Optimization of a glancing angle for simultaneous trace elemental analysis by using a portable total reflection X-ray fluorescence spectrometer

By using a portable total reflection X-ray fluorescence spectrometer with a 1 W X-ray tube, a specimen containing nanograms of Ca, Sc, Ti, V, Cr, Mn, Fe, and Ni is measured at several glancing angles of incident X-rays. Continuum X-rays are used as the excitation source. The intensities of the spectral background which degrades sensitivity to trace elements are decreased with a decrease of the glancing angle, and all these elements are detected at the glancing angle of 0.13° smaller than the critical angle for total reflection of the incident X-rays (0.20°). An optimum glancing angle for simultaneously detecting these trace elements is around 0.13°, and detection limits at 0.13° are sub-nanograms to ten nanograms.     

Portable,lightweight, low power,ion chromatographic system with open tubular capillary columns

Basic operation principles of a lightweight, low power, low cost, portable ion chromatograph utilizing open tubular ion chromatography in capillary columns coated with multi-layer polymeric stationary phases are demonstrated. A minimalistic configuration of a portable IC instrument was developed that does not require any chromatographic eluent delivery system, nor sample injection device as it uses gravity-based eluent flow and hydrodynamic sample injection adopted from capillary electrophoresis. As a detection device, an inexpensive commercially available capacitance sensor is used that has been shown to be a suitable substitute for contactless conductivity detection in capillary separation systems. The built-in temperature sensor allows for baseline drift correction typically encountered in conductivity/capacitance measurements without thermostating device. The whole instrument does not require any power supply for its operation, except the detection and data acquisition part that is provided by a USB port of a Netbook computer. It is extremely lightweight, its total weight including the Netbook computer is less than 2.5 kg and it can be continuously operated for more than 8 h. Several parameters of the instrument, such as detection cell design, eluent delivery systems and data treatment were optimized as well as the composition of eluent for non-suppressed ion chromatographic analysis of common inorganic cations (Na⁺, NH₄⁺, K⁺, Cs⁺, Ca²⁺, Mg²⁺, transition metals). Low conductivity eluents based on weakly complexing organic acids such as tartaric, oxalic or pyridine-2,6-dicarboxylic acids were used with contactless capacitance detection for simultaneous separation of mono- and divalent cations. Separation of Na⁺ and NH₄⁺ cations was optimized by addition of 18-crown-6 to the eluent. The best separation of 6 metal cations commonly present in various environmental samples was accomplished in less than 30 min using a 1.75 mM pyridine-2,6-dicarboxylic acid and 3 mM 18-crown-6 eluent with excellent repeatability (below 2%) and detection limits in the low micromolar range. The analysis of field samples is demonstrated; the concentrations of common inorganic cations in river water, mineral water and snow samples were determined.     

A portable lab‐on‐a‐chip instrument based on MCE with dual top–bottom capacitive coupled contactless conductivity detector in replaceable cell cartridge

A new design for a compact portable lab‐on‐a‐chip instrument based on MCE and dual capacitively coupled contactless conductivity detection (dC⁴D) is described. The instrument is battery powered with total dimension of 14 × 25 × 8 cm³ (w × l × h), and weighs 1.2 kg. The device consists of a front electrophoresis compartment which has the chip holder and the chip, the associated high‐voltage electrodes for electrophoresis injection and separation and the detector. The detection cell is integrated into the device housing with an exchangeable plug‐and‐play cartridge format. The design of the dC⁴D cell has been optimized for maximum performance. The cartridge includes the top–bottom excitation and pick up electrodes incorporated into the cell and connected to push‐pull self‐latching pins that are insulated with plastic. The metal frame of the cartridge is grounded completely to eliminate electronic interferences. The cartridge is designed to clamp a thin fluidic chip at the detection point. The cartridges are replaceable whereby different cartridges have different detection electrode configurations to employ according to the sensitivity or resolution needed in the specific analytical application. The second compartment consists of all the electronics, data acquisition card, high‐voltage modules of up to ±5 kV both polarity, and batteries for 10 h of operation. The improved detector performance is illustrated by the electrophoresis analysis of six cations (NH₄⁺, K⁺, Ca²⁺, Na⁺, Mg²⁺, Li⁺) with a detection limit of approximately 5 μM and the analysis of the anions (Br^?, Cl^?, NO₂^?, NO₃^?, SO₄^2?, F^?) with a detection limit of about 3 μM. Analytical capabilities of the instrument for food and medical applications were evaluated by simultaneous detection of organic and inorganic acids in fruit juice and inorganic cations and anions in rabbit blood samples and human urine samples are also demonstrated.     

