Transcript Determination of metal concentrations in surface waters and soils
Ivane Javakhishvili Tbilisi State University
Faculty of Exact and Natural Sciences Substance Research Institute
Ketevan Museridze
[email protected]
Determination of Metal Concentrations in Surface Waters and Soils Using Atomic Absorption Spectrometer
Atomic absorption spectroscopy is a common technique used in many chemical measurements requiring a high degree of precision and accuracy, such as food & drug safety, clinical diagnostics and environmental sampling.
Atomic absorption spectrometers may be used to analyze the concentration of over 70 different elements in a given sample solution, making them a very valuable instrument in any laboratory.
Method
We used Atomic-Absorption spectrometer AAnalyst 800 (Producer – company PerkinElmer Inc., USA; year of produce – 2003) for determination of the metal concentration in water ( Cu, Pb, Zn, Ni, Co, Mo, Cr, Mn, Cd, Ag) and soil ( Cu, Pb, Zn, Ni, Co) samples. Electrothermal and flame methods of atomization were used.
A spectrometer is fully operated via computer, using the software support WinLab32. The given program provides full automatic control of the device, allows us to make changes in the methods, memorize and receive information of measurements of the particular group of elements in a desirable form.
The basic components of an atomic absorption instrument:
The light source that emits the spectrum of the element of interest; An “Absorption cell” in which atoms of the sample are produced (flame, graphite furnace); A monochromator for light dispersion; A detector that measures the light intensity; A display that shows the reading after it has been processed by the instrument electronics.
Light source Sample Cell Flame or Furnace Specific Light Measurement Monochromator Detector Electronics Readout
The light source (hollow cathode lamp) emits a spectrum specific to the element of which it is made, which is focused through the sample cell into the monochromator.
The method of heavy metal definition via Atomic-absorption spectrometer is based on the properties of specific metal atoms to absorb specific wavelength of light. The electronics will measure light attenuation and convert those readings to the actual metal concentration of the sample.
Putting lamps for various metals
The lamp holder with positions for 8 source lamps allows having 8 lamps simultaneously that are prepared for work and can pass from one element to another.
Process of measurements
Choose a desired method of atomization by means of the computer, with use of software support WinLab32 1.
When using the electrothermal atomization method the aliqoute part of a sample is put in a graphite furnace of the spectometer using sampling device (autosampler) According to the programme, heating of a sample is performed in the inert gas (argon) stream, including drying, incineration, atomization of a sample and clean-out of the furnaces.
2. The flame atomization method is also used. The injectoration of the analyzed portion of the sample in the flame of a torch is performed by means of capillary. The mix of air – acetylene is used for the formation of a flame.
Reactants and equipment are necessary for measurements
Adjustable pipette
A nitric acid of special cleanliness Deionized water Adjustable pipettes Measuring Flasks Gaseous Argon of high cleanliness Gaseous Acetylene of high cleanliness Atomic Spectroscopy Single-Element Pure Standards.
Measuring Flasks Standards
Kura (
მტკვარი
-Mtkvari) Starting in northeastern Turkey, it flows through Turkey to Georgia, then to Azerbaijan, and enters the Caspian Sea. The total length of the river is 1,515 kilometers.
Water sample preparation for measurement
Soil sampling
10
Prior to atomic absorption spectroscopy analysis, some samples (soil) must be digested to ensure for accurate analyte measurement, which can be performed by using
BERGHOF speedwave MWS-3
The Berghof
MWS-3 microwave pressure digestion system enables
considerably shorter sample preparation times to be achieved (with digestion duration of 15-20 minutes on average) for sophisticated analysis and routine laboratory application.
Preparing soil samples
We put sample of dried soil in a mortar; Crushed it with pestel and sieved (150 µm); Weighed approximately four grams of sample with the precision of 0.001 gram; Put the sample into a fission container of microwave system;
Added to the sample hydrocloric acid of 21 mililiter; Then added drop by drop nitric acid of 7 mililiter; Fissured it according to the program; Filtered the obtained extract in 50 ml measuring retort, washed off residue on the filter with deionized water; Measured metals in the obtained filtrate.
Quality Assurance of Measurements
Transport Blank -
Distilled water taken from the laboratory to the sampling site and returned to the laboratory unopened; it is used to document contamination caused by the laboratory conditions, transporting and field handling procedures.
Transfer Blank -
Distilled water which is subject to all aspects of sampling and analysis excluding the contact with all samplers and apparatus; it is used for checking the possible contamination from the environment.
Rinsate (equipment) blank
Distilled water which is subject to all aspects of sampling and analysis including the contact with all samplers and apparatus; it is used to determine the quality of cleanliness of samplers and apparatus for sampling before sending them to the field site.
Check-out standards –
Sample with known concentration of analyte , is used for checking that the analytical accuracy is under control and the level of displacement caused by calibration is satisfactory.
Analytical duplicate
– two identical aliquots of sample collected at the same time, at the same place and handled in exactly the same manner; they are used as a measure of precision associated with sample handling, storage, preparation, and analytical procedures.
Blanks
– distilled water to which all reagents are added in the same volumes that are used in the same processing. It should be carried through the complete resulting from the analytical process.
# 1 2 3 4 5 6 7 8 9 10 Metal
Cu Pb Zn Ni Co Mo Cr Mn Cd Ag
Obtained Results
MDL µ g/l
Method Detection Limit
1.5
River Water µ g/l
9.8
0.7
1.5
0.5
0.7
0.3
0.1
0.3
0.05
0.1
0.70
12.8
1.12
0.12
3.2
2.2
12.4
0.050
0.100
Soil mg/kg
40.59
9.3
62.13
43.95
3.06
Future work The world’s largest lysimeter network
SOILCan investigates material and water fluxes in the soil as well as soil balances. This kind of data is lacking world-wide, but is absolutely crucial for the development and improvement of models for the exchange processes between the biosphere, atmosphere and hydrosphere.
References
AAnalyst 600/800 atomic absorption spectrometers http://www.perkinelmer.com/CMSResources/Images/44-74392BRO_AAnalyst600800.pdf
D.Kekelidze, G.Kekelidze, K.Tsetskhladze, G.Tsotadze, O. Sulava. The Use of Atom-Absorption Spectrometer Perkin-Elmer AAnalist800 During the Surface Water Analysis. Problems of river Monitoring and Ecological Safety of south Caucasus. U.S. Civilian Research and Development Foundation. pp. 228 233.
T. Jakhutashvili, N.Kekelidze, E.Tulashvili. Some Aspects of Methodology of Works on Quality Assurance of Measurements at Field and Laboratory Researches. Problems of river Monitoring and Ecological Safety of south Caucasus. U.S. Civilian Research and Development Foundation. pp. 3003-3008.
Atomic Absorption Spectroscopy.
http://www.aurorabiomed.com/atomic-absorption-spectroscopy.htm
Atomic absorption spectroscopy.
http://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy tereno-newsletter-2011-1-engl.
http://teodoor.icg.kfa-juelich.de/tereno-newsletter/newsletter/tereno-newsletter-2011-1-engl.pdf/view TERENO – Finding local solutions to global change.
http://www.trio-medien.de/uploads/media/TERENO-Imagebrosch%C3%BCre.pdf