Glucoraphanin extraction from Cardaria draba: Part 2. Countercurrent extraction,bioactivity and toxicity testing

Glucoraphanin is a potentially valuable plant compound that has shown efficacy in the treatment of hypertension and the removal of carcinogens in animals. Our recent work determined the optimum extraction conditions for the recovery of high amounts of glucoraphanin from the noxious weed Cardaria draba in a single‐staged batch extractor. In this study, a multiple contact, countercurrent flow extraction process was used to achieve further improvements in glucoraphanin recovery. The yield increased by 1.5 times when compared with a single, batch contact extraction. A three‐stage process was sufficient to extract over 90% of the glucoraphanin from C draba at a dry weight plant loading of 50 g dm^?3. The experimental results at several solids loadings agreed with the leaching theory and the theoretical model was used to predict the number of stages needed to extract all the glucoraphanin from C draba at high solids loadings. Finally the efficacy and toxicity of the crude glucoraphanin extracts were tested using hepatoma cells. The efficacy was found to be much higher than single‐stage extracts, confirming that cell efficacy is related to the increased quantity of glucoraphanin extracted due to countercurrent operation. The crude extract demonstrated negligible acute toxicity to the hepatoma cells. Copyright © 2005 Society of Chemical Industry     

Analysis of a 3-D system function measured for magnetic particle imaging

Magnetic particle imaging (MPI) is a new tomographic imaging approach that can quantitatively map magnetic nanoparticle distributions in vivo. It is capable of volumetric real-time imaging at particle concentrations low enough to enable clinical applications. For image reconstruction in 3-D MPI, a system function (SF) is used, which describes the relation between the acquired MPI signal and the spatial origin of the signal. The SF depends on the instrumental configuration, the applied field sequence, and the magnetic particle characteristics. Its properties reflect the quality of the spatial encoding process. This work presents a detailed analysis of a measured SF to give experimental evidence that 3-D MPI encodes information using a set of 3-D spatial patterns or basis functions that is stored in the SF. This resembles filling 3-D k-space in magnetic resonance imaging, but is faster since all information is gathered simultaneously over a broad acquisition bandwidth. A frequency domain analysis shows that the finest structures that can be encoded with the presented SF are as small as 0.6 mm. SF simulations are performed to demonstrate that larger particle cores extend the set of basis functions towards higher resolution and that the experimentally observed spatial patterns require the existence of particles with core sizes of about 30 nm in the calibration sample. A simple formula is presented that qualitatively describes the basis functions to be expected at a certain frequency.     

Exposure of an adult population to perfluorinated substances using duplicate diet portions and biomonitoring data

Because dietary intake is supposed to be an important route of human exposure we quantified the dietary intake of perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorohexane sulfonate (PFHxS), perfluorohexanoate (PFHxA), and perfluorooctane sulfonamide (PFOSA) using 214 duplicate diet samples. The study was carried out with a study population of 15 female and 16 male healthy subjects aged 16-45 years. The participants collected daily duplicate diet samples over seven consecutive days in 2005. Duplicate samples were homogenized and their ultrasonic extracts were cleaned up by SPE and subjected to HPLC-ESI-MS/MS. In addition, individual intakes were estimated based on blood levels of PFOS and PFOA using a pharmacokinetic model. Blood samples were collected once during the sampling period. The median (90th percentile) daily dietary intake of PFOS and PFOA was 1.4 ng/kg b.w. (3.8 ng/kg b.w.) and 2.9 ng/kg b.w. (8.4 ng/kg b.w.), respectively. PFHxS and PFHxA could be detected only in some samples above detection limit with median (maximum) daily intakes of 2.0 ng/kg b.w. (4.0 ng/kg b.w.) and 4.3 ng/kg b.w. (9.2 ng/kg b.w.), respectively. Because PFOSA could not be detected above the limit of detection of 0.2 ng/g f.w. this indirect route of exposure seems to be of less significance. Overall, the results of this study demonstrate that the German population is exposed to PFOS and PFOA, but the median dietary intake did not reach the recommended tolerable daily intake by far. Biomonitoring data predict an exposure in a comparable range. We suppose that, normally, food intake is the main source of exposure of the general population to PFOS and PFOA.     

Hydrodynamic and microbial processes controlling nitrate in a fissured-porous karst aquifer of the Franconian Alb, southern Germany

