Quality control — International Reference Materials

Regular use of certified reference materials and/or internal quality control secondary reference materials... 

If the ocean sciences are to move forward and adopt the regular use of reference materials, the advantages of using such materials (and the pit-falls of not using them) need to be more broadly disseminated. Proposal and journal article reviewers should question the analytical quality control of measurements made without the benefit of reference materials. Outreach focused on how to use reference materials in the ocean sciences will further increase the awareness of the individual investigators and provide a focus for proper handling and application of a laboratory s internal reference materials. 

You could decide to use control charts and to analyse certified reference materials (see chapter 13 and 14). Control charts are a simple, but effective tool for internal quality control. Internal quality control is one of a number of concerted measures that analytical chemists can take to ensure that the data produced in the laboratory are fit for their intended purpose. ... 

Internal quality assurance is concerned with maintaining precision within a single laboratory, where the importance of keeping careful records, based on reference materials and using appropriate control charts is well established. External quality assurance involves reference materials obtained from an outside body, and is a method for testing the bias of laboratory results. In practice, internal quality assurance mainly has to do with laboratory precision, whereas external quality assurance mainly has to do with laboratory bias (ISO 5725,1986). 

Quality control measurements were performed using a validated inter-analytical methods. Accuracy for blood and liver matrices was determined by analysis of international reference materials. Bovine Blood CRM 195 and Bovine Liver CRM 185... 

Quality control (QC) refers to the operational techniques and activities that are used to fulfill requirements for quality. Internal quality control comprises the routine practical procedures that enable the analytical chemist to make a decision on whether to accept a result or a group of results as fit for purpose, or reject them and repeat the analysis. Tools for quality control include the use of reference standards and certified reference materials, the use of positive (spiked or incurred) and negative control samples and control charts, replicate analyses, and proficiency tests. Quality control in the laboratory is discussed in more detail in Section 10.5 of this chapter. 

Analytical Quality Control Services (1998) AQCS Intercomparison Runs Reference Materials 1998-1999. International Atomic Energy Agency, Vienna. 

The primary purposes for which reference materials are employed are encompassed within the laboratory Quality Assurance Procedures. Quality assurance comprises a number of management responsibilities which focus on how the laboratory is organized, how it deals with situations, how it interacts with users, together with analytical responsibilities re internal quality control and external quality assessment (Sargent 1995 Burnett 1996). Ideally each component follows a documented protocol and written records of all activities are maintained. 

Ihnat M (1994) Development of a new series of agricultural/food reference materials for analytical quality control of elemental determinations. J AOAC International 77 1605-1627. 

Maaskant j, Boekholt A, Jenks P and Rucinski R (1998) An international interlaboratory study for the production of a sewage sludge certified reference material for routine use in inorganic quality control. Fresenius J Anal Chem 360 406-409. 

The previous chapters of this book have discussed the many activities which laboratories undertake to help ensure the quality of the analytical results that are produced. There are many aspects of quality assurance and quality control that analysts carry out on a day-to-day basis to help them produce reliable results. Control charts are used to monitor method performance and identify when problems have arisen, and Certified Reference Materials are used to evaluate any bias in the results produced. These activities are sometimes referred to as internal quality control (IQC). In addition to all of these activities, it is extremely useful for laboratories to obtain an independent check of their performance and to be able to compare their performance with that of other laboratories carrying out similar types of analyses. This is achieved by taking part in interlaboratory studies. There are two main types of interlaboratory studies, namely proficiency testing (PT) schemes and collaborative studies (also known as collaborative trials). 

Internal quality control is undertaken by the inclusion of particular reference materials, called control materials , into the analytical sequence and by duplicate analysis. The control materials should, wherever possible, be representative of the test materials under consideration in respect of matrix composition, the state of physical preparation and the concentration range of the analyte. As the control materials are treated in exactly the same way as the test materials, they are regarded as surrogates that can be used to characterise the performance of the analytical system, both at a specific time and over longer intervals. Internal quality control is a final check of the correct execution of all of the procedures (including calibration) that are prescribed in the analytical protocol and all of the other quality assurance measures that underlie good analytical practice. IQC is therefore necessarily retrospective. It is also required to be as far as possible independent of the analytical protocol, especially the calibration, that it is designed to test. 

