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