Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p8
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 8/9)
Character Range: 735383–738429

so that all relevant information may be easily retrieved. This helps establish chain-of-custody of the sample and traceability of all data, and enables reviewing the analysis during an audit or investigation of a questionable result.

This data retention requirement applies to both hard copy data and data in electronic formats. Laboratories should ensure adequate electronic data storage and backup to ensure data and documentation relating to analyses can be retained.

3.5              Field duplicate and secondary duplicate (split) samples
These field QC processes are implemented by the site assessor rather than the laboratory though laboratories and sample collectors should both be aware of the requirement and purpose.

    3.5.1         Field duplicate
Field Duplicate: a blind field replicate sample submitted to the laboratory to provide a check of the precision (repeatability) of the laboratory's analysis.

At least 5% of samples (i.e. 1 in 20 samples) should include a larger than normal quantity of soil collected from the same sampling point, removed from the ground in a single action if possible, and mixed as thoroughly as practicable and divided into two vessels. These samples should be submitted to the laboratory as two individual samples and coded separately to avoid identification of their common source.

A similar test of analysis repeatability is provided by re-submission of previously analysed samples, provided the stability of analyte is adequate under the storage conditions used between the two submission dates.

Data for primary and duplicate is collated and reported as a relative percent difference (RPD) of the mean concentration of both samples. If results show greater than 30% difference, a review should be conducted of the cause (e.g. instrument calibration, extraction efficiency, appropriateness of the method used, etc.).

    3.5.2         Secondary duplicate
Secondary Duplicate: a blind field replicate sample submitted to a secondary laboratory (inter-laboratory check sample) to provide a check of the analytical performance of the primary laboratory and specifically, the reproducibility of primary laboratory data.

At least 5% of samples from a site should be homogenised and split, with one duplicate sample set submitted to a secondary laboratory (independently accredited for ISO 17025, by NATA or one of its mutual recognition agreement partners) and the remaining samples submitted to the primary laboratory. The duplicate sample should be submitted independently and coded to avoid identity as a duplicate sample. The client should stipulate that each laboratory analyses the split samples for the same analytes using, as far as possible, the same methods recommended in these guidelines.

For comparability of data, there should be minimal delay in sample submission to each laboratory to allow minimum time difference between analyses, especially for analysis of volatile analytes. It is best practice to submit the secondary duplicate ('check sample') directly to the secondary