Certified reference materials proficiency testing

Magnitude of the response caused by a certain amount of analyte Alternatively, certified reference materials, samples analyzed with reference methods or proficiency test materials may be apphed... 

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). 

Provided the sample matrix and analyte concentration are appropriate, matrix Certified Reference Materials (CRMs) can make ideal proficiency testing samples. The assigned value is the certified value given on the certificate accompanying the CRM. The certificate will also give an uncertainty estimate for the certified value, and the use of CRMs allows the traceability of analytical data to be established. However, matrix CRM availability is limited and the materials are often expensive. Hence, Certified Reference Materials are seldom used as PT samples. 

Contaminated Land Proficiency Testing Scheme Control of Substances Hazardous to Health Certified Reference Material cumulative sum... 

Among the elements of quality control in mycotoxin analysis, proficiency tests, control materials (reference materials and certified reference materials), traceability in spiking, and recovery checks have been demonstrated to be particularly relevant. 

Analyzing control materials alongside the test samples greatly improves proficiency in mycotoxin analysis. Certified reference materials (CRMs) represent ideal control materials, due to their statement of uncertainty and traceability, and they should be routinely used as much as possible. Unfortunately, as outstanding as the improvements made in the last decade have been, even though the list of CRMs in the area of mycotoxins is rather long, it is still insufficient. A list of the available reference materials in the mycotoxins area is reported in Table 1 the issue has been reviewed by Boenke (27). 

The selection of an analytical technique and the development of procedures and operating conditions are only one part of the process for achieving reliable measurements. Among the first steps of the validation figure the assessment of the method precision this parameter must be assessed between analysts and days. Appropriate precision, although necessary for reliable work, is not sufficient to guarantee accurate results Evaluation of sample matrix effect, development, and analysis of spiked samples, analysis of Certified Reference Materials (CRM) of similar composition for which the Pb concentration has been established by other laboratories and comparison of results between laboratories (proficiency testing) are equally important [13]. 

Researcher and analyst need to ensure the correct use of blanks, standards, certified reference materials and understand the purpose of traceability, proficiency testing schemes and laboratory accreditation. 

Around 1600 European laboratories responded to the questionnaire (Table 5.3). From the answers received in the different countries, it was clear that many laboratories are not familiar with the term CRM and that confusion exists between certified and non-certified reference materials, between matrix RMs and calibrants. Besides RMs and CRMs it also became clear that many laboratories were not aware of the existence and even the meaning of proficiency testing. 

Ten-year horizon, considering the recent evolution in the development of measurement instruments, the CRM demand should grow about 5% per annum because their usage is growing from a smaller base, the needs for non-certified reference materials (e.g. for proficiency testing in support of laboratory accreditation) should increase by 10% per annum. 

Precision within a laboratory can be tightly controlled by the operation of internal quality control schemes. This can be achieved by undertaking replicated analysis of samples and/or possibly by analysing replicate samples. The analysis of certified reference materials offers a means whereby bias can be estimated. Another means of estimating a laboratory s performance is via participation in inter-laboratory proficiency-testing schemes. Originally, external quality control or inter-laboratory proficiency-testing schemes had been made available to assist laboratories to identify those areas where remedial action was considered necessary, in order to improve the quality of data... 

Method accuracy should be demonstrated through regular participation in suitable proficiency testing programs (when available) and use of certified reference materials in calibration (when available). 

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. 

All methods are hindered by the poor availability of PA reference standards, the lack of interlaboratory validation of methods and proficiency tests, and the lack of certified reference materials. 

There are different reasons for interlaboratory tests. One is method validation, e.g. prior to the standardization of characterization of reference materials, which have to be certified. The third and most important for quahty assurance is proficiency testing of laboratories. There are different requirements for each type of interlaboratory test. 

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