Comprehensive quality control programme for serology and nucleic acid testing using an Internet-based application

The National Serology Reference Laboratory, Australia (NRL) has quality assured the serology for high risk blood-borne infections since 1985, commencing with anti-Human Immunodeficiency Virus (HIV) enzyme immunoassays and later extending the programmes to other blood-borne virus testing and to nucleic acid testing. A quality control (QC) programme was considered the most appropriate manner in which to achieve real-time monitoring. An Internet-based application, EDCNet, facilitates the entry of results of QC sample testing and returns the analysed results instantaneously. Results can be displayed in a variety of tables and charts, so that QC results from blood service and diagnostic laboratories can be monitored. Comparison of results between laboratories using the same system offers monitoring of accuracy, while within-laboratory comparisons offer monitoring of the assay precision. More than 200,000 data points were submitted to EDCNet in 2002 from blood service laboratories as well as from diagnostic laboratories. Analysis of reagent batch variability was determined, e.g. the coefficient of variation between batches of seven assays used to detect anti-hepatitis C virus (HCV) antibodies ranged from 4.9% to 21.6%. Using EDCNet, laboratories can monitor both precision and accuracy of results by comparison with the results of other laboratories. The system may be a highly cost-effective method for maintaining quality.

The increasing demands of quality assurance in chemical testing

The chemical and microbiological testing community is going through a rather difficult period of change. Publication of ISO/IEC 17025 (General requirements for the competence of Calibration and Testing Laboratories, 1999) [1] is placing additional demands on testing laboratories to ensure traceability and estimate uncertainty in their measurements. At the same time, laboratories must remain mindful of the need to provide relevant, timely and economic services to their clients. International Accreditation New Zealand (IANZ) and its accredited laboratories are currently focussing on establishing realistic methods for ensuring traceability to national and international standards and estimating measurement uncertainty. To this end, IANZ recognizes that it has an important role in providing as much advice and assistance as possible, not only to its accredited chemical laboratories but also to all those contemplating accreditation in New Zealand.

EQUIP: a worldwide program to ensure the quality of urinary iodine procedures

In 2001 the Centers for Disease Control and Prevention (CDC) established a program, Ensuring the Quality of Urinary Iodine Procedures (EQUIP); to assist laboratories around the world and assess the accuracy of their urinary iodine (UI). CDC designed EQUIP to issue unknown specimens to participating laboratories three times per year. Each laboratory was asked to analyze unknown samples in duplicate on three different days. During the first five rounds of EQUIP, 41 laboratories participated, measuring unknown samples and reporting their results to CDC. CDC used these results to prepare a statistical report for the laboratories. Feedback to the laboratories provided external confirmation regarding performance. As a group, laboratory performance improved; several laboratories made considerable improvement. Several laboratories that showed no improvement have ordered new equipment or are arranging for additional training. EQUIP is a key tool used to support laboratory quality assurance in an effort to eliminate iodine deficiency disorders (IDD) in the world.

Correlation between repeated measurements: bane and boon of the GUM approach to the uncertainty of measurement

With measurement uncertainty estimation accounting for all relevant uncertainty contributions, the results of measurements using the same procedure on different objects or samples may no longer be considered as being independent, and correlations have to be taken into account. For this purpose, a simple approximation for the estimation of covariances is derived and applied to the estimation of uncertainty for some basic combinations of two measurement results. This covariance estimate is also applied to the estimation of uncertainty for the mean value of the results of replicate measurements on the same object or sample.

In defence of the correlation coefficient

The relationship between calibrated range, residual standard deviation and correlation coefficient r is discussed. It is shown that in typical chemical calibration applications with appropriately distributed calibration points (particularly, with range comparable to mean and with approximately even or with ‘successive dilution’ spacing), the linear correlation coefficient has valid application as a routine criterion for acceptable fit if used with due care.

Accounting for bias in measurement uncertainty estimation

Generic issues and current approaches in the evaluation of bias studies with respect to estimation of measurement uncertainty are discussed, focusing on two main scenarios. In the first, for a within-laboratory assessment of a fully developed uncertainty budget, bias studies are carried out to verify the pre-established performance of a measurement procedure, and design corrective actions if necessary. In the second scenario, for an estimation of measurement uncertainty from within-laboratory validation data, bias studies are carried out to calibrate the whole measurement procedure and evaluate its performance, more specifically to estimate the uncertainty of measurement by combination of bias and precision estimates.

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Update on COMAR: the Internet database for certified reference materials

This paper describes the COMAR database for certified reference materials (CRMs). The Web-based version of COMAR is freely accessible via the Internet. COMAR was established to assist laboratories in finding the CRMs needed. The database is maintained in a collaboration of the world’s major CRM producers. The planned changes in the database as agreed at the last COMAR council meeting in Prague in May 2006 are indicated.

Measurement uncertainty and the use of reference materials

The use of (certified) reference materials and quality control materials can form a suitable basis for evaluating measurement uncertainty of routine measurements. In particular when these materials are used for quality control purposes, it is not always evident how the quality control data can be used in the uncertainty budget of a routine measurement. Current guidance documents on the evaluation of measurement uncertainty and the use of reference materials treat this subject only in part, or in very generic terms. ISO/REMCO has established a new working group that will provide practical guidance and examples on how to use quality control data in the evaluation of measurement uncertainty. A short introduction to the subject is given.

