It is essential that clients of X-ray Mineral Services (XMS) have full confidence in the data produced by our analytical procedures.
Our internal quality assurance (QA) and quality control (QC) procedures include:
All in-house methods are fully documented and procedures followed from receipt of samples to issue of the final report.
Regular training ensures all staff are familiar with our methods and are kept updated with any changes to procedure.
Regular repeat analyses are an integral part of our QA process to recognise any potential issues during the sample preparation.
Samples with known compositions are randomly processed in the same way as routine samples to maintain performance and reproducibility of the analytical procedure.
Cross-check with the use of independent methods
The accuracy and precision of mineral quantification of each batch of samples analysed is confirmed using the following independent methods:
- Reference Intensity Ratio (RIR)
When available XRF data is used along with XRD data to cross-check results using a mass balance calculation
Reference material analysis
The routine performance of our 4 diffractometers is validated on a weekly basis, using mineral standards of known composition.
The performance of our XRF spectrometer is monitored by daily analysis of 3 validation beads prepared from certified reference materials (CRMs). The data is checked to ensure that results are within preset limits for key elements. If any element is outside these limits the instrument is drift corrected and the analysis repeated to ensure the instrument is within specification.
Analysis of synthetic standard mixtures of known composition
The accuracy and precision of the mineralogical quantification is verified against synthetic mixtures of known composition. These mixtures are prepared from appropriate mineral standards to resemble real rocks. This is the only way to check the accuracy and precision of a technique applied to natural samples.
Most of the minerals are quantified within 2 wt.% absolute error. For more information click here.
Round robin proficiency tests
To assess the accuracy of our XRD and XRF data against external laboratories from around the world XMS participate in a variety of round robin tests including:
- international quantitative phase analysis (QPA) proficiency tests for XRD. For more information click here.
- GeoPT - a major international proficiency test organised by the International Association of Geoanalysts. For more information click here.
The Reynolds Cup
The Reynolds Cup is a biennial round-robin competition held by the Clay Minerals Society for quantitative phase analysis on synthetic mixtures of pure standards that represent realistic rocks. In 2018, we were placed 8th position overall out of 88 participants. In 2016, we achieved 4th position on the carbonate-bearing shale sample out of 83 participants. For more information click here.