Proficiency testing in analytical chemistry, microbiology and laboratory medicine: working discussions on current practice and future directions

A summary of the working group (WG) discussions on proficiency testing (PT) and external quality assessment (EQA) held at the Eurachem Workshop, Rome, 5–7 October 2008 is provided. The eight WG’s covered a range of issues concerned with current practice and future directions; how frequently should laboratories participate in PT/EQA? (WG1); developments in PT/EQA within the EU—what is required in future? (WG2); what issues do developing countries face with regards to PT/EQA? (WG3), what issues are specific to microbiology PT/EQA? (WG4); what new fields are emerging for PT/EQA? (WG5); what will be the impact of the new ISO/IEC 17043 standard? (WG6); do current PT/EQA schemes meet the needs of participants? (WG7); and what are the issues that affect the quality of proficiency test items? (WG8). Delegates with different backgrounds were on each WG in order to capture a range of views and experience from a number of different sectors. Working group representatives included PT/EQA providers, participants in PT/EQA schemes and end users of PT results such as accreditation bodies and regulatory authorities, from countries around the world.     

Proficiency testing in analytical chemistry, microbiology and laboratory medicine: working group discussions on current practice and future directions

A summary of the working group (WG) discussions on proficiency testing (PT) and external quality assessment (EQA) held at the joint EURACHEM/CITAC/EQALM workshop, Bracknell, UK, 16–18 February 2003 is provided. The nine WGs covered a range of issues concerned with current practice and future directions; PT/EQA as a tool for regulators (WG1); PT/EQA as a tool for accreditation (WG2); evaluation of performance and uncertainty (WG3); frequency of PT/EQA participation (WG4); selection of appropriate PT/EQA schemes (WG5); added value of PT/EQA and cost benefit evaluation (WG6); global harmonisation and rationalisation (WG7); new technical areas and challenges in PT/EQA (WG8); and accreditation of PT/EQA providers (WG9). Participants with different backgrounds were on each WG in order to capture a range of views and experience from different sectors. The discussions reflected on the keynote lectures and built, in many cases, on discussions at previous workshops in 2000 and 2002.     

Proficiency testing in analytical chemistry,microbiology and laboratory medicine: discussions on current practice and future directions

Accreditation and Quality Assurance - A summary of the working group discussions on proficiency testing (PT) and external quality assessment (EQA) held at the Eurachem Workshop, Portorož,...     

Method validation in analytical sciences: discussions on current practice and future challenges

Accreditation and Quality Assurance - Eurachem held a workshop on method validation in analytical sciences in Gent, Belgium, on 9–10 May 2016. A summary of the working group discussions is...     

Derivatization in the current practice of analytical chemistry

A case is presented that analytical derivatization merits consideration in the development of modern analyses. The review demonstrates that there is sufficient data in the current literature to support such a contention. Whether using high-technology instrumentation or immunological methods that are also inherently specific and highly sensitive, investment of time and reagents pays off in higher sensitivity and improved structural information. Moreover, considerable development of automation in methods that employ analytical derivatizations has begun to answer concerns about cost-effective use of these reactions. However, the literature also cautions that such desired outcomes need to account for the complexity of the factors controlling the reaction rates for different molecules and the possibility of artefacts associated with oxygen. In biomedical analyses, there is also a particular need to take cognizance of the biochemistry involved in the formation of the analytes.     

Proficiency testing in analytical laboratories: how to make it work

 This paper covers the role of proficiency testing schemes in providing an occasional but objective means of assessing and documenting the reliability of the data produced by a laboratory, and in encouraging the production of data that are "fit-for-purpose". A number of aspects of proficiency testing are examined in order to highlight features critical for their successful implementation. Aspects that are considered are: accreditation, the economics and scope of proficiency testing schemes, methods of scoring, assigned values, the target value of standard deviation σ_p, the homogeneity of the distributed material, proficiency testing in relation to other quality assurance measures and whether proficiency testing is effective. Stress is placed on the importance of any proficiency testing scheme adhering to a protocol that is recognised, preferably internationally. It is also important that the results from the scheme are transparent to both participating laboratory and its "customer". Received: 03 November 1995 Accepted: 20 November 1995     

Integrating accreditation, good laboratory practice and good manufacturing practice in an industrial analytical laboratory

