介电谱技术检测乙醇汽油中乙醇含量

根据乙醇汽油中乙醇含量不同时介电特性也不同的特点,提出一种快速测定乙醇汽油中乙醇含量的介电谱新方法。对配制的22个样品的介电谱进行了分析,对预测乙醇含量的不同数学模型做了比较。结果表明,用偏最小二乘法建立模型能实现对22个样品的准确预测,绝大多数结果能够满足国家标准方法对误差的要求,说明介电谱技术可以应用于现场快速检测乙醇汽油中的乙醇含量。     

Smith-chart diagnostics for multi-GHz time-domain-reflectometry dielectric spectroscopy

A time-domain-reflectometry Smith-chart display is demonstrated to be a valuable diagnostic tool in a variety of situations in time-domain-reflectometry dielectric spectroscopy. A relative reflection coefficient is formed by dividing the Laplace transform of the reflected sample transient by the Laplace transform of the empty-sensor transient and displaying in the complex plane, with the approximate sensor admittance read from susceptance and conductance circles. The Smith chart provides, as a diagnostic tool, an initial estimate of the dielectric behavior in the multi-GHz range and a means of identifying artifacts in acquisition and Laplace transform, in a way which does not require multiple steps of calibration and is only one step removed from the direct transient. Results are presented for a simple 3.5-mm flat sensor immersed in various liquid media, showing variations in the Smith chart for typical variations in sample permittivity, loss, and conductivity. Results are matched to vector network analyzer (VNA) measurement over an identical frequency range, as well as to finite-element field simulation. Results are also presented for a 3.5-mm sensor with various terminating pin lengths, typically employed at low frequencies and low permittivity media to increase sensor capacitance. For an unshielded pin, the Smith chart detects reflections from sample boundaries and measures the effectiveness of shielding used to eliminate these reflections. For a shielded pin, it characterizes the effect of pin length on the susceptance variation and the onset of pin resonance at high frequencies and high-permittivity values. The effect of artifacts appearing in the Smith chart on the actual calibration is shown by tracking them through the calibration process to the final result. Results are also presented for a 9-mm flat termination used for concrete hydration monitoring, showing effects of transmission-line discontinuities within a terminating plug and the onset of waveguide-like modes in a surrounding shield, with results compared to VNA measurement.     

溶栓胶囊红外光谱法的鉴别研究

本文采用红外光谱法及二阶导数谱对不同批次的溶栓胶囊(Plasmin capsules)进行无损快速鉴别研究。实验研究表明,不同批次的溶栓胶囊其蛋白(酶)的成分都和原料有不同程度差别,并且加入的辅料的量也有较明显的不同。辅料的添加量直接影响溶栓胶囊的生物活性。最后对各个批次的溶栓胶囊做重复性实验,发现红外谱图有一定的波动,说明药品的均匀性较差。     

Crystallization of poly(l-lactid acid) monitored by dielectric relaxation spectroscopy and atomic force microscopy

An investigation was carried out on the crystallization process of poly(l ‐lactid acid) by dielectric relaxation spectroscopy and atomic force microscopy. Experimental results were generated by dielectric relaxation spectroscopy over a wide range of frequency and temperature in both the wholly amorphous state and during crystallization. The variation of the average relaxation time was studied during crystallization at 80 °C and the temperature dependence of this relaxation time for wholly amorphous and crystallized samples was analysed. This behaviour was modelled by Havriliak‐Negami and Vogel‐Fulcher equations. The sensitivity of the segmental dynamics to the degree of crystallinity was analysed, taking into account the relaxing segments and the thickness of the amorphous layer between lamellae. The morphologies obtained during crystallization processes at 80, 130 and 150 °C were monitored by atomic force microscopy at both the lamellar level and by analysing the multilayered superstructures formed. Hedrites, intermediate structures between single lamellar crystals and mature spherulites, were found to appear at the highest temperatures, whereas no evidence of hedrites was found at 80 °C, the spherulites seemed to be constructed from a framework of individual dominant lamellae that splay apart and branch. Complementary to the atomic force microscopy study, the evolution of the obtained morphologies was also followed by optical microscopy. Supporting evidence about the thermal behaviour of the polymers was obtained with differential scanning calorimetry.     

