as EDTA acts as a hexadentate ligand. Two nitrogen and four oxygen are electron donors.
(b)
\[\begin{array}{cc}
\phantom{.}\ce{^-OOC-CH2}\phantom{........................}\ce{CH2-COO^-}\phantom{.}\\
\phantom{.}\backslash\phantom{.....................}/\phantom{.}\\
\phantom{.}\ce{^{\bullet}_{\bullet}{N}-CH2-CH2-N^{\bullet}_{\bullet}}\phantom{.}\\
\phantom{.}/\phantom{.....................}\backslash\phantom{.}\\
\phantom{.}\ce{^-OOC-CH2}\phantom{.......................}\ce{CH2-COO^-}\phantom{.}\\
\end{array}\]