Wim Cofino

Wageningen University & Research | WUR · Wageningen Enviromental Research

To survey the conformity and quality of results among laboratories for microplastics determination worldwide, an international laboratory intercomparison and development exercise was organized. The 34 participants were requested to determine the polymer type and number or mass of polymer particles in 12 samples, i.e. six samples containing of pre-p...

https://doi.org/10.1016/j.chemolab.2018.01.003 (open access) Abstract In this paper we present the ab-initio derivation of an estimator for the mean and variance of a sample of data, such as obtained from proficiency tests. This estimator has already been used for some time in this kind of analyses, but a thorough derivation together with a detail...

Marine monitoring programs provide data that are essential for marine management. The reliability of such data is underpinned by proficiency tests. In the context of Quasimeme, a proficiency testing program for the marine environment, a statistical model has been developed in 2000 to evaluate data sets. The mathematical basis of this model has been...

Data from the measurement of silicate, acenaphthylene, and DDT in the marine environment are used to examine the Cofino model. This is a model for the inference of population characteristics from experimental data using uncertainties. It uses mathematical principles taken from quantum mechanics and provides an alternative to robust statistics for o...

An increasing number of reports confirm the world-wide presence of the perfluoroalkyl substances (PFASs). As a consequence, the demand for qualitative and quantitative environmental occurrence data requires accurate risk assessments. To improve the analytical quality of the determination of PFASs in food and environmental samples, a 4th internation...

The first worldwide interlaboratory study on organophosphorus flame retardants (PFRs) was organized to improve the quality of the data reported in the literature. The study involved standard solutions, dust, fish oil and sediment samples.The differences in coefficients of variation (CV) between the samples were related more to PFR concentration (wi...

Het doel van het project HSZD01 (“Negotiating uncertainties”) is om zekerheden en onzekerheden in kennis over zoetwaterbeschikbaarheid in de Zuidwestelijke Delta in kaart te brengen. Dit is gedaan aan de hand van de casestudie MER “Waterkwaliteit Krammer Volkerak-Zoommeer” (periode 2000-2010), mede in de context tot de wens voor herstel Estuariene...

Policymakers are often dissatisfied by the lack of what they consider useful information to support water management. Analysis of this 'water information gap' shows that this is caused by a lack of proper communication between information users and information producers. To improve this communication the process of specification of information need...

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 in...

There is mutual dissatisfaction among policy makers and monitoring specialists about producing what is considered useful information for policy development, implementation and evaluation. Insufficient or inappropriate communication between information users and producers is considered to be a main cause for this water information gap. This paper te...

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-b...

De laatste jaren zijn verschillende artikelen en rapporten verschenen over het meten van freatische grondwaterstanden, waarbij de term 'numerieke verdroging' is gebruikt. Numerieke verdroging wordt gebruikt om onjuiste schattingen van de freatische grondwaterstand, als gevolg van alle veranderingen in meten en interpreteren, aan te geven. Hoog tijd...

Chromium, chlorobiphenyls, and aluminum in marine matrices are some of the chemicals that, when measured by different laboratories, give rise to bimodal datasets. Bimodality in proficiency test (PT) data often results from the use of different chemical analytical methods or by contamination. The Cofino model provides an alternative approach to robu...

Data from the measurement of silicate, acenaphthylene, and DDT in the marine environment are used to examine the Cofino model. This is a model for the inference of population characteristics from experimental data using uncertainties. It uses mathematical principles taken from quantum mechanics and provides an alternative to robust statistics for o...

Russia’s new Water Code means its water resources remain under federal jurisdiction. However, this shouldn’t rule out transboundary water cooperation. After acknowledging the current situation regarding water resources management in Russia, this paper presents three instances of transboundary cooperation, two case studies concerning nations within...

