QuEChERS-分散固相萃取-气相色谱-质谱法测定牛乳中喹氧灵残留     

齐晓茹  苏运聪  李飞  李兴佳  张耀广  柴艳兵 《乳业科学与技术》2019,(3):25-29

建立气相色谱-质谱联用技术测定牛乳中喹氧灵残留量的检测方法。以乙腈作为提取剂,借助分散固相萃取(填料为C18和N-丙基乙二胺)作为净化手段,经Agilent HP-5MS色谱柱分离,通过基质匹配外标法校正定量。结果表明:目标物在0.00~1.00μg/mL范围内线性关系良好,R2>0.998 7,样品基质在3个添加水平(5、10、20μg/kg)下的回收率为83.2%~100.8%,相对标准偏差为2.1%~4.3%,定量限为5μg/kg;该方法步骤简单、可靠、稳定,可以推广应用于牛乳中喹氧灵含量的测定;采用该方法对75个奶户牛乳中喹氧灵含量进行测定,结果均小于国家限量值。  相似文献   

Comparison of three continuous positive airway pressure (CPAP) interfaces in healthy Beagle dogs during medetomidine–propofol constant rate infusions     

Carolina Meira  Fabiola B. Joerger  Annette P.N. Kutter  Andreas Waldmann  Simone K. Ringer  Stephan H. Böehm  Samuel Iff  Martina Mosing 《Veterinary anaesthesia and analgesia》2018,45(2):145-157

Objective

To compare the efficacy of three continuous positive airway pressure (CPAP) interfaces in dogs on gas exchange, lung volumes, amount of leak during CPAP and rebreathing in case of equipment failure or disconnection.

Study design

Randomized, prospective, crossover, experimental trial.

Animals

Ten purpose-bred Beagle dogs.

Methods

Dogs were in dorsal recumbency during medetomidine–propofol constant rate infusions, breathing room air. Three interfaces were tested in each dog in a consecutive random order: custom-made mask (M), conical face mask (FM) and helmet (H). End-expiratory lung impedance (EELI) measured by electrical impedance tomography was assessed with no interface (baseline), with the interface only (No-CPAP for 3 minutes) and at 15 minutes of 7 cmH₂O CPAP (CPAP-delivery). PaO₂ was assessed at No-CPAP and CPAP-delivery, partial pressure of inspired carbon dioxide (PICO₂; rebreathing assessment) at No-CPAP and the interface leak (ΔP_leak) at CPAP-delivery. Mixed-effects linear regression models were used for statistical analysis (p < 0.05).

Results

During CPAP-delivery, all interfaces increased EELI by 7% (p < 0.001). Higher ΔP_leak was observed with M and H (9 cmH₂O) in comparison with FM (1 cmH₂O) (p < 0.001). At No-CPAP, less rebreathing occurred with M (0.5 kPa, 4 mmHg) than with FM (1.8 kPa, 14 mmHg) and with H (1.4 kPa, 11 mmHg), but also lower PaO₂ was measured with M (9.3 kPa, 70 mmHg) than with H (11.9 kPa, 90 mmHg) and FM (10.8 kPa, 81 mmHg).

Conclusions and clinical relevance

All three interfaces can be used to provide adequate CPAP in dogs. The leak during CPAP-delivery and the risk of rebreathing and hypoxaemia, when CPAP is not maintained, can be significant. Therefore, animals should always be supervised during administration of CPAP with any of the three interfaces. The performance of the custom-made M was not superior to the other interfaces.  相似文献   

Comparison of the dietary fiber digestibility and fermentability of feedstuffs determined by conventional methods and in vitro gas production technique in pigs     

C. N. Chen  T. T. Lee 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(4):201-207

Abstract

This study evaluated the accuracy of an in vitro 2-step method combined with an in vitro gas production technique (2+IVGPT) for the estimation of dietary fiber (DF) digestibility coefficient and fermentability of feedstuffs in the large intestine of growing pigs. Digestibility coefficients of corn, wheat, soybean meal, and wheat bran, estimated by the in vitro methods, including the 2-step, 3-step, 2+IVGPT, and in vivo were compared. The fermentation characteristics of feedstuffs were also determined through the 2+IVGPT. The results showed that the in vivo DF digestibility coefficient of wheat bran was 0.39, which was similar to the result estimated by the 2+IVGPT (0.40). In regard to the fermentation characteristics, the lowest maximum rate of gas production (R_max) was obtained for wheat bran (11.0 ml h^?1). To conclude, in vivo total tract digestibility of DF in the fibrous feedstuff (e.g. wheat bran) could be accurately estimated by the 2+IVGPT.  相似文献   

