Willy Baeyens

High resolution distribution of trace elements in the calcite shell layer of modern mytilus edulis: environmental and biological controls

Abstract Mussels of a similar size, originating from the same population, have been grown in the field and the high resolution distribution of Mg, Mn, Sr, Ba and Pb in their calcite shell layer, as determined by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry, has been compared to temporal variations of environmental parameters. All elements exhibit cyclic variations with an annual periodicity. The Mg, Sr and Pb cycles show great similarity and are characterised by a broad maximum during spring and early summer. These profiles cannot be explained by seasonal variations in the seawater composition. Skeletal Mg covaries reproducibly with temperature during spring but this covariation is abruptly interrupted after the spring phytoplankton bloom. The absence of a constant Mg-temperature relationship over the year hampers the direct use of Mg in M. edulis calcite as a high resolution temperature proxy. The sharp peak that is dominating each skeletal Ba cycle coincides with the annual algal biomass maximum and presumably reflects elevated concentrations of particulate Ba, associated with the spring phytoplankton bloom. Similarly, elevated skeletal Mn concentrations during spring might reflect bloom-induced increases in particulate Mn. Skeletal δ 13 C shows a seasonal variation, characterised by a minimum that coincides with the Mn maximum. These δ 13 C variations are not in equilibrium with the seasonal δ 13 C trend of the seawater dissolved inorganic carbon and presumably reflect fluctuations in the contribution of metabolic carbon to the shell carbonate, corresponding to seasonal variations in the mussel’s respiration rate.

Accumulation of trace metals in the muscle and liver tissues of five fish species from the Persian Gulf

In this study, concentrations of 16 elements were quantified in muscles and livers of 141 fishes belonging to five commercially species. It was also our intention to evaluate potential risks to human health associated with seafood consumption. The grunt, flathead, greasy grouper, tiger-tooth croaker and silver pomfret fish species were obtained from Abadan, Deylam, Bushehr-Nirogah, Dayyer port, Lengeh port and Abbas port in Hormozgan, Bushehr and Khozesran provinces at the Iranian waters of the Persian Gulf. The contents of Al, As, Be, Cd, Cr, Co, Cu, Fe, Pb, Mn, Mo, Ni, Sb, Tl, V and Zn in fish muscles and livers were determined by Inductively Coupled Plasma Mass Spectrometry (ICP MS), after digestion in a CEM (Mars 5) microwave oven using nitric acid and hydrogen peroxide. Our results indicated that almost all metals were more accumulated in younger flathead, greasy grouper and tiger-tooth fishes. Contrary to the other fish species, grunt seems to stronger accumulating elements in the older fishes. Strong and positive correlations were observed in three or more of the fish species between V, Al, Fe, Tl, Co and Pb. The results confirmed that fish muscle and liver tissues appeared to be good bio-indicators for identification of coastal areas exposed to metallic contaminants. The results also showed that the element levels in the muscles of all fishes in our study were lower than the maximum allowable concentrations and pose no threat to public health, except for arsenic.

General description of the Scheldt estuary

A general description of the Scheldt estuary,including the hydrology, the sediment transport, theproductivity and the biodegradation with respect totheir influence on the trace metal behaviour in theScheldt estuary, is given.The river basin can be divided in several sectionsaccording to their morphological, hydrodynamical andsedimentary properties. The zone from km 78 to 55,which corresponds roughly with the salinity zone from2 to 10 psu, is the zone of high turbidity, highsedimentation and of oxygen depletion, especially inthe summer period. That area is called the geochemicalfilter because the solid/dissolved distribution of thetrace metals is controlled by redox,adsorption/desorption, complexation andprecipitation/coprecipitation processes. Thesedimentation rate in that area is estimated at280 Mkg y-1.In the downstream estuary the phytoplankton activityincreases due to the restoration of oxygen and to themuch lower turbidity values. That area is called thebiological filter because incorporation of tracemetals by the plankton communities lowers the tracemetal concentrations during the productivity period,while transformation of metal species, especiallyobserved with mercury, occurs during that period too.

ACCUMULATION OF SUSPENDED BARITE AT MESOPELAGIC DEPTHS AND EXPORT PRODUCTION IN THE SOUTHERN OCEAN

The relation between the accumulation of barite (BaSO4) microcrystals in suspended matter from the mesopelagic depth region (100 to 600 meters) and the type of production in the euphotic layer (new versus recycled) was studied for different Southern Ocean environments. Considerable subsurface barite accumulated in waters characterized by maintained new production and limited grazing pressure during the growth season. On the other hand, little if any barite accumulated in areas where relatively large amounts of photosynthetically fixed carbon were transferred to the microheterotrophic community and where recycled production became predominant.

