Lyophilized human whole blood for internal and external quality assurance of lead in blood assays

Summary Lyophilized human whole blood control material containing lead was prepared for internal and external quality assurance to evaluate and improve the analytical performance of lead.The samples were prepared in four different concentrations from outdated human whole blood stabilized with glucose and a citrate/phosphate buffer and provided under clean room conditions to avoid contamination. The lyophilized samples are easy to reconstitute with water. The materials were evaluated according to a statistical model.The lead concentrations in the specimens are close to blood lead levels usually following environmental and industrial exposure, particular in occupational health to the control of lead exposure at work regulations. The materials are available to the commercial as well as the scientific community.The Danish External Quality Assessment Scheme (DEQAS) for lead in blood is intended to complement the internal quality control for the Danish laboratories assaying lead in blood. During 1990 the scheme will be tested in an international external assessment scheme.     

The use of reference materials in the fossil fuels quality control

The determination of trace elements in fossil fuels is of primary importance to achieve correct evaluation of environmental impact of power plants. The characterization of coals and fuel oils can be carried out by several analytical techniques such as ICP-MS, FI-HG-AAS, ETA-AAS, ICP-AES and XRF. The accuracy of the analysis, done to routine basis, can be systematically checked by means of the reference materials available or comparing the results obtained by different techniques. Quality control activities in the field of trace element determination in fossil fuels (coal and fuel oil) are described. The determination of As, Hg and Se in coals was carried out by different techniques (NAA, FI-HG-AAS and FI-ICP-MS) together with the determination of several trace metals in residual fuel oils by NAA, ETA-AAS and ICP-MS. The use of certified reference materials in order to check the accuracy of procedures is discussed and the results obtained for NIST 1632a and NIST 1632b (coal samples) and NIST 1634b and NIST 1619 (fuel oil samples) are reported.     

Bovine reference materials for accuracy control of blood lead analysis

Summary There is a lack of suitable commercially available reference materials for controlling the accuracy of determinations of trace elements in body fluids. This is a particular problem with blood lead measurements where results on individual patients or findings of population surveys may have major clinical, environmental or economic implications.Bovine blood haemolysate surrogate reference materials for internal accuracy control of blood lead measurements have been used systematically over the past decade by the SAS Trace Elements Sub-group in Britain. They have also been used by participating laboratories in the European Community Screening Programme for blood lead in an effort to harmonise the data.The seven SAS laboratories have collaborated in assigning values for blood lead concentration to three specially prepared batches of bovine reference materials between 1984 and 1987. The results show that it is possible for a small group of specialist laboratories to accurately and reproducibly assign values for reference materials in this way, so as to be suitable for use in internal accuracy control. Moreover, it has been possible to demonstrate the stability of the materials over a two-year period. This procedure offers a useful model for improving the accuracy of other assays of clinical interest.

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Rinder-Referenzmaterialien zur Richtigkeitskontrolle von Bleianalysen in Blut

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Presented on behalf of the Trace Elements Sub-group of the Supraregional Assay Service (SAS) of the U.K. National Health Service     

Fit-for-purpose shellfish reference materials for internal and external quality control in the analysis of phycotoxins

The need for reference materials for quality control of analysis of foodstuffs has been stressed frequently. This has been particularly true in the phycotoxins field, where there is a great shortage of both pure calibration standards and reference materials. Worldwide there are very few independent bodies that produce certified reference materials for phycotoxins, the main producers currently being the National Research Council Canada and the Japanese Food Research Laboratory. Limited availability of contaminated shellfish and algae, as well as the time and knowledge necessary for the production of adequate reference materials, continuously lead to limited editions of certified reference materials and even more limited production of in-house reference materials. The restricted availability of in-house quality control materials promotes the rapid use of the limited certified reference materials, which in turn hampers the production of the suite of materials required globally for complete protection of public health. This paper outlines the various options that analysts can pursue in the use of reference materials for internal and external quality control, with a view to optimising the efforts of both reference materials users and reference materials producers. For this purpose, the logical sequence is reviewed from the discovery of a new bioactive compound in shellfish, through initial method development up to regulation for food safety purposes including accepted reference methods. Subsequently, the requirements for and efforts typically spent in the production and characterisation of laboratory reference materials, certified reference materials and other test materials used in inter-laboratory studies or proficiency testing, in the area of marine biotoxins are evaluated. Particular emphasis is put on practical advice for the preparation of in-house reference materials. The intricate link between reference material characterisation and method performance is outlined to give guidance on the appropriate in-house method validation in the rapidly developing field of phycotoxins.      

