Examining Elements in CerealsA Real World ProjectBy Nicole Dixon and Amanda Lagace
Purpose The purpose of our experiment was to analyze the mineral
content in cereal products in order to make a comparison to the reported values. The content analyses of sodium, potassium, magnesium, calcium, copper, iron, and zinc were performed by the ICP-OES, and the analyses of iron and zinc were performed again using the AA. We analyzed the content using a calibration curve made from standards of various concentrations, and the cereal products we analyzed were Cheerios, Total, Oatmeal Crisp, and Cocoa Puffs.
Method•We began this procedure by creating 1L of 0.1M nitric acid to use as a solvent.
•We then created standards for the experiment. We made standards from the sodium, potassium, magnesium, calcium, copper, iron, and zinc stock solutions in concentrations of 10ppm, 20ppm, 30ppm, 40ppm, and 50ppm in 100mL volumetric flasks with nitric acid. We also set aside a blank of nitric acid for analysis.
•We then created our cereal samples for analysis. We first crushed 0.1g of cereal with a mortar and pestle and dissolved it in 100mL of nitric acid. We used a stir plate for several minutes in order to dissolve most of the sample. What could not be dissolved we filtered out of the solution with filter paper.
•We ran the blank, standards, and samples on the ICP for the presence of the seven elements. We used the information from the standard to create a calibration curve in order to determine the concentration of the elements in the samples.
•We then ran the blank, standards, and samples on the AA for the presence of zinc and iron, using the information from the standards again to create a calibration curve to determine the sample concentrations.
•We used the concentration determined by experimentation to compare to the reported values on the cereal boxes and we calculated the percent difference between the two.
Data
Cereal Samples Massed Out
Cheerios 0.101 g
Total 0.1064 g
Oatmeal Crisp 0.1012 g
Cocoa Puffs 0.1016 g
Data-AAAA Data
Sample Absorbance10 ppm 0.20920 ppm 0.42530 ppm 0.64040 ppm 0.88250 ppm 0.850
Oatmeal Crisp 0.162Cheerios 0.260
Total 0.021Cocoa Puffs 0.019
Sample Absorbance10 ppm 0.61020 ppm 1.80530 ppm 1.86040 ppm 1.88850 ppm 1.917
Oatmeal Crisp 1.732Cheerios 0.183
Total 0.080Cocoa Puffs 0.117
IronZinc
Iron:
Zinc
AA Calibration Curves
5 10 15 20 25 30 35 40 45 50 550
0.5
1f(x) = 0.01739 x + 0.0795000000000001R² = 0.924460477838903
Absorbance vs. Con-centration
Iron
Concentration (ppm)
Concentr
ati
on
5 10 15 20 25 30 35 40 45 50 550
0.51
1.52
2.5
f(x) = 0.02697 x + 0.8069R² = 0.571895181770579
Absorbance vs. Concen-tration
Zinc
Concentration (ppm)
Absorb
ance
Data-ICP
Sample Ca Int. (c/s) Cu Int. (c/s) Fe Int. (c/s) K Int. (c/s) Mg Int. (c/s) Na Int. (c/s) Zn Int. (c/s)
10 ppm 2975345 28152 34371 463324 401600 1172474 420913
20 ppm 4993901 63703 71769 894113 689372 2144804 603284
30 ppm 7341610 96232 109049 1353595 1051647 3381446 767545
40 ppm 9354119 122977 141546 1556369 1221686 4200734 837377
50 ppm N/A 143857 184411 1908458 1495157 5395084 907003
Oatmeal Crisp 620447 486.01 3596.0 139844 55575 742545 11474
Cheerios 1408208 240.00 1890.9 286040 64344 870787 4006.0
Total 10086059 186.06 3185.2 166009 72996 897222 4970.9
Cocoa Puffs 1432715 140.70 1288.6 122246 37250 896478 2056.0
ICP Calibration Curves
5 10 15 20 25 30 35 40 45 50 550
2000000
4000000
6000000
8000000
10000000f(x) = 214840.31 x + 795236R² = 0.9990442795859
Intensity vs. Concentration Calcium
Concentration (ppm)
Inte
nsit
y (
c/s
)
5 10 15 20 25 30 35 40 45 50 550
50000
100000
150000
200000
f(x) = 2906.84 x + 3778.99999999999R² = 0.989572013716158
Intensity vs. Concentration Copper
Concentration (ppm)
Inte
nsit
y (
c/s
)
ICP Calibration Curves (cont)
5 10 15 20 25 30 35 40 45 50 550
50000
