Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 5/9)
Character Range: 727121–730149

3.3.2         Method blank
This refers to the component of the analytical signal that is not derived from the sample but from reagents, glassware, analytical instruments, etc. It can be determined by processing solvents and reagents in exactly the same manner as for samples. When laboratories report method blanks, the uncorrected result and the method blank should be reported in the same units of measurement.

There should be at least one method blank per process batch.

Method blank data is reported with the primary sample data, thus enabling the site assessor to assess potential method bias for the relevant analytes.

    3.3.3         Laboratory duplicate analysis
This is the analysis of a duplicate sample from the same process batch. If possible, the sample selected for duplicate analysis should have an easily measurable analyte concentration. The variation between duplicate analyses should be recorded for each process batch, to provide an estimate of the method precision and sample heterogeneity.

Samples reasonably perceived to contain target analytes should be chosen for the duplicate analyses, though samples with obviously high concentrations of interferents—which will likely require subsequent dilution of sample extracts and raised LORs—should not be used for duplicate analysis. There should be at least one duplicate per process batch, or two duplicates if the process batch exceeds 10 samples.

If results show greater than 30% difference, the analyst should review the appropriateness of the method being used.

Duplicate analysis data is reported with the primary sample data, thus enabling the site assessor to assess method precision for the relevant analytes.

    3.3.4         Laboratory control sample
A laboratory control sample (LCS) comprises a standard reference material, or a matrix of proven known concentration or a control matrix spiked with all analytes representative of the analyte class. Representative samples of either material should be spiked at concentrations equivalent to the midpoint of the preceding linear calibration or continuing calibration check, upon which sample quantification will be based. Thus the concentrations should be easily quantified and be within the range of concentrations expected for real samples.

The LCS should be from an independent source to the calibration standard, unless an ICV (independent calibration verification) is used to confirm the validity of the primary calibration.

There should be at least one LCS per process batch.

LCS percent recovery data is reported with the primary sample data, thus enabling the site assessor to assess method accuracy for all targeted analytes, as distinct from method accuracy for site-specific soil samples (see Section 3.3.5 Matrix spikes below). The laboratory should use statistically derived quality control limits from ongoing LCS percent recovery data, for all target analytes, and report such QC limits with the sample data.

    3.3.5         Matrix spikes
A matrix is the component or