The use of solution thermochemistry in quality control methods in pharmaceutical analysis

Some of the procedures that have been reported for the determination of the active ingredients in dosage forms of some ethical pharmaceutical products are reviewed. The requirements of methods for quality control and the advantages of using thermochemical methods to achieve them are discussed.     

Rapid and reliable determination of elevated blood lead levels

Summary For the control of lead exposed persons the most important parameter is the blood lead (PbB) level. Since for PbB in various countries maximal permissible threshold levels exist, analytical methods with high precision and accuracy are required. During the continuous control of a lead exposed collective two in principle well suited methods have been compared: graphite furnace AAS (GFAA), evaluation against control samples with known lead contents, and staircase stripping voltammetry directly applied in dilute blood, evaluation against calibration solutions. The GFAAS procedure obtained on average, depending on the number of subsamples and firings per sample, an imprecision from about 2.5 to about 5%, the voltammetric procedure one of 5%. Sample throughput is comparable at the same imprecision. Accuracy of both procedures could be checked by mass spectrometric isotope dilution analysis (MS-IDA) and differential pulse anodic stripping voltammetry (DPASV) after complete digestion and was found to be quite satisfactory.

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Rasche und zuverlässige Bestimmung erhöhter Blutbleispiegel

Zusammenfassung Bei der Überwachung bleibelasteter Personen ist die Ermittlung der Blutbleikonzentration (PbB) der wichtigste Parameter. Da für PbB in zahlreichen Ländern maximal zulässige Konzentrationen festgelegt wurden, müssen hohe Anforderungen an Präzision und Richtigkeit der angewandten Analysenverfahren gestellt werden. Bei der laufenden Überwachung eines bleibelasteten Kollektivs konnten zwei prinzipiell hierfür besonders geeignete Methoden miteinander verglichen werden: Graphitofen-AAS (GFAAS), Auswertung gegen Kontrollproben mit bekanntem Bleigehalt, und Staircase-Stripping-Voltammetrie direkt im verdünnten Blut, Auswertung gegen zwei Eichlösungen. Das GFAAS-Verfahren erreicht im Mittel eine Unpräzision von ca. 2,5 bis ca. 5% abhängig von der Zahl der Aliquote und Einzelmessungen pro Probe, das voltammetrische Verfahren eine Unpräzision von ca. 5%. Der Probendurchsatz ist bei vergleichbarer Unpräzision etwa gleich. Die Richtigkeit beider Verfahren wurde mit Hilfe der Isotopenverdünnungs-Massenspektrometrie (MS-IDA) sowie der differentiellen anodischen Pulsinversvoltammetrie (DPASV) nach vollständigem Aufschluß überprüft; sie ist recht zufriedenstellend.

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Dedicated to Prof. Dr. W. Fresenius on the occasion of his 70th birthday     

Performance tests and internal quality control activities for the routine analytical use of composite electrodes

The use of a solid electrode in routine analytical work is proposed as a good alternative for electroanalytical detection. The performance of the electrode for oxidative voltammetry was studied for the model compound, catechol. Some theoretical aspects of the preparation and features of the PVC-graphite composite electrode are shown. A protocol has been described for its construction and general advice for the appropriate use. Quality control activities were designed to check the performance of the electrode. Received: 7 October 2000 Accepted: 19 July 2001     

Development of candidate reference materials for the measurement of lead in bone

The production of modest quantities of candidate bone lead (Pb) reference materials is described, and an optimized production procedure is presented. The reference materials were developed to enable an assessment of the interlaboratory agreement of laboratories measuring Pb in bone; method validation; and for calibration of solid sampling techniques such as laser ablation ICP-MS. Long bones obtained from Pb-dosed and undosed animals were selected to produce four different pools of a candidate powdered bone reference material. The Pb concentrations of these pools reflect both environmental and occupational exposure levels in humans. The animal bones were harvested post mortem, cleaned, defatted, and broken into pieces using the brittle fracture technique at liquid nitrogen temperature. The bone pieces were then ground in a knife mill to produce fragments of 2-mm size. These were further ground in an ultra-centrifugal mill, resulting in finely powdered bone material that was homogenized and then sampled-scooped into vials. Testing for contamination and homogeneity was performed via instrumental methods of analysis.

