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How to get the most from your data with the help of Certified Reference Material

Certified Reference Materials (CRM’s) are of great assistance with portable XRF data Quality Assurance and Quality Control (QAQC). CRM’s provide a check for elemental concentrations, in addition to checking for low level contamination of the XRF instrument.

A question Portable Spectral Services (PSS) is frequently asked is: “how do I use CRM’s with portable XRF to get the best result?”

There a numerous ways to utilise CRM’s and often relies on the specifics of individual project goals and intended outcomes. The following are what PSS suggest to be taken into consideration generally when using CRM’s:

  • Analyse a CRM and a blank standard every 20 to 30 samples
  • Monitor the expected result for an element(s) of interest in the CRM to maintain confidence in the results
  • Use a quartz blank to monitor low-level contamination in the tube of the instrument

QAQC

One way of doing QAQC on the fly is to analyse your selected CRMs 10 times each at 60 seconds per scan. This will provide a general understanding of the range of results to be expected from the CRMs for that specific XRF instrument.

From this, one would then calculate the minimum and maximum thresholds for some selected elements, often those related to the project. For example, this may be Cu, Zn and Pb. This is achieved by taking the average of the values, then calculating the standard deviation times by two. To find the minimum value, minus the average by the SD*2. To get the maximum values, add the SD*2 to the average.

For example,

 

Once the minimum and maximum values have been  ascertained, the value can be used to monitor the CRM results during sample analysis. This ensures better data collection as any contaminants or instrument deviation will be noticed during the CRM check, rather than end of day. Including CRM’s in a QAQC procedure therefore can help speed up the identification of any problems in sampling. It also ensures the data is reliable and consistent throughout the project. It will also assist in determining if any adjustments are required to ensure the XRF is collecting good quality data that is fit for purpose. 

If you wish to purchase some CRM’s for an upcoming project, check out PSS online shop. PSS can also aid in selecting the most appropriate CRM’s, get in contact and we will be happy to assist. 

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