Examining Elements in Cereals

Report
Examining Elements in Cereals
A Real World Project
By 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
Iron
Zinc
Data-AA

AA Data
Iron:
Sample
10 ppm
20 ppm
30 ppm
40 ppm
50 ppm
Oatmeal Crisp
Cheerios
Total
Cocoa Puffs
Absorbance
0.209
0.425
0.640
0.882
0.850
0.162
0.260
0.021
0.019
Sample
10 ppm
20 ppm
30 ppm
40 ppm
50 ppm
Oatmeal Crisp
Cheerios
Total
Cocoa Puffs
Absorbance
0.610
1.805
1.860
1.888
1.917
1.732
0.183
0.080
0.117
Zinc
AA Calibration Curves
Absorbance vs. Concentration
Iron
y = 0.0174x + 0.0795
R² = 0.9245
0.8
0.6
0.4
0.2
0
0
10
20
30
40
Concentration (ppm)
50
60
Absorbance vs. Concentration
y = 0.027x + 0.8069
Zinc
R² = 0.5719
2.5
Absorbance
Concentration
1
2
1.5
1
0.5
0
0
10
20
30
40
Concentration (ppm)
50
60
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
Intensity vs. Concentration
y = 214840x + 795236
Calcium
R² = 0.999
14000000
10000000
8000000
6000000
4000000
2000000
0
0
10
20
30
40
Concentration (ppm)
50
60
Intensity vs. Concentration
y = 2906.8x + 3779
Copper
R² = 0.9896
Intensity (c/s)
Intensity (c/s)
12000000
160000
140000
120000
100000
80000
60000
40000
20000
0
0
10
20
30
40
Concentration (ppm)
50
60
ICP Calibration Curves (cont)
Intensity vs. Concentration
y = 3698.6x - 2727.9
Iron
R² = 0.9986
200000
100000
50000
0
0
10
20
30
40
Concentration (ppm)
50
60
Intensity vs. Concentration
y = 35525x + 169415
Potassium
R² = 0.984
2500000
Intensity (c/s)
Intensity (c/s)
150000
2000000
1500000
1000000
500000
0
0
10
20
30
40
Concentration (ppm)
50
60
ICP Calibration Curves (cont)
1600000
1400000
1200000
1000000
800000
600000
400000
200000
0
0
10
20
30
40
Concentration (ppm)
50
60
Intensity vs. Concentration
y = 105012x + 108563
Sodium
R² = 0.9971
6000000
Intensity (c/s)
Intensity (c/s)
Intensity vs. Concentration
y = 27194x + 156064
Magnesium
R² = 0.9892
5000000
4000000
3000000
2000000
1000000
0
0
10
20
30
40
Concentration (ppm)
50
60
ICP Calibration Curves (cont)
Intensity vs. Concentration
y = 12063x + 345343
Zinc
R² = 0.9494
Intensity (c/s)
1000000
800000
600000
400000
200000
0
0
10
20
30
40
Concentration (ppm)
50
60
Even More Data
Reported values of elements in one serving of each cereal product:
Sodium
Potassium
Calcium
Iron
Zinc
Magnesium
Copper
Cheerios
160mg
170mg
100mg
6.75mg
3.75mg
35mg
Not reported
Total
140mg
90mg
1000mg
15mg
15mg
21mg
Not reported
Oatmeal Crisp
125mg
190mg
20mg
7.5mg
Not reported
35mg
Not reported
Cocoa Puffs
150mg
70mg
100mg
3.75mg
3.75mg
14mg
0.04mg
Calculated theoretical values of elements in 0.1g of cereal in 100mL of solvent based on reported values
Sodium
Potassium
Calcium
Iron
Zinc
Magnesium
Copper
Cheerios
5.771ppm
6.132ppm
3.607ppm
0.2435ppm
0.3527ppm
1.2625ppm
Not reported
Total
4.965ppm
3.192ppm
35.467ppm
0.532ppm
0.532ppm
0.7448ppm
Not reported
Oatmeal Crisp
2.108ppm
3.205ppm
0.3373ppm
0.1265ppm
0.5903ppm
Not reported
Not reported
Cocoa Puffs
5.644ppm
2.634ppm
3.763ppm
0.1411ppm
0.1411ppm
0.5268ppm
0.0015ppm
Sample Calculations
Example Calculations of Theoretical Values:
Calculations Used
ICP (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
Results
Cheerios – 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%
Results
Total - 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%
Results
Oatmeal 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
---
Results
Cocoa 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
Cocoa Puffs - AA
170.04%
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.


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