The new ISO Guide 80: Guidance for the in-house preparation of quality control materials (QCMs)

Reference materials (RMs) are widely used in measurement laboratories for a variety of purposes, and it is important to recognise that the material most appropriate for a particular application should be used. Certified reference materials (CRMs) are used for method validation, the calibration of a measurement system and all other aspects of the evaluation of the measurement system where the trueness of the measurement result is required. For other aspects, such as quality control, precision studies, the checking of the variability between operators, where the results are compared relatively, any suitable reference material can be used. ISO/REMCO, the ISO Committee on Reference Materials, has prepared ISO Guide 80, a guidance document for the in-house preparation of quality control materials (QCMs). QCMs are mostly used to monitor the performance of laboratory methods that have already been validated over time to be able to detect change or when a method goes out of statistical control. QCMs are RMs and as such have to be sufficiently homogeneous and stable for the intended use. QCMs are usually prepared in-house by laboratory staff for in-house use only, and therefore, the requirements for “in-house” QCMs are less demanding than those for a CRM. For example, transport issues are not of concern. The quality assessment of QCMs should involve homogeneity and stability assessments, and a limited characterisation of the material to provide an indication of its relevant property values and their variation, prior to use.     

A proficiency test scheme for the quality control of black tea and development of quality control material for internal quality control

A proficiency test (PT) was organized for quality control analysis of black tea. Test materials for the analyses of total content of powder tea, moisture, total ash, acid-insoluble ash, water-soluble ash, alkalinity of water-soluble ash, water extract, crude fiber and caffeine were sent to the participant laboratories (n:43) in 2009. The assigned value, standard deviation of the parameters and z-scores of the participant laboratories were calculated using the data reported by the participants. The percentage of the reported results for analytes was found to be ranged from 67.5 to 100%. Acceptable z-scores were achieved by 80.5–97.5% of the participant laboratories. More than 15% of unacceptable results were obtained for acid-insoluble ash and caffeine analyses. The quality control material for quality control analysis of black tea was developed from the remaining material.     

Application of standard materials and standard reference materials in the analysis of lead in blood

Summary Valuable information can be obtained at little expenses from quality control samples prepared in-house to monitor the determination of blood lead by atomic absorption spectrophotometry. Commercially manufactured control materials can also be used for this purpose. These materials are compared to standard reference materials which at present are available.The relative standard deviations for analysis of NBS standard reference materials were 15.4–2.8% (range 60–754 g/l) and in agreement with the relative standard deviation estimated for the analytical method. The corresponding figures for BCR control reference materials were lower: 1.1–1.4% (range 134–795 g/l).The average analytical bias demonstrated by analysis of NBS standard reference material and BCR control reference material were 3–6% (range 795–60 g/l) and in agreement with bias estimated by analysis of commercially manufactured and in-house prepared control materials.     

Alternative methods for internal quality control in research laboratories for environmental analysis: a programme for the performance evaluation of equipment, methods and staff

In analytical research laboratories, the problem of quality assurance is more difficult to solve than in laboratories devoted exclusively to routine analysis: the former usually have to deal with a much greater variety of samples and may have to develop entirely new methods of analysis. For research laboratories we have developed several alternative methods of quality assurance. These methods can be used to distinguish between different analytical methods, between different types of equipment, between different levels of skill among laboratory technicians, or even between the performance of technicians of the same level of skill.     

