Determination of Iron in Natural Water by Spectrophotometry.

1670 Words Mar 9th, 2013 7 Pages
Title: Determination of Iron in Natural water by Spectrophotometry.
Aim: To determine the iron in natural water by spectrophotometry.
Abstract: The iron in natural water was determined by utilizing spectrophotometric analysis. That was done by measuring the absorbance of five Fe(oPH)2+3 standards at 510 nm. From that information, a calibration curve was plotted and used to find the amount of Fe2+ that was in two unknown water samples based on the absorbance readings obtained with them at 510nm. The equation of the line was found to be y=0.1765x + 0.0705. It was then determined that there was no iron present in water sample A, while for water sample B, the iron was present in the proportions of 0.9037ppm, 1.614x10-5M and 9.037x10-3%.
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Method: Standard iron solutions, sodium acetate solution, 10% hydroxylamine hydrochloride, 1-10 phenanthroline and solvent blank solutions were prepared before hand to use throughout the experiment. 2.00, 4.00, 6.00, 8.00 and 10.00 mL of iron stock solution were pipetted into five 100mL volumetric flasks. To each flask, 1mL of 10% hydroxylamine hydrocholride, 10 mL of sodium acetate and 10mL of 1,10-phenanthroline solution was added. The mixture was allowed to stand for 10 minutes then made up to the mark with distilled water. The absorbance of all five standards solutions were determined with respect to the blank at 510 nm. 10.0mL of water sample was transferred to a 100mL volumetric flask, and treated exactly the same way as the standards, measuring the absorbance with respect to the blank.
Concentration of Fe(oPH)2+ | Absorbance at 510nm | 1 | 0.251 | 2 | 0.424 | 3 | 0.587 | 4 | 0.785 | 5 | 0.482 | Unknown | Absorbance at 510nm | A | -0.07 | B | 0.023 |

Table 1 showing the absorbance obtained at a wavelength of 510nm, using a OHAUS spectrophotometer, for concentrations of Fe(oPH)2+ of (1,2,3,4,5)ppms and two unknown water samples A and B.
(i) Equation of the line: y=0.1765x + 0.0705. Sample A absorbance -0.007, hence, that value does not have to be substituted in the equation as it is a known fact that a negative absorbance reading means there is no iron