Proficiency Testing (PT) Schemes entail the organisation, development and evaluation of tests of the same items or similar items by several laboratories, according to predefined conditions. It is a requirement of ISO 17025 that laboratories participate in inter-comparison programs and/or PT schemes. In addition, any laboratory that wishes to prove the quality of its analytical results in an independent manner should participate in PT schemes, since the integrity of the analytical results is directly linked to the quality of service or product, as well as market credibility and brand image offered by the service provider.

Participation in PT schemes is an essential tool to demonstrate the technical competence of a laboratory as it allows for the following:

  • Comparison of a laboratory’s own results with those obtained by other laboratories;
  • Confirmation of the correct initial validation of a method;
  • Use the data obtained from participating PT schemes for validation of measurement methods;
  • Determine systematic errors;
  • Improve the test method used;
  • Learn from the methods used by other laboratories;
  • Monitor the accuracy and precision of a method;
  • Encourage collaboration between laboratories; and
  • Demonstrate technical competence against third parties.




Joining Qotho’s PT Schemes eliminates the need for in-house laboratories to plan, organise and execute their own schemes, which may prove time-consuming and laborious. Samples submitted are typical of those analysed by laboratories on a daily basis, thus replicating the laboratories’ daily testing of samples received from customers – no additional preparation or deviation from routine sampling is required. A significant and advantageous benefit is that Qotho is an independent ISO Accredited Service Provider. Hence, utilising our services eliminates the possibility of biased interpretation of results, which may be experienced when operating in-house schemes.

Our PT Schemes are executed using standardised method preparation of samples in accordance with ISO standards, and as a provider with SANAS ISO/IEC 17043 Accreditation, compliance with the requirements of this standard is objectively demonstrated.

In addition to its ISO 17043 accreditation, Qotho Laboratory Services operates in compliance with the guidelines of the following international standards:

  • ISO/IEC 13528 – Statistical methods for use in proficiency testing by inter-laboratory comparisons;
  • ISO 17034 – General requirements for the competence of reference material producers;
  • IUPAC – International Harmonized Protocol for proficiency testing of analytical chemistry laboratories; and
  • ISO 5725-2 – Accuracy of measurement methods and results (Part 2)

Current PT Scheme offerings include:

  • Chrome (ore, concentrate, slag and ferrochrome)
  • Iron (low and high-grade ore)
  • Manganese (low and high-grade ore, metal – ferromanganese or silicomanganese)
  • Nickel (ore and concentrate)
  • Cobalt (concentrate)
  • Copper (ore, concentrate, tails and cathode impurities)
  • PGM’s (ore, concentrate and tails)
  • Smelter Reductants
  • Zinc
  • Gold