Protein characteristics in grass–clover silages according to wilting rate and fermentation pattern          下载免费PDF全文

A. K. Bakken  M. Vaga  M. Hetta  Å. T. Randby  H. Steinshamn 《Grass and Forage Science》2017,72(4):626-639

Effects of wilting rate and fermentation stimulators and inhibitors on protein characteristics of forages typical for organic production were assessed using traditional analytical methods and a gas production in vitro assay. The hypotheses were that the proportion of the crude protein (CP) fraction that was soluble would be lowest, and the protein feed value highest, under rapid wilting and restricted fermentation. The solubility of the CP fraction varied according to treatments and between a first and a second cut, with moderate and high content of clover respectively. It was, however, of minor importance for the protein value, both calculated as amino acids absorbed in the small intestine (AAT₂₀) and estimated as effective utilizable crude protein (uCP₀₄) by the in vitro assay. In ensiled herbage, AAT₂₀ was highest in rapidly wilted and restrictedly fermented silages made from a first cut dominated by highly digestible grasses. Silages from the second cut dominated by red clover were far lower in AAT₂₀. The in vitro assay did not separate silages according to herbage composition or wilting rate, but ranked restrictedly fermented above extensively fermented with regard to protein supply. The assay might still have caught the characteristics that determine the true protein value in vivo.  相似文献   

大气CO_2倍增条件下冬小麦气体交换对高温干旱及复水过程的响应     

郭丽丽  张茜茜  郝立华  乔雅君  陈文娜  卢云泽  李菲  曹旭  王清涛  郑云普 《作物学报》2019,45(6):949-956

探究大气CO_2浓度倍增条件下冬小麦气体交换参数对高温干旱及复水过程的生理响应机制,有助于提高生态过程模型的模拟精度,更加准确地预测全球气候变化对农田生态系统初级生产力及其生态服务功能的影响。利用4个可精准控制CO_2浓度和温度的大型人工气候室,研究了CO_2浓度倍增条件下高温干旱及复水过程对冬小麦气孔特征和气体交换参数的影响。结果表明, CO_2浓度倍增(E)导致冬小麦远轴面气孔密度增加、气孔宽度减小、气孔空间分布规则程度降低,但提高叶片的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)。高温干旱(HD)使叶片气孔长度、密度、周长和面积减小,导致叶片气体交换参数均显著下降。然而,高CO_2浓度及高温干旱(EHD)导致气体交换参数下降幅度相对较小,表明高CO_2浓度对高温干旱具有一定的缓解作用。此外,干旱复水后,不同处理条件下冬小麦叶片气体交换参数均有所升高,但高温干旱下叶片的气体交换参数仍未能恢复到对照水平,暗示光合器官可能在高温干旱时遭到损伤和破坏。  相似文献   

气相色谱-串联质谱法检测乙氧氟草醚、唑草酮和乙螨唑在4种香辛料中的残留     

焦斌  徐军  贾爽爽  吴小虎  刘新刚  董丰收  郑永权 《农药学学报》2019,21(1):97-104

建立了气相色谱-三重四极杆串联质谱 (GC-MS/MS)检测留兰香、桂皮、薄荷和月桂叶中乙氧氟草醚、唑草酮、乙螨唑残留的分析方法。4种香辛料用超纯水饱和，乙腈提取，无水硫酸镁及氯化钠盐析，氨基/石墨化碳黑 (NH₂-Carb) 固相萃取柱净化，多反应监测模式，气相色谱-串联质谱测定。结果表明:乙氧氟草醚在0.002 5~2 mg/L范围内，唑草酮和乙螨唑在0.01~2 mg/L范围内，3种农药的进样质量浓度与对应的峰面积间呈良好的线性关系，r > 0.99；乙氧氟草醚在0.025、0.5和2 mg/kg 3个添加水平下，在4种香辛料中的平均回收率在86%~112%之间，相对标准偏差 (RSD)在2.4%~9.6%之间；唑草酮在0.2、0.5和2 mg/kg 3个添加水平下的平均回收率在87%~114%之间，RSD在2.4%~11%之间；乙螨唑在0.5、2和5 mg/kg 3个添加水平下的平均回收率在86%~116%之间，RSD在3.2%~11%之间。乙氧氟草醚、唑草酮和乙螨唑在4种香辛料中的定量限 (LOQ) 分别为0.025、0.2和0.5 mg/kg。  相似文献   

Does interspecific competition change the barley's response and recovery from heat wave?     