 The Analytical Laboratory of BASF is a central service unit for chemical analysis which can be used by all departments within the company. It carries out routine as well as non-routine work and has a high amount of R&D orders. A quality system conforming with GMP rules was installed in the 1970s, followed by a GLP system about 6 years later. In 1995 an EN 45001 certificate was granted, which also stated the conformity with ISO 9002. A "types of test" orientated system was chosen for accreditation. This was better suited to the needs of a testing laboratory with a high amount of non-routine work than a purely test-procedure orientated accreditation. An integrated quality system has now been developed from these activities. It has partly common elements and partly differing elements taking into account specific regulations. For example, instrument calibration, staff training, validation of test procedures and the use of computerized systems are covered by uniform rules. Other elements such as handling of samples and report generation are arranged according to the individual requirements of the various standards. Rules and regulations are laid down in a system of documents which comprise the quality manual, general standard operating procedures (SOPs), laboratory-specific SOPs and test procedures. The quality system has been accepted by other accreditiation bodies on application of special accreditations (workplace safety, biodegradable polymers). But it has had no advantageous influence on getting GLP certification. An integrated system is very complex and requires appreciable resources. Management of processes and documentation can only be handled by extensive use of computers. Frequent training of staff and internal audits are necessary to keep the system at an acceptable level. In order to reduce the complexity of quality management regulations a harmonization of the different quality systems would be desirable. Received: 1 October 1998 · Accepted: 10 January 1999     

Resonance light scattering and derived techniques in analytical chemistry: past, present, and future

From 1993 to 1995, with a conventional fluorescence spectrophotometer (CFS) (convenient) and working in a synchronous scan model (easy-to-use), Pasternack et al. proposed the resonance light-scattering (RLS) technique, to efficiently characterize self-assemblies or self-aggregations of chromophores with good electronic coupling. Incident wavelengths were specially considered within their absorption envelopes (rather unorthodox), and their amplified signals were observed (good sensitivity and selectivity). Due to these absorbing benefits, RLS technique, as a novel readout method, commenced on its exciting analytical tours soon after Liu et al. and especially Li et al., separately, set out their corresponding pioneering investigations from 1995 to 1997. From then on, it has received an increasing attention by analysts, as a consequence exhibiting more and more fascinating analytical applications. Moreover, various attractive RLS-derived techniques have been developed successively to improve it or to enlarge its possibilities. Later on, Liu et al. and Li et al., Tabak et al., Yguerabide et al., Huang et al., Lakowicz et al. and Fernández Band et al. have made their outstanding contributions. In this review, we concentrate on major achievements of RLS in analytical chemistry for over a decade, involving the developments and analytical applications of RLS derived techniques treated as an impacting progress of RLS technique in analytical chemistry. Finally, an indication of future directions of RLS technique in analytical chemistry is provided.     

The clinical chemistry laboratory: current status, problems and diagnostic prospects

Although increased automation, advanced analytical techniques and sophisticated information technology have greatly improved the performance and quality in medical laboratory testing, several studies show that significant amounts of errors occur. Detailed analysis revealed that most of the errors occur in the preanalytical phase, while fewer errors occur in the intra- and post-analytical phase. The majority of errors are caused by wrong sampling or occur during transport to the laboratory. This review focuses on the analytical procedures in a large central laboratory. Possible problems are described by following samples from the patient to the laboratory and back. Finally, the advantages and disadvantages of point-of-care testing versus central laboratory are compared.     

Inductively coupled plasma-atomic emission spectroscopy: Its present and future position in analytical chemistry

