Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p9
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 9/9)
Character Range: 738160–739414

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 laboratory to minimise time in transit.

Data for primary and duplicate is collated as a relative percent difference (RPD) of the mean concentration determined by both laboratories. Higher variations can be expected for organic analyses compared to inorganic analyses, and for samples with low analyte concentrations or non-homogeneous samples.

If results show greater than 30% difference, a review should be conducted of both laboratories and of the appropriateness of the methods being used.

    3.5.3         Replicates for volatile organic compound analysis
For analysis of volatile organic compounds (VOCs), field duplicate and secondary duplicate samples should be created as rapidly as possible by halving the sample and placing each half in a smaller container, compacting and topping up to achieve zero headspace in each, attempting to minimise volatile losses. They should be submitted as soon as possible to the laboratory/ies to prevent loss while in storage or transit.