escape from the cooler. This precaution may not be necessary if "blue" ice or other contained
coolants are used.
As specified in Chapter One of SW 846, a temperature history of the samples should
be maintained as a quality control measure. This is done by recording the temperature on the
chain of custody record (Section 7.6) before the sample containers are sealed for shipment.
Upon receipt of the shipment, the laboratory should record the temperature on the
chain of custody record.
Holding time refers to the period that begins when the sample is collected from the
well and ends with its extraction or analysis. Holding time is not measured from the time the
laboratory receives the samples.
Chain of Custody and Records Management
A chain of custody procedure should be designed to allow the owner/operator to
reconstruct how and under what circumstances a sample was collected, including any
problems encountered. Chapter One of SW 846 contains a complete description of chain of 
custody and records management. The chain of custody procedure is intended to prevent
misidentification of the samples, to prevent tampering with the samples during shipping and
storage, to allow easy identification of any tampering, and to allow for the easy tracking of
Sample Labels
To prevent sample misidentification, the owner/operator should affix a label to each
sample container. Sample labels should be sufficiently durable to remain legible even when
wet. Sample labels should contain, at a minimum, the following information:
Sample identification number;
Name and signature of collector;
Date and time of collection;
Place of collection; and
Parameters requested (if space permits).
The samples can be labeled by recording the above information directly on the sample
containers. Alternatively, the owner/operator may use multiple part labels consisting of a
unique identification number that is placed on the container. At least two copies of the
descriptive information for the samples (referenced to the identification number) should be
November 1992
7 25






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