Development, investigation, and optimization of an electrothermal vaporization unit with an axially focusing convection upstream for analysis of trace elements [Elektronische Ressource] / vorgelegt von Alexander Trenin

Informations

• Publié par: justus-liebig-universitat_giessen
• Publié le: 01 janvier 2006
• Nombre de lectures: 10
• Langue: English
• Poids de l'ouvrage: 7 Mo

Extrait

Development, Investigation, and Optimization of an
Electrothermal Vaporization Unit with an Axially Focusing
Convection Upstream for Analysis of Trace Elements









Inaugural-Dissertation
zur Erlangung des Doktorgrades
der Naturwissenschaften
der Justus-Liebig-Universität Gießen
Fachbereich 07 / Mathematik und Informatik, Physik, Geographie










vorgelegt von
Alexander Trenin
aus Kasan, Russische Föderation





I. Physikalisches Institut der Justus-Liebig-Universität Gießen
Juni 2006 2
Contents
CONTENTS........................................................................................................................................................... 2
SUMMARY........................................................................................................................ 5
ZUSAMMENFASSUNG..................................................................................................................................... 10
LIST OF ABBREVIATIONS............................................................................................................................. 16
1. INTRODUCTION AND PROBLEM STATEMENT............................................................................. 17
2. EXPERIMENTAL..................................................................................................................................... 24
2.1 ETV-AFC INSTRUMENTATION............................................................................................................ 24
2.1.1 Principle ........................................................................................................................................ 24
2.1.2 Construction and flow scheme....................................................................................................... 25
2.1.3 Temperature monitoring................................................................................................................ 27
2.1.4 External generator of gaseous additives to the internal flow ........................................................ 27
2.2 EXPERIMENTAL ARRANGEMENT.......................................................................................................... 28
2.2.1 Experimental arrangement for intra-furnace ETV sampling......................................................... 28
2.2.2 Principle of CFS spectrometry ...................................................................................................... 29
2.2.3 Software for ETV-EP CS-CFS measurement controlling and data acquisition............................. 31
2.2.4 for CS-CFS spectra evaluation....................................................................................... 32
2.3 AEROSOL TRANSPORT, DIVIDING, AND DOSING ................................................................................... 33
2.3.1 Principle ........................................................................................................................................ 33
2.3.2 Electrostatic sampling ................................................................................................................... 37
2.4 SAMPLES AND REAGENTS.................................................................................................................... 38
2.5 OPERATIVE PARAMETERS AND PROCEDURES 39
2.5.1 Sample analysis with intra-furnace EP ......................................................................................... 39
2.5.2 Sample analysis with external 10-fold precipitation unit .............................................................. 40
2.5.3 Sample analysis with addition of aqueous and gaseous modifiers ................................................ 40
2.5.4 Determination of analyte TEs........................................................................................................ 41
2.5.5 SEM and TEM investigations ........................................................................................................ 42
2.5.6 Temperature measurements in the upstream ................................................................................. 42
2.5.7 Determination of GF carbon losses...............................................................................................42
3. INVESTIGATION AND OPTIMIZATION OF THE ETV-AFC SETUP: INFLUENCES OF GF
CARBON, MODIFIERS, AND GASEOUS ADDITIVES ON THE TRANSPORT PROCESS OF
SAMPLE ANALYTES........................................................................................................................................ 44
Contents 3
3.1 ETV DEVELOPMENT............................................................................................................................ 44
3.1.1 Axially focusing convection (AFC) tube ........................................................................................ 44
3.1.2 Radiation shielding........................................................................................................................ 45
3.1.3 Comparison of analytical performances for ETV-FT and ETV-AFC instruments......................... 47
3.2 OPTIMIZATION AND CONTROLLING OF THE GF HEATING CONDITIONS................................................. 48
3.3 OPTIMIZATION OF THE ETV FLOW DISTRIBUTION ............................................................................... 50
3.4 MEASUREMENT OF TEMPERATURE DEPENDENCES ON THE AXIS OF THE AFC TUBE............................. 51
3.5 INVESTIGATION OF THE INFLUENCE OF GF CARBON ON ANALYTE TE 57
3.6 SEM AND TEM INVESTIGATION OF GF CARBON PARTICLES............................................................... 62
3.7 MODIFIER EFFECTS.............................................................................................................................. 66
3.7.1 Determination of analyte TEs with addition of K, Mg, and Pd modifiers...................................... 66
3.7.2 Determination of analyte TEs with C H addition to the ETV internal gas flow.......................... 68 6 12
3.7.3 Determination of anaby combined use of C H , KNO and Pd(NO ) ........................... 70 6 12 3 3 2
3.7.4 Behavior of the corona discharge current in presence of C H ................................................... 75 6 12
4. PLATFORM-TO-PLATFORM SAMPLE TRANSFER, DILUTION, DISTRIBUTION, AND
DOSING VIA ELECTROTHERMAL VAPORIZATION AND ELECTROSTATIC DEPOSITION....... 78
4.1 PRECISION AND REPRODUCIBILITY OF MEASUREMENTS ...................................................................... 79
4.2 FURTHER APPLICATIONS OF THE 10-FOLD PRECIPITATION UNIT .......................................................... 81
5. COMPUTER MODELING OF THE DYNAMICS OF SAMPLE ANALYTES AND GRAPHITE
FURNACE CARBON IN THE AXIALLY FOCUSING CONVECTION UPSTREAM.............................. 83
5.1 CONDENSATION PROCESSES ................................................................................................................ 83
5.1.1 Homogeneous analyte condensation ............................................................................................. 83
5.1.2 Heterogeneous analyte condensation ............................................................................................ 84
5.2 KINETIC MODEL .................................................................................................................................. 86
5.2.1 Rate of the carbon condensation process ...................................................................................... 87
5.2.2 Rate of the analyte condensation process 89
5.2.3 Attachment function....................................................................................................................... 90
5.2.4 Analyte distribution function ......................................................................................................... 91
5.2.5 Temperature dependence of the gas phase diffusion coefficients .................................................. 93
5.2.6 Estimation of evaporation rates for analytes and carbon.............................................................. 94
5.3 RESULTS AND DISCUSSION .................................................................................................................. 96
5.3.1 Carbon condensation......... 97
5.3.2 Analyte dynamics without condensation...................................................................................... 102
5.3.3 Analyte dynamics with condensation........................................................................................... 102
5.3.4 Influence of modifiers on analyte condensation .......................................................................... 109
5.3.5 Comparison with experimental data............................................................................................ 109
6. CONCLUSIONS ...................................................................................................................................... 112
APPENDIX ........................................................................................................................................................ 116
Contents 4
A.1 LIST OF FIGURES....................................................................