Development of Miniaturized Electrochemiluminescence Instrument using Multi‐pixel Photon Counter as the Optical Detector

We developed a miniaturized electrochemiluminescence (ECL) instrument coupled with a light‐emitting diode‐based bipolar electrochemical sensor (LED‐BPES). This instrument composes of a microcontroller circuit, a power supply circuit, a potentiostat, an optical detecting circuit, and a communication circuit. The multi‐pixel photon counter (MPPC), which is low‐cost, small‐size, and wide‐range in optical measurements, is chosen as the optical detector. The LED‐BPES composes of a disposable screen‐printed carbon electrode (SPCE) and a surface‐mount red LED. Depended on the closed bipolar electrode (C‐BPE) structure, the LED‐BPES not only avoids the employment of unstable and complex ECL reactions but also offers a cost‐effective alternative for the over‐priced ECL reagents by using a mini‐size commercial LED as the luminescent producer. The combination of MPPC and LED‐BPES helps to set up the simplified and downsized instrument system with low price and high efficiency. The presented instrument coupled with LED‐BPES works excellent in electroactive molecules detection and has great potential in the application of heavy metal ions detection.     

翡翠成分、结构和矿物组成的无损分析

利用便携式能量色散型X射线荧光(portable energy-dispersive X-ray fluorescence,PXRF)、外束质子激发X射线(external beam proton induced X-ray emission,PIXE)、X射线衍射(X-ray diffraction,XRD)和激光拉...     

R-3000便携式拉曼光谱仪在翡翠鉴定中的应用

使用R-3000便携式拉曼光谱仪,对缅甸原料、腾冲工艺的3个翡翠饰件和一个昆明古玩城所购翡翠挂件进行了无损鉴定。通过对检测样品拉曼光谱的比较研究,得出了有2个样品是由天然翡翠原料所制成;有一个样品含石蜡填充物;而有一个样品与天然翡翠无关,而是由石英岩（SiO2）为主要材料制成的,是假翡翠的结论。说明了R-3000便携式拉曼光谱仪,在玉石翡翠检测鉴定中是十分方便、快捷、准确的。     

基于便携式拉曼高光谱成像技术的散装奶粉中硫脲可视化现场快速检测方法研究

硫脲是一种含氮量高、毒性较大的潜在蛋白掺假化合物,常规的实验室检测方法过程复杂、效率低,无法满足口岸对大批次散装奶粉样本质量快速筛查的需求。为解决口岸抽样监管缺乏快速实时评价方法的难题,利用自主搭建的便携式点扫描拉曼高光谱成像系统,开发了一种简单高效的奶粉中硫脲现场可视化快速检测方法,确保散装奶粉在进出口环节的精准监管。研究以不同添加浓度（0.005%~2.000%）的硫脲奶粉混合物为样本,分别用Whittaker平滑方法和自适应迭代重加权惩罚最小二乘算法（airPLS）消除光谱数据的背景随机噪音信号和荧光背景干扰,峰值识别后对硫脲特征位移处的单波段数据进行二值化处理,得到混合样本感兴趣区域的二值热图,通过二值图中硫脲像素点的有无和坐标,对奶粉中的硫脲进行定性判别和定位分析。进一步分析得感兴趣区域内硫脲像素点数目与添加浓度的关系,结果表明随着添加浓度的增加,硫脲像素点数目呈线性增长趋势,其中线性拟合的决定系数(R2)为0.991 3,硫脲的最低检出浓度为0.05%。在0.25%,0.60%,1.20%和1.50%的添加水平下,利用像素点数目和线性拟合关系预测奶粉中硫脲的浓度,结果显示预测浓度的相对误差范围为-9.41%~4.01%,相对标准偏差小于7%。该点扫描拉曼高光谱成像系统能在10 min内完成单个样本的检测,结合软件控制系统,实时对奶粉中的硫脲颗粒进行定性、定量和污染分布分析,方法简单高效、准确性好、灵敏度高、稳定性强,为口岸现场对散装奶粉中硫脲掺假物的实时快速检测提供了技术监管手段,能显著提升口岸现场散装样本的监管环节质量评价的精准性,为进口奶粉快速通关提供技术保障。     