IntroductionThe holistic philosophyThe elements of an holistic projectFunctionsCommunicationFuture developmentsReferences

Quality systems for samplingDevelopment of a sampling strategyDocumentation and planningValidation of samplingExecution of the sampling planQuality control practicesReferences

This paper extends a recent report on a model to establish population characteristics to include censored data. The theoretical background is given. The application given in this paper is limited to left-censored data, i.e. less than values, but the principles can also be adopted for other types of censored data. The model gives robust estimates of...

This paper extends a recent report on a model to establish population characteristics to include censored data. The theoretical background is given. The application given in this paper is limited to left-censored data, i.e. less than values, but the principles can also be adopted for other types of censored data. The model gives robust estimates of...

Several critical steps in the analytical procedure for organotin compounds in the environment are identified in this paper and solutions are suggested. In particular, an improved procedure for quenching excess Grignard reagent is described. After insight into the nature of losses was obtained, the use of internal standards made it possible to reduc...

The European strategy for dioxin monitoring of the food chain has defined high-resolution gas chromatography coupled to high-resolution mass spectrometry (HRGC/HRMS) method as the confirmatory method that can provide reliable and comparable results at sub-parts per trillion (ppt) level. This paper describes the first inter-laboratory study on dioxi...

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...

A hydrological model was constructed with the commercially available modelling environment ECoS for the calculation of mixing plots of dissolved pesticide concentrations in the Scheldt Estuary. The model was based on a one-dimensional advection-dispersion equation and dispersion coefficients were calculated from measured salinity profiles. The mode...

As part of the Fluxes of Agrochemicals into the Marine Environment (FAME) project, the gross fluxes of selected pesticides (i.e. the herbicides atrazine, simazine, alachlor and metolachlor, the atrazine degradation product desethylatrazine, the insecticide dichlorvos and the antifouling agent Irgarol 1051) transported by the river Scheldt and the C...

The aim of this paper is to analyze the potential of indicators for integrated river basin management and to develop a set of indicators for the management of transboundary river basins. An indicator, comprising a variable or some aggregation of variables, describes a system or process such that it has significance beyond the face value of its comp...

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 deviat...

A method is developed for the determination of polar pesticides and their transformation products [atrazine, deethylatrazine, deisopropylatrazine, hydroxyatrazine, diuron, 3,4-dichlorophenylmethylurea, 3,4-dichlorophenylurea (DPU), monuron, bentazone, anthranil-isopropylamide, chloridazon, metolachlor] in surface, estuarine and sea water samples at...

The Fluxes of Agrochemicals into the Marine Environment (FAME) project, which was funded by the European Union, studied the presence and fate of pesticides in major European river/estuary systems. As part of the cooperation within FAME, samples from four rivers were sent to all participants. Each laboratory analyzed the samples with a range of tech...

In order to control the quality of butyl- and phenyltin compound determinations in sediment, the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a project, the final aim of which is to certify a freshwater sediment for its contents of a range of organotin compounds (mono-, di- and tributyltin, and...

The stability of both tributyltin (TBT) and triphenyltin (TPT) in water, sediment, oysters and cockles was studied over a period of 18 months using several storage conditions. Butyltins were stable in unacidified sea-water stored in polycarbonate bottles in the dark at 4 degrees C for 7 months, but half of the TBT concentration was lost after 540 d...

The analytical techniques used for the determination of butyltin compounds in biological tissues are generally based on a succession of steps (e.g., extraction, derivatization, separation, detection) which are all prone to systematic errors. An interlaboratory programme performed at the EU level and based on a stepwise approach has enabled one to i...

An analytical procedure was developed that enables routine analysis of four estrogenic hormones in concentrations below 1 ng/l in surface water and waste water. The recovery was 88-98% with a limit of detection of 0.1-2.4 ng/l depending on the compound and the matrix measured. This method was used to determine the occurrence of 17 beta-estradiol, 1...

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, pa...

Bioaccumulation of non-, mono-, and di-ortho-substituted chlorobiphenyls (CBs) was investigated in four species of mustelids (weasel, stoat, polecat, and otter) and their preys, from a restricted area in the northern part of The Netherlands. Diets of these mustelids ranged from terrestrial (weasel, stoat, and polecat) to aquatic (otter). Diet-speci...

