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161.
Fabrication of a macro segmented flow analysis (MSFA) system based on reconfiguration of the manifold by adjustment of the sample/reagent ratio, has been found to produce a sensitive method for orthophosphate analysis based on colorimetric detection at 880 nm. Optimization of sample tube length, reaction temperature and molybdate concentration in the carrier solutions has been carried out. The larger sample tube internal diameter led to the combined advantages of better sensitivities, wider working range and higher sample throughput over most existing methods. Using the optimized conditions of 50.0 cm sample tube length (1.6 mm i.d.), 37.0 °C reaction temperature and 0.0113 M molybdate concentration in the carrier solution, the calibration model for orthophosphate standard solutions was found to be linear (y = 0.04895x + 0.003561; correlation coefficient, r2=0.9970) over the working range 0.01-2.00 mg l−1 orthophosphate. The volume of the sample injected was 1.396 ml at a flow rate of 6.0 ml min−1. The sample throughput of this MSFA method was 40 samples per an hour, with a detection limit of 4.0 μg l−1, and %R.S.D.’s below 5%. The MSFA method was successfully applied to analysis of water and wastewater samples. 相似文献
162.
Yong Guo 《Tetrahedron letters》2004,45(34):6477-6480
A new charge-transfer complex, consisting of dihydroxymethyl di-(2-pyrrolyl)methane and tetracyanoquinodimethane (TCNQ), has been designed to high selectively distinguish cysteine from other amino acids in water/organic solvent mixtures through the visual color change from blue to nearly colorless. The excellent system properties make the supramolecular assembly a highly selective colorimetric probe for monitoring cysteine. 相似文献
163.
Summary A simple and specific HPLC method with coulometric detection was developed for the determination of 2′-acetyl erythromycin
and erythromycin in human plasma. Methyl tert-butyl ether was used as the extraction solvent after alkalization of plasma
samples. The plasma extracts were chromatographed on a reverse phase column using 4-component mobile phase. The manual sample
preparation procedure was modified so that it could also be applied to the robotic system (Zymate™ Laboratory Automation System). The linear range was 0.25–7.0 μg/ml. The quantitation limit for 2′-acetyl erythromycin and
erythromycin was 0.05 μg/ml. Equivalent manual and robotic sample preparation methods were used to analyze a large number
of plasma samples. 相似文献
164.
Oudhoff KA Macka M Haddad PR Schoenmakers PJ Kok WT 《Journal of chromatography. A》2005,1068(1):183-187
A capacitively coupled contactless conductivity detection (CCD) system has been applied for the detection of neutral synthetic polymers in capillary size-exclusion electrokinetic chromatography (SEEC). Polystyrene standards, that were used as a model compounds, were separated on a capillary column packed with porous 10 microm silica particles with an electrokinetically driven mobile phase, and detected by CCD and UV detection simultaneously. Mass-calibration curves for polystyrene were constructed. Satisfactory results were obtained for the linearity, the run-to-run repeatability (<0.2% for the relative retention and <4% for the peak area) and the robustness of the detector. One of the major issues in this preliminary study was to investigate the origin of the peaks observed for the polystyrene standards. The effect of the molar mass of the polystyrenes on the sensitivity was small. Therefore, the signals obtained could not be explained as the result of an increased viscosity and a decreased solution conductivity of the solute zone. An alternative hypothesis is suggested, and recommendations for further research are given. 相似文献
165.
氯氮平、去甲氯氮平及奥氮平的高效液相色谱电化学检测特性的研究 总被引:2,自引:0,他引:2
采用高效液相色谱安培电化学检测法 ,考察了氯氮平、去甲氯氮平和奥氮平在不同 pH值流动相下的色谱分离情况及其色谱峰高与检测电压的关系。结果表明 ,氯氮平、去甲氯氮平和奥氮平的保留时间均随流动相 pH值的升高而延长 ;在pH值为 4 5 6和 5 5 6的流动相中 ,均可实现基线分离。 3种化合物的色谱峰高与检测电压之间呈典型的“S”型曲线 ,pH值升高时该曲线均左移。氯氮平、去甲氯氮平和奥氮平的检测电压必须大于产生最大氧化电流的最低电压才能得到稳定的检测电流。这种典型的“S”型伏安曲线对于化合物的定量和定性检测具有重要意义。 相似文献
166.
Summary The use of non-segmented flow, post-column reaction detection is evaluated for use with miniaturized HPLC. Non-segmented open-tubular reactors with internal diameters 0.1 mm to 0.25 mm and packed-bed reactors with internal diameters of 1 mm, filled with 5 and 10 m particles are evaluated theoretically and experimentally with respect to band broadening and pressure drop characteristics. An integrated system consisting of miniaturized HPLC (1 mm i. d.) columns and compatible hardware is described. An example of the separation of catecholamines is given. 相似文献
167.
An enhanced etched electrochemical (EC) detection technique has been developed for CE in micron inner diameter capillaries. The design improvements allow for better alignment between the capillary bore and the electrode. This new method involves utilizing a carbon fiber microelectrode and etching both the carbon fiber and the detection end of a micrometer-sized inner diameter capillary to limit dead volume and analyte diffusion at the amperometric EC detector. To understand the factors affecting enhanced detector efficiency, a detailed examination of the relationship between detector design and performance has been completed by exploring the effects of varying electrode diameter, tip shape, and size, in addition to the etch length of the capillary outlet. The enhanced detection provides peak efficiencies as high as 75000 theoretical plates and estimated detection limits as low as 40 nM for dopamine. This etched detection method should further facilitate volume-limited sample analysis by CE. 相似文献
168.
The use of composite biosensors for multianalyte detection strategies is discussed. Graphite–Teflon rigid composite biosensors offer the possibility of coimmobilization of several enzymes by simple physical inclusion in the bulk of the electrode matrix with no covalent linkages. A novel trienzyme graphite–Teflon–glucose oxidase (GOD)–alcohol oxidase (AOD)–peroxidase (HRP)–ferrocene bisosensor yielded amperometric steady-state currents similar to those obtained with graphite–Teflon–GOD–HRP–ferrocene and graphite–Teflon–AOD–HRP–ferrocene electrodes for the same concentration of glucose and ethanol, respectively. The performance of the trienzyme biosensor for multianalyte detection was evaluated with the simultaneous determination of glucose and ethanol after separation by HPLC, in samples of sweet wine. The simultaneous analysis of several analytes in the same sample should imply that, with an adequate dilution, the concentration levels of the analytes can be included within the ranges of linearity of the corresponding calibration plots. The use of two composite biosensors in a parallel configuration, so that different analytes can be simultaneously detected with no need of chromatographic separation, is also discussed. The usefulness of this approach was evaluated by the simultaneous analysis of glucose and ethanol in sweet wine, and of glucose and lactic acid in red wine. 相似文献
169.
170.
Cyclic voltammetry in a perfluorocarbon emulsion based blood substitute (PEBS) was evaluated. The intent was to determine how PEBS affects the voltammetry of four representative electroactive compounds: potassium ferricyanide, ruthenium(II) trisbipyridine (rutris), hydroquinone, and 2,6‐dichloroindophenol (DCIP). Voltammograms in 0–20% PEBS‐Tris buffer mixtures are affected by PEBS, but reasonably well‐defined voltammograms are obtained in as much as 20% v/v. This report also shows that PEBS has only a small effect on amperometric detection of the reaction between DCIP and nicotinamide adenine dinucleotide (NADH), which has importance in clinical homogeneous immunoassays. Results support continued exploration of voltammetry/amperometry for quantitative analysis in this medium. 相似文献