CTI provides heavy metal chemical analysis services related to quality control samples, which are mainly used for method verification and confirmation, quality assurance of the testing process, etc., and can be used for blind samples for on-site review, supervisory review, reassessment and unannounced inspections by regulatory agencies. It can be used for internal audit, daily quality supervision, quality assessment, personnel assessment, method comparison, personnel comparison, equipment comparison, etc. accused samples or blind samples of the laboratory.