The accreditation of laboratories is increasingly demanded as evidence of the reliability of the data they produce, and is therefore of strategic importance to laboratories for maintaining and/or increasing their level of competitiveness. Although accreditation is increasingly developed in sectors such as food quality control, it is less common for...

The present study aims to develop river ecosystem indicators, in particular for the River Rhine, on the basis of theoretical concepts describing natural rivers. The study includes river ecology concepts on zonation, stream hydraulics, river continuum, nutrient spiralling, serial discontinuity, flood pulse, riverine productivity and catchment hierar...

Analytical procedures are developed for the identification and quantification of pesticides in the marine environment. Concentrations in the marine environment are expected to be at or below the low ng/l level, which requires preconcentration of analytes and improved detection. Off-line solid phase extraction (SPE) was combined with large-volume in...

The decline of the populations of otters in Western Europe is assumed to be related to the accumulation of polychlorinated biphenyls (PCBs) in this species. A study was conducted to investigate the trophic transfer of non-ortho, mono-ortho-, and di-ortho-substituted PCBs in the food web of the otter (Lutra lutra) in the Oude Venen lake system in th...

A detailed assessment programme has been developed by the QUASIMEME Scientific Assessment Group to evaluate the results of the five rounds of the interlaboratory studies for the main mandatory chemical determinands in European Marine Monitoring Programmes. Two robust statistical algorithms were evaluated and one applied systematically to the study...

The EU project QUASIMEME 1993–1996 has now developed in two directions. The inter-laboratory studies have been extended to incorporate the UK National Marine AQC test requirement by extending the range of determinands to include aqueous samples for trace metals and organic contaminants as well as the nutrients. The Laboratory Performance Studies (L...

The EU project ‘QUASIMEME’ was established to provide comprehensive knowledge of the quality of chemical measurements made in marine monitoring programmes, to determine the underlying causes of poor inter-laboratory agreement for these measurements and to provide stepwise improvement. The quality of analytical performance of all laboratories in the...

The Standards, Measurements and Testing Programme (SM&T) of the European Commission (continuation of the BCR and Measurements and Testing Programmes) aims to contribute to the harmonization and improvement of methods and measurements carried out within the European Union and hence to the comparability of data necessary for e.g. trade activities, mo...

The contamination level of the s-triazine herbicide Irgarol 1051, which is used as the active ingredient in antifouling paints, was studied in the Western Scheldt estuary. The combined use of large-volume injection gas chromatography and ion trap (MS–MS) detection, enabled identification and quantification at the 0.1–1 ng/l level. By using tandem m...

An extensive study on the presence of nine organotin compounds (OTs) in a freshwater foodweb was made, using newly developed analytical procedures in order to obtain insight in accumulation and degradation processes. Tributyltin (TBT), Triphenyltin (TPT) and their degradation products were detected. Zebra mussels, eel, roach, bream, pike, perch, an...

The formation of pyrene metabolites by the temestrial isopod Porcellio scaber (Latr.) was studied following exposure for 13 days to 100 μg/g pyrene in its food. An alkaline hydrolysis method with subsequent liquid-liquid extraction was developed to determine the metabolite content, especially 1-hydroxypyrene. Synchronous Fluorescence Spectroscopy (...

In the context of the 1994 QUASIMEME programme, Laboratory Performance Studies were conducted on trace metals in marine sediments, digests of marine sediments, mussel tissue and plaice muscle tissue. This paper describes the design of the Laboratory Performance Study and presents an overview of the results.

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,...

Tributyltin (TBT) measurements in a food web in the freshwater Lake Westeinder are used to calibrate an integrated fate and bioaccumulation model with special attention given to exposure pathways. The Dutch ban on antifouling paints containing TBT is simulated with a load reduction scenario. By integrating Monte-Carlo sampling with a calibration pr...

