Introduction: The main difference between various chemicals is colour. The white light composed of wide range range of wavel waveleng ength th that that is in ultrav ultraviol iolet, et, visib visible le and infrar infrared ed region region.. Wavel Wavelen ength gth and frequ frequenc ency y diffe differs rs for each each latte latterr region region.. As light light passe passes s throug through h or bounce bounce off off from from a colou coloured red compo compound und,, certai certain n amount amount of energ energy y is absor absorbed bed which which all those those colou coloured red compound have similarity in conjugated double-double bond structure such as alizarin and benzen benzene. e.
or this this purpo purpose, se, ultravio ultraviolet let-vi -visib sible le spectr spectrosc oscopy opy is used used to measur measure e the
absorption within ultraviolet-visible region with the usage of light from visible region or near!" light region. region. The absorptio absorption n is affected affected by the colour or the presence presence of conjugat conjugated ed double bond of a compound. #uring the absorption of !" light, the molecules e$periences electronic transition which quite similar to fluorescence spectroscopy. spectroscopy.
Purpose: To determine the concentration of iron in food sample %&ilo 'rea(fast cereal)
Procedure: *tandard +reparation The standards used in this e$periment involve iron %) nitrate, potassium thiocyanate and hydrochloride acid solutions. The involved chemicals are prepared by their following concentrations ./& 01l and ./& 2*13 solutions. The standards are prepared as described in the following table and the volume is mar(ed up with distilled water to calibrated mar( in /ml volumetric flas(. "olume of ./&
"olume of ./& 01l
"olume of ./&
e%345)5 in m6 8 / /8 7
in m6 7 /8 / 8
2*13 in m6
7.8
Total "olume in m6
77.8
ood *ample +reparation The sample %&ilo 1ereal) is grinded using mortar and pestle which is then about 7.8g of sample is obtained. The weighed sample is treated with high heat and left to cool down to room temperature. With the addition of /ml of ./& 01l solution and /ml of distilled water, the mi$ture is filtered which the obtained filtrate is mi$ed with 7.8m6 of ./& 2*13 solution. The sample is then tested with uv-vis.
Data: *tandard *td / *td 7 *td 5 *td ; *td 8 *ample %2o(o 1runch)
1oncentration %m&ol96) . .78 .8 .<8 /. ./
&ean .:/ .77/5 .;<75 .<8; .=7: .>=
Discussion The e$periment is starts with the ma(ing of standards. A series of standards consists of ./& iron %) nitrate mi$ed with ./& hydrochloric acid %01l) and ./& potassium thiocyanate solution. The / st reaction of iron %) nitrate and hydrochloric acid described as? @q /? e %345)5 01l B e1l5 0345 The product is iron %) chloride which is then treated with potassium thiocyanate solution of ./& which produces? @q 7? e1l5 2*13 B e %*13) 5 21l The 7nd reaction produces iron %) thiocyanate solution, having deep red colour, is used as the analyte in a series of ., .78, .8, .<8 and /. m&ol96 standards. The standards are tested using uv-vis device and the produced correlation coefficient is at .===: with the calibration equation, absB .=5/8/C1onc. The sample is prepared by the grinding the sample using mortar and pestle, to increase the surface area and to ease the weighing in acquiring 7.8g of sample. The obtained sample is then treated with high temperature, dry ashing, to remove organic matter from the sample. The produced product is charcoal-li(e mass, is then mi$ed with /.& hydrochloric acid and water, /m6 each and then passes through a filter to separate insoluble matter from the mi$ture. The filtrate is again mi$ed with 7.8m6 of ./& 2*13 and tested using !v-vis. The chemical reaction is similar to @q /D 7, since the iron within the food sample is used instead of iron %) nitrate solution. The obtained concentration of iron in food sample %&ilo) is at ./m&ol per litre.
Conclusion: The concentration of iron in &ilo cereal is at ./m&ol per litre
References /. 3ote on Eas 1hromatography, 10& 7: by &dm aridah 0anum 0j 'adrun 7. nformation of E1, http?99en.wi(ipedia.org9wi(i9EasFchromatography 5. 3otes on E1 10& 5/7 4. +icture, http?99www.files.chem.vt.edu9chem-ed9spec9uv-vis9graphics9spectrometer/.gif