Summary This review (with 179 references) is mainly intended to facilitate judgements about the present and future position of inductively coupled plasma-atomic emission spectrometry (ICP-AES) among both various established spectroscopic methods and AES methods based on novel plasma sources for liquid analysis. It is considered that a thorough and critical comparison of the capabilities and cost of ICP-AES with those of the existing outfit of a laboratory must be made in each individual situation separately to judge whether ICP-AES as a supplement to or a replacement of one or more established techniques is an economic proposition. From this point of view ICP-AES is reviewed as a relatively new method for the analysis of liquids and dissolved solids.The principle of the method and the basic instrumentation are briefly outlined. The distinction between low-power argon ICPs and high-power nitrogen-argon ICPs is pointed out and the viability of both approaches in the analysis of real samples is noted. Analytical performance is discussed in terms of detection limits, precision, accuracy and dynamic range. Applications of real-sample analysis are given as illustrative examples.A list is included of the best detection limits of 67 elements in aqueous solutions as reported for argon ICPs operated with pneumatic and ultrasonic nebulizers. Detection limits of 15 elements in oil are given to illustrate the potentials of low-power argon ICPs in the field of organic liquid analysis. The detection limits of As, Sb, Bi, Se and Te as achieved by combining hydride generation with an argon ICP, are presented to demonstrate recent progress in the determination of elements for which the detection power was hitherto less satisfactory than desired.With regard to precision, the behaviour of ICPs is pointed out as fluctuation-nose limited systems that are dominated by a relative standard deviation (RSD) of 1 % in both background and net signals as generated in the source. The dependence of the RSD in the eventually measured net signals (gross signal minus background signal) on the ratio of concentration to detection limit is discussed.An extensive discussion of accuracy incorporates detailed reference to factors such as spectral interferences and reagent impurities, nebulization and transport interferences, solute vaporization interferences, and ionization interferences, which may affect the accuracy attained in ICP-AES. It is shown that ICP-AES is relatively free from interferences so that a fair degree of accuracy can be reached, if proper precautions are taken, which, in comparison with AES methods using other excitation sources, or AAS, are not excessive. It is added, however, that the measures needed to ensure fair accuracy will become increasingly severe as the analyte concentration approaches the detection limit more closely or the composition of the sample becomes more complex. It is noted that under these conditions the problems that arc spectroscopists had to face in trace analysis using dc arc spectrography are again encountered, in particular as regards the correct isolation of a net line signal from a background spectrum whose structure depends on the sample composition.The advantages of the large linear dynamic range of three to five orders of magnitude are mentioned.The numerous applications of ICP-AES reported in literature are illustrated with a list of classes of materials for which analyses were described recently.Spectrometers enter into the discussion as indispensable parts of ICP equipment that are necessary for complete analytical instruments and the price of which may be a multiple of that of the ICP source itself. Alternative spectrometers for ICP-AES are grouped into three categories depending on the type of analysis problem: 1) general survey analysis, 2) routine multielement analysis and non-routine multielement analysis with limited flexibility, and 3) flexible single-element analysis.This classification, which fits in with general cost and performance considerations, is used as a convenient basis in the subsequent assessment of the position of ICP-AES among established spectroscopic methods. This assessment encompasses comparisons of the capabilities of ICP-AES, flame AES, flame and furnace atomic absorption spectrometry (AAS), de arc AES, spark AES, and X-ray fluorescence spectrometry (XRFS).The position of ICPs with respect to alternative novel plasma sources for liquid analysis by AES is discussed in the light of the historic development. This eventually led to the present situation in which there are at least twelve manufacturers of spectroscopic equipment that are marketing ICP apparatus and one marketing a dc plasma source for liquid analysis, while a renewed commercialization of a capacitively coupled microwave plasma (CMP) is stimulating new interests in CMPs. As to microwave-induced plasmas (MIP), attention is drawn in particular to the TM₀₁₀ cavity that permits the generation of atmospheric pressure plasmas in helium. These have excellent characteristics as element-selective detectors in gas chromatography and also have many potential applications in multielement and single-element analysis in general, especially for the analysis of microsamples, if these are separately evaporated and atomized, e.g. by electrothermal means, prior to their introduction into the MIP.

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ICP-AES: Gegenwärtige und zukünftige Stellung in der Analytischen Chemie

