Quality Assurance

A certified standard and blank assay are run with each batch of samples. In addition, a replicate assay is run on every 10th sample to be used for checking the reproducibility of the assays to highlight any “nugget effects” that may be present (see below).
All certified standard runs are graphed weekly to monitor the performance of the laboratory. Our warning limit is 2 times the standard deviation and our control limit is 3 times the standard deviation. Any work order with a standard running outside the warning limit will have selected re-assays performed, and any work order with a standard running outside the control limit will have the entire batch of samples re-analyzed.

All QC data run with each work order is kept with the client’s file. If desired, the client may have all the blanks and QC standards reported separately. All quality control graphs are available upon request.

The laboratory also keeps daily log books for the sample throughput. These logs record all information pertaining to, who performed the analysis, when the analysis was done, how the analysis was performed and what other samples were analyzed at the same time. This is done to help eliminate the possibility of misrepresentation and cross-contamination of the client’s samples.
In our Sample Preparation area, we regularly select random samples for screen analysis to ensure grain size is being achieved (Reject: 90% -8 mesh, Pulp: 90% -150 mesh). Also, re-cuts on samples are performed from the original reject to check reproducibility.
Our AA and ICP instruments are calibrated using ISO traceable calibration standards and our quality control standards are created from separate stock solutions. Our instruments are directly tied to our LIMS program eliminating the need for manual data entry, hence, reducing human error.

Overcoming the “Nugget Effect”

Non-reproducible check assays may be an indication of nugget problems within the sample and we recommend that further analysis be performed to generate a better representation of the sample.  Such additional analyses may include replication, pulp metallic, screen analysis, gravimetric verification, and cyanide leach.