Sampling is just the beginning of the analytical process. On the way from sampling to the test report a lot of different requirements for high quality measurements have to be considered. There are external quality assurance requirements on the quality management system (e.g. accreditation, certification, GLP), internal quality assurance tools (e.g. method validation, the use of certified reference material, control charts) and external quality assurance measures (e.g. interlaboratoiy tests). 

The authors would like to point out particularly that the present book can only provide a selection of the many commercially available fragrance and flavor materials. Also not included are compounds with exclusive uses that are not commonly/generally available ( captives ) as well as substances that are too new to be judged as to whether they will And a successful place in the market. Analytical data on natural raw materials that can be obtained by means of new analytical techniques are not explicitly mentioned if the analytical techniques have not yet reached international standardization. Flowever, reference is made to this in the corresponding literature and in the chapter on Quality Control. ... 

Analytical method validation forms the first level of QA in the laboratory. Analytical quality assurance (AQA) is the complete set of measures a laboratory must undertake to ensure that it is able to achieve high-quality data continuously. Besides the use of validation and/or standardized methods, these measures are effective IQC procedures (use of reference materials, control charts, etc.), with participation in proficiency testing schemes and accreditation to an international standard, normally ISO/IEC 17025 [4]. Method validation and the different aspects of QA form the subject of Section 8.2.3. 

In recent years the term qualimetrics has been coined to refer to the use of chemometrics for the purposes of quality control (Massart et al. 1997). ft relates particularly to the use of multivariate analysis of process control measurements. Other texts on quality assurance in chemical laboratories include the latest edition of Garfield s book published by AOAC International (Garfield et al. 2000), material published through the Valid Analytical Measurement program by the LGC (Prichard 1995), and books from the Royal Society of Chemistry (Parkany 1993,1995 Sargent and MacKay 1995). Wenclawiak et al. (2004) have edited a series of Microsoft PowerPoint presentations on aspects of quality assurance. 

Thermal analysis is a useful tool in the quality control of many incoming routine materials, which can be tested against a reference standard developed internally by analysing a large number of samples of known performance criteria to ensure that the quality of supplies is maintained. Solid elastomers can be identified by glass transition temperature (Tg) [70]. The rubber industry uses thousands of different raw materials, and this number is steadily increasing. These materials are listed in [172]. 

Customarily, frozen serum stored at — 70°C or below is used for internal quality control of serum steroid analysis. However, for international reference preparations it becomes very difficult to transport the material in the frozen state, due to the postal and customs delays. 

The particle size distributions of 15 International Atomic Energy Agency and 16 National Institute of Standards and Technology reference materials (RMs) were measured by laser diffraction to determine their potential as reference or quality control materials in that less than 100 mg are required. Most of the materials are commercially available as environmental and biological reference materials (RMs) [137]. 

For practical reasons, most analytical laboratories are not in a position to check accuracy internally, without an external source of reference materials. To overcome some of the difficulties in checking the accuracy of analytical results, the IAEA provides the Analytical Quality Control Services (AQCS) Programme to assist laboratories in assessing the quality of their work. AQCS co-ordinates intercomparison studies and supplies reference materials. Participation is on a voluntary basis and at minimum cost. Information supplied by laboratories taking part in the intercomparisons is treated as confidential. 

ICP-AES offers rapid, multi-element determinations. Its sensitivity is lower than that of either ICP-MS or AA-GTA, but it can handle higher levels of total dissolved solids than ICP-MS and is much faster than AA-GTA. The results obtained are in comparison with all the equipment used by about 100 laboratories that are participating in the Environmental Laboratory Approval Program. The quality of the performance relating to equipment as well as the analyst in such international collaborative programs implies the use of certified reference materials for calibration and control samples to ensure a certain level of traceability of the measurements and finally the degree of assurance of reliability. 

Various types of control charts, a tool that is most often used for internal quality control purposes, are often based on values given by reference materials. For this purpose, in-house reference materials should be preferably used, as certified reference materials are too expensive to be used to monitor the stability of the measurement process. 

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