Zusammenfassung Diese Übersicht (mit 179 Literaturzitaten) beabsichtigt hauptsächlich, die gegenwärtige und zukünftige Stellung der atomaren Emissions-Spektrometrie unter Verwendung eines induktiv gekoppelten Hochfrequenz-Plasmas (ICP-AES) sowohl unter den verschiedenen herkömmlichen, »bewährten« spektroskopischen Methoden als auch unter den AES-Methoden mit neuen Plasmaquellen für Flüssigkeitsanalysen zu verdeutlichen. Nach gründlichem und kritischem Vergleich der Leistungsfähigkeit und Kosten der ICP-AES gegenüber schon bestehenden Laboreinrichtungen muß die Wirtschaftlichkeit der ICP-AES je nach Situation als mögliche Ergänzung oder als möglicher Ersatz zu den herkömmlichen Techniken bewertet werden. Im Hinblick darauf wird die ICP-AES als eine relativ neue Methode zur Analyse von Flüssigkeiten und gelösten Feststoffen untersucht.Das Prinzip der Methode und die Grundausrüstung werden kurz erklärt. Dabei wird auf den Unterschied eines Argon-ICPs niedriger Leistung gegenüber einem Stickstoff-Argon-ICP hoher Leistung hingewiesen und die Fähigkeit dieser beiden Arten für Analysen realer Proben besprochen. Die Analysenfähigkeit im allgemeinen wird anhand von Nachweisgrenzen, Genauigkeit, Richtigkeit und dynamischem Bereich diskutiert. Typische Anwendungsbeispiele werden erwähnt.Eine Zusammenstellung der besten Nachweisgrenzen von 67 Elementen in wäßrigen Lösungen wird für Argon-ICPs mit pneumatisch und mit Ultraschall betriebenem Zerstäuber gegeben. Nachweisgrenzen von 15 Elementen in Öl werden angeführt, um die Anwendungsmöglichkeiten von Argon-ICPs niedriger Leistung auch im Bereich der organischen Flüssigkeitsanalysen zu zeigen. Die Nachweisgrenzen von As, Sb, Bi, Se und Te, die durch eine Kombination von Hydridbildung und Argon-ICP erreichbar sind, werden dargestellt, um den neuesten Fortschritt in der Elementbestimmung zu zeigen, wo bisher das Nachweisvermögen noch nicht ausreichend war.Bei der Behandlung der Genauigkeit wird auf die Eigenschaft des ICPs als ein durch Schwankungsrauschen in der Lichtquelle begrenztes System hingewiesen, was durch die relative Standardabweichung (RSD) von 1 %, sowohl in den Untergrund- als auch Nettosignalen, wie sie die Quelle selbst bewirkt, deutlich wird. Die Abhängigkeit der RSD in den schließlich gemessenen Nettosignalen (Bruttosignal minus Untergrundsignal) vom Verhältnis Konzentration zu Nachweisgrenzen wird diskutiert.Eine ausführliche Besprechung der Richtigkeit umfaßt detaillierte Angaben über Faktoren wie spektrale Interferenzen, Reagensunreinheiten, Zerstäubungsund Transportinterferenzen, Verdampfungsinterferenzen und schließlich Ionisationsinterferenzen, die alle für die erreichte Richtigkeit ausschlaggebend sein dürften. Es wird gezeigt, daß die ICP-AES relativ frei von Interferenzen ist, so daß gute Richtigkeit in beträchtlichem Maß erreicht werden kann, wenn geeignete Vorsichtsmaßnahmen getroffen werden, die weniger aufwendig als diejenigen anderer AES-Methoden oder der AAS sind. Es wird jedoch ausgeführt, daß die zur Erzielung guter Richtigkeit erforderlichen Maßnahmen, immer aufwendiger werden, sobald die Analysenkonzentration sich mehr und mehr der Nachweisgrenze nähert oder die Proben komplexer werden. Dazu ist zu sagen, daß hier wieder die gleichen Probleme auftauchen, mit denen sich die Bogenspektroskopiker bei der Anwendung des Gleichstrombogens in der Spurenanalyse zu befassen hatten, besonders hinsichtlich der korrekten Abtrennung eines Nettosignals vom Untergrundspektrum, dessen Struktur von der Probenzusammensetzung abhängt.Der Vorteil des großen linearen dynamischen Bereichs über drei bis fünf Größenordnungen wird erwähnt.Die zahlreichen Anwendungen der ICP-AES werden in einer Liste nach denjenigen Matrialklassen aufgeführt, die in der neuesten Literatur beschrieben sind.Spektrometer werden als unentbehrlicher Teil einer ICP-Ausrüstung diskutiert, der zu einem vollständigen Analysengerät gehört und dessen Preis ein Vielfaches von dem der ICP-Quelle selbst betragen kann. Die unterschiedlichen Spektrometer für die ICP-AES werden in drei Gruppen eingeteilt, abhängig von der Art des Analysenproblems: 1. Allgemeine Übersichtsanalysen, 2. routinemäßige Multielementanalysen und nichtroutinemäßige Multielementanalysen mit beschränkter Flexibilität, und 3. flexible Einzelelementanalysen. Diese Klassifikation, angepaßt an die allgemeinen Kosten und Leistungsbetrachtungen, wird als nützliche Basis zur nachfolgenden Einschätzung der Stellung der ICPAES unter den herkömmlichen, »bewährten« spektroskopischen Methoden verwendet. Diese Einschätzung schließt Leistungsvergleiche zwischen ICP-AES, Flammen-AES, Flammen- und Ofenatomabsorptionsspektrometrie, Gleichstrombogen-AES, Funken-AES und Röntgenfluorescenzspektrometrie (XRFS) ein.Die Stellung des ICPs gegenüber anderen neuen Plasmaquellen für Flüssigkeitsanalysen durch AES wird im Hinblick auf die geschichtliche Entwicklung behandelt. Diese führte schließlich zu der heutigen Situation, wo mindestens 12 Hersteller von Spektrometerausrüstungen ICP-Geräte (einer mit einer Gleichstromplasmaquelle) anbieten, währenddem erneuter Handel mit einem kapazitiv gekoppelten Mikrowellenplasma (CMP) neue Interessen an CMPs weckt. Was Mikrowellen induzierte Plasmen (MIP) betrifft, wird die Aufmerksamkeit speziell auf den TM₀₁₀-Hohlraum gerichtet, der die Erzeugung von Helium-Plasmen bei atmosphärischem Druck ermöglicht. Diese MIPs haben ausgezeichnete Eigenschaften als element-selektive Detektoren in der Gas-Chromatographie und bieten auch viele Verwendungsmöglichkeiten bei allgemeinen Multielement- und Einzelelementanalysen, speziell für Mikroproben, wenn diese vor der Eingabe in das MIP getrennt verdampft und atomisiert werden (z.B. elektrothermisch).

