TRD: Institute for Plant Production: Laboratory Services: SOIL, WATER AND PLANT TISSUE LAB
Quality procedures
In order to ensure that the high quality standards for analysis performed are achieved, the results of control samples are constantly monitored and evaluated.
More than 10% of all samples analysed by the laboratory are control samples. This implies the analysis of a sample with a known concentration of the specific element in question. The accuracy of all processes involved in the analysis is thereby evaluated. If there are significant deviations in analysis results, all samples involved are reanalysed.
In order to rule out and detect any possible contamination in laboratory procedures, a reagent blank is analysed with every set of samples that is extracted or digested. This reagent blank includes any and all reagents that are used in the analytical process and is carried through the entire process, including extraction and filtering or digestion.
To verify and monitor the sample preparation and workflow integrity, approximately 5% of the work requests are re-submitted as unknown samples to the laboratory. These samples are split at sample reception, renamed, and follow all laboratory procedures. The identities of these samples are unknown to the laboratory staff.
The following elements are all determined from extracts analysed on ICP (Inductively Coupled Plasma Spectrometer): P, K, Ca, Mg, Na, Cu, Zn, Mn, Fe, Al, B and S.
Control over these results is maintained by the ICP through the analysis and comparison of standard solutions with preset values. A solution with known concentration is analysed as every first, 22nd, or last sample, and the results are compared with the known results preset in its memory.
If significant differences are detected, the instrument will recalibrate and reanalyse the control solution and, subsequently, the previously analysed samples. If there are still marked differences, the instrument will shut down, ensuring quality results.
The samples analysed by the laboratory are inherently heterogeneous. Furthermore, with all these procedures in place and although the laboratory personnel are totally committed to delivering a quality service, it is not impossible that results may be queried.
The laboratory will re-analyse such queried samples free of charge.
As a valued client, you are therefore welcome to bring any uncertainties with regards to results under the attention of the laboratory management and it shall be treated accordingly.
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