Miniaturized and automated sample pretreatment for determination of PCBs in environmental aqueous samples using an on-line microporous membrane liquid-liquid extraction-gas chromatography system

A new, fast, and automated sample pretreatment technique for determination of lipophilic organic compounds in aqueous samples has been developed and applied to the determination of polychlorinated biphenyls (PCBs) in environmental river water. It is based on miniaturized microporous membrane liquid-liquid extraction coupled on-line to gas chromatography (GC) with electron capture detection. The heart of the system that simultaneously connects the sample pretreatment step to the final GC analysis has been named the extracting syringe (ESy). The ESy carries a miniaturized membrane extraction card attached to an electrically and mechanically designed installment and is mounted directly over a GC injector for fully automated injection of the extract. A method was developed to extract 10 PCB congeners from 1-mL water samples (after addition of 40% acetonitrile) with an extraction time of 10 min. The optimized methodology showed good linearity (in the dynamic concentration range of 5 ng L(-)(1)-1 microg L(-)(1)), enrichment factors of 33-40 times, repeatable extractions (RSD 2-5%, n = 4), and low detection limits (2-3 ng L(-)(1)). Acetonitrile had to be added to the samples in order to overcome the influence of PCB adsorption on the repeatability of extraction and enrichment and to minimize the overall memory effect (OME). OME and carryover depended not only on the concentration of the organic solvent added to the sample and that used in the washing procedure but also on whether the extracting card was changed or not. When an optimized washing procedure was applied, the OME was approximately 0.2% at high concentrations (i.e., 1 microg L(-)(1)). When each extraction took place in a new extraction card, no OME was detected. Additionally, no significant adsorption onto glass surfaces or a matrix effect on extraction was noticed. The main features of this methodology are good extraction repeatability, low detection limits at short extraction time, and the unsurpassed characteristic of no detectable OME in the entire system when each sample is processed in a new card. The total consumption of organic (nonchlorinated) solvents is less than 5 mL per sample.     

Discriminative touch and emotional touch.

Somatic sensation comprises four main modalities, each relaying tactile, thermal, painful, or pruritic (itch) information to the central nervous system. These input channels can be further classified as subserving a sensory function of spatial and temporal localization, discrimination, and provision of essential information for controlling and guiding exploratory tactile behaviours, and an affective function that is widely recognized as providing the afferent neural input driving the subjective experience of pain, but not so widely recognized as also providing the subjective experience of affiliative or emotional somatic pleasure of touch. The discriminative properties of tactile sensation are mediated by a class of fast-conducting myelinated peripheral nerve fibres--A-beta fibres--whereas the rewarding, emotional properties of touch are hypothesized to be mediated by a class of unmyelinated peripheral nerve fibres--CT afferents (C tactile)--that have biophysical, electrophysiological, neurobiological, and anatomical properties that drive the temporally delayed emotional somatic system. CT afferents have not been found in the glabrous skin of the hand in spite of numerous electrophysiological explorations of this area. Hence, it seems reasonable to conclude that they are lacking in the glabrous skin. A full understanding of the behavioural and affective consequences of the differential innervation of CT afferents awaits a fuller understanding of their function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distinction of Leu and Ile Using a Ruthenium(II) complex by MALDI-LIFT-TOF/TOF-MS analysis

The novel N-terminal labeling method using a ruthenium(II) complex derivative characteristically indicated a(n) and d(n) (N-terminal) fragment ions in high sensitivity by MS/MS analysis (MALDI-LIFT or ESI-CID). Although these fragment ions depended on a fragmentation process by MS/MS analytical methods to some degree, each case indicated similar side-chain cleavage patterns. The labeling method allows accurate distinction of amino acid residues by MS/MS analysis even if the residues are structural isomers such as leucine and isoleucine. The method was applied to long-chain peptides and provided easy and rapid N-terminal sequencing.     

Equilibrium sampling through membranes of freely dissolved copper concentrations with selective hollow fiber membranes and the spectrophotometric detection of a metal stripping agent

A sensitive spectrophotometric method for the determination of freely dissolved copper concentrations in aqueous samples after preconcentration with hollow fiber membrane extraction has been developed. The method is based on the equilibrium sampling through a selective membrane into an acceptor solution containing 4-(pyridyl-2-azo)resorcinol (PAR), which serves as stripping agent and metal indicator. Negligible extraction of interferences and equilibrium enrichment of copper allowed for selective spectrophotometric determination of the Cu-PAR complex. Some important extraction parameters such as acceptor composition, shaking, equilibrium time, and sample volume were studied. The optimized methodology showed good linearity in the range of 5-100 microg/L, an enrichment factor of 93, good repeatability and reproducibility (RSDs < 6%, n = 6), and a detection limit of 4 microg/L. The cationic metals Ni2+, C(2+, Cd2+, Fe3+, Pb2+, Zn2+, and Mn2+ were shown not to interfere with the measurement of Cu2+. Measurements on samples containing mixtures of various ligands and cations were in good agreement with theoretically calculated concentrations, and the method was also applied to environmental samples. The developed technique requires less labor and less sophisticated equipment than conventional methods typically based on atomic absorption spectrometry or ICP.     

