Wim P. Cofino

First world-wide interlaboratory study on polybrominated diphenylethers (PBDEs).

The first world-wide interlaboratory study on PBDEs, organised between November 1999 and April 2000, involved five biological samples, two sediments and two standard solutions. These materials were sent to 26 participants in nine different countries. Results were returned from 18 laboratories. The results reported for BDE 47 were acceptable with a range of relative standard deviations (Rsd) of 17-40%. Results for the BDEs 99 (Rsd 25-77%), BDE 100 (Rsd 19-48%), 153 (Rsd 30-48%) and 154 (Rsd 25-43%) showed that a further improvement of these analyses is needed. The BDE 209 analysis is not under the control of the participating laboratories. The data reported for the biota samples were very variable and for the two sediments Rsd values of 48% and 78% were obtained. It is recommended that analysts pay more attention to the special requirements for the BDE 209 analysis such as avoiding exposure to intensive light and exposure for too long times to too high temperatures.

Critical review of the analysis of non- and mono-ortho-chlorobiphenyls

The various methods for the determination of non-ortho and mono-ortho-chlorobiphenyls are critically reviewed. Matrix, sample preparation, extraction, clean-up, fractionation and group separation methods, chromatographic separation (gas, liquid and supercritical fluid chromatography), as well as the various detection methods, multi-residue methods, quality control and method validation are discussed. For each topic, an overview is given of the current status of the field and recommendations for the most appropriate analytical approach are presented.

Design and evaluation of the QUASIMEME inter-laboratory performance studies: A test case for robust statistics☆

The QUASIMEME laboratory performance studies have been designed according to the recent IUPAC/ISO protocol. An overview of the design is given and, in addition to the Z-score for ranking the bias of laboratories, a term called ‘P score’ is introduced as an aid to the assessment of the precision of the laboratories. The data have been evaluated using robust statistics. Little information is available on practical applications of robust statistics for the evaluation of inter-laboratory studies, therefore, part of the data have been used to compare two different algorithms for robust statistics and the conventional ISO 5725 procedure. The data obtained from these intercomparison studies are heterogeneous in nature, and it is concluded that robust statistics have distinct advantages in assessing the data, but should not be used without a critical examination of the dataset.

A new model for the inference of population characteristics from experimental data using uncertainties. Application to interlaboratory studies

Abstract A new model to make inferences about population characteristics from experimental datasets is presented. It derives concepts and procedures from quantum chemistry. The model uses the observed values and the uncertainty estimates thereof. It provides the different modes of the distribution and for each mode the expectation value, the standard deviation and a percentage indicating the fraction of observations encompassed. An implementation of the model that does not require uncertainty estimates is provided too. In this paper, the model is elaborated and applied to the evaluation of interlaboratory studies. It has, however, a much wider generic application. It is demonstrated that the model can cope with asymmetric, strongly tailing and multimodal distributions and that it is superior to existing techniques (e.g. ISO 5725, robust statistics).

The use of gas chromatography with ion-trap MS/MS detection for the determination of planar PCBs in biota and sediment.

Combining capillary GC with ion-trap detection in the MS/MS mode allows the determination of trace levels of the highly toxic PCB congeners, CB 77, 126 and 169 in complex biological tissues, suspended matter and sediment. The high selectivity and sensitivity of MS/MS detection in the resonant and non-resonant modes yield detection limits of 60 fg, 300 fg and 200 fg for CB 77, 126, and 169, respectively.

Analyzing the Data-Rich-But-Information-Poor Syndrome in Dutch Water Management in Historical Perspective

Water quality monitoring has developed over the past century from an unplanned, isolated activity into an important discipline in water management. This development also brought about a discontent between information users and information producers about the usefulness and usability of information, in literature often referred to as the data-rich-but-information-poor syndrome. This article aims to gain a better understanding of this issue by studying the developments over some five decades of Dutch national water quality monitoring, by analyzing four studies in which the role and use of information are discussed from different perspectives, and by relating this to what is considered in literature as useful information. The article concludes that a “water information gap” exists which is rooted in different mutual perceptions and expectations between the two groups on what useful information is, that can be overcome by improving the communication. Such communication should be based on willingness to understand and deal with different mindframes and should be based on a methodology that guides and structures the interactions.

A methodology to bridge the water information gap

The metaphor of the water information gap is used to describe the discontent between information users and information producers about the use of and need for specific information. This paper describes the rugby-ball methodology for specification of information needs that was developed on the basis of an analysis of the water information gap and insights from the literature on policy- and decision-analysis, problem-structuring, and information management. The methodology consists of a process-architecture to manage the process of assessing information needs and a structure to organise the information needs related to water policy objectives. The methodology was developed and enhanced through a Reflection-in-Action process in which interaction between ideas and practice leads to improved results. The paper describes the methodology and its development, and concludes both on the development process and on the abilities of the methodology to narrow the water information gap.

The 1993 QUASIMEME laboratory-performance study: Trace metals in sediments and standard solutions

Abstract The assessment of the QUASIMEME laboratory-performance study for trace metals in a silty and sandy sediment is given. Data for the determination of the five mandatory metals (Cd, Cu, Pb, Hg and Zn) are reported along with the normalizers Al and TOC. The differences between the concentrations found using partial (such as aqua regia) and total (such as HF or non-destructive determinations) methods are critically evaluated. High blank values were found to affect the long-term precision of a number of laboratories. The overall assessment for bias was made using the IUPAC/ISO protocol based on Z-scores. P-scores were used to assess the precision of laboratories.

The preparation, testing and certification of two freshwater sediment reference materials for polycyclic aromatic hydrocarbons and polychlorinated biphenyls : BCR CRM 535 and CRM 536

Within the framework of the Standards, Measurements and Testing Programme of the European Commission, a certification campaign was conducted for two freshwater sediment reference materials for polycyclic aromatic hydrocarbons and polychlorinated biphenyls, respectively. The sediments were collected from a Dutch river, dried, ground, homogenized, packed and tested on stability and homogeneity. The materials were then analyzed by a group of laboratories with proven competence in the field. The contents of seven PAHs (pyrene, benz(a)anthracene, benzo(a)pyrene, benzo(e)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene and indeno(1,2,3-cd)pyrene) were certified in one material (CRM 535), and the contents of 13 PCBs (IUPAC Nos. 28, 52, 101, 105, 118, 128, 138, 149, 153, 156, 163, 170 and 180) in the other (CRM 536). The materials are available from the Community Bureau of Reference of the European Commission (BCR) to all laboratories that want to validate their PAH or PCB methods for trueness. Copyright (C) 1999 Elsevier Science B.V.

A journey through quality control

The Euroanalysis VII conference in Vienna included a two-day session: Quality Assurance in Analytical Chemistry. The contributions comprised 15 lectures devoted to: intra-laboratory quality measures, inter-laboratory control, formal aspects and accreditation and implementation. The paper presents an overview of the main items developed by the contributors.