The comparability of data from accredited laboratories is not always as good as customers would desire. A number of reasons for this fact are given. Clients of laboratories do not specify methodology, which may lead to the application of systematically different methods or to methodology with improper performance characteristics. Laboratories do no...

One of the major prerequisites for the certification of various analytes in different Certified Reference Materials (CRMs) is that the analytical methods used are of verified performance and, hence, that no systematic errors have been left undetected. In the case of difficult measurements, research and feasibility studies are often necessary to ens...

The quality of products, services and commodities is an important issue in modern society. It is generally realized that poor quality can cause economic losses or impair human health or the environment. Customers increasingly demand evidence of the quality of products or services. Accreditation meets this need — it serves as a token that an organiz...

In the present survey zebra mussels were used as biomonitors to evaluate concentrations of nine organotin compounds (OTs) in Dutch fresh waters. To this end mussels were sampled at 56 locations throughout the country at the end of the summer of 1992. Variations in OT concentrations in zebra mussels were studied at two locations near potato crops th...

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,...

This paper describes an attempt to derive a median effect level (EC50) of PCBs for reproduction of mink based on experimental literature data. Unfortunately, the conditions of the mink studies carried out during the last two decades vary widely, which makes it difficult to establish unequivocal dose-effect relationships. This study describes an att...

Society has a great demand for environmental analyses. Decisions on the management of waste materials are based on chemical data. Legislation imposes the acquisition of concentrations of a variety of constituents. Environmental taxes may be based on the concentrations of specific compounds. The need for sanitation measures may be assessed through a...

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 usin...

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...

Organotin compounds (OTs) were analyzed after derivatization using a methyl Grignard reagent with gas chromatography with ion trap detection (GC-ITD) for detection. GC-ITD allows full scan mass spectrometry at trace levels and thus allows good verification of the presence of the OTs. With the described methods all currently used OT biocides can be...

In a joint Industry program, the composition and the environmental risk of produced water discharges on the Dutch Continental Shelf was investigated, along with the investigation of existing heavy metal removal technology potentially suitable for offshore application. On fifteen gas platforms and four oil platforms on the Dutch Continental Shelf sa...

The presence and concentrations of non-ortho-, mono-ortho-, and di-ortho-substituted PCB congeners in the polecat (n = 7), a member of the mustelid family, were investigated. PCBs were extracted with a Soxhlet apparatus. After cleanup the non-ortho-substituted PCB congeners were separated from the other PCBs by HPLC. Determinations were accomplishe...

In der modernen Gesellschaft spielt die Qualität von Erzeugnissen, Dienstleistungen und Waren eine wichtige Rolle. Mangelhafte Qualität kann zu wirtschaftlichen Verlusten führen und die menschliche Gesundheit oder die Umwelt beeinträchtigen. Verbraucher verlangen immer häufiger Aussagen über die Qualität von Erzeugnissen und Dienstleistungen. Die A...

This chapter discusses quality assurance in environmental analysis. Environmental management depends on information on a wide range of compounds. Unreliable or inaccurate information may lead to large economic losses, such as sanitation measures that may be taken needlessly, or to unacceptable risks for the environment or human health if necessary...

Quality Assurance and Quality Control of the chemical measurement of the mandatory determinands in the Marine Environmental Monitoring Programmes (MEMPs), e.g. the North Sea Task Force (NSTF) and the Joint Monitoring Group of the Oslo and Paris Commissions, are to be developed in an international total quality management project supported by the EC...

Methods are described for the analysis of environmental samples like water, sediment and suspended matter for the determination of all organotin compounds (OTs) that are currently used as biocides: tributyltin (TBT), triphenyltin (TPT), tricyclohexyltin (TCT) and fenbutatin oxide (FBTO). In water also five degradation products (di and mono substitu...

Tandem mass spectrometry is a very sensitive method for the identification of organic compounds in mixtures. The first mass spectrometer serves to ionize all components of the mixture and to select out a major ion, most often the molecular ion of the compound(s) of interest, which is then fragmented by injection into a region containing a neutral g...