基于温度修正模型的柴油凝点快速检测方法

便携式近红外光谱仪现场快速检测是近红外光谱分析领域的一个重要的发展趋势。为了实现快速检测,便携式近红外光谱仪一般不配备温控装置,因此环境温度的变化会带来较大的测量误差。如何降低环境温度对检测结果带来的误差,是便携式近红外光谱仪在现场快速检测领域大规模推广所需要解决的一个重要问题。柴油的凝点值是评价柴油品质和适用范围的一个重要指标,对柴油凝点进行快速检测有重要的经济意义。通过便携式光谱仪采集了50种具有不同凝点的柴油样品在近红外波段（950～1 650 nm）的吸收光谱,研究了环境温度变化下的基于近红外光谱分析的柴油凝点快速检测方法。此光谱仪为基于数字微镜设计的便携式光谱仪,针对现场快检而研发,未配备温控样品池。在环境温度T₀=25 ℃时基于偏最小二乘法建立了柴油凝点的预测模型,并分别将不同环境温度（T_E=-10,0,10,20,30,40和50 ℃）条件下测量的近红外光谱带入上述凝点预测模型,分析预测偏差随环境温度相对参考值变化(T_E-T₀)的依赖关系。通过一次函数对预测误差随环境温度的变化关系进行拟合,发现凝点预测偏差的平均值随环境温度的变化关系为Δｃ＝-0.019 8(T_E-T₀)。将环境温度的修正因子带入25 ℃条件下预测模型,建立了针对环境温度变化的温度修正模型。在温度修正以后,10 ℃条件下预测凝点的均方根误差由原来的14.6降为8.8,相关系数由原来的0.4提升为0.7。研究表明,本温度修正模型可以有效降低环境温度对预测结果带来的误差。基于此温度修正模型,可以显著降低近红外光谱分析建模过程的工作量,在某一特定温度条件下建立预测模型后将此温度修正项带入模型即可用于在其他环境温度条件下进行柴油凝点值的预测,而不需要在其他多个温度条件下分别建立预测模型,可显著提高建模效率和便携式近红外光谱快速检测的温度适应性。     

Detection of fuel-oxidizer explosives utilizing portable capillary electrophoresis with wipe-based sampling

Portable analytical instrumentation that can provide an alarm indication for the presence of explosives and related components is critical for the identification of explosives-based hazards and threats. Many explosives incident reports involve an inorganic oxidizer-fuel mixture which can include pyrotechnics, fireworks, flash powders, black powders, black powder substitutes, and improvised or homemade explosives. A portable CE instrument with targeted analysis of common inorganic oxidizer ions, for example, chlorate, perchlorate, and nitrate, was used here as a rapid detection platform. Unlike frequently used gas-phase separation and detection instrumentation such as ion mobility spectrometry (IMS), an automated liquid extraction mechanism is required for CE separation using acetate paper sample collection wipes. Target inorganic oxidizers were inkjet-printed onto sample wipes to investigate instrument response relative to the collected analyte spatial distribution. Overall, analyte signal intensities increased with off-center sample deposition due to improved sample extraction from wipes and no change in response was observed for varied array distributions across wipes. The system demonstrated sub 200 ng detection limits for all target analytes, with further improvement when normalizing to an internal standard.