Minerals Quality Control

ALS Laboratory Group’s Mineral Division, ALS, has developed and implemented at each of its locations a Quality Management System (QMS) designed to ensure the production of consistently reliable data. The system covers all laboratory activities and takes into consideration the requirements of ISO standards.

The QMS operates under global and regional Quality Control (QC) teams responsible for the execution and monitoring of ALS’s various Quality Assurance (QA) and Quality Control programs in each department, on a regular basis. Audited both internally and by outside parties, these programs include, but are not limited to, proficiency testing of a variety of parameters, ensuring that all key methods have standard operating procedures (SOPs) that are in place and being followed properly, and ensuring that quality control standards are producing consistent results.

The Quality Assurance program at ALS is a multi-level program involving every area of our operations that is enhanced by a corporate culture dedicated to the encouragement of excellence in measurement techniques. The program involves clearly defined quality control procedures for sample preparation and analysis, plus a quality assessment stage that includes data review and statistical analysis. QA/QC reports are available with every Certificate of Analysis and we can provide custom reports at any time.

 More details on our Quality Assurance program are available on request.

Accreditation

Perhaps the most important aspect of the QMS is the process of external auditing by recognized organizations and the maintaining of ISO registrations and accreditations. ISO registration and accreditation provides independent verification for our clients that a QMS is in operation at the location in question. Most ALS laboratories are registered or are pending registration to ISO 9001:2000, and a number of analytical facilities have received ISO 17025 accreditations for specific laboratory procedures.

For certificates and scopes of accreditations for individual locations, please refer to the laboratory locations section of this site and navigate to the appropriate laboratory's Quality page.

Aside from laboratory registration, ALS has been a leader in participating in and sponsoring the Assayer Certification program in the Canadian province of British Columbia, one of the few jurisdictions that maintains a rigorous assayer registration program. We have on staff a number of Registered Assayers who have undergone extensive theoretical and practical training and passed comprehensive examinations prior to receiving their certificates.

Proficiency Testing

As part of our ISO 17025 accreditation ALS laboratories participate in a number of international proficiency tests, such as those managed by CANMET and Geostats. Both of these agencies circulate samples for analysis twice a year and evaluate the performance of participating laboratories.

Documentation

All sample preparation and analytical procedures have been assigned unique code numbers so that we always know exactly which procedure is to be followed. Each code is fully documented by written procedures that contain unique filenames and a revision number. Senior technical staff and the Quality Assurance Manager must approve any new revision. All new methods must go through a process of method validation that ensures the proposed procedure conforms to reasonable standards with respect to such critical parameters as accuracy, precision and detection limit.

Assessment Procedures

Evaluation of Routine Quality Control Data

ALS standard operating procedures require the analysis of quality control samples (reference materials, duplicates and blanks) with all sample batches. As part of the assessment of every data set, results from the control samples are evaluated to ensure they meet set standards determined by the precision and accuracy requirements of the method.

In the event that any reference material or duplicate result falls outside the established control limits, an Error Report is automatically generated. This ensures the person evaluating the sample set for data release is made aware that a problem may exist with the data set and investigation can be initiated.

All data generated from quality control samples is automatically captured and retained in a separate database used for Quality Assessment. Control charts for in-house reference materials from frequently used analytical methods are regularly generated and evaluated by senior technical staff to ensure internal specifications for precision and accuracy are being met.

Quality Control Reports

Quality control data for reference materials and duplicates are routinely reported to clients so that they may monitor laboratory data independently. These reports are generated at no charge to the client and are issued together with the Certificates of Analysis. QC data summaries and customised QC reports are also available. Please contact our Quality Assurance Department to request custom QC reports.

Round Robin Exchanges

Quality Assurance staff control monthly inter-laboratory test programs covering both gold and base metal determinations to monitor the quality of data generated by our network of laboratories. The Quality Assurance group selects and circulates the samples and then evaluates the performance of each laboratory through statistical analysis.

Quality Control

Sample Preparation

As part of our routine procedures, ALS uses barren wash material between sample preparation batches and, where necessary, between highly mineralised samples. This cleaning material is tested before use to ensure no contaminants are present and results are retained for reference. In addition, logs are maintained for all sample preparation activities. In the event a problem with a prep batch is identified, these logs can be used to trace the sample batch preparation and initiate appropriate action.

Monitoring of sample preparation tasks to ensure size specifications is done at every location. Results are automatically collected on-line and control charts done as we would for any analytical test. Results are available on-line for clients and managements to review.

Prepared sample pulps are sent to the appropriate analytical department to be assayed. The following are some of the standard quality control protocols that are in effect throughout all our analytical facilities:

Sample Classification and Separation

Material, which is expected to contain higher levels of metals, such as panning concentrates, ores and mineralised samples, is routed through separate high-grade areas to minimise the chance of contamination.

Equipment and Layout

Separate analytical departments have been established to specialise in certain areas of analysis; for example, fire assay, ICPAES and ICPMS spectroscopy services, geochemical analysis, and high-grade assays. Even within a specific department, we have physically separated facilities to handle the classified samples. For example, the fire assay department is subdivided into different areas that handle trace gold, assay-level gold and concentrates and bullion. Each area has its own dedicated equipment such as furnaces, crucibles and glassware. The main objective is of course contamination control.

