What is the importance of chain of custody documentation in environmental sampling?

The importance of chain of custody documentation in environmental sampling is to maintain a complete and accurate record of the sample's possession from the point of collection to the point of analysis, ensuring the integrity and defensibility of the analytical results. Chain of custody (COC) documentation is a legal record that tracks the handling and storage of a sample, demonstrating that it has not been tampered with or compromised during its journey from the field to the laboratory. The COC form typically includes information such as the sample identification number, date and time of collection, location of collection, name of the sampler, analyses requested, and signatures of all individuals who have handled the sample, along with the dates and times of transfer. Proper COC documentation is essential for ensuring that the analytical data is legally defensible and can be used in regulatory compliance, enforcement actions, or litigation. Without a proper COC, there is no guarantee that the sample analyzed in the laboratory is the same sample that was collected in the field, and the analytical results may be deemed invalid. The COC form is typically sealed with the sample container to prevent tampering. The laboratory will also maintain its own internal chain of custody procedures to track the sample within the lab. Any break in the chain of custody can raise questions about the validity of the data.