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You have no doubt
heard about Chain of Custody (COC)
issues in the many forensic TV shows on our screens. The shows where faulty documentation
destroys an otherwise carefully prepared case and the criminal goes free! So exactly what is a COC? It is the chronological ‘paper’ trail,
showing the collection, transfer, receipt, analysis, storage, and disposal of a
sample. At all stages, the sample is in someone’s custody—that person is responsible for it.
The COC is just as important in environmental and agricultural sciences -the integrity of the sampling, testing and
reporting chain is very important, as the test results might also be used as
evidence in court cases. For example, if a factory is accused of dumping toxic
waste that runs into rivers and makes people ill, any samples taken to prove or
disprove this must be handled correctly from ‘A to Z’ , as indicated by the
Field sampling is an important part of the environmental and agricultural sciences and evidence of this is the first step shown in a COC. Samplers
might collect anything from invertebrates and algae samples from rivers for
ecological sampling, crop seed samples for analysis, mine bore water samples or contaminated soil samples from
reclamation projects. Sampling procedures usually
follow government, EPA or other standard guidelines and the samples are logged
on the required forms. Samples are often collected in special containers including
sterile jars, bottles with preservatives (to try and minimise the degradation of
the sample), vials for organic testing etc. Once sampled, they must be
correctly stored (often at temperatures <6oC) and they can then be
transferred to a laboratory (lab) for testing (second step in the COC). At the
lab, the sample receiver will check the integrity and storage of the sample and
will log the sample in for testing (step 3).
An example of a COC
for sample collection, delivery and receipt at a testing lab is shown above.
All respective sections have to be completed and signed off by the relevant
person (sampler, transporter and lab receiver—all shown encircled in red). Once
in the lab, the storage, testing, reporting and disposal must all be similarly
controlled, with each step in the process correctly documented.
To find out more about
environmental sampling and testing, have a look
at our Environmental-Chemistry course which starts at basics and leads you into the fascinating world of chemicals in our environment. Or
check out our Environmental-assessment