Origin and fate of organic carbon in the freshwater part of the Scheldt Estuary as traced by stable carbon isotope composition

We investigated the seasonal and geographical variation in the stable carbon isotope ratios of total dissolved inorganic carbon (δ13 cdic) and suspended matter(δ13 CPOC) in the freshwater part of the River Scheldt. Two major sources of particulate organic matter (POM) occur in this riverine system: riverine phytoplankton and terrestrial detritus. In winter the lowest δ13 cdic values are observed due to enhanced input of CO2 from decomposition of13C-depleted terrestrial plant detritus (average δ13Cdic=-14.3‰). During summer, when litter input from terrestrial flora is the lowest, water column respiration on POM of terrestrial origin is also the lowest as evidenced by less negative δ13Cdic values (average δ13Cdic =−9.9‰). In winter the phytoplankton biomass is low, as indicated by low chlorophyll a concentrations (Chl a < 4.5 μgl−1), compared to summer when chlorophyll a concentrations can rise to a maximum of 54 μgl−1. Furthermore, in winter the very narrow range of δ13 Cpoc (from -26.5 to -27.6‰) is associated with relatively high C/N ratios (C/N > 9) suggesting that in winter a major fraction of POC is derived from allochthonous matter. In summer δ13 cpoc exhibits a very wide range of values, with the most negative values coinciding with high Chl a concentrations and low C/N ratios (C/N< 8). This suggests predominance of phytoplankton carbon in the total particulate carbon pool, utilising a dissolved inorganic carbon reservoir, which is already significantly depleted in13C. Using a simple two source mixing approach a reconstruction of the relative importance of phytoplankton to the total POC pool and of13C/12C fractionation by phytoplankton is attempted.

In-Line and Real-Time Process Monitoring of a Freeze Drying Process Using Raman and NIR Spectroscopy as Complementary Process Analytical Technology (PAT) Tools

The aim of the present study was to examine the complementary properties of Raman and near infrared (NIR) spectroscopy as PAT tools for the fast, noninvasive, nondestructive and in-line process monitoring of a freeze drying process. Therefore, Raman and NIR probes were built in the freeze dryer chamber, allowing simultaneous process monitoring. A 5% (w/v) mannitol solution was used as model for freeze drying. Raman and NIR spectra were continuously collected during freeze drying (one Raman and NIR spectrum/min) and the spectra were analyzed using principal component analysis (PCA) and multivariate curve resolution (MCR). Raman spectroscopy was able to supply information about (i) the mannitol solid state throughout the entire process, (ii) the endpoint of freezing (endpoint of mannitol crystallization), and (iii) several physical and chemical phenomena occurring during the process (onset of ice nucleation, onset of mannitol crystallization). NIR spectroscopy proved to be a more sensitive tool to monitor the critical aspects during drying: (i) endpoint of ice sublimation and (ii) monitoring the release of hydrate water during storage. Furthermore, via NIR spectroscopy some Raman observations were confirmed: start of ice nucleation, end of mannitol crystallization and solid state characteristics of the end product. When Raman and NIR monitoring were performed on the same vial, the Raman signal was saturated during the freezing step caused by reflected NIR light reaching the Raman detector. Therefore, NIR and Raman measurements were done on a different vial. Also the importance of the position of the probes (Raman probe above the vial and NIR probe at the bottom of the sidewall of the vial) in order to obtain all required critical information is outlined. Combining Raman and NIR spectroscopy for the simultaneous monitoring of freeze drying allows monitoring almost all critical freeze drying process aspects. Both techniques do not only complement each other, they also provided mutual confirmation of specific conclusions.

Raman spectroscopy as a process analytical technology (PAT) tool for the in-line monitoring and understanding of a powder blending process

The aim of this study is to propose a strategy to implement a PAT system in the blending step of pharmaceutical production processes. It was examined whether Raman spectroscopy can be used as PAT tool for the in-line and real-time endpoint monitoring and understanding of a powder blending process. A screening design was used to identify and understand the significant effects of two process variables (blending speed and loading of the blender) and of a formulation variable (concentration of active pharmaceutical ingredient (API): diltiazem hydrochloride) upon the required blending time (response variable). Interactions between the variables were investigated as well. A Soft Independent Modelling of Class Analogy (SIMCA) model was developed to determine the homogeneity of the blends in-line and real-time using Raman spectroscopy in combination with a fiber optical immersion probe. One blending experiment was monitored using Raman and NIR spectroscopy simultaneously. This was done to verify whether two independent monitoring tools can confirm each others endpoint conclusions. The analysis of the experimental design results showed that the measured endpoints were excessively rounded due to the large measurement intervals relative to the first blending times. This resulted in effects and critical effects which cannot be interpreted properly. To be able to study the effects properly, the ratio between the blending times and the measurement intervals should be sufficiently high. In this study, it anyway was demonstrated that Raman spectroscopy is a suitable PAT tool for the endpoint control of a powder blending process. Raman spectroscopy not only allowed in-line and real-time monitoring of the blend homogeneity, but also helped to understand the process better in combination with experimental design. Furthermore, the correctness of the Raman endpoint conclusions was demonstrated for one process by using a second independent endpoint monitoring tool (NIR spectroscopy). Hence, the use of two independent techniques for the control of one response variable not only means a mutual confirmation of both methods, but also provides a higher certainty in the determined endpoint.

