Understanding Quality Control in Analytical Chemistry

The quality of the analysis carried out by a laboratory can have implications in many, many areas. A prime consideration of a quality control system is that it should be designed to make operations easier and to help employees do their job, it should not be viewed as a negative.

Quality Control

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Quality control can be a real influence on the culture of a laboratory. The quality system can also have significant safety implications as labs may be handling hazardous samples and reagents.

Reliability and integrity of results could influence how the lab is funded and may be important in controlling costs and budgets. Customer loyalty may be influenced by the quality of the analysis carried out. The use of consumables such as reagents may also be influenced by the quality system. The quality system should help the personnel involved in the analysis to do their jobs well and not hinder them.

Quality control should be all-encompassing and cover every aspect of the analytical process. There are two main components to any quality system, Quality Assurance, and Quality Control.

  • Quality Assurance is the system of verification that the whole process of analytical testing is within acceptable limits.
  • Quality Control includes the processes and procedures established to ensure efficient accurate results are achieved and to measure any non-conformance.

One of the aims of the quality system in an analytical laboratory should be that every analytical measurement will produce a sufficiently accurate result that it is fit for purpose and it will enable the user to make appropriate decisions.

The three stages of an analytical experiment

The quality system for an analytical experiment should cover the three stages.

The Pre-analysis stage will need to consider things like;

  • Identification of what is being tested and how that will be done.
  • Standard procedures for sample collection, it is important that samples are obtained consistently and safely and placed in the correct type of containers.
  • Labeling and dating samples to be analyzed to ensure there is no possibility of confusing similar-looking samples.
  • Ensuring suitable containers, packaging, and transport are used to get the sample from the sampling point to the testing laboratory.
  • Samples in the laboratory should be stored correctly to ensure there is no contamination or deterioration of the sample.
  • Back-up samples may be required for additional or backup checks so a sample may need to be split and each part must be correctly labeled and stored.

The Analytical stage will need SOP’s (Standard Operating Practices) that include;

  • Documented training and competence records to ensure that analysts are capable of following the procedures and interpreting the results. The quality system will also include how trained and competent Chemists are allocated to specific tasks.
  • The process of analysis should be defined so that any analysis carried out is repeatable and can be carried out many times in an identical fashion
  • The possibility of introducing errors through the equipment should be eliminated through correct maintenance and calibration. All maintenance and calibration should be specified and recorded.
  • An inventory of the date and quantity of samples and reagents in the laboratory should be in place. There should also be a schedule that shows when samples should be analyzed.
  • Any actions taken in the event of non-compliance and any remedial action must also be recorded

SOPs for all analyses and procedures should be documented and easily accessible for laboratory staff.

The Post Analysis stage will include;

  • How results are calculated and recorded. There is sometimes a complex relationship between analytical methods, sample concentrations, limits of detection, etc., therefore the management of Analytical Quality Control may require a statistical approach to determine whether the results obtained are acceptable. Wherever possible automatic calculation methods should be considered to minimize the chances of manual calculation errors.
  • A procedure that defines how all results should be recorded correctly and communicated to interested parties such as managers and customers in a timely, accurate, and user-friendly manner.
  • Procedure for how the staff has their competence and training requirements assessed regularly. All assessments and requirements should be recorded.
  • Regular auditing should be undertaken to ensure that the quality system is followed and that compliance with any relevant quality standards such as ISO9000, ISO 17025 is maintained.

In addition to the analysis process, a quality system will be linked to the whole organization’s quality system so that the laboratory is not working in isolation but is working in harmony with other parts of the organization and its customers.

Other areas of quality control

There are several other areas to consider within the Analytical Chemistry system. The quality manual will also cover such as

Organisation and Personnel: Management structure and personnel along with their functions and capabilities and any training received should be part of the quality control system. Skills and training requirements and conformance with SOP’s should be recorded.

Equipment and Reagents: All lab equipment should be documented along with purpose and capability. Servicing and calibration requirements and details of who would be capable of operating the equipment should be in a quality control system.

Similarly, the purchase and shelf life of reagents and samples should be on record and the inventory reviewed regularly. The inventory should also record any handling requirements for hazardous materials documented along with any training carried out.

Documents and records and Compliance and Traceability: All results, errors, non-conformances, corrective measures should be recorded. The whole system should be audited periodically to confirm reliability and compliance with internal and external standards

It is essential for any analytical laboratory, large or small, should be able to prove that its results are accurate and all results can be traced back and verified if required,

International standards such as WHO or ISO certification and accreditation may also be important for customer confidence and company credibility.

Facilities and safety: Any quality system will also enhance safety by documenting correct storage of hazardous materials and correct operation of dangerous equipment and machinery along with the correct installation of safety showers, eyewash facilities, fire fighting equipment, etc.

Process control and process improvement: The management of all activities from sampling to testing to reporting to disposal of samples must be included in a Quality System. Any organization should continually challenge itself to improve on its performance and document any improvements.

It is important to understand that Quality Control in Analytical Chemistry is not simply about the actual analytical experiment. Quality Control should be all-encompassing covering every aspect of a chemical experiment or analysis from concept to completion.

The role of the people involved and all the procedures and operations that go before and after the experiment can have a large influence on the quality of the analytical results produced. Likewise, equipment and reagents can significantly impact the quality of any analytical analysis. Quality control is not just about processes and SOP’s it is also about a mindset and culture in an organization and laboratory.

Laboratories which have good quality control should be safe, efficient, and reliable. Any queries about analyses should be easily traceable and verifiable. Quality Control carried out correctly will be a great asset to any laboratory,


Further Reading

Last Updated: Oct 21, 2021

Oliver Trevelyan

Written by

Oliver Trevelyan

Oliver is a graduate in Chemical Engineering from the University of Surrey and has 25 years of experience in industrial water treatment in the UK and abroad. He has worked extensively in steam system controls and energy management. Oliver writes on science, engineering, and the environment.


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