BC
ILN
Thompson Rivers University
Sample Analysis Using Atomic
Absorption Spectroscopy (AAS)
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BC
ILN
Analysis of Iron by Atomic Absorption
Spectroscopy (AAS)
• What we want you to learn from this experiment
• Lab Introduction
• Standard and Sample Preparation
• Dilution of the Fe Unknown
• Submitting Your Samples to the BC-ILN
• Using the Atomic Absorption Spectrophotometer
• Treatment of Data & Results
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ILN
What we want you to learn from this
experiment:
• The general principles of Atomic Absorption Spectroscopy
(AAS) as an analytical technique
• Prepare a sample for quantitative analysis
• Identify the main parts of the flame AAS and understand
their purpose
• Explain why the lamp wavelength is set at 372 nm
• Determine whether or not a particular element is present
in a solution through the presence or absence of a signal
from an atomic absorption transition
Continued…
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ILN
What we want you to learn from this
experiment:
• Prepare standard solutions containing known amounts of
an element using a Mohr pipet and volumetric flasks
• Use experimental data to construct a calibration curve,
perform dilution calculations, and calculate the amount of
an unknown element in a sample
• Assess experimental results to determine accuracy and
suggest reasons for any discrepancy or experimental error
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ILN
AAS Theory
• AAS is an instrumental method of quantitative and
qualitative analysis
• Uses an Atomic Absorption Spectrophotometer
• Uses the characteristic absorption spectrum associated
with each element, such as iron
• Identifies elements present in a wide variety of
substances, such as a commercially available multivitamin
which contains a wide variety of chemical species including
minerals considered to be beneficial to human health
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ILN
AAS Block Diagram
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Theory
• During AAS analysis, an
aqueous sample is sprayed
into a flame which supplies
the energy to dissociate a
sample into ground state
atoms
 This is known as
Sample Atomization
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ILN
Atomic Absorption Spectroscopy
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Theory
The absorbance of the sample is directly proportional to
the concentration of analyte atoms in the sample
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ILN
Fe (Multivitamin) Solution
• Obtain a multivitamin tablet and
record the brand name and
mass of iron per tablet
• Place the tablet in a 150 mL
beaker and add 20 mL of 6.0 M
hydrochloric acid (HCl)
• Swirl gently and let stand while
preparing the standards
To be continued…
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ILN
Fe Standard Solutions
• Use five 100 mL volumetric flasks and a Mohr pipet to
prepare a series of solutions containing approx. 1, 2, 3, 4
and 5 mL of 500 mg/L calibrating stock solution
• Read and record the actual volume used accurately to
two decimal places in your data book
• Fill each flask to the mark with deionized water
• Invert the flask several times to ensure thorough mixing
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ILN
Fe (Multivitamin) Solution
…Continued from before
• Heat the 150 mL beaker on a
hotplate in the fumehood, swirling
periodically and note observations
• Prepare a fluted filter paper and
gravity filtration apparatus
• Gravity filter the solution into a
100 mL volumetric flask
• Rinse and fill to the mark with
deionized water
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Dilution
• Obtain 40 mL of the prepared
unknown Fe solution
• Use a 25 mL volumetric pipet
to dilute exactly 25.00 mL of
unknown Fe solution into a
100 mL volumetric flask
• Fill to the mark with deionized
water
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Prepare your labeled autosampler tubes for
submission to the BC-ILN
• Your instructor will supply you with autosampler tubes
with caps and a rack to put them in for submission
• Label the tubes and organized them in the rack provided
3 cm
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During your scheduled instrument time…
• Go to your computer station get connected to the BC-ILN
• Ask your instructor to show you how to operate the Atomic
Absorption Spectrophotometer
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ILN
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Graphing the Results
Figure 2. Calibration Curve for Iron prepared using a Varian AAS model 55B
Title
0.200
0.150
Absorbance
BC
Label Axis
with Units
Calibration
Curve
0.100
0.082
0.050
10.5
0.000
0
5
10
15
20
25
Concentration of Fe (mg/L)
Label Unknown
Values
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ILN
Data-Book
Page No.
Experiment
Title
Date
Brand
Information
Observations
Stock
Solution
Neat Tables
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