Wednesday, 3 June 2020
Quick QC Guide to Monitoring Labs with SD Intervals
Austmine Limited
/ Categories: Press Releases

Quick QC Guide to Monitoring Labs with SD Intervals

For any given analyte-method pair, the two standard deviation interval (or window) provides an indication of a level of performance that might reasonably be expected from a laboratory being monitored by a CRM in a quality control program. The SD's we provide encapsulate errors attributable to measurement uncertainty and CRM variability. For an effective CRM, the contribution of CRM variability should be negligible in comparison to measurement errors. The SD values thus include all sources of measurement uncertainty: between-lab variance, within-run variance (precision errors) and CRM variability. OREAS prepared reference materials have a level of homogeneity such that the observed variance from repeat analyses has its origin almost exclusively in the analytical process rather than the reference material itself.

How to use the 2SD Performance Gate window
  • Failure if two consecutive results on same side
  • 5% of all 2SD failures will be due to chance
How to use the 3SD Performance Gate window
  • individual outlier
  • 0.3% of all 3SD failures will be due to chance

Control limits are calculated from filtered data sets comprising the best laboratories operating under ideal conditions. Therefore, not all labs are capable of achieving recommended control limits and user discretion is therefore advised. 


OREAS® CRMs provide quality assurance to your database by mitigating the risk of bad data passing undetected.

Over the years ORE Pty Ltd has pioneered a number of technological advances that have enabled the production of CRMs from ore deposits to an unparalleled level of homogeneity. We offer a guarantee* of the homogeneity of gold (and PGE's) in all OREAS® and custom CRMs irrespective of the presence of coarse gold in the source materials.

Our latest innovation is the introduction of SuperCRMs® to the OREAS® range. SuperCRMs® feature certification of full analyte ICP-OES and ICP-MS suites by a range of digestion methods. Up to 179 analytes are characterised in a single CRM making them ideally suited as a control in ICP applications. With over 74 SuperCRMs® available from a range of over 210 OREAS® CRMs, there is every chance of a close match to the matrix of your field samples.
*we guarantee a 1RSD of <1% for a typical 30g fire assay charge weight calculated from the SD of 20 x 1g INAA samples by using the known relationship between SD and sample size (Ingamells & Switzer, 1973).


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