2. Coffee is an important study
tool for many college students.
It is important to ensure heavy
metal concentrations are kept
to a minimum.
We chose to focus on analyzing
the concentrations of Zn, Cd,
and Pb.
3. FlameAtomic Absorbance Spectroscopy was
used to determine metal concentrations.
Cation Exchange was used to preconcentrate
the samples before analysis.
4. Two samples (~3 tablespoons each) were
obtained from regular store bought coffee.
One sample was brewed hot and the other
cold.
5. The hot coffee was brewed in 500 mL of
water at 200 F for five minutes.
The cold was brewed in 500 mL of water and
stored in the refrigerator over two days.
6. Once brewed, the large coffee grounds were
filtered from each solution.
30mL of the hot and cold solutions were
obtained for analysis by FAAS.
7. It became apparent the metal concentration
would be too low to measure directly by
FAAS.
This was corrected by concentrating the
samples through Cation Exchange.
8. 300 mL of each solution was filtered
through the column containing sodium
form Chelex 100.
9. A 15mL concentrated sample was collected
by eluting the column with 15mL of 2M HCl.
Sample preparation was now complete and
ready for analysis by FAAS.
10. Analytical standard solutions were made of
each metal to be analyzed (Pb, Cd, and Zn).
The standards were prepared to compare the
sample concentrations to the concentrations
likely present in coffee.
11. The concentrations of each metal calibration
standards are as follows: Zinc (0.2,0.5,0.7,1
p.p.m.), Cadmium (0.2,0.5,0.7,1 p.p.m.), Lead
(0.5,1,2.5,5.0 p.p.m.).
Each sample was acidified to 1%
volume:volume with trace metal grade
HydrochloricAcid to ensure the metals were
solvated into the matrix and could easily be
analyzed via FAAS.
12. Cadmium, Zinc, and Lead hollow cathode
lamps were selected for analysis of each
sample individually.
The fuel mixture chosen was an acetylene
and air mixture with a flame height of 15.6
millimeters and a flow rate of 1.2 L/min for
Cadmium and Zinc and 1.1 L/min. for Lead.
Each element was analyzed at a specific
wavelength
(Cd:22.8nm,Pb:217nm,Zn:213.9nm)
13. First the corresponding metals calibration
curve was ran starting with the blank and
increasing to highest concentration.
Second the five samples were ran for
detection of each metal individually.
14. Metal Unconcentrated
Cold (ppm)
Unconcentrated
Hot (ppm)
Concentrated Cold
(ppm)
Concentrated
Hot (ppm)
Detection
Standard
(ppm)
Cadmium -.0037 -.0042 -.0004 .0049 -.0035
Lead -.0818 -.0802 .0228 .0266 .0060
Zinc .2800 .2815 .2211 .5772 .2187
15. During the experiment a known error was
made while preparing the detection standard.
The standard was acidified 1%
volume:volume with trace metal grade HCL.
In further research this would not be done.
16. When the detection standard was ran
through the column the acid competed for
binding sites with the metals.
This resulted in results that were much lower
than anticipated at 0.5 ppb for Cadmium and
0.9 ppb for Lead. However, Zinc
concentration was at 32 ppb which is much
higher than the desired 10 ppb.
17. Overall the results were as anticipated with
concentrations being low for each
Using the hot brewing method increased the
concentration of all metals in both
concentrated and unconcentrated samples
with the exception of unconcentrated
Lead.metal.
18. We believe coffee is
safe, in regards to
heavy metals, due to
the extremely low
concentrations of
these metals.
To reduce exposure to
heavy metals from
coffee, the cold
brewing method
should be utilized.
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Plexa™ PCX Cation Exchange Resin in Flow Injection Column Preconcentration
System for Metal Determination by Flame Atomic Absorption Spectrometry."
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"Chelex® 100 Resin." Chelex® 100 Resin. BIORAD, n.d.Web. 28 Apr. 2015.
<http://www.bio-rad.com/en-us/product/chelex-100-resin>.
"Coffee Maker." How to Make Coffee in a. Folgers Coffee, n.d.Web. 28 Apr. 2015.
<http://www.folgerscoffee.com/coffee-how-to/how-to-make-coffee/coffee-
maker>.
Pai, Su-Cheng,Tien-Hsi Fang, Cheng-Tung A. Chen, and Kwung-Lung Jeng. "A
Low Contamination Chelex-100Technique for Shipboard Pre-concentration of
Heavy Metals in Seawater." Marine Chemistry 29 (1990): 295-306. Web.
Rahmi, D.,Y. Zhu, E. Fujimori,T. Umemura, and H. Haraguchi. "Multielement
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