Simultaneous determination of trace elements using multi-element graphite furnace atomic absorption spectrometry [Elektronische Ressource] / von Khaled Elsherif

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• Publié par: universitat_duisburg-essen
• Publié le: 01 janvier 2009
• Nombre de lectures: 34
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Simultaneous Determination of Trace
Elements using Multi-Element Graphite
Furnace Atomic Absorption Spectrometry
dem Fachbereich Chemie (IAC)
der Universität Duisburg-Essen
Zur Erlangung des akademischen Grades eines
Dr. rer. nat.
genehmigte Dissertation
von
Khaled Elsherif
aus Benghazi / Libyen
Referent: Prof. Dr. Heinz-Martin Kuss
Korreferent: Priv. Doz. Dr. Ursula Telgheder
Datum der Einreichung 11.12.2008
Datum der mündlichen Prüfung 24.03.2009
Acknowledgements
I am indebted to many people for their long-lasting support and encouragement which was
invaluable for the successful completion of this research work. In the following lines some of
them are gratefully acknowledged. However, I am aware of the fact that there are many more
and these words cannot express the gratitude and respect I feel for all of those.
Firstly, I like to take this opportunity to thank the people who provided scientific and financial
support to make this work possible. I must thank Prof. Dr. Heinz-Martin Kuss who initiated
the thesis projects, offered me a warm welcome in his group and gave me the unique
opportunity to use the research facilities in his lab.
My sincere thanks go to many friends and colleagues for scientific discussion, advice and
continuous support always so greatly appreciated, among them Dr. Abdelsalam Asweisi and
Dr. Bülend Bayraktar who introduced me to the secrets of Graphite Furnace Atomic
Absorption spectroscopy and for many valuable ideas and suggestions. I like to express
further greatest thanks for help and encouragement to my friends Dr. Roman Rodreguez,
Rajab El-kailany, Nabil Bader and others.
Last but by no means least, I like to thank my family and close relatives for general education
and the opportunity to start and pursue a career in science. I am particularly indebted to my
parents for their never-ending encouragement and ongoing support. Very special thanks go to
my wife for her patience during my work and finding supporting words of deep sense, not
always related to science but to life in general.


Abstract
Simultaneous Multi-Element Atomic Absorption Spectrometer (SIMAA 6000) has been
used to determine groups of elements (up to four) simultaneously, by using 2-operating and 4-
operating modes. A direct, simple, fast and accurate methodology for the simultaneous multi-
element determination have developed. Compromised conditions (e.g. temperature program
and use of universal modifier) for the multi-element mode have been determined. The
temperature program has been carefully optimized for the multi-element mode taking into
account all analytes to be determined. The optimization depends on the elements to be
determined simultaneously and the matrix. Also, a universal powerful matrix modifier has
been used in order to increase the stability of the elements (especially the volatile elements).
This has permitted the use of a common temperature program including volatile and less
volatile elements. The Pd+Mg mixture modifier has stabilized the high and mid volatile
elements. For less volatile elements, the modifier had no stabilization effect on these
elements. But the modifier in this case has prevented the formation of refractory compounds
which increase the volatilization process of these elements. Ir coating of the tube or platform
has extended significantly the tube lifetime. The sensitivity values for the multi-element
determination were comparable to those of the single-element. The decreasing in sensitivity
values is a result of using higher atomization temperature in the multi-element mode and/or
decreasing the lamp intensities. The detection limits values of the multi-element
determination were higher than those of the single-element which is mainly as a result of
decreasing the lamp intensities in the multi-element mode compared to the single-element
mode. Another effect which could cause the higher detection limits is the use of higher
atomization temperature. The operational conditions (the temperatures, use of modifier, and
the operating mode) have affected the absorption signals of the elements. This effect has
appeared in terms of increasing or decreasing the appearance time, peak height, and peak
width. The accuracy of the methods was tested by analyzing number of certified materials and
the concentrations obtained were in good agreement with certified values
I. Table of Contents

II. List of Figures .................................................................................................................... 7
III. List of Tables........ 13
1 Introduction to Multi-Element Graphite Furnace Atomic Absorption Spectrometry ...... 19
1.1 Review...................................................................................................................... 19
1.2 Basic Features of the GFAAS .................................................................................. 20
1.2.1 System Design..................................................................................................20
1.2.2 Temperature Program.......................................................................................21
1.2.2.1 Drying Step21
1.2.2.2 Pyrolysis Step...............................................................................................22
1.2.2.3 Atomization Step..........................................................................................22
1.2.2.4 Cleaning Step23
1.2.3 Background Correction....................................................................................24
1.2.3.1 Continuum Source........................................................................................24
1.2.3.2 Self-Reversal Methods.................................................................................24
1.2.3.3 Zeeman-Effect..............................................................................................25
1.2.4 Atomization Mechanism & Stabilization in Graphite Furnace........................ 27
1.3 Simultaneous Multi-Element Graphite Furnace AAS Systems ............................... 29
1.3.1 Line Source Multi-Element Systems................................................................ 30
1.3.1.1 Model Z-9000 from Hitachi ......................................................................... 30
1.3.1.2 AA Scan 4 from Thermo-Jarrell Ash ........................................................... 30
1.3.1.3 Analyte 5 (Leeman Labs)............................................................................. 31
1.3.1.4 SIMAA 6000 from Perkin-Elmer................................................................. 31
1.3.2 Continuum Source Multi-Element Systems..................................................... 31
1.3.3 Summary..........................................................................................................32
2 SIMAA 6000 Design and the Multi-Element Compromised Conditions ........................ 33
12.1 Overview..................................................................................................................33
2.2 Basic Features of SIMAA 6000 System .................................................................. 33
2.2.1 Furnace Design (Transversely Heated Graphite Atomizer THGA)................. 35
2.2.1.1 The Stabilized Temperature Platform Furnace (STPF)................................ 36
2.2.2 The Tetrahedral Echelle Polychromator Optical System (TEP) ...................... 38
2.2.3 Solid-State Detector.........................................................................................40
2.3 Compromised Conditions for Simultaneous Multi-Element Determinations .......... 41
2.3.1 Pyrolysis and Atomization Temperatures ........................................................ 42
2.3.2 Chemical Modification.....................................................................................43
2.4 Important Terms.......................................................................................................46
2.4.1 Sensitivity and Characteristic...........................................................................46
2.4.2 The Detection Limits........................................................................................ 47
3 Aims................................................................................................................................. 49
4 Experimental Section.......................................................................................................50
4.1 Instrumentation.........................................................................................................50
4.2 Reagents and Standard Solutions ............................................................................. 50
4.3 Sample Preparation..................................................................................................52
4.3.1 Trace Elements Urine Sample (Seronorm 0511545) ....................................... 52
4.3.2 Lyphocheck Urine Metals Control-Level 1 (69061)........................................ 53
4.3.3 Pork Liver (GBW 08551), Pig Kidney (BCR-CRM 186), and Bovine Liver
(NIST-SRM 1577b).......................................................................................................... 53
4.3.4 Tea Sample (GBW 08505)...............................