Chemistry,commentary and community: Discussion of “The NaDyBr<Subscript>4</Subscript> complex: its molecular structure and thermodynamic properties” by Varga and Hargittai

The molecular geometries, relative stabilities, binding energies, and dissociation energies of NaDyBr₄ and its molecular ion are discussed. Both the bidentate and tridentate isomers are stable for the neutral species, while only the bidentate form is stable for NaDyBr₄ ⁺.

Branched trichain sulfosuccinates as novel water in CO2 dispersants

A series of highly branched trichain sulfosuccinate surfactants have been synthesized and studied in condensed CO₂ and aqueous environments. Aqueous critical micelle concentrations (CMCs) showed a general trend of increasing CMC with decreasing chain length, whereas increased branching appeared to increase solubility in CO₂ and aid the dispersion of water. Near infrared spectra confirmed observed cloud with a large increase in solubility above the cloud pressures in this solvent.

Model-based measurement uncertainty evaluation,with applications in testing

Basic concepts and implementations of the model-based approach to uncertainty evaluation are discussed. One implementation is that of the law of propagation of uncertainty with the use of the central limit theorem as recommended in the Guide to the expression of uncertainty in measurement (GUM). Another is the propagation of distributions, the subject of a supplemental guide to the GUM, which is at an advanced stage of development. It falls in the category of other analytical and numerical methods indicated in the GUM. Two testing applications are used to illustrate the principles: tennis-ball rebound and tensile strength.

A novel Ce<Superscript>III</Superscript>-cyclam type complex and its redox chemistry in aqueous solutions

A new Ce^III complex was synthesized by mixing the ligand “dioxocyclam” with Ce^III ions at pH 8.0 and its redox properties were investigated.

Preparation, structural, and optical features of two-dimensional cross-linked DNA/gold-nanoparticle conjugates

The formation and the optical features of two-dimensional aggregates formed by DNA-directed immobilization and cross-linking of bifunctional DNA–gold nanoparticles at flat gold substrates are analyzed. The samples are structurally characterized by atomic force microscopy to evaluate the particle size, the particle densities, and the degree of aggregation. The optical characteristics determined by UV/visible measurements are correlated with the structural features observed.

Food anaphylaxis

    Figure Avoidance is the primary measure in food allergy confirmed

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Chemistry, commentary, and community: discussion of “an examination of the vaporization enthalpies and vapor pressures of pyrazine, pyrimidine, pyridazine, and 1,3,5-triazine” by Lipkind and Chickos

Vaporization enthalpies for the isomeric diazines were discussed within the context of recent measurements and estimation techniques. It is suggested that pyridazine shows enigmatic behavior.

Metrological traceability: I make it 42; you make it 42; but is it the same 42?

The paper reproduces a talk given at a 2-day symposium on quality assurance in chemistry held in Brisbane, Australia in 2005. Intended for an audience of analysts in the field, the theme of the symposium drew inspiration from the series of books by Douglas Adams “The Hitchhiker's Guide to the Galaxy”. An introduction to basic concepts of metrological traceability is followed by a discussion of practical steps to ensure metrological traceability of field measurement results. The relationship between metrological traceability and comparability of measurement results is discussed. To achieve metrological traceability in the field, the use of appropriate certified reference materials for calibration is recommended. Examples of atmospheric carbon dioxide and roadside breathalyzer measurements are given.

Modeling of solvent viscosity effects on the electroreduction of Pt(II) aquachlorocomplexes

Solvent dynamics effects on the electroreduction of [PtCl₃(H₂O)]⁻ at a mercury electrode are explored in the framework of Sumi–Marcus model using an efficient computational scheme. According to results of density functional calculations, the second electron transfer step may be regarded as rate controlling. The nonmonotonous influence of solvent viscosity on the reaction rate is predicted and explained in terms of the saddle point avoidance. The results of model calculations are employed to interpret experimental data reported earlier in the literature.

The Australian perspective

This presentation deals with issues of comparability and traceability in food analysis in Australia from several perspectives. This includes the current national (Australian) and increasingly international (Codex) performance-based approach to food analysis. The Australian food regulatory process will be described, particularly those aspects that impact on the analysis of food in a regulatory sense. This section will also describe two areas where specific methods have been mandated in legislation and discuss two case studies where the analytical method has impacted on the elaboration of standards. Other areas to be covered include regulation/requirements relating to supply/availability of reference materials, the use of proficiency testing as a means of ensuring comparability, and, finally, some thoughts on what role BIPM/CCQM may play in the analysis of food.Electronic Supplementary Material  Supplementary material is available for this article at

Encapsulating of single quantum dots into polymer particles

Single semiconductor quantum dots were embedded into polymer particles with diameters below 0.1 μm by an emulsion polymerization procedure or via a secondary dispersion approach. The photoluminescence properties of the nanocrystals are retained upon encapsulation, as demonstrated by fluorescence confocal microscopy.