环境监测现场采样质量影响因素分析

在环境监测工作中,现场采样质量直接关系到监测结果的精准度。分析了环境监测现场采样质量的影响因素,从现场采样方案编制、准备阶段、现场采样、样品运输四个方面,探讨了现场采样质量的控制措施。     

用MATLAB实现连续信号采样和重建的教学实践

本文利用MATLAB实现了连续时间信号的采样及重构,并以f(t)=Sa(t)为例,分别以过采样、等采样、欠采样三种情况,绘出原信号、采样信号、重构信号的时域波形图,可以让学生加深对采样定理的理解和掌握以及对信号恢复的必要性。     

环境监测现场采样的质量控制举措和建议

现场采样监测作为环境监测的首要环节,是整个环境监测分析工作的前提和基础。采样一旦出现质量问题会直接影响监测结果的准确性,后续监测工作将失去意义。本文对现场采样过程中的影响因素及目前现场采集水、气、固体等不同样品时的注意事项进行了逐一分析,并结合自身多年现场监测工作经验从采样前准备、采样中及采样后等环节进行质量控制举措的探讨,提出了现场采样改进建议,从源头开始提高监测数据质量。     

中美粉尘采样方法对比研究

通过中美两国粉尘采样方法有关标准的对比研究,找出两国在粉尘职业接触限值、采样设备及采样策略等方面的异同,为我国粉尘采样技术的发展提供一些规范方面的借鉴。     

蔬菜与水果农药残留检测中的质量控制措施

<正>采样的质量控制要进行农药残留检测,必须进行采样。工作人员在采样前,必须有科学的采样计划,使用正确的采样方法。由于产地的实际情况不同,要使用与之相对应的采样法。对于不同种类的蔬菜水果,采样的量也有所差异。采样完成后,要按照规定做好保存工作,进行编号。样品必须被快速送到实验室进行分析,保证样品能真实反映总     

环境监测现场采样质量控制措施研究

现场采样是环境监测的重要环节,能够为环境监测提供必要的参考数据和决策依据,从而进行更加科学、全面的环境评价,对于提升环境监测质量具有重要意义。但是由于现场采样受到多种因素的影响,导致采样质量不稳定因素增多,严重影响环境监测的最终效果。因此,强化对环境监测现场采样质量控制措施的研究势在必行。本文主要分析了环境监测现场采样的质量影响因素,旨在进一步提高现场采样质量控制效果,为提高环境监测结果的准确性和参考性提供保障。     

国内外粮食中真菌毒素采样标准对比及分析

真菌毒素广泛存在于粮油等食品中,危害人类和动物的健康。由于粮油等食品中真菌毒素的污染分布不均匀,因此科学、合理、经济的采样(扦样)计划尤为重要。梳理了国内外粮食的采样标准,并对每个标准适用范围、是否适合真菌毒素、各个采样环节规定进行比较分析。国际采样标准就不同的食品类别或真菌毒素(污染物)的各个采样环节的要求进行了系统阐述,涵盖了粮食中真菌毒素的采样要求。目前国内没有系统的针对粮食中真菌毒素采样标准。通过对国内外相关标准的研究,为提出符合我国种粮散户多、运输工具规格不同、大中小粮仓乃至高大平房仓等不同储运环节粮食中真菌毒素的科学、有效、公正的采样方案提供了一定的参考。     

DNPH-硅胶管采样条件对VOCs检出的影响

采用Sep-Pak DNPH-silica吸附管对室内空气中羰基化合物采样,分析了在不同流速和温度下对各羰基化合物的吸附效率。试验结果表明,两者对采样效率影响明显,采样流量不宜大,环境温度宜略高,且在任何采样条件下,均存在穿透现象。     

高速ADC驱动电路建立时间的准确测量

为了提高建立时间的测量精度,提出了一种新型测量方法.该方法直接用ADC多次采样运放的输出信号,通过采样边缘移动的方法得到ADC的采样序列,最后通过采样序列绘制建立时间曲线,从而有效去除测试仪器寄生电容和电感的影响,提高测量的精确度.     

国外禽畜胴体非破坏性微生物样品采集方法分析

屠宰生产线上禽畜胴体微生物样品采集方法分可破坏性采样和非破坏性采样。本文收集并分析了国际标准化组织(International Standardization Organization,ISO)、美国农业部、新西兰食品安全局以及澳大利亚检验检疫局关于禽畜胴体非破坏性微生物样品采集的方法,其包括湿-干拭子法(wet and dry swab method)、海绵拭子法(sponge sampling method)和纱布敷料法(gauze tampon method)、胴体冲洗采样法,不同屠宰工艺不同微生物目标其采样时机、采样位点、采样频率和微生物限量不尽相同,以期为我国禽畜产品加工生产和安全监控提供采样技术参考。     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.     

Analysis for organic residues from aids to polymerization used to make plastics intended for food contact

Polymers intended for food contact use have been analysed for organic residues which could be attributed to a range of substances employed as polymerization aids (e.g. initiators and catalysts). A wide range of polymers was extracted with solvents and the extracts analysed by gas chromatography-mass spectrometry (GC-MS). The overwhelming majority of substances identified were not derived from aids to polymerization but were oligomers, additives and adventitious contaminants. However, a small number of substances were identified as initiator residues. These included tetramethylsuccinonitrile (TMSN) which was observed in two polymers and it derived from recombination of two azobisisobutyronitrile (AIBN) initiator radicals. Methyl benzoate, benzoic acid, biphenyl and phenyl benzoate were detected in one poly(methyl methacrylate) sample and in two polyvinylchlorides and they are thought to be derived from benzoyl peroxide initiator. TMSN was subsequently targeted for analysis of poly-(methyl methacrylate) plastics using proton nuclear magnetic resonance spectrometry (¹     

Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants

Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.     

The Ministry of Environmental Protection Issued "Feasible Technology Guidelines for Pollution Prevention and Control in Wood Pulping Process of the Paper Industry (Trial)" and Two Other Guiding Technical Documents

On December 27t＂, 2013, the Ministry of Environmenta Protection announced that, in order to implement ＂The Environmental Protection Law of the People＇ s Republic of China＂, improve the working system in environmenta protection technologies, and promote technologica advancement in pollution prevention, the Ministry of Environmental Protection sponsored the formulation of three guiding technical documents including ＂Feasible Technology Guidelines for Pollution Prevention and Contro n Wood Pulping Process of the Paper Industry （Trial）＂     

1~(st) Intelli-Tissue~ EcoEc Tissue Machine Supplied by PMP Group Successfully Put into Operation in China

正On April 29th,2014,Intelli-Tissue EcoEc tissue machine supplied by PMP Group successfully put into operation at Hebei Xuesong Paper Co.,Ltd.,this is the first such kind of paper machine of PMP Group in China.