Organic-resistant screen-printed graphitic electrodes: Application to on-site monitoring of liquid fuels

This work presents the potential application of organic-resistant screen-printed graphitic electrodes (SPGEs) for fuel analysis. The required analysis of the antioxidant 2,6-di-tert-butylphenol (2,6-DTBP) in biodiesel and jet fuel is demonstrated as a proof-of-concept. The screen-printing of graphite, Ag/AgCl and insulator inks on a polyester substrate (250 μm thickness) resulted in SPGEs highly compatible with liquid fuels. SPGEs were placed on a batch-injection analysis (BIA) cell, which was filled with a hydroethanolic solution containing 99% v/v ethanol and 0.1 mol L⁻¹ HClO₄ (electrolyte). An electronic micropipette was connected to the cell to perform injections (100 μL) of sample or standard solutions. Over 200 injections can be injected continuously without replacing electrolyte and SPGE strip. Amperometric detection (+1.1 V vs. Ag/AgCl) of 2,6-DTBP provided fast (around 8 s) and precise (RSD = 0.7%, n = 12) determinations using an external calibration curve. The method was applied for the analysis of biodiesel and aviation jet fuel samples and comparable results with liquid and gas chromatographic analyses, typically required for biodiesel and jet fuel samples, were obtained. Hence, these SPGE strips are completely compatible with organic samples and their combination with the BIA cell shows great promise for routine and portable analysis of fuels and other organic liquid samples without requiring sophisticated sample treatments.     

钒钛磁铁矿样品主、次元素的快速分析方法研究

采用SI-PIN半导体探测器、241Am激发源和2048通道分析器及自行研制的SI-PIN 2000便携式X荧光分析仪,对钒钛磁铁矿直接粉末样品中Ti,V,Cr,Mn,Fe,Co,Ni,Cu等8个主、次元素进行了分析应用研究。文章叙述了所采用的直接粉末样品法的样品盒结构、基体校正的α系数计算方法、重叠干扰校正原则和漂移校正的方法,并且给出了所选择的分析条件和样品制备方法,分析过程简单、结果准确、分析速度快,特别适应矿山、冶金的生产原料分析需要,有良好的应用前景, 与封闭正比计数器X射线荧光分析仪相比,检出限降低了1个数量级。     

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.     

便携式短波近红外光谱仪器检测土壤总氮含量研究

基于便携式短波近红外光谱技术检测了土壤总氮含量。采集浙江省文城地区农田土壤样本243个,将土壤样本分为三组,一组未经过粉碎、过筛等处理,一组做过2 mm筛处理,一组过0.5 mm筛过处理,采用usb4000便携式光谱获取土壤光谱数据,结合(savitzky-golay, SG)平滑算法,波长压缩算法和小波变换对原始数据进行预处理,然后采用竞争性自适应重加权、随机青蛙和连续投影算法进行特征波长选择。基于全光谱建立了偏最小二乘回归和基于特征波长建立了极限学习机和LS-SVM模型。结果表明过筛处理后的样本模型结果优于未过筛的样本模型结果,过0.5 mm筛处理的土壤样本模型预测结果略优于过2 mm筛处理的土壤样本模型预测结果,最优预测集的决定系数为0.63,预测均方根误差为0.007 9,剩余预测偏差为1.58。表明便携式仪器检测土壤总氮含量,经过过筛处理的土壤样品检测结果优于未过筛土壤样品检测结果,建议土壤样品检测总氮含量时需经过过筛处理,这样得到的结果较为理想,在此基础上采用性能较好的光谱仪器采集数据,以减小原始光谱噪声。     

Triple-channel portable capillary electrophoresis instrument with individual background electrolytes for the concurrent separations of anionic and cationic species

