PTV-LV-GC/MS/MS as screening and complementary method to HRMS for the monitoring of dioxin levels in food and feed

Recent developments in trapping efficiency inside ion trap mass spectrometer permitted to lower instrument detection limit (IDL). An IDL of 200 fg μl⁻¹ injected with a signal-to-noise ratio of 5:1 for tetrachlorodibenzo-p-dioxin (TCDD) was obtained by gas chromatography coupled to a quadrupole ion storage mass spectrometer in tandem mode (GC/MS/MS). Coupling large volume programmable temperature vaporizer (PTV-LV) injection to GC/MS/MS provides an alternative and complementary method to classical splitless-GC injection connected to high-resolution mass spectrometry (splitless-GC/HRMS) method for dioxin monitoring in food and feed.

An injection volume of 10 μl was found to be the best compromise between the sensitivity requirements and the robustness required for a high throughput method. PTV-LV-GC/MS/MS and Splitless-GC/HRMS were compared by performing analysis on five different matrices such as beef fat, yolk eggs, milk powder, animal feed and serum samples covering a concentration range of two orders of magnitude (i.e. 0.2–25 ng WHO-TEQ kg⁻¹). An analysis of variance (ANOVA) was carried out. Fisher tests pointed out that the method effect for all the 2,3,7,8 congeners was not significant, indicating that the null hypothesis (H₀: μ₁=μ₂=…=μ_n) was not rejected. Moreover, the interaction effects between methods and matrices were not significant for most of the 2,3,7,8 congeners. However, three congeners (2,3,7,8-TCDF; 1,2,3,4,7,8-HxCDD and 1,2,3,4,6,7,8-HpCDD) were characterized by P-values lower than the significance level (=0.05). In toxic equivalence (TEQ), the study showed that no significant bias was observed between the two methods. Consequently, PTV-LV-GC/MS/MS is an attractive technique and can be used as a cost effective complementary method to HRMS for dioxin levels monitoring in food and feed.     

基于现场可编程门阵列单探测器复合轴控制技术

为了解决空间激光通信系统中单探测器复合轴结构的粗精解耦难题,通过分析二维关联控制矩阵,得出粗精跟踪解耦的必要条件,提出了一种单探测器复合轴结构的工作方式.在跟踪过程中,相机直接配合子轴执行器完成精跟踪工作,而主轴的跟踪信息由子轴的角度偏转器来提供,同时所有的图像处理算法、位置检测算法、以及粗精伺服控制算法都在现场可编程门阵列中实现,完成了系统的轻小型化设计.实验搭建了测试系统,并对现场可编程门阵列硬件和系统跟踪性能进行测试,结果表明单探测器复合控制系统可以实现跟踪准确度优于3μrad,为工程化奠定了良好的基础.     

合肥光源逐圈束流位置监测系统中的定时系统

 定时系统是合肥光源逐圈束流位置监测和相空间测量系统中的重要组成部分,其主要目的是为数据采集卡提供与环内电子束团同步的时钟信号。该系统包含高速ECL时钟成形、分频电路、程控延时电路、控制模块等部分。可实现延时范围0～220ns,最小延时步距0.5ns,调整精度0.1ns,时钟抖动小于200ps。系统控制软件基于客户/服务器结构,操作灵活、方便。     

基于CPLD工作模式可调的线阵CCD驱动电路设计

针对传统驱动电路一旦做出修改,则需对硬件或程序进行改变的缺点,以型号为TCD1707D的线阵CCD为例,介绍了一种工作模式可调的驱动方法.该方法是利用复杂可编程逻辑器件和控制外端结合,通过分别设置内外触发来实现的.在外触发模式下,利用外触发脉冲,可由用户控制CCD的曝光和信号输出时间;内触发时,可以调节CCD的积分时间和驱动频率.为提高信号输出质量,针对EMC问题给出了线阵CCD的外围驱动电路.实验结果表明,该方法调试方便、电路结构简单、集成度较高、输出信号可靠稳定、受干扰小,可配合多种用户需要,对高速精确测量及线阵推扫模式具有一定参考价值.     

HLT500高低温试验箱PLC控制系统

介绍了以PLC(可编程控制器)为核心的高低温试验箱电控系统,着重介绍了可编程逻辑控制器PLC的选择和可编程控制器的程序编译。     

NorTRACK product tracking system—development and implementation

This paper presents the experience gained by developers and users with implementation and operation of NorTRACK^TM, a real-time computerized product tracking system. A Programmable Logic Controller (PLC) collects and transfers data in real time to NorTRACK’s Oracle^TM database on a Windows NT^TM server network. After extensive development and Beta testing at MDS Nordion’s Canadian Irradiation Centre in Montreal, Canada, NorTRACK was installed in January 1997 with a new irradiation facility in Ethicon Endo-Surgery Inc.’s Albuquerque plant in the United States. NorTRACK communicates with the irradiator control and safety system, the plant's central manufacturing database, an innovative pallet staging and tote loading robot, and an automated dosimetry reading system. This integrated system allows the sterilization facility to monitor the irradiator operation and the flow of many products, through varied processing modes, continuously and reliably. As a result of operating with NorTRACK, both MDS Nordion’s CIC facility and the Endo-Surgery manufacturing site, are beginning to realize unique benefits in their respective operations. MDS Nordion is also initiating several future product enhancements and additional productivity modules. This paper describes the NorTRACK system, the various stages of the development project and Beta tests, and the experience of the users to date in their operations.     

基于FPGA的脉冲电源及其控制系统设计

针对等离子体特定领域的应用需求,研制了一种基于上位机监控且具有手动/自动控制功能的脉冲电源。详细介绍了脉冲电源主电路、检测电路、驱动电路、数字脉宽调制（DPWM）产生模块以及脉冲变压器的设计方法。该电源采用现场可编程门阵列（FPGA）作为主控芯片,产生DPWM信号及继电器控制信号,经驱动电路放大后驱动逆变全桥及继电器。设计了过温和短路保护电路,通过DS18B20温度传感器和QBC10PS5霍尔电流传感器对电源模块的工作温度和电流进行实时采样。实际应用测试表明,该电源满足设计指标要求。     

并行多处理机系统中的光纤互连网络的设计与实现

在并行多处理机系统中应用光纤互连网络完成处理单元之间的数据交换,可以极大地提高系统中数据通信的速率、带宽、抗干扰性和准确可靠性.本文详细阐述了并行多处理机系统的体系结构、实现方法、性能分析和实验结果.     

Analysis of whole congener mixtures of polybromodiphenyl ethers by gas chromatography–mass spectrometry in both environmental and biological samples at femtogram levels

A sensitive and selective method for the determination of the whole congener distribution of polybromodiphenyl ethers in environmental and biological samples in one single instrumental run is described. The method is based on gas chromatography coupled to low-resolution mass spectrometry in negative ion chemical ionization mode. It allows determination of these compounds at concentration levels lower than 10⁻¹⁴ g. A programmed temperature vaporization injector has been used to ensure maximum compound transfer to the chromatographic column while maintaining low thermal degradation levels of the more brominated congeners. Selectivity was increased by modification of the MS source parameters for optimization of the abundance of the high mass fragment ions. Under optimized condition, good repeatability (1.7–9.1%) and reproducibility (4.1–20%), and low detection limits, ranging between 1.5 and 15 pg ml⁻¹, were obtained. These features afforded reliable quantification of these compounds in snow and human samples at the concentrations in which these compounds are found.