     

Proficiency testing in food microbiology: experience from implementation of ISO/IEC 17043 and ISO/TS 22117

The proficiency testing (PT) scheme ??AQUA?? for food microbiology was organised by the Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe) according to ISO/IEC 17043 and ISO/TS 22117. This paper describes the IZSVe experience on the application of the above-mentioned standards for the PTs, with focus on the Enterobacteriaceae enumeration one. Freeze-dried food matrices contaminated with American Type Culture Collection bacterial strains were used as test samples for each microbiological PT organised by IZSVe. The sample homogeneity and stability were verified prior to distribution to participants and throughout the PT, respectively. The participating laboratories analysed samples using their routine methods, and results were transmitted to IZSVe. Data and methods used by each participating laboratory were analysed in order to evaluate the laboratory performance. With reference to the Enterobacteriaceae PT, the test samples were homogeneous and stable. In addition, most laboratory results were obtained using equivalent test methods. Statistical approaches applied to analyse data generated from all participating laboratories revealed similar outcomes as no significant outlying count and only 5?% of unacceptable results were observed. Finally, the z-score, with the standard deviation that does not vary from round toround, was applied to compare and to evaluate the performance of each laboratory over time highlighting possible persistent trends over several rounds.     

Past, present, and future of applications of electroanalytical techniques in analytical and physical organic chemistry

After a brief introduction describing the main milestones in the development of DC polarography (DCP) as well as linear sweep (LSV) and cyclic voltammetry (CV), attention is paid to first applications of DCP in the reduction of organic compounds. In aqueous solutions the electron transfer (ET) is often accompanied by a proton transfer. Limiting currents in DCP enable investigation of kinetics of chemical reactions preceding ET. Dependence of the limiting current on concentration of a reagent, like H⁺ or OH^{??/sup> ions, enables determination of rate constants (k) of very fast reactions, with k values between 104 and 1010?L?mol???s??, comparable with those studied by relaxation methods. Application of CV is most advantageous for investigation of rates of chemical reactions following the ET. Comparison of analytical applications of DCP (reductions) with those of LSV (oxidations) is given. Apart from fast reactions taking place before the ET in the solution in the vicinity of the electrode surface, DCP can also be used for investigation of slower reactions, taking place in the bulk of the solution. Data obtained by DCP for determination of equilibrium (K) and rate (k) constants of reactions of organic compounds. Hence, DCP can be used in physical organic chemistry of solutions, in some cases complementing data obtained by UV–vis spectrophotometry. Some examples of determinations of K and k are given. Uncertain future of practical analytical applications of DCP and LSV is discussed as is the brighter future of applications in physical organic chemistry. As the main factor limiting successful applications is considered the limited opportunity for education of future research advisors in academia and group supervisors in industry.}