The portable capillary electrophoresis instrument is automated and features three independent channels with different background electrolytes to allow the concurrent optimized determination of three different categories of charged analytes. The fluidic system is based on a miniature manifold which is based on mechanically milled channels for injection of samples and buffers. The planar manifold pattern was designed to minimize the number of electronic valves required for each channel. The system utilizes pneumatic pressurization to transport solutions at the grounded as well as the high voltage side of the separation capillaries. The instrument has a compact design, with all components arranged in a briefcase with dimensions of 45 (w) × 35 (d) × 15 cm (h) and a weight of about 15 kg. It can operate continuously for 8 h in the battery-powered mode if only one electrophoresis channel is in use, or for about 2.5 h in the case of simultaneous employment of all three channels. The different operations, i.e. capillary flushing, rinsing of the interfaces at both capillary ends, sample injection and electrophoretic separation, are activated automatically with a control program featuring a graphical user interface. For demonstration, the system was employed successfully for the concurrent separation of different inorganic cations and anions, organic preservatives, additives and artificial sweeteners in various beverage and food matrices.     

便携式拉曼光谱仪用于合成大麻素类物质快速定性分析探究

我国于2021年7月将合成大麻素类物质整类列入管制,在一线查缉现场对疑似合成大麻素样品进行快速定性分析是办案民警的迫切需求。研究系统考察了拉曼光谱对合成大麻素的整体区分能力,比较了四款手持式拉曼光谱仪分析实际缴获样品时的结果差异,探讨了制约拉曼光谱在一线查缉现场广泛应用的原因。ProTT-EZRaman-A7便携式拉曼光谱仪的整体性能介于台式拉曼和手持式拉曼之间,选用该仪器采集了90种合成大麻素对照品的拉曼光谱,并利用兼容性强的KnowItAll软件建立了90种合成大麻素通用拉曼光谱库。分析90种合成大麻素的拉曼光谱,结果表明,当不存在荧光干扰时,拉曼光谱可以区分所有合成大麻素物质,但对部分结构相差一个甲基、卤素原子等的结构类似物区分度欠佳。不同款拉曼光谱仪的性能差异大,为考察其原因,本研究选用了四款手持式拉曼光谱仪分别对120份实际缴获合成大麻素样品进行了测定,随后使用KnowItAll软件并选用包含90种合成大麻素的通用拉曼光谱库对每张光谱图进行谱库检索。四款手持式拉曼光谱仪的正确匹配率分别为71.7%, 68.3%, 46.7%和24.2%。抗荧光干扰能力和分辨率的不同是造成不同...     

近红外光谱和模式识别的菊花品种无损鉴别

菊花为菊科植物菊的头状花序,滁菊、贡菊、杭菊和亳菊是常见的几类药用品种菊花.不同品种菊花在外观上具有极大的相似性,非专业人员仅凭肉眼难以对其进行准确鉴别分析.常规仪器分析法检测成本较高,分析时间较长,且需要对样品进行破坏性处理,影响了产品的二次销售.近红外光谱技术作为近年来快速发展起来的一种绿色、简单、快速的新型检测技...     

A switchable-oxidative cellulose filter paper bearing immobilized Mn(III)-salen complex for alcohol oxidation

Surface modifications of polysaccharide filter papers can alter their catalytic properties significantly. In particular, polysaccharides have gained increasing interest in the development of heterogeneous catalysts. This wok introduces a new approach to the heterogeneous/ sustainable catalytic system preparation based on a catalytic filter paper modified by silylation followed by immobilization of a Mn(III)-salen complex as a novel “catalytic filtration” or “portable catalysis”. Oxidation of alcohols as well as direct conversion of alcohols to Schiff bases and oximes were performed by filtration and passing the reactants through the modified filter paper. Oxidation of benzyl alcohol in the presence of molecular oxygen and NaOCl, selectively leads to aldehydes and carboxylic acids, respectively. The direct conversion of alcohols to Schiff bases and oximes resulted in the formation of insoluble products on the filter paper. Another advantage of the modified filter paper was its stability and reusability for several times with preservation of the catalytic activity and swellability, which no shrinkage during consecutive wetting–drying cycles was observed. Also, a deep study was conducted over mechanism, reusability/stability, and control experiments of the alcohol oxidation. This study gave new insights into the catalytic propensities of a cellulose filter paper via filtration of reactants.     

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.