Strategies for internal quality control in antidoping analyses

Internal quality control (IQC) is one of the most important elements contributing to quality assurance in the laboratory. In this study, the strategy for the implementation of an IQC program to monitor performance of the analytical procedures used in an antidoping control laboratory is presented. Different IQC parameters have been defined according to the aim of the method (qualitative or quantitative, screening or confirmation). They are based on the analysis of control and calibration samples in each analytical batch and on the use of an internal standard in chromatographic methods. IQC parameters for chromatographic and immunological methods and the acceptance criteria used to check the quality control data obtained are described and discussed. These IQC procedures have been applied during routine antidoping analyses of more than 5000 samples per year in a laboratory accredited by the International Olympic Committee (IOC) and meeting the requirements of the quality standard ISO 17025.     

The use of standards for quality control in activation analysis

The control of analytical data by randomly inserted standards or reference materials is quantified in terms of elementary statistics. The consequences of a given number of standard aliquots are interpreted on the basis of the a priori expectation on the average defective fraction. It appears that, in most cases, standards serve to detect sudden large errors only. Some practical examples are considered.     

The complementary use of radioanalytical methods and trace analysis methods for the characterisation of environmental IAEA reference materials

The IAEA laboratories have access to both nuclear analytical methods and conventional instrumental methods for trace analysis for the characterisation of its environmental and biological reference materials. A technical concept integrating the homogeneity data, the recommended test portion mass and the uncertainty on the trace element concentrations is explored using a combination of INAA, XRF, ICP-MS, ICP-AES, and AAS. The above approach is illustrated by selected examples of reference materials currently under evaluation for their trace element content. They include some or all of the following elements Al, As, Br, Ca, Cd, Co, Cr, Cs, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, Rb, Se, Sr, Th, U, Zn in environmental biomonitor organisms (lichen, algae) and air dust filters.     

The use of hydrothermal methods in the synthesis of novel open-framework materials

The preparation of inorganic compounds, exhibiting open-framework structures, by hydrothermal methods has been presented. To illustrate the efficacy of this approach, few select examples encompassing a wide variety and diversity in the structures have been provided. In all the cases, good quality single crystals were obtained, which were used for the elucidation of the structure. In the first example, simple inorganic network compounds based on phosphite and arsenate are described. In the second example, inorganic-organic hybrid compounds involving phosphite/arsenate along with oxalate units are presented. In the third example, new coordination polymers with interesting structures are given. The examples presented are representative of the type and variety of compounds one can prepare by careful choice of the reaction conditions.     

Certified reference materials (CRM's) for the quality of measurement

Summary A survey of procedures for analytical quality control with emphasis on the use of certified reference materials is given. Requirements for the use and for the preparation of reference materials are presented.     

Nanotechnology-Derived materials: Potential risk in preparation and use

Nanomaterials are increasingly used for commercial purposes owing to their specific physicochemical properties. At the same time, the associated potential risks still remain to be elucidated. In this context, the biocompatibility and toxicity of new nanomaterials were discussed.     

Quality control in the analysis of lead and cadmium in blood

Summary An extensive quality control programme has been developed within a global UNEP/WHO project on Assessment of Exposure to Lead and Cadmium through Biological Monitoring. This project was coordinated by the Karolinska Institute (Department of Environmental Hygiene) and the National (Swedish) Institute of Environmental Medicine. The project was carried out within the framework of UNEP's Global Environmental Monitoring System (GEMS) and was initiated in 1978 on the basis of recommendations from a UNEP/WHO meeting of a Government Expert Group on Health-Related Monitoring.On termination of the project in 1981 it was decided to extend the analytical QC assurance programme on a periodic basis in order to maintain the analytical capability of the participating laboratories. A QC programme was conducted by our Institute in a follow-up study of the above mentioned UNEP/WHO programme and for a National Swedish Board of Occupational Safety and Health project, as well as for a recently concluded project in which a decrease in bloodlead levels in residents of Stockholm for the period 1980–1984 was established.In the latter project decreased blood-lead levels of about 20% were found in samples stored frozen (–20 ° C) for 4 years. This finding stimulated a study of the long-term stability of our QC samples. Results of lead and cadmium analyses performed for each QC sample during 1980–1985 were computerized. The results showed that the QC samples appeared to be stable for 2–3 years when stored at –20 °C. The losses of cadmium were 5 –10% in 5–6 years of storage at –20 ° C and seem to be less than those of lead (7–15%). Analysis of several QC sets, prepared on different occasions, but analyzed on the same day, confirmed that losses occur.