Page 138 - Catalog Instruments and Supplies

138 SCP SCIENCE
Standards Reagents and CRMs

what standards do i need?
so many types to choose from!

STANDARDS FOR THE ANALYTICAL TESTING LABORATORY

1. CALIBRATION STANDARDS

CALIBRATING INSTRUMENTS TO GET THE MOST ACCURATE RESULTS

Calibration is a key aspect of any indirect measurement technique SCP SCIENCE offers superior quality standards to master the
including ICP-OES and ICP-MS. To ensure precise analysis, several above criteria, in the form of:
important factors to consider in the calibration process:
1. Single-element standards at 1K, 10K and 50K ppm for
• Precision of the calibration standards (uncertainty) laboratories to prepare their own blends of standards.
Eg. 1006 +/- 4 ppm
2. Multi-element standards in commonly-used combinations and
• Matching of acid matrix used in preparing calibration standards concentrations, directly based on EPA, USP or other methods.
to the samples for analysis. These can be used directly as calibration standards, or as QC
Eg. When using 3% HNO3 in calibration standards, be sure to standards, to verify the original calibration curve.
have a similar amount of acid in the analysis samples.
3. Custom-prepared standards to:
• Matching of overall elemental matrix (element and concentration
of calibration standards) to the samples for analysis a. Save the end user valuable time by meeting specific
Eg. a calibration curve with little or no sodium would not be calibration needs;
useful for analyzing elements in seawater unless the samples
were pre-treated to remove the sodium via a technique such as b. Removing additional sources of uncertainty in
Solid Phase Extraction (see page 123). preparation;

c. Providing direct NIST traceability.

INSTRUMENT AND TECHNICIAN VARIABILITY AND BIAS

Electronic, optical and mechanical components usually cause instruments to perform differently over time which can, in turn, lead to changes in
sensitivity, resolution and repeatability. Add to that, the variability in technique and consistency from one technician to another, this complex set of
variables can make it very difficult to predict the reliability of the results for a given sample.

Internal standards effectively provide a correction factor to compensate for changes in instrument performance by comparing the results for a given
reference element. The ratio of analyte to reference will negate the variation in nebulizer uptake rate and other analytical anomalies. Simply choose
an element that is not present in your sample matrix and add a constant quantity manually or via an SCP SCIENCE Mixing Kit, see page 111.

2. quality control STANDARDS 3. pecheck STANDARDS

QC standards are spot-checks of a known element or elements peCHECK standards are typically provided to the lab, often
against a calibration curve, to determine if system variability and bias as blind samples, to provide objective performance evaluation,
are within control and to identify problems at their onset to ensure
reliability of data. Typically recommended frequencies for running including the preparation of standards and calibration of the
QC-checks vary from 1-in-5 to 1-in-10 samples.
instrument.

4. matrix REFERENCE MATERIALS

METHOD DEVELOPMENT AND VALIDATION

Whether validating currently accepted analytical methods, or developing a proprietary method from scratch, MRMs can play a critical role in
the process. SCP SCIENCE MRMs are designed to closely imitate field-samples and are prepared in accordance with ISO Guides 31, 34
and 35, and therefore, can be used to validate every step from typical sample preparation through to final analysis. Comparing your laboratory’s
results to the round-robin certified consensus values, confidence intervals, and tolerance intervals, will provide a clear image of your laboratory’s
performance and method capabilities.

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