Mercury in the Southern North Sea and Scheldt estuary

Abstract Dissolved and particulate mercury and methylmercury concentrations were determined in the Southern Bight of the North Sea and the Scheldt estuary in the period 1991–1999. Mercury and methylmercury concentrations are higher before 1995 than after 1995, especially in the fluvial part. The North Sea: In the offshore stations, dissolved Hg concentrations are generally higher in winter than in summer while the reverse is true for particulate Hg K D values ( K D =the concentration of particulate Hg (Hg P in pmol kg −1 ) divided by the concentration of dissolved Hg (Hg D in pmol l −1 )) range from 100,000 to 1000,000 l kg −1 . Dissolved methylmercury concentrations vary from 0.05 to 0.25 pmol l −1 in summer and from d.l. to 0.23 pmol l −1 in winter and particulate methylmercury concentrations from 1.8 to 36 pmol g −1 in summer and from 0.9 to 21 pmol g −1 in winter. The K D ranges from 9,000 to 219,000 l kg −1 . The Scheldt estuary: In winter, dissolved Hg concentrations are elevated in the upper estuary, decrease exponentially in the low salinity range followed by a very slow decrease towards the mouth. In summer, they are low in the fluvial part, increase in the low salinity range or in the mid-estuary and sometimes show an increase in the lower estuary. Particulate Hg concentrations do not show any seasonal trend. Dissolved MMHg concentrations are much lower in winter, when maximum concentrations are found in the upper estuary, than in summer. In summer, the MMHg concentrations are low at low salinity, they show a first increase in the salinity range from 3 to 12, a decrease in the mid-estuary and a second increase in the lower estuary. The highest particulate MMHg concentrations are found in the upper estuary, while in the lower estuary generally lower and more constant values are observed. The ratio of dissolved MMHg to dissolved Hg (cruise averages between 1.3% and 20%), is higher than the ratio of particulate MMHg to particulate Hg (cruise averages of 0.27–0.90%). The K D values for MMHg are lower in the summer (30,000–65,000) than in autumn and winter (77,000–114,000). The Scheldt river: In the fluvial part of the Scheldt, dissolved increases in the most upstream stations, while particulate Hg shows no particular pattern. Dissolved MMHg ranges from 0.1 to 0.39 pmol l −1 and particulate MMHg from 3.1 to 43.5 pmol g −1 . The MMHg concentrations are comparable to those found in the estuary and no seasonal variations could be observed.

Recent developments of enantioseparation techniques for adrenergic drugs using liquid chromatography and capillary electrophoresis: a review.

This review provides the achievements of enantioseparation of adrenergic drugs and application of these methods in clinical and pharmaceutical analysis. The adrenergic agonist and antagonist drugs are analyzed in the direct and indirect modes by liquid chromatography (LC) and capillary electrophoresis (CE). Other chromatographic enantioseparation methods including super- and sub-critical fluid chromatography (SFC), and capillary electrochromatography (CEC) are presented likewise to analyse the cited compounds. The different separation processes for these drugs are briefly discussed and some applications are presented.

MERCURY SPECIATION IN THE SCHELDT ESTUARY

Surface waters of the Scheldt Estuary were sampled on various occasions between 1991 and 1994. Longitudinal particulate Hg (PM) concentrations ranged from 0.4 – 1.7 μgHg/g and are essentially controlled by physical mixing of polluted fluvial particulates with relatively unpolluted marine particulates. Total dissolved mercury (TDM)concentrations ranged from 0.5 to 5.2 ng/L and are strongly influenced by removal and mobilization processes in the upper estuary, while in the lower estuary mixing processes cause a progressive decrease in TDM towards the mouth. Speciation studies showed that dissolved Hg is predominantly bound to strong complexing ligands (organic substances) in the upper estuary, but this fraction decreases with increasing salinity. In June 1993, however, the reactive mercury fraction was also high in the upper estuary. Model calculations showed that a conditional stability constant for Hg- humic acid interactions of 1019 was a good estimate for the Scheldt estuary. Dissolved methylmercury was analyzed on three occasions. Significant seasonal variations were observed with concentrations ranging from 11 to 120 pg/L in the winter and 80 to 400 pg/L in summer. Supersaturation of Hg° is observed throughout the whole estuary resulting in an estimated evasion flux of 140–1400 ng/m2 day.