岗梅与毛冬青的二维红外相关光谱鉴别研究

采用红外光谱法(FTIR)并结合二维相关光谱(Two-dimensionalInfrared CorrelationSpectrocopy)分析技术,对岗梅与毛冬青进行无损快速鉴别研究。岗梅与毛冬青皆为冬青属植物,其外形极其相似,加工成饮片后更易混淆,因此通过红外光谱对其进行无损快速鉴别研究。两种药材在一维谱上几乎没有显著差别,因此需要借助二阶导数谱和二维红外光谱对其进行进一步的研究。结果表明:通过岗梅与毛冬青的红外光谱并结合二维相关谱完全可以将其区别开来。该方法快速、准确,对中药的鉴别提供一种新的方法和手段。     

Quality and anti-adulteration control of vegetable oils through microwave dielectric spectroscopy

Quality control of vegetable oils is becoming more stringent, and strict laws are being enforced, especially for avoiding adulteration. The public bodies that are responsible for the prevention of the adulteration of foodstuffs necessitate methods of analysis that could facilitate large-scale in situ controls. Similarly, oil producers constantly strive to speed up internal quality control. As a direct consequence, there is an increasing demand for innovative methods of analysis that could guarantee real-time in situ monitoring and provide adequate accuracy. On such bases, the present work addresses the possibility of monitoring qualitative characteristics of vegetable oils through microwave dielectric spectroscopy. To this purpose, the Cole–Cole dielectric parameters of different vegetable oils are evaluated through an innovative automatable procedure that suitably combines traditional TDR measurements, SOL calibration, frequency domain processing, TL modelling and, finally, a minimization routine. The proposed procedure is carried out first on different “pure” oils and, secondly, on some oil mixtures. The obtained results confirm that different dielectric characteristics are associated with different oils, thus confirming the considerable potential of dielectric spectroscopy for quality and anti-adulteration control purposes, especially in view of practical applications.     

宽频介电谱仪故障排除2例

简单介绍宽频介电谱仪的工作原理,详细讨论使用之中出现的各种故障及消除故障的方法与措施。     

气相色谱法测定煤制低碳烯烃水中的含氧化合物

采用气相色谱建立了煤制烯烃水中18种含氧化合物的测定方法。通过实验优化色谱分离条件,确立了外标定量的分析方法,考察了方法的精密度和准确度,并对煤制烯烃的水样进行了测定。结果表明,煤制烯烃水中所含的18种含氧化合物的标准曲线均呈现良好的线性关系,相关系数均大于0.99。煤制烯烃水样中的加标回收率在90.5～110.7%之间,方法的准确性可以满足实际分析的需要。实际煤制烯烃水样的分析结果表明,其水相产物中含氧化合物的总质量分数为0.55～20.77%;其中甲醇和丙酮的含量相对较高,甲醇含量越高,煤制烯烃反应中甲醇的转化率就越低,其他含氧化合物种类和含量越多,煤制烯烃过程有较多副反应发生。该方法简单、快速,对煤制烯烃水相产物中含氧化合物的定量分析具有重要意义。     

红外光谱法与党参及其伪品夜关门的分析与鉴定

采用红外光谱三级鉴定法分析鉴别党参及其伪品夜关门。伪品夜关门一维红外光谱图和二阶导数谱分别与草酸钙标准谱图相比较,都验证该药材中含有一定量草酸钙。此外,谱图还验证党参及其伪品夜关门都在不同程度上含有糖苷类化合物和有机酯类化合物,而不同的是党参所含芳香类化合物高于夜关门。该方法不仅可以快速有效地鉴别党参及其伪品夜关门,还提供两者的有机酯类化合物以及芳香类和糖苷类化合物具有很大差别的一些有用的结构信息。因此,运用红外光谱法可以快速有效地分析和鉴定党参及其伪品夜关门。