1) Internal audits of the laboratory operations, performed by the QA officer and supervisor.
2) On-site evaluations by outside experts to ensure that the laboratory and its personnel are following an acceptable QA pro-grem
3) Performance evaluation studies, in which the QA officer works with the supervisor to incorporate unknown challenge sam-ples into routine analytical runs and laboratories are encouraged to participate in state and national proficiency testing and accred-itation programs. The collaborative studies confirm the abilies of alaboratory to generate acceptable data comparable to those of other laboratories and identify potential problems