ABSTRACT
CONTENTS Sample Pretreatment Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Sample Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 What Fiter Pore Size to Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Functions of Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 Which Parameters to Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 Sources of Error and Bias in Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 Filtration Methods and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Filter Preconditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Sample Preservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Objectives of Sample Preservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Physical Preservation Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 Chemical Preservation Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Another group of parameter-specific field protocols that must be evaluated and included in the SAP are methods for sample pretreatment, including sample filtration and physical and chemical preservation. Sample pretreatment must be performed at the wellhead at the time of sample collection to ensure that physical and chemical changes do not occur in the samples during the time that the sample is collected and after the sample container has been filled and capped. ASTM International has published Standard Guides that address both types of sample pretreatment. ASTM Standard D 6564 (ASTM, 2006a) provides a detailed guide for field filtration of ground-water samples, and ASTM Standard D 6517 (ASTM, 2006b) discusses physical and chemical preservation methods for ground-water samples. Each type of sample pretreatment is discussed subsequently.
Sample Filtration
