Analytical Chemistry: The Analysis of Fe in Geritol - Lab Report Example

Analytical Chemistry Objectives: *To analyze, spectrophotometrically, a sample of Geritol syrup to determine the quantity ofiron present in one dose and one gram of the syrup; *To obtain absorption spectrum of the tris(1,10-phenanthroline)iron(II) complex using a standard Fe (II) solution; *To calculate the molar absorptivity of the colored compound, iron-1,10- phenanthroline from the standard plot. Abstract A sample of Geritol syrup was analyzed for its iron content by the o-phenanthroline method. The intensely orange-red colored complex formed, i.e., iron-1,10-phenanthroline was read at 508 nm in a spectrophotometer (2 different models namely, Ocean Optics Spectrometer and Spectronic 20 Spectrophotometer). The absorbance values obtained with the two instruments were, respectively, 0.214 and 0.241 corresponding to 0.019544g and 0.02174g of Fe in one dose of Geritol syrup. That is, 0.001135g and 0.001262g of Fe per gram of Geritol syrup. The molar absorptivity of the iron-1,10-phenanthroline compound, as calculated from the calibration curve obtained with the Ocean Optics instrument was13733. This value was about 17% higher than the value reported in literature perhaps due to instrument noise. Introduction Iron is a transition element which plays an important role in the chemistry of living systems. Proteins containing iron (Fe) participate in two main processes, oxygen transport and electron transfer (i.e., oxidation–reduction) reactions. For example, a major part of the Fe in the human body is present in the protein, hemoglobin in blood which is involved in transporting oxygen and carbon dioxide bound to the iron moiety. The Fe-containing enzymes called cytochromes play a critical role in the energy production cycle of all respiring cells, being a part of the electron transport system and aided by the two readily interconvertible oxidation states Fe(II) and Fe(III) of the Fe moiety. Human beings obtain all the Fe needed for their physiological needs from diet. A deficiency of this mineral leads to anemia. Dietary supplements of iron (as a ferrous salt) in the form of multivitamin-multimineral tablets are administered to help alleviate this condition. As Fe is a mineral found in many over-the-counter supplements, an overdose of Fe can occur unwittingly, and an overdose can be extremely severe in children (Zieve et al., 2009). The analysis of Fe in Geritol, a multivitamins-with-iron formulation, reported here was based on spectrophotometry. Spectrophotometric analysis is one of the most common analytical techniques available for quantitative analyses of compounds. Figure 1 shows the essential parts of a spectrophotometer. Samples can be analyzed spectrophotometrically for iron by forming the reddish-orange tris complex of iron (II) with 1,10-phenanthroline (C12H8N2, ortho-phenanthroline or o-Phenanthroline), a tricyclic nitrogen heterocyclic compound that reacts with ferrous iron to form the strongly colored complex thus: Fe 2+ + 3 o-Phenanthroline  Fe(o-Phenanthroline)3 2+  This complex absorbs light in the visible region rather strongly with a maximum absorbance occurring around 508 nm and is very stable, the color intensity not changing appreciably over long periods of time. However, the reaction will only occur when Fe is present in the Fe(II) oxidation state. Also, Fe(II) is easily oxidized to Fe(III) in the presence of acid and water. Therefore, hydroquinone, a reducing agent, is added to the solution. Procedure: (a) Reagents The following reagents were prepared using reagent grade chemicals. Hydroquinone: 10 g dissolved in 1L water. Solution freshly prepared and stored in an amber bottle. Trisodium citrate: 25 g/L in water o-Phenanthroline: 2.5 g dissolved in 100 mL of ethanol and added to 900 mL of water. Solution stored in an amber bottle. Standard Fe (0.04 mg Fe/mL): Prepared by dissolving 0.2835 g of reagent-grade Fe(NH4)2(SO4)2.6H2O in water in a 1-L volumetric flask containing 1 mL of concentrated H2SO4. (b)Preparation of Geritol dilutions for analysis The weight (W1) of the clean and dry dosage cup was measured on an analytical balance. Geritol syrup was filled to the mark in the dosage cup and the weight of cup plus Geritol (W2) was similarly measured. The weight of the syrup equivalent to one dose was calculated by subtracting W1 from W2. The entire contents of one dosage cup were added, with 2 rinsings with small portions ( Read More

Also, Fe(II) is easily oxidized to Fe(III) in the presence of acid and water. Therefore, hydroquinone, a reducing agent, is added to the solution. Procedure: (a) Reagents The following reagents were prepared using reagent grade chemicals. Hydroquinone: 10 g dissolved in 1L water. Solution freshly prepared and stored in an amber bottle. Trisodium citrate: 25 g/L in water o-Phenanthroline: 2.5 g dissolved in 100 mL of ethanol and added to 900 mL of water. Solution stored in an amber bottle.

Standard Fe (0.04 mg Fe/mL): Prepared by dissolving 0.2835 g of reagent-grade Fe(NH4)2(SO4)2.6H2O in water in a 1-L volumetric flask containing 1 mL of concentrated H2SO4. (b)Preparation of Geritol dilutions for analysis The weight (W1) of the clean and dry dosage cup was measured on an analytical balance. Geritol syrup was filled to the mark in the dosage cup and the weight of cup plus Geritol (W2) was similarly measured. The weight of the syrup equivalent to one dose was calculated by subtracting W1 from W2.

The entire contents of one dosage cup were added, with 2 rinsings with small portions (

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