Temporal trends of polybrominated diphenyl ethers and hexabromocyclododecane in milk from Stockholm mothers, 1980-2004

Environmental and human exposures to brominated flame retardants (BFR) have been of emerging concern since some BFR are persistent and bioaccumulative compounds. Among those, polybrominated diphenyl ethers (PBDE) have frequently been reported in low to high ng/g concentrations in human blood around the world while hexabromocyclododecane (HBCDD) only occasionally has been reported and then in the low ppb concentrations in human blood. The present study concerns PBDE congener and HBCDD concentrations in human milk from Stockholm from 1980 to 2004. HBCDD concentrations has increased four to five times since 1980 until 2002 but seems to have stabilized at this concentration in the last years (2003/04). Similarly, BDE-153 has continued to increase at least to 2001, after which it has stabilized in the mother's milk. Other PBDE congeners with four to five bromine substituents peaked 5 years earlier (1995) and are all decreasing. DecaBDE (BDE-209) is not a suitable biomarker for time trend studies according to the present results, showing no changes over time. This is likely due to its short apparent half-life in humans and poor transfer from blood to milk.     

Serum concentrations of neutral and phenolic organohalogens in pregnant women and some of their infants in The Netherlands

As part of a large European Union (EU)-funded comparative toxicology and human epidemiology study, EU-Compare, a selection of organohalogen compounds (OHCs) was analyzed in maternal serum, collected at the 35th week of pregnancy, and in cord serum of a number of their infants to determine maternal concentrations and to investigate the extent of transplacental transfer of these compounds. Eight neutral OHCs were analyzed: one polychlorinated biphenyl (PCB: CB-153),4,4'-DDE, five polybrominated diphenyl ethers (PBDEs: BDE-47, BDE-99, BDE-100, BDE-153, and BDE-154), and hexabromocyclododecane (HBCDD). Five phenolic OHCs were analyzed: three hydroxylated PCBs (40H-CB-107, 40H-CB-146, and 40H-CB-187), one hydroxylated PBDE (60H-BDE-47), and pentachlorophenol (PCP). All OHCs, except 60H-BDE-47, were present in maternal and cord serum. The historically identified OHCs showed the highest concentration: 4,4'-DDE (median value 89 ng/g lipid in maternal serum and 68 ng/g lipid in cord serum) and PCP (median value 970 pg/g serum in maternal serum and 1500 pg/g serum in cord serum). HBCDD and the PBDEs were present at much lower concentrations. We conclude that OHCs are present in the serum of pregnant women, and all compounds tested are transferred over the placenta. Because transfer is occurring at a critical stage of infant development, investigation of the health impact is urgent.     

测定硫酸软骨素相对分子质量及其分布的方法

开发了一种简单、微量的测定硫酸软骨素相对分子质量(Mr)的方法。首先用Mr已知的硫酸软骨素校正葡聚糖凝胶G-200色谱柱和琼脂糖凝胶6B色谱柱。然后采用凝胶色谱法用已校正的色谱柱测定Mw未知的硫酸软骨素样品的Mr及其分布,并考察洗脱液离子强度变化的影响。在95%置信度下,重复测定的Mw均值变动为Mw±3%。     

VanA-type vancomycin-resistant enterococci (VRE) remain prevalent in poultry carcasses 3 years after avoparcin was banned

Avoparcin was used as a growth promoting feed additive in Norwegian broiler and turkey production from 1986 until it was banned in 1995, when an association between vancomycin-resistant enterococci (VRE) and avoparcin use became apparent. A recent study regarding faecal samples documented a continuing high prevalence of VRE among Norwegian poultry 3 years after avoparcin was banned. In the present study, carcasses of broilers and turkeys from farms where avoparcin had previously been in use and carcasses of layer chickens from farms where avoparcin had never been used were examined for the presence of VRE. One carcass from each of 150 different farms was included. By a direct plating method, VRE were isolated from 30 of 100 samples of broilers and turkeys, but not from any samples of layer chickens. When an enrichment step was included, VRE were isolated from a total of 81 of the 100 samples of broilers and turkeys and from nine of the 50 samples of layer chickens. All VRE isolated were highly resistant to vancomycin (MIC > or = 256 microg/ml) and possessed the vanA gene. These results correspond to the prevalence of VRE recently documented in faecal samples from Norwegian poultry. The present study reveals a high prevalence of VRE in broiler and turkey carcasses. Consequently, consumers are exposed to VRE when handling raw poultry meat, although the public health significance of such exposure is unclear.