bsc chemistry 2.1 experiments

1. Name : MunasheC Mazodze
Program : Bachelor of Science Honors Degreein Chemistry
Reg no : C14123361T
Course : laboratory Chemistry (III)
Experiment : 4
Level : 2:1
Title : Flame atomic absorption spectrophotometry
Date : 27 April 2014
Aims : To determine Ksp of Copper
: Detection of sensitivity of the FAAS and interferences from matrix
Effects
: manipulate techniques associated with use of FAAS

2. Introduction
Atomic absorption spectroscopy is a method particularly suited to the measurement
of small amounts of elements, usually metals, in a sample Sadans (2009). The
element to be determined is dissociated from its environment so that it exists as
free atoms in the ground state. Atoms in this state readily absorb electromagnetic
radiation at wavelengths corresponding to excitation to higher energy levels. The
extent of this energy absorption from a radiation source is measured photometrical
and compared with standard samples containing known amounts of the element.
The method is unusually simple, sensitive and selective.according to Haouron
(2009) he dissociation of an element from its initial matrix is generally
accomplished by putting the sample into solution and aspirating it into a flame.
The flame is located between a radiation source of the required wavelength and a
detector in a manner analogous to a spectrophotometer cell The sample solution is
drawn into the burner-nebulizer by a stream of air and mixed with air and fuel (in
the figure, acetylene). Most of the sample solution passes into the nebulizer
chamber as droplets, which settle out and pass down the drain tube. The remaining
solvent passes as a mist to the burner head, where the solvent evaporates and the
solute is dissociated into atoms by the heat of the flame. The number of atoms
reaching this point in the operation is only a small fraction of the total. For high
sensitivity, as many as possible of these atoms present in the flame should absorb
radiation from the source. The ideal source for this purpose would be of high
intensity at the wavelength needed for the element being determined, but of low
intensity at all other wavelengths. The nearest approach to this ideal is a lamp
generally of hollow cathode design, whose cathode contains the element being
determined. The hot cathode emits energy at the wavelengths most likely to be
absorbed by the element in the sample. This characteristic provides not only
sensitivity, but also selectivity, as other elements in the sample generally will not
absorb close enough to the chosen wavelength to interfere in the measurement
Ghaedhi (2007). The wavelength of interest is isolated by a monochromator placed
between the sample and the detector to reduce background interference. Most often
a grating is used for this purpose. Solutions more concentrated than 10-3 to 10-5 M
should be diluted to bring them into this range. Only small volumes of solution, on
the order of a few milliliters, are required. A large fraction of the elements can be
determined by atomic absorption techniques Skoog (2007). Many applications of
atomic absorption to analysis of trace metals in a 51 variety of organic, inorganic,
and biological systems have been developed and are replacing lower, more tedious
techniques. In agreement with Hodrejarv (1991), atomic absorption has been found
to be exceptionally satisfactory for the determination of magnesium in cast iron in
the 0.002 to 0.1% concentration range, and of silver, zinc, copper and lead in

3. cadmium metal in the 0.004 to 0.4% concentration range. In this experiment, trace
copper in nickel metal is determined. Although atomic absorption has caught on
quickly as a rapid, useful analytical method, it does have limitations. The chief
problems are instrument drift due to changes in lamp intensity or wavelength
calibration with time and, because of the extreme sensitivity of the method, trace
contamination from reagents, water, and surroundings during sample preparation
and analysis. Frequent rechecks of instrument operation with standard solutions
and care in the preparation and handling of both standard and sample solutions
contribute to improved accuracy and precision of the technique.
Apparatus and reagents
Copperhollow cathode lamp
Perkin-Elmer r3110 absorptionspectro photometer
Computer with monitor and printer
8× 100ml volumetric flasks
1000ml volumetric flask
10 ml graduated pipette and pipette filer
Cu(NO)3, CuCI2, CuBr2, CuSO4 stocksolutions (250ppm)
Saturated coppersalts for Ksp Cupric Iodate, Cupric Carbonate and cupric oxalate
Experimental procedure
1000ppm stocksolution of Cu(NO)3 was prepared in a volumetric flask and 100
ml 0f each 1, 3, 5,7 9, 25 and 50ppm solutions were prepared by serial dilution
from the stocksolution with de-ionized water. And to cater for the matrix effects
5ppm solutions of Cu (NO)3, CuCI2, CuBr2, CuSO4 were prepared and aspirated
then absorbance’s were recorded. Then after these samples have been run through

4. AAS 5g of EDTA was added to each solution thoroughly shake and absorbances
were recorded.
Absorbance’s fromeach from each Coppersolutions were recorded with the
instrument set to optimum conditions., the calibration curves were recorded for
each standard as shown in the print out. The matrix effects samples were run.
Results and calculations
Table 1 measurement of copper standards
type Absorbance(nm) Concentration
(ppm)
Blank 0.0016 0.000
Std 1 0.1550 1.000
Std 2 0.3500 3.000
Std 3 0.5401 5.000
Std 4 0.7632 7.000
Std 5 0.9374 9.000
Unk
sample
0.4483 3.7928
rep 0.4492 3.8017
rep 0.4518 3.8277
AVG 0.4498 3.8074

5. Table 2: instrument optimization
Element Cu
Turret number 1
Lamp current low 6
Lamb current high 0
Wavelength 324.8
Slit width 0.5
Lamp mode BGC-D2
Treatment of data
1.) On table
2.)sample solution is aspirated by a pneumatic analytical nebulizer,
transformed into an aerosol
3.)on graph
4.)
y = 0.1024x + 0.0354
R² = 0.9959
0
0.2
0.4
0.6
0.8
1
1.2
0 2 4 6 8 10
Absorbance(nm)
concentration (ppm)
Calibration curve for Copper

6. Discussion
Calibration curve Cu was constructed at optimum conditions. The linear range for
Cu was between 2.0-12.0 ppm. The regression equation, the correlation coefficient
(R2) and the detection limit obtained by this proposed technique were y = 0.0124x
+ 0.352 Cu. the Calibration curve was obtained using Calibration standards, and
the samples were analyzed. The results obtained were collected and further
calculations were interpreted using Microsoft Office Excel Worksheet. The
experiment includes preliminarily calibration. The unknown sample of Cu was
analyzed and the Copper content in the samples was out of the calibration range.
These samples were further diluted and brought into the range. These changes in
the concentrations of Cu standards may be due to loss of sample during procedure
or cross contamination of both the standards Skoog (2007). The results were more
precise and reproducible. The method developed for Copper was optimized in such
a way that the working conditions can precise and accurate and also addition of
EDTA caterd for the matrix effects Duran (2008)
reference
Sardans. (2009). Determination of As, Cd, Cu, Hg and Pb in biological Samples
by modern electro thermal atomic absorption spectrometry. 97-112. 19
Haroun. (2008). Analysis of heavy metals during composting of the tannery Sludge
using physicochemical and spectroscopic techniques. 111-119.
Hödrejärv. (1999). Pseudo-total analysis for metallic elements in siliceous soil By
acid digestion and flame atomic absorption spectrometry. 293-301.
Ghaedi. (2007). Cloud point extraction for the determination of copper, nickel and
cobalt ions in environmental samples by flame atomic absorption Spectrometry.
533-540.
Duran. (2008). Simultaneous preconcentration of co (ii), Ni (ii), cu (ii), and cd (ii)
from environmental samples on amber lite xad-2000 column and determination by
faas. 292
D.A Skoog, Principles of instrumental Analysis, 4th edition, chapter 10, 2007