ISO guide

ISO Guide 62 1996 General requirements for bodies operating assessment and certification/registration of quality systems... 

ISO 9000 is not a statutory requirement and neither is certification, hence certification is voluntary. However, suppliers may be under pressure to obtain registration to ISO 9001, ISO 9002, or ISO 9003 in order to tender for contracts. Within the ISO 9000 certification scheme, the certification industry is regulated by accreditation bodies. An International Accreditation Forum (lAF) attempts to harmonize accreditation practices world-wide through ISO Guide 61. The accreditation bodies authorize certification bodies to conduct certification to prescribed standards - a process that is called accreditation. The accreditation body performs witness audits and desk audits of the certification body to ensure compliance with the conditions of accreditation. 

To receive ISO 9000 accreditation, a certification body must meet the requirements of ISO Guide 62 and EN 45012, which invokes ISO 10011. There is normally a mark of accreditation (a Grown and Tick in the case of UKAS accreditation) that certification bodies use to signify their credibility. Once accredited, a certification body may perform audits on suppliers offering products and services within the scope of accreditation. In theory, accreditation is granted only if the certification body has expertise (i.e. competent auditors) for the particular industry sectors (EAG codes) requested. 

The 1982 White Paper on Standards, Quality and International Competitiveness was concurrent with increasing interest in the techniques of quality assurance and the need for international harmonization of standards and the reciprocal recognition of certification. It is worth noting that the ISO 9000 series of standards on Quality Systems 1987 followed the layout of BS 5750 1979 almost clause by clause. ISO Guide 39 covers the general requirements for inspection bodies. Auditing on behalf of certification bodies is part of the inspecting authorities role. 

The basis for the preparation and use of reference materials (RMs) is given in ISO Guides 30-35. These documents deal with the following aspects of the preparation and use of RMs... 

The definition of a certified reference material (CRM) is given in ISO Guide 30 (1992) and it forms the root of all other ISO Guides ... 

The most important document, accompanying a CRM is its certificate. ISO Guide 31 (1981) provides guidance for the establishment of certificates, labeling of CRMs, and certification reports. The certificate contains among other information the certified values and their respective uncertainties. As important as this information is the traceability statement, which defines to what references the CRM is traceable. Ideally, a CRM is traceable to a suitable (combination) of SI units. This is not always possible, so other stated references may appear here. Especially when certifying matrix reference materials, making the measurements traceable to SI does not imply that the CRM is traceable to SI as well. The steps necessary to transform the sample into a state that can be measured may have a serious impact on the traceability of the values, and thus on the traceability statement. 

There are two main uses of a RM calibration and method performance checking. ISO Guide 32 (1997) deals with the use of RMs for calibration purposes. RMs used for calibration purposes are usually RMs prepared by synthetic means. Commonly, the property values of these RMs are known from preparation, and verified by some kind of suitable measurement technique. This can be a technique directly providing a value for a property of interest, or a technique that allows the comparison of the new material against older measurement standards. 

ISO Guide 32 provides guidance in two ways. Apart from the guidance on using RMs for calibration purposes, it also provides information on the preparation and use of calibrants in a laboratory, and checking them against other RMs or measurement standards. 

ISO Guide 33 (1998) deals with other uses of RMs. It elaborates on various uses of RMs, excluding calibration, which is the subject of ISO Guide 32. In most cases, RMs are used as a quality control measure, i.e. to assess the performance of a measurement method. Most matrix RMs are produced with this purpose in mind. Other purposes of RMs are the maintenance of conventional scales, such as the octane number and the pH scale. ISO Guide 33 provides guidance on the proper use of RMs, and therefore it is together with ISO Guide 32 the most important document for users of CRMs. 

The result from a measurement on a RM is commonly a difference between the observed value and the certified value. This difference is called measurement bias, and can, appreciating both the uncertainty on the RM as well as the imcertainty added during the measurement, be tested for (statistical) significance. ISO Guide 33... 

Whereas ISO Guide 34 sets requirements for the quality system of a GRM producer, ISO Guide 35 (1989) provides guidance on how to implement many of these requirements. Among these, the document also provides a general and statistical outline of the process that leads to CRMs. The current edition of ISO Guide 35 is a little outdated, but stiU most of the contents are valid. 

The characterization of a reference material can take place in different ways. Depending on the source cited, there are three or four mainstream approaches ISO Guide 35 (1989) distinguishes between three ... 

Traceability of measurement results is essential in the establishment of a certified reference material. As stipulated in ISO Guides 30 and 35, a certified reference material can only be certified if there is an uncertainty statement with a traceability statement. Basically, traceability means anchoring. In classical analytical chemistry, that SI system is often the best choice as a reference (= anchoring poinf). However, there is a wide range of parameters either defined by a method or defined by the... 

ISO Guide 25 (1990) Guidelines for assessing the competence of calibration and testing laboratories. International Organization for Standardization, Geneva. 

ISO Guide 34 (1996) Quality system guidehnes for the production of reference materials. (Revised March 1998 as ISO/REMCO document No 464 General requirements for the competence of reference material producers . The revised Guide 34 will appear early 2000.) International Organization for Standardization, Geneva. 

ISO GUIDE 35 (1989) Certification of reference materials - General and statistical principles. International Standards Organization, Geneva. 

ATCC issues Certificates of Analysis with cultures. Although ATCC Certificate of Analysis do not meet the specific requirements of ISO Guide 31, they do show that the biological RM culture has been authenticated and/or specific characteristics have been verified. Each ATCC Certificate of Analysis is lot-specific and includes expiration dates, the specific seeds used for propagation, and selected biochemical and morphological characteristics that are indicative of the culture. ATCC also aims to provide a Product Sheet for each microbial culture, with instructions for propagation, special features of the organism, and any imusual observations or properties. 

This Section describes one of the first successful attempts, by a multi national project team funded by the European Commission s DC XII, to produce and certify a microbiological CRM that is both fit for purpose and meets the requirements of the ISO Guides. The first results are two bacterial strains, Enterococcus faecium (CRM 506) and Salmonella typhimurium (CRM 507) (fanning et al. 1995). Both are available as part of the EU BCR range of CRMs. 

The development of these CRMs has shown that it is possible to produce CRMs for public health microbiology and that whilst such a CRM can largely meet the ISO Guides requirements it does not completely satisfy all the requirements of CRMs. It has also demonstrated that their manufacture and certification places considerable challenges before the producers. 

Where the CRS is to be employed as an assay standard, the extent of testing is very much greater. A number of ways for the assignment of content values of reference materials have been described (ISO Guide 34 1996) ... 

The ISO guide is particularly concerned with the establishment of reference materials which contain the analyte as a small, or even trace, quantity in a complex matrix. These reference materials serve as measurement benchmarks when applying an appropriate analytical procedure for the determination of an analyte in the sample. The value attributed to the reference material is usually the mean of residts obtained from a variety of methods and laboratories. Thus, the value attributed to the substance may have a high degree of uncertainty. A particular reference material is subjected to the same procedure as the test samples so that greater confidence can be given to the results of the test samples provided that the value found for the reference material falls within the given uncertainty. 

ISO Document N 464 (1998) General requirements for the competence of reference materials producers, revised ISO Guide 34. International Standards Organization, Geneva. 

As mentioned before, RM producers go to great lengths, as are required by the ISO Guide 31 (1996) to prove homogeneity and stability, and to establish the best sample size and storage conditions for an optimal shelf life. This information is normally provided in the RM certificate. Nevertheless, users must pay particular attention to a number of procedures in the use of RMs to avoid invalid results. 

---