Diffusive sampling of methyl isocyanate using 4-nitro-7-piperazinobenzo-2-oxa-1,3-diazole (NBDPZ) as derivatizing agent

A diffusive sampling method for the determination of methyl isocyanate (MIC) in air is introduced. MIC is collected using a glass fiber filter impregnated with 4-nitro-7-piperazinobenzo-2-oxa-1,3-diazole (NBDPZ). The urea derivative formed is desorbed from the filter with acetonitrile and analyzed by means of high-performance liquid chromatography (HPLC) using fluorescence detection (FLD) with lambdaex = 471 nm and lambdaex = 540 nm. Additionally, a method was developed using tandem mass spectrometric (MS-MS) detection, which was performed as selected reaction monitoring (SRM) on the transition [MIC-NBDPZ + H]+ (m/z 307) to [NBDPZ + H]+ (m/z 250). The diffusive sampler was tested with MIC concentrations between 1 and 35 microg m(-3). The sampling periods varied from 15 min to 8 h, and the relative humidity (RH) was set from 20% up to 80%. The sampling rate for all 15 min experiments was determined to be 15.0 mL min(-1) (using HPLC-FLD) with a relative standard deviation of 9.9% for 56 experiments. At 80% RH, only 15 min sampling gave acceptable results. Further experiments revealed that humidity did not affect the MIC derivative but the reagent on the filter prior to and during sampling. The sampling rate for all experiments (including long term sampling) performed at 20% RH was found to be 15.0 mL min(-1) with a relative standard deviation of 6.3% (N = 42). The limit of quantification was 3 microg m(-3) (LC-MS-MS: 1.3 microg m(-3)) for 15 min sampling periods and 0.2 microg m(-3) (LC-MS-MS: 0.15 microg m(-3)) for 8 h sampling runs applying fluorescence detection.     

Development of a diffusive sampling method for determination of methyl isocyanate in air

A diffusive sampling method for determination of methyl isocyanate in air has been developed. A glass fibre filter impregnated with 1-(2-methoxyphenyl)piperazine in a commercially available diffusive sampling device was used to collect methyl isocyanate and the derivative formed was analysed with LC-MS/MS. The sampling rate was determined to be 15.6 ml min(-1), with a relative standard deviation of 7.3%. The sampler was validated for sampling periods from 15 min to 8 h, for relative humidities from 20% to 80% and for concentrations from I to 46 microg m(-3). A field validation was also made and the diffusive sampling results showed no difference compared to a pumped reference method. The impregnated filters have to be stored apart from the diffusive sampler housing and loaded into the sampler prior to each sampling.     

Evaluation of two adsorbents for diffusive sampling and thermal desorption-gas chromatographic analysis of monoterpenes in air

Tube type samplers with two different adsorbents, Chromosorb 106 and Tenax TA, were evaluated by laboratory experiments and field tests for simultaneous diffusive sampling of alpha-pinene, beta-pinene and delta 3-carene and subsequent thermal desorption-gas chromatographic analysis. No statistically significant effects of exposure time, concentrations of monoterpenes or relative humidity were found for samplers with Chromosorb 106 when running a factorial design, with the exception of the adsorption of delta 3-carene, for which some weak effects were noted. Samplers with Tenax TA were affected by the sampling time as well as the concentration for all terpenes, with a strong interaction effect between these two factors. The terpenes showed good storage stability on both adsorbents. No effect of back-diffusion was noted when using Chromosorb 106, while Tenax TA showed some back-diffusion effects. The uptake rates, in ml min-1, for the terpenes on Chromosorb 106 were 0.36 for alpha-pinene, 0.36 for beta-pinene and 0.40 for delta 3-carene. The corresponding average values on Tenax TA were 0.30 for alpha-pinene, 0.32 for beta-pinene and 0.38 for delta 3-carene. The field validation proved that diffusive sampling on Chromosorb 106 agreed well with pumped sampling on charcoal for stationary samples, while the personal samples indicated a discrepancy of 25% between Chromosorb 106 and charcoal samples. Tenax TA generally gave lower results than Chromosorb 106 in all field samples. Samplers packed with Chromosorb 106 could be used to monitor terpene levels in workplaces such as sawmills. The major advantages with this method are the sampling procedure, which is simple to perform compared to other techniques, the easily automated analysis procedure and the possibility to reuse the samplers.     

气相色谱/质谱法分析食品中的丙烯酰胺

要揭示烹调食物中有无丙烯酰胺,需对可疑食品进行检测。经典的方法是用水从食品中提取出丙烯酸胺,再将其转化成溴化衍生物。文章描述了这些衍生物的电子轰击和正离子化学电离响应和谱图。另外,还介绍了一种更直接、更简便的方法,包括丙烯酰胺提取和直接进样,并用正离子化学电离进行分析。这种监测方法快速、可靠,检测限低。     

Within-and among-clutch variation of organochlorine residues in eggs of black-crowned night-herons

Within-clutch variability of DDE and PCB residues in eggs from 62 clutches of black-crowned night-herons (Nycticorax nycticorax) was small (12% and 17%) compared to among-clutch variability (88% and 83%). Significant correlations between concentrations of DDE (median r=0.8885) and of PCBs (median r=0.8244) occurred when 501 correlations were run on two randomly selected eggs from within the same clutch; no significant correlation occurred for either concentrations of DDE (median r=0.0353) or PCBs (median r=–0.0843) when eggs were not restricted to the same clutch but were restricted to the same colony. The probability of finding infrequently detected organochlorine contaminants (e.g., DDT, cis-chlordane) in eggs from the same clutch varied from 43–96% and increased as the chemical became more prevalent and the number of eggs per clutch became smaller. These results further support one of the basic assumptions of the sample egg technique, that the chemical residues in one egg in a clutch accurately reflect residues in the remaining eggs of the clutch.     

