SPEClATlON OF ARSENIC AND NEUTRON ACTIVATION ANALYSIS Youqing Shi

215 Pages·2002·10.27 MB·English

SPEClATlON OF ARSENIC
BY CHEMICAL SEPARATIONS
AND NEUTRON ACTIVATION ANALYSIS
Youqing Shi
Submitted in partial fulfîllment of the requirements
for the degree of Doctor of Philosophy
at
Dalhousie University
Halifax, Nova Scotia
2000 December
O Copyright by Youqing Shi, 2000
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TABLE OF CONTENTS
Table of contents
List of Tables
List of Figures
Abstracts
List of Abbreviations and Symbols
Acknowledgements
1. INTRODUCTION
1.1 Chemical Speciation
1.2 Speciation Techniques
1.3 Neutron Activation Analysis
1.4 Importance of Speciation of Arsenic
1.5 Objectives
2. LITERATURE SURVEY
Solvent Extraction in Speciation Analysis of Arsenic
Coprecipitation and Solid-Phase Extraction in Speciation
Analysis of Arsenic
Hydride Generation, Cryotrapping and Thermal
Desorption in Speciation Analysis of Arsenic
Ion-Exchange Chromatography in Speciation Analysis of
Arsenic
Sp eciation of Arsenic by High-performance Liquid
Chromatography
v
2.6 Speciation of Arsenic by Electrochemical Techniques
2.7 Methods for Speciation of Arsenic Based on NAA
3.1 Neutron Activation Andysis
3.1.1 Neutron Irradiation Facility and Counting
S ystems
3.1- 2 Elemental Comparator Standards for NAA
3.1.3 Comparator Standards for Speciation Analysis
3.2 Materials and Apparatus for Separation Methods
3.2.1 Speciation Standards
3.2.2 Reagents
3.2.3 HPLC System
3.2.4 Other Apparatus and Equipment
3.3 Certified Reference Materials
3 -4 Preparation of Disodium Monomethylarsonate
3.4.1 Synthesis and Purification of MMA
3.4.2 Identification of MMA
3 -5 Sample Collection and Preparation
3 S. 1 Natural Water Sample Collection
3.5.2 Filtration and Acidification of Water Samples
3.5 -3 Lyophilization of Fish Samples
3.5.4 Homogenization of Fish Sarnples
3.6 General Procedures for Solvent Extraction
3.7 Generai Procedure for Solid-P hase Extraction
vi
3 -7.1 Adsorption of HDBDC on XAD-4 Resin
3 J.2 Soiid-phase Extraction Experiment
3 -8 General Procedure for Ion-exchanger Chromatography
3.8.1 Static Distribution Experiments
3.8.2 Column Separation
3 -9 General Procedure for HPLC Separati on
4. DEVELOPMENT OF METHODS FOR THE SPECIATION
OF ARSENIC
4.1 Separation of Arsenic Species by Cation Exchange
Chromatography
4.1.1 Distribution Coeficients of Arsenic, Antimony
and Selenium Species
4.1.2 Elution of Arsenic Species from the Cation
Exchange Column
4.1.3 Effect of Column Height on the Retention of
DMA
4.1.4 Elution of DMA and AsB from the Cation
Exchange Column
4.1.5 Conclusions
4.2 Separation of Arsenic, Antimony and Selenium Species
by Solvent Extraction
Selection of a Solvent
Selection of a Chelating Agent and pH
Effect of pH on the Extraction of MMA, DMA
and AsB
Back Extraction of As@), Sb@) and S e o
vii
4.2.5 EEectofPhaseVolumeRatioonExtractionand
Back Extradon
4.2.6 StabilityofPDCComplexesofAs(IIi),Sb(IIQ
and S e o
4.2.8 Reduction and Extraction of MMA, DMA and
AsB and Their Potential Interference to the
Determination of As(V) Species
4.3 Separation of Arsenic, Antimony and Selenium Species
by Solid-phase Extraction
4.3.1 Preparation of Chelating Agent Impregnated
Resin
4.3.1.1 Spectrophotometnc Determination of
Chaleting Agents
4.3.1.2 Adsorption of Various Forms of
Chelating Agents
4.3.1- 3 Rate of Adsorption
4.3 - 1- 4 Adsorption Isotherm
4.3.2 Separation of Arsenic, Antimony and SeIenium
Species by SPE
4.3 -3 Conclusions
4.4 Separation of Arsenic Species by HPLC
4.4.1 General Considerations for Coupling HPLC with
NAA
4.4.2 Separation of A@) from AsB by HPLC
4.4.3 Separation of AsB, DMA and MMA by HPLC
4.4.4 Separation of As(m), As(V) and MMA by
HPLC
4.4.5 Setection of a Fraction Volume
4.4.6 Potential Multielement Speciation Analysis by
HPLC-NAA
4.4.7 Conclusions
5. SPECIATION OF ARSENIC, ANTlMONY AND SELENZUM
IN NATURAI.. WATERS
5.1 Solvent Extraction of Inorganic Arsenic, Antimony and
Selenium Species
5.1.1 Sensitivities and Detection Limits for Arsenic
and Antimony
5.1.2 Sensitivities and Detection Limits for Seleniurn
5.1- 3 Determination of Inorganic Arsenic, Antimony
and Selenium
5.1.4 Inorganic Arsenic, Antimony and Selenium in
CRMs
5.2 Detennination of Inorganic and Organic Arsenic in
Natural Waters
5.2.1 Rewmmended Scheme for Speciation of
Arsenic in Natural Waters
5.2.2 Speciation of Arsenic in a Riverine Water CRM
5.2.3 Sensitivities and Detection Limits for Various
Arsenic Species
6. SPECIATION OF ARSENIC IN SEAFOODS
6.1 Method for Extraction of Arsenic Species fiom Fish
6.1.1 Selection of Solvents
6.1.2 Effect of Number of Extractions on Extraction
Yield
6.1.3 Effect of Lipid Content on Extraction Yield
6.2 Recomrnended Scheme for Speciation of Arsenic in Fish
Samples
6.3 Determination of Arsenic by INAA
6.3.1 Determination of Total Arsenic
6.3.2 Deterrnination of Residual Arsenic after
Methanol-MIBK- Water Extraction
6.3 -3 Determination of lipid-soluble Arsenic
6.3.4 QuaIity Assurance for Arsenic by INAA
6.4 Speciation of Arsenic in Selected Fish Samples
6.4.1 Total Arsenic
6.4.2 Lipid-Soluble Arsenic
6.4.4 Spiking Experiments
6.4.5 Accuracy of Measurements
6.4.6 Detection Limits
7. CONCLUSIONS AND RECOMMENDATIONS
REFERENCES
LIST OF TABLES
Table
1.1 A summary of separation and detection techniques used
for speciation analysis
Sp eciation of arsenic by solvent extraction
Speciation of arsenic by coprecipitation and solid-phase
extraction
Speciation of arsenic by hydride generation,
cryotrapping and selective volatilization
Speciation of arsenic by open column ion exchange
chromatography
p K v alues of some weak acids of arsenic
Speciation of arsenic by HPLC
Speciation of arsenic by NAA
Nuclear data for some elements of interest
I(d of various species on cation exchange resin at
different conditions
Recovery of Asw), S b 0a nd &(IV) by using
different solvents
Back extraction recovenes by different concentrations
of HNO3
Loss of As(III) during evaporation of MIBK
Reduction yields of AiV), S b 0 a nd S e ob y 5% L-
cysteine solution at different pH
Yields of extractable reduction products of MMq DMA
and AsB
Adsorption of dithiocarbarnate on XAD-4 resin
Values for the Freundlich equation constants