NG28 provides chemical analysis services for standard substances 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 accused samples or blind samples such as laboratory internal audit, daily quality supervision, quality assessment, personnel assessment, method comparison, personnel comparison, and equipment comparison.