Jrat&#x; altauskait&#x;  Austra Dik&#x;aityt&#x;  Diana Mi&#x;kelyt&#x;  Giedr&#x; Kacien&#x;  Gintar&#x; Sujetovien&#x;  Irena Janu&#x;kaitien&#x;  Sandra Sakalauskien&#x;  Jurga Miliauskien&#x;  Romualdas Juknys 《Journal of Agronomy and Crop Science》2019,205(4):401-413

Different species have different sensitivity to heat waves; therefore, interspecific competition may affect the crop response to heat waves. We investigated the effects of heat waves on spring barley (Hordeum vulgare L.) grown with and without wild mustard (Sinapis arvensis L.) as well as the recovery of barleys from stress. The plants were exposed to a 7‐day 35/28ºC (day/night) heat wave at ambient CO₂ (400 μmol/mol) and elevated CO₂ (800 μmol/mol). All seedlings were rehydrated and returned to control conditions (21/14ºC, CO₂ 400 μmol/mol) after the cease of heat wave and grown for a 7‐day period of recovery. Heat wave had more pronounced negative effect on the barley's aboveground biomass under competition with mustard, whereas the response of root biomass was not influenced by the presence of weeds. The heat wave induced reductions in barley's photosynthetic rate, stomatal conductance and water use efficiency under interspecific competition were higher compared to monocultured conditions. Interspecific competition impaired and delayed the recovery of barley's biomass production and leaf gas exchange parameters after heat wave. Elevated CO₂ slightly mitigated negative heat wave impact on the growth and leaf gas exchange parameters but had no effect during the recovery period.  相似文献   

油气管道全生命周期完整性管理体系的构建     

陈朋超  冯文兴  燕冰川 《油气储运》2020,(1):40-47

为了加强油气管道风险防控,将完整性管理理念引入中国管道行业。引进、消化、吸收国外油气管道完整性管理的先进方法,结合中国油气管道实际情况进行再创新:制定了覆盖管道建设、运行、废弃处置全生命周期的“564”完整性管理工作流程,建立了包含管道完整性管理、科技研发、技术服务、推广应用的全链条组织架构,形成了完备的完整性管理数据、标准、技术及人才保障体系。油气管道全生命周期完整性管理提升了管道本质安全,取得了明显成效,探索实践中形成的模式、标准规范不仅确保了油气管道安全平稳运行,也为行业发展提供了参考范例。  相似文献   

海洋石油多相流立管严重段塞流控制方法     

程兵  李彦辉  李清平  陈绍凯 《油气储运》2013,(12):1285-1288

基于对国外严重段塞流控制方法的调研，评述了国内采用的3种严重段塞控制方法：GLCC小型分离器法、自动节流法及气举法。将GLCC与原段塞流捕集器结合使用，解决了QK17—2油田的段塞问题，节省了大量空间和资金；在文昌油田成功安装了一套在线监测和自动节流系统，使生产更为稳定，产量更高；在中海油联合开发的西非某深水油田，设计安装了气举环空和注气系统，用于段塞控制和增产油气。这些实际工程经验可为油气田严重段塞流控制方案的设计提供参考。（表1，图4，参6）  相似文献   

智慧管网建设进展及存在问题     

黄  聂中文  黄晶  于永志  王永吉  单超  冯骋  孔芋丁 《油气储运》2020,(1):16-24

随着中国油气管道骨干管网初具规模,运维体系日趋完善以及大数据、人工智能、物联网技术的应用,智慧管网的建设成为可能。以中国石油天然气集团有限公司智慧管网的建设为例,基于智慧管网现有设计方案,梳理了现阶段智慧管网在科技、信息、物联网方面各个系统的建设进展,介绍了中俄东线和中缅油气管道试点工程的最新成果,提出了智慧管网建设仍需解决的问题。通过明确智慧管网建设的原则及目标,实践探索出一条智慧管网建设的有效途径,最终实现“数据全面统一、感知交互可视、系统融合互连、供应精准匹配、运行智能高效、预测预警可控”的管道智能化运行目标。  相似文献