Abstract This extended essay is on spectophotometric determination of iron found in different parts of the broccoli, Brassica oleracea and the effects of incubating temperature on the iron content. Spectophotometry quantification was adopted. Iron(II) was reacted with orthophenanthroline solution to produce orange-red colour complex exhibiting a maximum absorption peak, λ max at 510nm. Beer-Lambert’s law is applied where the absorbance reading is directly proportional to the concentration of the sample. A standard calibration curve for iron(II) solution was plotted which shows a significant (P<0.05) and good correlation (R2 = 0.9929) between concentration and absorbance. Samples from different parts of the broccoli (buds, stems and base) was obtained, heated to ash and dissolved in hydrochloric acid(4.0M) to form the required solution. Broccoli bud samples were incubated in water of different temperatures (24.0°C, 60.0°C, 80.0°C and 100.0°C) for the second part of the investigation. Statistical results show a significantly higher (P<0.05) iron content at the buds compared to the stems and the base of the broccoli. The amount of iron in the buds and the stems are 2.90mg dm-3g-1 to 0.30mg dm-3g-1 respectively, indicating 90% higher iron content in the buds. Investigation on different incubating temperature shows a negative correlation between incubating temperature and iron content. Statistical results showed a significant decrease in iron content observed only when the incubating temperature is at 100°C. Iron content for control sample(24.0°C), 8.30mg dm -3g-1 decreases to 2.65mg dm-3g-1 at 100.0°C, implying a significant 61% drop. Incubating temperatures of 60°C to 80°C result to a range of decrease of iron content between 1.8% and 25%. Statistical tests were carried out for all results to support the significant difference between the samples (P<0.05).
The conclusion was that the iron content is highest at the buds of the broccoli and increasing incubating temperature decreases iron content. (296 words only) 2