Concentrations and stable isotope compositions of nitrate from 11 karst springs in the Franconian Alb (southern Germany) were determined during low flow and high flow conditions to assess sources and processes affecting groundwater nitrate. During low flow, nitrate concentrations in groundwater were around 0.10 mM in springs draining forested catchments, whereas in agricultural areas nitrate concentrations were typically higher reaching up to 0.93 mM. The isotopic composition of groundwater nitrate during low flow (delta15N values of -3.1 to 6.7% per hundred, delta180 values of +2.1 to 4.0% per hundred) in concert with concentration data suggests that nitrate is formed by nitrification in forest and agricultural soils. In addition, synthetic fertilizer N that has undergone immobilization and subsequent remineralization likely constitutes an additional nitrate source in agriculturally used catchments. During recharge conditions, concentrations and delta15N values of groundwater nitrate changed little, but delta18O values were significantly elevated (up to 24.5%o per hundred suggesting that around 25% of the nitrate was directly derived from atmospheric deposition. Groundwater dating revealed that low nitrate concentrations in groundwater (_> or =0 years) are consistent with a mixture of old low nitrate-containing and young water, the latter being affected by anthropogenic N inputs predominantly in the agriculturally used catchment areas during the last few decades. Thermodynamic and hydrogeological evidence also suggests that denitrification may have occurred in the porous rock matrix of the karst aquifer. This study demonstrates that a combination of hydrodynamic, chemical, and isotopic approaches provides unique insights into the sources and the biogeochemical history of nitrate in karst aquifers, and therefore constitutes a valuable tool for assessing the vulnerability of karst aquifers to nitrate pollution in dependence on land use and assessing their self-purification capacity.     

Intra- and interlaboratory reproducibility of ultra performance liquid chromatography-time-of-flight mass spectrometry for urinary metabolic profiling

Liquid chromatography coupled to mass spectrometry (LC-MS) is a major platform in metabolic profiling but has not yet been comprehensively assessed as to its repeatability and reproducibility across multiple spectrometers and laboratories. Here we report results of a large interlaboratory reproducibility study of ultra performance (UP) LC-MS of human urine. A total of 14 stable isotope labeled standard compounds were spiked into a pooled human urine sample, which was subject to a 2- to 16-fold dilution series and run by UPLC coupled to time-of-flight MS at three different laboratories all using the same platform. In each lab, identical samples were run in two phases, separated by at least 1 week, to assess between-day reproducibility. Overall, platform reproducibility was good with median mass accuracies below 12 ppm, median retention time drifts of less than 0.73 s and coefficients of variation of intensity of less than 18% across laboratories and ionization modes. We found that the intensity response was highly linear within each run, with a median R(2) of 0.95 and 0.93 in positive and negative ionization modes. Between-day reproducibility was also high with a mean R(2) of 0.93 for a linear relationship between the intensities of ions recorded in the two phases across the laboratories and modes. Most importantly, between-lab reproducibility was excellent with median R(2) values of 0.96 and 0.98 for positive and negative ionization modes, respectively, across all pairs of laboratories. Interestingly, the three laboratories observed different amounts of adduct formation, but this did not appear to be related to reproducibility observed in each laboratory. These studies show that UPLC-MS is fit for the purpose of targeted urinary metabolite analysis but that care must be taken to optimize laboratory systems for quantitative detection due to variable adduct formation over many compound classes.     

The influence of particle orientation on the loading condition of pebbles in fluvial gravel

The loading conditions of pebbles in fluvial gravel deposits were studied with different degrees of preferred particle orientation. Sediments that are comprised of non-spherical particles often show a preferred particle orientation, due to dynamic sedimentation. Here, the impact of this effect on the loading conditions of the particles and its implication on particle breakage was investigated by using discrete element simulations in three dimensions. The numerical models are based on the size and shape distribution of pebbles from a natural gravel sample. In addition, the particle size in some of the models was chosen to be uniform, to study the influence of the particle size distribution on the loading condition. Fluvial pebbles, whose shapes can be at best approximated by ellipsoids, were efficiently simulated in the discrete element models by the use of clumps. The results show that a preferred orientation of approximate ellipsoidal sedimentary particles has only a minor effect on the number and the position of particle contacts but leads to a significant load transfer from the rim to the centre of the oblate sides of the ellipsoidal particles, in comparison to an assembly of arbitrarily oriented particles. The comparison of the different particle size models indicates that the influence of the particle size distribution on the loading condition is relatively low. The results have significant implications for the breakage rate of non-spherical particles in sediments under load.     

Depth profiling for the identification of unknown substances and concealed content at remote distances using time-resolved stand-off Raman spectroscopy

Time-resolved stand-off Raman spectroscopy was used to determine both the position and identity of substances relative to each other at remote distances (up to tens of meters). Spectral information of three xylene isomers, toluene, and sodium chlorate was obtained at a distance of 12 m from the setup. Pairs and triplets of these samples were placed at varying distances (10-60 cm) relative to each other. Via the photon time of flight the distance between the individual samples was determined to an accuracy of 7% (corresponding to a few cm) of the physically measured distance. Furthermore, at a distance of 40 m, time-resolved Raman depth profiling was used to detect sodium chlorate in a white plastic container that was non-transparent to the human eye. The combination of the ranging capabilities of Raman LIDAR (sample location usually determined using prior knowledge of the analyte of interest) with stand-off Raman spectroscopy (analyte detection at remote distances) provides the capability for depth profile identification of unknown substances and analysis of concealed content in distant objects. To achieve these results, a 532 nm laser with a pulse length of 4.4 ns was synchronized to an intensified charge-coupled device camera with a minimum gate width of 500 ps. For automated data analysis a multivariate curve resolution algorithm was employed.