Method Statement Thiocyanate
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Revised on 12/09/02
Contents
Introduction
Principle
Performance
Characteristics
Range
of Application
Limit of
Detection
Analytical
Quality Control
Introduction
The performance of this method is validated in accordance with
internationally recognised procedures.
This procedure describes the determination of thiocyanate in soils
and waters by a colorimetric measurement using ferric nitrate at an
acidic pH.
Principle
A filtered soil extract or water sample is used for the
determination. At an acidic pH (<2), ferric ion (Fe3+) and
thiocyanate (SCN) form an intense red colour which is read
colorimetrically at 460 nm.
Performance
Characteristics
Substances Determined
Thiocyanate (SCN) in soils and waters.
Range of Application
Limit of Detection
Soil samples 10 mg / kg
Aqueous samples 1 mg / l
Analytical Quality
Control
Analytical quality control is maintained by a number of measures:
Multi-point calibration with
authentic standards (with defined minimum performance
characteristics)
Analysis of control samples within
each analytical batch, such as independent standards, matrix spikes
or reference materials
Analysis of reagent/method blanks
within each analytical batch
Ongoing quality assured by the use
of control charts in conjunction with warning and action limits for
the QC sample data
Participation in external
proficiency testing and interlaboratory schemes such as LGC CONTEST,
HSE WASP, CSL FAPAS
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