Supplies and Materials

For most of our analyses, we use only reagents and chemicals that are certified reagent grade or better. Because of the volume of supplies that we purchase, we are able to insist upon extremely stringent requirements to our suppliers. For example, the litharge (lead oxide) that we purchase for fire assay measurements must have a negligible gold content according to contractual obligations with the supplier. Similarly, the acids that we purchase must not contain any levels of metal impurities that could affect trace or ultratrace measurements. We devote a considerable amount of time and energy to testing of supplies and reagents to verify that they do meet our specifications.

Cleanliness

Wherever possible we use disposable test tubes to eliminate carryover from previous use. All other glassware is rigorously cleaned prior to re-use. Glassware that has contained samples with very high metal concentrations is flagged for special cleaning (typically acid-leaching) in addition to the normal procedure. In the fire assay department, we have an automated system to flag any crucible found to have contained a sample with elevated gold content. The crucible is automatically discarded rather than re-used. In addition, crucible logs are maintained for all fusion batches so crucible use can be tracked.

Analysis of Blanks, Standards and Duplicates

Our routine quality control testing includes the analysis of blanks, reference materials and duplicates. All results from quality control samples become part of a separate database that we use for Quality Assessment. All reference materials used at ALS are either primary, certified reference, or in-house reference materials that have undergone a rigorous validation process.

Accuracy and Precision

Accuracy is generally defined as the degree of agreement of a measured value with the true or certified value. Usually we can ascertain the accuracy of our methods by measuring certified reference materials, if they are available. Accuracy is also monitored by participation in proficiency tests and internal round robin exchanges as well as comparison of results against different analytical techniques.

Precision is generally defined as the degree of agreement of repeated measurements of the same parameter and is expressed quantitatively as the standard deviation. The precision (standard deviation) of a method varies as a function of concentration and must therefore be measured throughout the concentration range of the analytical procedure. We use statistical analysis of duplicate pairs data to establish precision for particular analytical procedures. Our specification for the precision of trace metal measurements is that it should be +/- 10% of the mean value at a concentration 50 times the detection limit. Our specification for assay measurements is that the precision should be +/- 5% of the mean value at a concentration 50 times the detection limit. Plots describing precision as a function of concentration are available for frequently used assay and trace metal parameters.

Check Analyses

In addition to our routine quality control analyses, check analyses are sometimes initiated by analytical department managers in order to confirm data for anomalous samples. Further review and requests for confirmatory analyses can be made by QA staff as a result of the Quality Assessment step.

Data Processing

As much as possible, analytical data is generated using computer-controlled instrumentation so that data is transferred electronically to our LIMS. This avoids data transcription errors. If manual data entry into the LIMS is required, all data is double checked by an independent reviewer to verify that the data is correct.

Additional Specific Quality Control Procedures

In addition to the universal QC procedures outlined above, we have a number of additional QC procedures that are carried out according to the measurement technique to be used:

• Fire Assay: Our assayers take numerous additional steps in the fire assay process. Fusion crucibles are carefully checked to ensure that no boilovers have occurred in the furnace. A boilover requires re-analysis of not just that sample but also of all its nearest neighbours in the furnace. We do visual checks of the fusion mixture to make sure that there has been a clean fusion with no lead "shotting". The size of the lead button is assessed and if it is either too small or too large, the fusion will be repeated. After cupellation, the precious metal bead is checked for size, colour and surface texture. A large bead or a gold hue will indicate a sample high in silver or gold, or both, and it must be handled with special care to control possible contamination. A pebbled bead surface can indicate the presence of platinum metals. A 'color de rosa' in the cupel can indicate the presence of tellurium, in which case the analysis will have to be repeated.
  
• ICP-AES: Our analysts review all of the data generated and will take particular note of samples with high concentrations of elements such as Fe and Al, which give significant interelement interferences. Similarly, they closely watch the concentrations of those elements such as thallium, tungsten and uranium, which are most affected by interelement interferences. Concentrations of elements in these situations are verified by examining the spectra in detail and by alternative methods such as AA when possible.
  
• XRF: For Whole Rock Analysis the XRF department uses a library of internationally certified reference materials, which cover the entire spectrum of geological host matrices. Cross checks between the XRF, ICP and Assay whole rock element procedures are done routinely. Anomalous samples are verified by duplicate fusions and checks by other procedures.
  
• ICP-MS: The combination of an inductively-coupled plasma source with a mass detector requires not just calibration of the response function for different concentrations of each element, but also the use of a number of internal standards covering the entire mass range, thus correcting for variations in the efficiency of the transport system that moves the sample from the plasma to the mass detector.
  
• AAS: All atomic absorption spectrometers (as well as all our other spectrometers) are, as part of our daily operations, tested for light throughput and stability and this information is maintained as part of the instrument software. If preset limits are exceeded the instrument will be optimised or repaired before it is operated again.
  
• Balance Maintenance Program: Balances are routinely tested by our laboratory technicians using certified weights. This confirms that balances are functioning properly. In addition, service technicians perform routine balance maintenance on a regular basis. This helps to improve our level of service by making certain that the balances are accurate and by minimising the number of breakdowns.