vIll CONTENTS 1.5. Postextraction procedures 21 1.5.1. Concentration of Sample Extracts 1.6. Quality Assurance and Quality Control during Sample Preparation 1. 1. Determination of Accuracy and Precision 16.2. Statistical Control 1.6.3. Matrix Control 164. Contamination control SECTION A EXTRACTION AND ENRICHMENT IN SAMPLE PREPARATION CHAPTER 2 PRINCIPLES OF EXTRACTION AND THE EXTRACTION OF SEMIVOLATILE ORGANICS FROM LIQUIDS Martha J. m. wells 2.1. Principles of Extraction 2.1.1. Volatilization 2. 1.3. Acid-Base Equilibria 2. 1.4. Distribution of Hydrophobic Ionogenic Organic Compounds 2.2. Liquid-Liquid Extraction 2. 2.1. Recovery 770 2.2. 2. Methodology 2.2.3. Procedures 2.2.4. Recent Advances in Techniques 2.3. Liquid-Solid Extraction 2.3.1. Sorption 2 4. Solid-Phase Extraction 2,41. Sorbents in spe 2.4.2. Sorbent selection 2.4.3. Recovery 4588%9 2.4. 4. Methodology1.5. Postextraction Procedures 21 1.5.1. Concentration of Sample Extracts 21 1.5.2. Sample Cleanup 22 1.6. Quality Assurance and Quality Control during Sample Preparation 25 1.6.1. Determination of Accuracy and Precision 28 1.6.2. Statistical Control 29 1.6.3. Matrix Control 31 1.6.4. Contamination Control 32 References 35 SECTION A EXTRACTION AND ENRICHMENT IN SAMPLE PREPARATION CHAPTER 2 PRINCIPLES OF EXTRACTION AND THE EXTRACTION OF SEMIVOLATILE ORGANICS FROM LIQUIDS 37 Martha J. M. Wells 2.1. Principles of Extraction 37 2.1.1. Volatilization 38 2.1.2. Hydrophobicity 43 2.1.3. Acid–Base Equilibria 50 2.1.4. Distribution of Hydrophobic Ionogenic Organic Compounds 57 2.2. Liquid–Liquid Extraction 57 2.2.1. Recovery 60 2.2.2. Methodology 66 2.2.3. Procedures 68 2.2.4. Recent Advances in Techniques 72 2.3. Liquid–Solid Extraction 74 2.3.1. Sorption 75 2.4. Solid-Phase Extraction 78 2.4.1. Sorbents in SPE 81 2.4.2. Sorbent Selection 96 2.4.3. Recovery 99 2.4.4. Methodology 108 viii contents