100000
150000
200000
f(x) = 3698.57 x − 2727.90000000001R² = 0.998590545617477
Intensity vs. ConcentrationIron
Concentration (ppm)
Inte
nsit
y
(c/s
)
5 10 15 20 25 30 35 40 45 50 550
500000
1000000
1500000
2000000
2500000
f(x) = 35525.24 x + 169414.6R² = 0.983990457552598
Intensity vs. ConcentrationPotassium
Concentration (ppm)
Inte
nsit
y (
c/s
)
ICP Calibration Curves (cont)
5 10 15 20 25 30 35 40 45 50 550
500000
1000000
1500000
2000000
f(x) = 27194.28 x + 156064R² = 0.98918451728549
Intensity vs. Concentration Magnesium
Concentration (ppm)
Inte
nsit
y (
c/s
)
5 10 15 20 25 30 35 40 45 50 550
1000000
2000000
3000000
4000000
5000000
6000000
f(x) = 105011.5 x + 108563.4R² = 0.997077768333118
Intensity vs. ConcentrationSodium
Concentration (ppm)
Inte
nsit
y (
c/s
)
ICP Calibration Curves (cont)
5 10 15 20 25 30 35 40 45 50 550
200000
400000
600000
800000
1000000f(x) = 12062.73 x + 345342.5R² = 0.949381779414573
Intensity vs. ConcentrationZinc
Concentration (ppm)
Inte
nsit
y (
c/s
)
Even More DataCheerios Total Oatmeal Crisp Cocoa Puffs
Sodium 160mg 140mg 125mg 150mgPotassium 170mg 90mg 190mg 70mgCalcium 100mg 1000mg 20mg 100mgIron 6.75mg 15mg 7.5mg 3.75mgZinc 3.75mg 15mg Not reported 3.75mgMagnesium 35mg 21mg 35mg 14mgCopper Not reported Not reported Not reported 0.04mg
Reported values of elements in one serving of each cereal product:
Cheerios Total Oatmeal Crisp Cocoa PuffsSodium 5.771ppm 4.965ppm 2.108ppm 5.644ppmPotassium 6.132ppm 3.192ppm 3.205ppm 2.634ppmCalcium 3.607ppm 35.467ppm 0.3373ppm 3.763ppmIron 0.2435ppm 0.532ppm 0.1265ppm 0.1411ppmZinc 0.3527ppm 0.532ppm 0.5903ppm 0.1411ppmMagnesium 1.2625ppm 0.7448ppm Not reported 0.5268ppmCopper Not reported Not reported Not reported 0.0015ppm
Calculated theoretical values of elements in 0.1g of cereal in 100mL of solvent based on reported values
Sample Calculations
Example Calculations of Theoretical Values:
Calculations UsedICP (Calibration Curves from Instrument
Na y= 108758x + 51823.3
K y= 44295.1x + 2010.58
Ca y= 246238x + 67399.6
Fe y= 3423.14x + 242.967
Mg y= 37115.8x + 2944.18
Zn y= 24438.6x + 171.203
Cu y= 2809.82x + 64.584
AA (Calibration Curves from Excel)
Fe y= 0.0124x + 0.0795
Zn y= 0.027x + 0.8069
ResultsCheerios – ICP
Element Concentration (ppm)
% Difference
Na 7.5301 30.48%
K 6.4122 4.57%
Ca 5.4452 50.96%
Fe 0.4814 97.70%
Mg 1.6543 31.03%
Zn 0.1569 55.51%
Cu 0.0625 ---
Cheerios – AA
Element Concentration (ppm)
% Difference
Fe 1.546 338.33%
Zn 12.5483 5053.05%
ResultsTotal - ICP
Element Concentration (ppm)
% Difference
Na 7.7732 56.56%
K 3.7024 15.52%
Ca 40.6869 14.72%
Fe 0.8595 61.56%
Mg 1.8874 153.41%
Zn 0.1964 63.08%
Cu 0.0432 ---
Total - AA
Element Concentration (ppm)
% Difference
Fe .6759 27.05%
Zn 1.0135 90.51%
ResultsOatmeal Crisp - ICP
Element Concentration (ppm)
% Difference
Na 6.3510 201.28%
K 3.1117 2.911%
Ca 2.2460 565.88%
Fe 0.9795 674.31%
Mg 1.4180 140.22%
Zn 0.4625 ---
Cu 0.14998 ---
Oatmeal Crisp - AA
Element Concentration (ppm)
% Difference
Fe 14.633 6080.63%
Zn 7.8185 ---
ResultsCocoa Puffs - ICP
Element Concentration (ppm)
% Difference
Na 7.7664 24.38%
K 2.7144 3.05%
Ca 5.5447 47.35%
Fe 0.3055 116.51%
Mg 0.9243 75.46%
Zn 0.0771 45.36%
Cu 0.0271 170.04%
Cocoa Puffs - AA
Element Concentration (ppm)
% Difference
Fe 0.9885 600.57%
Zn 0.9170 549.9%
Conclusions The best results came from Potassium. The cereal with the lowest percent
differences overall was Cheerios. The cereal with the worst numbers
was Oatmeal Crisp. The worst results elementally was iron. Most of the elements with higher
percent differences were those with lower reported concentrations in the cereals.
What Went Wrong (Possibly)Dissolving the flaky cereals. Filtering the cereals. Concentrations of standards.Low concentration of cereal in
the samples. (Used 0.1g in 100 mL)
Difference between ICP and AA.