ABSTRACT
Sample custody is the process of protecting the samples collected and analyzed by the laboratory. Sample custody documentation has to involve all of the records that have been composed during the sample collection and through the laboratory analytical processes. All documentation must be signed or initialed by the responsible person, and recorded with waterproof ink. If all of the samples and documentation are checked and accepted, samples have to be logged into a laboratory log book. Each sample receives a laboratory identification number given to the sample label. An important part of the laboratory custodian's work is the proper storage of the samples and the documentation of the holding time. Sample pretreatment prior to the actual analysis, such as digestion, extraction, distillation, filtration, etc. has to be documented on a sample preparation log form. All numerical data relating to the preparation processes and that need further calculations should be briefly documented.
