Foppe Smedes

Spiking of performance reference compounds in low density polyethylene and silicone passive water samplers.

A method for spiking performance reference compounds (PRCs) into low density polyethylene (LDPE) and silicone polymers is described. This method is based on equilibration of the polymers in aqueous/methanolic solutions of PRCs. Equilibration times range from minutes to hours for perdeuterated polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) with a hydrophobicity in the range 3.9 < logKow < 7.7. Best results were obtained for methanol-water ratios of 80/20 (v/v). The method allows for the use of PRCs for in situ calibration of the uptake kinetics of these solvent-free sampling phases in a similar way as for semipermeable membrane devices (SPMDs).

Normalization procedures for sediment contaminants in spatial and temporal trend monitoring

Rational pollution, or the effectiveness of natural attenuation assessments based upon estimating the degree of contamination, critically depends on the basis of a sound normalization to take into account heterogeneous sedimentary environments. By normalizing the measured contaminant concentration patterns for the sediment characteristics, the inherent variability can be reduced and so allow a more meaningful assessment of both the spatial distributions and the temporal trends. A brief overview and guidance in the methodology available for choosing an appropriate site-specific normalization approach is presented. This is followed by general recommendations with respect to the choice of normalizer and the necessary geochemical and statistical quality assurance methods, with support from the results of recent international intercomparison exercises within the QUASH (Quality Assurance of Sample Handling) programme, as well as discussions within the International Commission on the Exploration of the Sea (ICES) working groups. The most important of these recommendations is the use of a two-tiered normalization approach including wet sieving (<63 microm), followed by an additional geochemical co-factor normalization.

Revisiting the Development of the Bligh and Dyer Total Lipid Determination Method

Abstract The experiments leading to the development of the most well-known method for total lipid determination in marine biological tissues ( Bligh, E. G. and Dyer, W. J. (1959) Can. J. Biochem. Physiol. 37, 911–917) were repeated in order to discover the secrets of its success. Along with measuring the phase volumes of the water/methanol/chloroform mixtures investigated by Bligh and Dyer, the phase compositions were determined by gas chromatograph (GC). An examination showed that, although Bligh and Dyer applied largely different solvent ratios, the composition of both phases varied only within a limited range resulting in an incomplete investigation of the effects of changing this factor. Using Bligh and Dyer’s solvent mixtures the recovered fraction of organic phase was found to be the key factor determining the extracted lipid yield. On its turn the recovered fraction was positively correlated to the size of the organic phase and its methanol content. Additional experiments applying new extraction points with higher methanol contents revealed an increase of extracted lipid. This increasing yield was mainly due to a better extraction of the phospholipids as could be deducted from lipid patterns recorded by normal phase high performance liquid chromatography (HPLC) using an evaporative mass detector.

Evaluation of the Bligh & Dyer lipid determination method

The Bligh & Dyer method for lipid determination has been used for many years in several different ways. To discover the success of this old method and assess the impact of deviations from it on the analytical result, the development of the method was evaluated using the equilibrium theory. In addition the actual phase compositions and phase volumes of their experiments were determined. Absorption of organic phase to the tissue appeared to be one of the main sources of incomplete extraction. The amount of lipid remaining in the aqueous phase is likely to be negligible, just like adsorption of lipids to the tissue. The kinetics of the extraction were promoted both by a multi-step extraction approach, and the methanol content. The latter is also expected to be a key parameter in determining the yield of lipid extraction.

Evaluation of the results of the QUASIMEME lipid intercomparison: the Bligh & Dyer total lipid extraction method

Abstract The results of the QUASIMEME lipid intercomparison exercise were evaluated in relation to the Bligh & Dyer (1959) total lipid extraction method. Most of the participants provided detailed information on their methods and a comparison was made based on the following parameters: drying temperature; subsampling; sample intake; solvent composition of the extraction—and partition mixture; the use of a second extraction; mixing method; and the use of filtration. Only a small number of laboratories applied conditions which conformed strictly to the original method of Bligh & Dyer (1959). Although these conditions were originally specified for cod muscle tissue, they are applicable to mussel tissue as well. Some differences in the results could be attributed to deviations from the original method, but none of them were significant with the exception of subsampling. The latter resulted in significant differences between laboratories that used the same extraction method, caused by an inappropriate compensation for the amount of organic phase absorbed by the tissue (Smedes & Thomasen, 1996).

Determination of (mono-, di- and) tributyltin in sediments. Analytical methods

Methods for the reliable determination of butyltin compounds in sediments are required for both national and international marine monitoring programmes. This evaluation of current commonly used approaches to the analysis identifies critical aspects of extraction, derivatisation, clean-up, separation, standardisation and detection with the objective of improving the analytical capabilities both of experienced laboratories and of those addressing the problems for the first time.

Predicting the bioaccumulation of polyaromatic hydrocarbons and polychlorinated biphenyls in benthic animals in sediments

There were two main objectives in this study. The first was to compare the accuracy of different prediction methods for the chemical concentrations of polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in the organism, based on the measured chemical concentrations existing in sediment dry matter or pore water. The predicted tissue concentrations were compared to the measured ones after 28-day laboratory test using oligochaeta worms (Lumbriculus variegatus). The second objective was to compare the bioaccumulation of PAHs and PCBs in the laboratory test with the in situ bioaccumulation of these compounds. Using the traditional organic carbon-water partitioning model, tissue concentrations were greatly overestimated, based on the concentrations in the sediment dry matter. Use of an additional correction factor for black carbon with a two-carbon model, significantly improved the bioaccumulation predictions, thus confirming that black carbon was important in binding the chemicals and reducing their accumulation. The predicted PAH tissue concentrations were, however, high compared to the observed values. The chemical concentrations were most accurately predicted from their freely dissolved pore water concentrations, determined using equilibrium passive sampling. The patterns of PCB and PAH accumulation in sediments for laboratory-exposed L. variegatus were similar to those in field-collected Lumbriculidae worms. Field-collected benthic invertebrates and L. variegatus accumulated less PAHs than PCBs with similar lipophilicity. The biota to sediment accumulation factors of PAHs tended to decrease with increasing sediment organic carbon normalized concentrations. The presented data yields bioconcentration factors (BCF) describing the chemical water-lipid partition, which were found to be higher than the octanol-water partition coefficients, but on a similar level with BCFs drawn from relevant literature. In conclusion, using the two-carbon model method, or the measured freely dissolved pore water concentrations method is recommended for predicting the bioaccumulation of PAHs and PCBs.