麦夸里岛毛皮海豹体内小塑料颗粒的来源和生物聚集

本文研究了从麦夸里岛上毛皮海豹(Arctocephalus spp.)粪便中发现的164个塑料颗粒(平均长度为4.1mm).其中41个塑料颗粒的电子显微照片显示,从其形状来看,没有一个可被确定为塑料颗柱原料--通常这样的颗粒是圆柱形和球形的.而海豹粪便中的164个塑料颗粒全都是7种颜色的角形颗粒(原料颗粒通常是透明的或白色的),并可被分为两类①沿晶体线碎裂的和可能是紫外线分解的;②被磨蚀成带有圆角的不规则形状(擦痕明显可见).白色、棕色、绿色、黄色以及蓝色是最常见的颜色.在成分上,它们来自于5种聚合物群聚乙烯93%;聚丙烯4%;多(1-CI-1-聚丁二烯)聚氯丁二烯2%;三聚氰胺-尿素(酚)(甲醛)树脂0.5%以及纤维素(绳纤维)0.5%.较大的群是漂浮的,比重小于海水.这些小塑料是由较大颗粒(碎片)分解而成的.它们看来是被水冲上岸的并在卵石海滩上受到研磨的塑料用品分解而成的.大多数颗粒(70%)肯定是由于经过不断的磨蚀而最后形成今天的形状.据假设,塑料颗粒被冲到海洋中,然后按其大小有选择地被一种中上层鱼--Electrona subaspera--吃掉,而这种鱼后来又被毛皮海豹吃掉.因此,这些塑料颗粒是由这种鱼和海豹在其正常的摄食过程中聚集的.     

DNA-based carrier detection and prenatal diagnosis of tyrosinase-negative oculocutaneous albinism (OCA1A)

We describe molecular prenatal diagnosis and carrier detection of tyrosinase-negative oculocutaneous albinism (OCA1A) in two families. In one family, we carried out DNA-based prenatal diagnosis of OCA1A. In the other family, mutation analysis and carrier detection obviated the need for prenatal diagnosis. Molecular analysis is safer and probably more accurate than fetoscopy and fetal scalp biopsy, and should become the method of first choice for prenatal diagnosis of OCA1.     

Our future in the Anthropocene biosphere

The COVID-19 pandemic has exposed an interconnected and tightly coupled globalized world in rapid change. This article sets the scientific stage for understanding and responding to such change for global sustainability and resilient societies. We provide a systemic overview of the current situation where people and nature are dynamically intertwined and embedded in the biosphere, placing shocks and extreme events as part of this dynamic; humanity has become the major force in shaping the future of the Earth system as a whole; and the scale and pace of the human dimension have caused climate change, rapid loss of biodiversity, growing inequalities, and loss of resilience to deal with uncertainty and surprise. Taken together, human actions are challenging the biosphere foundation for a prosperous development of civilizations. The Anthropocene reality—of rising system-wide turbulence—calls for transformative change towards sustainable futures. Emerging technologies, social innovations, broader shifts in cultural repertoires, as well as a diverse portfolio of active stewardship of human actions in support of a resilient biosphere are highlighted as essential parts of such transformations.     

Influences of perfluorooctanoic acid on the aggregation of multi-walled carbon nanotubes

The aggregation of multi-walled carbon nanotubes (MWCNTs) in the aqueous phase not only inhibits their extensive utilization in various aspects but also dominates their environmental fate and transport.The role of surfactants at low concentration in the aggregation of MWCNTs has been studied,however the effect of perfluorinated surfactants at low concentration is uncertain.To understand this interfacial phenomenon,the influences of perfluorooctanoic acid (PFOA),and sodium dodecyl sulfate (SDS) as a control,on MWCNT aggregation in the aqueous phase were examined by the UV absorbency method.Influences of pH and cationic species on the critical coagulation concentration (CCC) value were evaluated.The CCC values were dependent on the concentration of PFOA,however a pronounced effect of SDS concentration on the CCC values was not observed.The CCC values of the MWCNTs were 51.6 mmol/L in NaCl and 0.28 mmol/L in CaCl 2 solutions,which suggested pronounced differences in the effects of Na+ and Ca2+ ions on the aggregation of the MWCNTs.The presence of both PFOA and SDS significantly decreased the CCC values of the MWCNTs in NaCl solution.The aggregation of the MWCNTs took place under acidic conditions and was not notably altered under neutral and alkaline conditions due to the electrostatic repulsion of deprotonated functional groups on the surface of the MWCNTs.