Hydrogen peroxide determination in estuarine and marine waters by flow injection with fluorescence detection

cited By 7International audienceno abstrac

Interference mechanisms and reduction during the speciation of organotin compounds by hydride generation, cryoseparation and detection by atomic absorption spectrometry

cited By 19International audienceInterferences generated by inorganic elements during the speciation of organotins and the effect of masking agents have been studied using hydride generation (HG) on-line with cryogenic trapping (CT), gas chromatographic (GC) separation and detection by atomic absorption spectrometry (AAS). This study was performed on a mixture of organotin species (monomethyltin (MMT), monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) at concentration levels of 5 ng of Sn of each in 50 ml of solution (100 ng I-1). Interfering elements (Al, As, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sb, Se or Zn) (100 μg), investigated individually in solution in the presence of the organotins, do not lead to the same signal depression for each organotin compound studied, possibly owing to different interference mechanisms. Interferences generated by inorganic elements can be partitioned between the solution and gaseous phases, showing that interferences may occur both during the solution and the gaseous steps for all organotins studied. Masking agents (EDTA and L-cysteine) to reduce interferences have been successfully used for organotin speciation. The presence of ethylenediaminetetraacetic acid (EDTA) in the reaction flask suppresses most of the interferences by forming complexes with the inorganic species and preventing them from reacting and altering the formation of DBT and TBT hydrides. However, EDTA also forms complexes with MMT and MBT. L-Cysteine improves the reproducibility and sensitivity of MBT determination and prevents the interfering effects of inorganic elements on the speciation of organotins. Interferences mechanisms are discussed

Stated references for ensuring traceability of chemical measurements for long-term environmental monitoring

cited By 27International audienceTraceability is now considered to be a key concept in chemical and biological measurement sciences. While this concept is increasingly used in many areas, it is still prone to misunderstandings with respect to more 'classical' terms such as e.g. accuracy. Traceability implies that measurement data are linked to stated references through an unbroken chain of comparisons, all with stated uncertainties. What does the word 'stated references' mean when it is applied to complex environmental analysis? This paper discusses how traceability can be conceived in the context of environmental monitoring, in particular the various stated references (documented standards, reference materials, environmental specimens) to which chemical environmental data may be linked to. © 2001 Elsevier Science B.V. All rights reserved

Preface

cited By 6International audienceno abstrac

Hyphenated techniques applied to environmental speciation studies

cited By 79International audienceImproved understanding of the environmental behaviour, fate and impact of trace metals and, more specifically, organometallic compounds requires techniques that are both highly selective and sensitive. Hybridization of separation techniques such as gas or liquid chromatography coupled to a wide variety of atomic spectrometry detectors has allowed significant progress to be made in the last decade. © 1992

Hyphenated Techniques Applied To The Speciation Of Organometallic Compounds In The Environment

cited By 10International audienceThis chapter discusses the wide array of hyphenated techniques, which illustrates the important technical progress made during the last decade. However, not one technique can substitute for all the others and they should be considered as complementary. If instrumental solutions can be considered satisfactory, very few are available commercially at present. The success of speciation information delivered is not only dependent on the instrumentation used. The growing demand for speciation analysis is still hampered by the cost of the solutions available and the sample through-put. In this respect, systems using on-line cryofocusing and chromatographic separation prior atomic spectrometry detection appear to be robust and sensitive, allowing a high sample through-out. Flow injection analysis is further elaborated. © 1993, Elsevier B.V. All rights reserved

Isotope ratios on transient signals with GC-MC-ICP-MS

cited By 41International audienceICP-MS instruments with multiple ion collectors (MC-ICP-MS) provide highly precise and accurate isotope ratio measurements. These instruments are easily coupled to chromatography, laser ablation or flow injection devices because of the ICP source, and thus attract general analytical interest for measurement of highly precise element isotope ratios on transient signals. Some few papers have been published today where MC-ICP-MS was employed for isotope ratios on transient signals, and in general, results are encouraging. Isotope ratio precision obtained is usually at least 10-fold superior compared to measurements with ICP-QMS. Nevertheless, most authors describe a drift of isotope ratios during the transient peak. This behaviour was either interpreted as a problem in the sample introduction system, or was related to instrumental mass bias drift, but has to date not been completely evaluated or explained. In this paper, we systematically investigate the drift observed on lead and mercury isotopes during short transient signals obtained from GC coupled to different MC-ICP-MS systems. We can clearly show that neither changes in instrumental mass bias, nor chromatographic fractionation effects are the source of the observed isotope ratio drift. An influence of analyte concentration on the observed drift was as well excluded as a source for this drift, because the slope on isotope ratios show the same values for different concentrations evaluated. In contrast, the peak width was found to influence the extent to which the isotope ratio drifts during peak elution. Thus, the relative intensity change per time seems to be an important factor for the measurements of transient signals with MC-ICP-MS. © 2004 Elsevier B.V. All rights reserved

Ensuring quality in long term environmental monitoring for chemical speciation

cited By 13International audienceThe awareness regarding quality assurance (QA) and quality control (QC) for environmental monitoring has considerably increased in the past few years, especially with respect to the determination of chemical species, since errors occurring at various levels may considerably affect the interpretation of results (e.g. studies of toxic impact, geochemical pathways, etc.). QA for environmental analysis covers a broad range of activities from sample collection to laboratory work and the approach for ensuring quality data should be considered in a global context. However, whereas great emphasis has been placed on QA within the laboratory, there have been few systematic attempts to evaluate risks of discrepancies related, for example, to field manipulations. The situation is even worse when monitoring is applied to relatively new fields such as chemical speciation. This paper outlines some of the main aspects of quality control of environmental analysis, including the validation of methods, sampling and sample handling, storage, etc., with special emphasis on the monitoring of chemical forms of elements (e.g. species of tin, mercury, lead and selenium)

Variability of butyltin determination in water and sediment samples from european coastal environments

cited By 10International audienceA large amount of data has appeared in the literature within the last few years dealing with the monitoring of butyltin compounds in coastal environments. However, the strategies used strongly differed from one author to another, which led to difficulties in the comparison of contamination levels and the evaluation of long‐term trends. In this paper, different causes of pitfalls due to uncontrolled sources of variability are addressed; they involve precautions to be undertaken for the monitoring of butylins in water and sediment, particularly: sample collection; sample pretreatment (filtration/centrifugation, acidification, sieving); sample storage (different methods for storage and drying procedures); variability over the same site; variations over a tidal cycle; and variability due to diffusion (e.g. due to flushing). Copyright © 1990 John Wiley & Sons Ltd

On‐Line speciation of mercury and methylmercury in aqueous samples by chromatography‐atomic fluorescence spectrometry after hydride generation

cited By 30International audienceA method is described for the determination of picogram amounts of inorganic mercury(II) and methylmercury(II) compounds in seawater. These compounds are first volatilized from the water samples by reduction to mercury (Hg0) and formation of methylmercury hydride (CH3HgH) by means of a sodium borohydride (NaBH4) solution and cryogenically focused onto a chromatographic stationary phase. Both mercury compounds are eluted according their boiling points and are passed through a pyrolysis tube, at 900°C, before entering the atomic flurescence detector. Absolute detection limits (3σ) are 1 and 2 pg for, respectively, inorganic mercury and methylmercury. For seawater analysis, detection limits of 0.1–1.0 ng I−1 can be achieved. Copyright © 1994 John Wiley & Sons, Ltd