The study of the sources, effects, and transport of organic pollutants in the environment has. been the subject of intense scrutiny in recent years. Since some of these compounds are considered to be toxic at very low concentrations, analysis methods are required that are capable of achieving accurate, precise determinations at lower than parts-per-billion concentrations. As environmental legislation in many countries is becoming stricter the quality control (QC) and quality assurance (QA) procedures are followed as per the specific methodologies employed.