Quality Assurance (QA) is a definite plan for laboratory operation that specifies standard procedures that help to produce data with defensible quality and reported results with a high level of confidence. It is a necessary part of data production, and it serves as a guide for the operation of the laboratory for production data quality. The basic requirements of a quality assurance program are to recognize possible errors and to develop techniques and plans, and to minimize errors. It also includes evaluating what was done and reporting evaluated data which are technically sound and legally defensible. Quality Control (QC) is a mechanism established to control errors. It is a set of measures within a sample analysis methodology to assure that the process is in control. Quality Assessment is the mechanism to verify that the system is operating within acceptable limits.