Schedule B3 - COAG Standing Council on Environment and Water

ut which:
• are not expected to be found in real samples
• will not interfere with quantification of any analyte of interest
• may be separately and independently quantified by virtue of, for example, chromatographic
separation or production of different mass ions in a GC/MS system.
Surrogates can provide a means of checking that no gross errors have occurred at any stage of
the procedure and which may cause significant analyte losses.
Surrogate spikes are only appropriate for analyses of organics, for example, chromatographic
analyses. Where they are used, they should be added to all samples being analysed and are
added to the analysis portion before extraction. Surrogate spike compounds may be deuterated,
alkylated or halogenated analogues, or structural isomers of analyte compounds.
4.2.7 Internal standards (where appropriate)
Use of internal standards is highly recommended for chromatographic analysis of organics and
some inorganic analyses, to check the consistency of the analytical step (e.g. injection volumes,
instrument sensitivity and retention times for chromatographic systems) and to provide a
reference against which results may be adjusted in case of variation (for organics analysis only).
Internal standards are added to each final extract solution, after all extraction, clean-up and
concentration steps. The addition is a constant amount of one or more compounds with
qualities like those listed above.
Adjustments for variations in injection volume and instrument sensitivity are made by
calibrating against the ratio of:
(peak height or area for analyte/s) : (peak height or area for internal standard/s).
Such adjustment should only occur where variation in internal standard signal is within predefined
limits.
Note: Chromatograms for final extracts may contain both internal and surrogate standards. The
compounds used for these standards may be similar but their addition at different analytical
stages provides different information.
Results of QC procedures should be recorded and maintained for a sufficient time to establish
method reliability, confidence intervals for analysis results and trends in precision and accuracy
over time or with variation of equipment or analyst.
4.3 Method validation
This is the process of obtaining data on a method in order to determine its characteristic
performance and to establish confidence that use of that method provides reliable results.
Method validation needs to be performed for each laboratory before being adopted and applied
to the analysis of actual samples.
All validation steps pertaining to the method should be recorded and retained while the
method is being used.
Method performance should be based on extraction of a CRM and/or spiked samples (NATA,
Technical note 17) or compared with a more rigorous method (such as Soxhlet extraction for
organic analytes).
<strong>Schedule</strong> <strong>B3</strong> - Guideline on laboratory analysis of potentially contaminated soils 9