Dissolved trace-metal (Cd, Cu, Pb, Zn, Hg) data held by ICES have been assessed and reviewed. Difficulties associated with sampling close to sources of known contamination, uncertainties over the quality of the sampling and analysis, and comparison of filtered and unfiltered samples complicated this assessment. For Cd and Cu, data of sufficient qua...

The Bremerhaven Workshop required chemical data to help interpret the biological findings. Polychlorobiphenyls, organochlorine pesticides, polycyclic aromatic hydrocarbons, total hydrocarbons and trace metals were determined in sediments, dab liver and benthic invertebrates collected at stations along the German Bight and drilling site transects. I...

An accurate extraction and measurement procedure to determine chlorinated biphenyls (CBs) in surface waters was developed, and sampling techniques for removing suspended matter (SPM) were investigated. The procedure involved a 10-L batch liquid-liquid extraction directly from the sample bottle to prevent loss due to adsorption to the wall. Exhausti...

A method has been developed for the determination of the organotin pesticides fentin, cyhexatin and fenbutatin oxide by high-performance liquid chromatography combined with UV photoconversion and post-column morin complexation followed by fluorescence detecton. After optimization of the relevant parameters the feasibility of the method for analysin...

The monitoring programme of the Public Works Department of the Netherlands has recently been updated and now comprises measurements in water, suspended particulate matter, biota and sediments. Recently, a programme including biological parameters has been developed and implemented. Some examples of results of long-time monitoring series are given....

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 contr...

A review is presented, with 27 references, of monitoring programmes with discussion on intercomparisons of determinations of trace metals in biota, sediments and sea-water and nutrients in sea-water. Problems with an inter-laboratory exercise in the determination of chlorinated biphenyls are reported. Future requirements for successful monitoring a...

Monitoring of the marine environment requires considerable resources. Effective programs providing information tailored to needs are essential. The design of monitoring programs should follow from a clear strategy, integrating informational needs, chemical, physical and biological processes, statistics, analytical aspects and specific (chemical or...

Polycyclic aromatic hydrocarbons (PAHs) in harbour sediment have been determined by means of Shpol'skii fluorometry. Fundamental aspects of this cryogenic high resolution technique are discussed. It provides characteristic spectra of aromatic molecules that can be successfully employed for identification purposes. Extra selectivity is obtained by m...

Site-selection spectroscopy, by using suitable laser line excitation, gives epectra of molecules on thin-layer chromatographic plates comparable in quality to Shpol'skii spectra. Pyrene is investigated as a model compound.

Quasilinear spectra of 1,3-perinaphthadiyl have been obtained in n-pentane and n-hexane by photolysis of cyclopropanoacenaphthylene. The spectra of the biradical display a large absorption-emission asymmetry, which is discussed in terms of vibronic coupling. Our analysis indicates that the two lowest excited electronic states are separated by less...

Highly resolved optical spectra of 1,4-perinaphthadiyl in n-pentane have been obtained. They are compared with previously reported spectra of 1,3-perinaphthadiyl. The energy difference between the two lowest excited triplet states is found to be about 350 cm−1. The order of the two lowest excited states is most probably different for the two biradi...

The Shpol'skii method yields quasilinear spectra of exo-naphtho [b:3,4] tricyclo [4.2.1.0.2,5] nonane 5 in n-hexane at 5 K. This result is discussed with reference to the “key and hole” rule. Highly resolved spectra of the 2,3-naphthoquinodimethane derivative 4 are obtained by photolysis of 5. The results are comparable with those of o-durylene 3.

Highly resolved emission and excitation spectra of phenalenyl are reported. Our semiempirical calculations predict E'' symmetry for the lowest excited state. Indeed, Jahn-Teller effects are observed. Force field calculations have been performed to determine the symmetries of vibrations visible in the spectra. The Jahn-Teller coupling is analysed wi...