改进计时电流法的数学模型和电路实现

当采用电化学计时电流法对样品进行检测时,由于检测系统的延迟,采集到的电化学信号会产生偏差,这种现象在多通道电化学信号快速采集时尤为明显.为克服该问题,我们提出一种新的电化学方法来快速产生电流峰值,通过测量峰值快速准确地测出被测物浓度.本文首先为该方法建立理论模型,推导出电流峰值与被测物的浓度关系;再引入经典控制理论中的控制环节来改进传统电化学电路以实现该方法,并加入峰值检测电路来准确获取电流峰值信号;最后,利用该方法研究K3[Fe(CN)6]和3,3′,5,5′-四甲基联苯胺(TMB)溶液的电化学反应,证明了本方法相比传统计时电流法具有更高的信噪比和灵敏度,电流峰值与浓度呈线性关系,并且检测结果不受采样时间延迟的影响,克服了计时电流法的不足.     

生物细胞电化学噪声分析仪的研制及应用

本文提出了细胞离子通道的生物电化学噪声测试方法,设计并研制了电极电位和电流噪声测试电路。普鲁士蓝修饰的玻碳电极作为钾离子传感器,以测量细胞钾离子通道的开关周期。试验结果表明,宫颈癌细胞(HeLa细胞)钾离子通道的电流噪声功率谱分别在0.04Hz和0.06Hz出现峰值,说明HeLa细胞钾离子通道的开关周期在16s至25s之间。对离子通道的开关周期11次测量结果的标准偏差(RSD)10%。     

同位素稀释热电离质谱法测定人血清中痕量铜和锌

采用热电离同位素稀释质谱法(ID-TIMS)准确测定了欧盟标准物质与测量研究院(EC-JRC-IRMM)组织的国际测量评估计划IMEP-17人血清样品中的痕量铜和锌。由于锌和铜都是易受污染的元素,本工作建立了仅用少量硝酸消解的低流程本底和适于热电离质谱测量的生物基体血清中痕量铜和锌的样品前处理方法;采用适当比例的硅胶和磷酸作为电离增强剂,在热电离质谱(TIMS)测量时获得了较高强度且稳定的铜和锌离子束;血清中痕量铜和锌的测量结果可直接溯源到国际单位mole。2种人血清样品中铜和锌测量结果的不确定度(k=2)分别为0.94%、0.83%和0.49%,测量值被EC-JRC-IRMM采用作为该样品的标准值。     

哌啶氮氧自由基与环糊精作用的电化学研究

采用循环伏安法测量水溶液中β-环糊精(β-CD)/哌啶氮氧自由基(以2,2,6,6-四甲基哌啶-1-氧化物(TEMPO)为例)体系氧化还原电位及峰值电流,并基于此探讨TEMPO与β-CD之间的包结反应。电化学测量表明,在pH=7.4的磷酸盐缓冲溶液中,以玻碳电极为工作电极,随β-CD浓度增大,β-CD/TEMPO体系的峰电位不断增大,峰电流不断减小。通过电位法测得TEMPO与β-CD的包络比为1∶1,包络常数KS为154L/mol,与电流法测得的包络常数基本吻合。     

丙烯腈和丙烯酰胺在浓硫氰酸钠水溶液中的共聚合

本文研究了丙烯腈和丙烯酰胺在52％NaSCN水溶液中的共聚合,主要就介质的pH值对共聚合反应的影响做了初步的探讨. 实验采用克分子比为15:85的丙烯酰胺(AAm)和丙烯腈(AN)的单体组成以偶氮二异丁腈(ABN)作为引发剂.在52％NaSCN水溶液中配成8%的溶液,用硫酸、氢氧化钠、醋酸调至所要的pH值,pH值是用雷磁24型酸度计测量的.在聚合管中,通氮除掉体     

香蕉型软糖中混合色素的一阶导数分光光度法测定

本文提出以一阶导数分光光度法测定香蕉型软糖中的混合色素。其中苹果绿在618和651nm处测量导数峰值之和,而柠檬黄则在175nm处减去苹果绿的干扰部份测量导数峰值之差。经实际样品分析验证获得了满意的结果,相对标准偏差为1.87％,回收率在95—100％之间。     

PVB掺杂有机无机复合SiO2增透膜的制备和表征

以聚乙烯醇缩丁醛(PVB)为有机掺杂剂,正硅酸乙酯为前驱体,氨水为催化剂,利用溶胶-凝胶法制备出了一种新型的有机无机复合二氧化硅增透膜。采用红外光谱、X射线衍射、粒度分析、紫外分光光度法、椭偏测定、原子力显微镜、静滴接触角测量等对膜层性质进行了表征。结果表明：PVB分子的引入并没有引起增透膜结构的变化。在相同的实验条件下,未经PVB掺杂的SiO₂增透膜在720 nm处的峰值透过率为99.8％,而PVB掺杂后的SiO₂复合膜在840 nm处的峰值透过率在99.9%以上。掺杂膜层变厚,峰值透过率朝长波方向移动。掺杂前后增透膜对水的接触角从29°增加到71°,膜层的疏水性得到明显提高。     

涂钼石墨管分子吸收光谱法测定微量氟

本文对AIF分子吸收光谱法测量微量氟进行研究.使用涂钼石墨管可使灵敏度有较大提高.采用铂空心阴极灯做光源,峰值吸收测量方式,复合基体改进剂并先于氟进样,二次干燥等诸项技术联合运用时,可使AIF-MAS法具有实用意义.方法的灵敏度为9.6×10~(11)g/1%A,精密度为4.9%,在测试的浓度范围内,有两个线性范围:0.075～0.6μg·ml~(-1);0.6～1.5ug·ml~(-1).     

复合纳米粒子修饰的柔性分子印迹传感器对四环素的检测研究

本文以酸化碳布(CC)作为柔性工作电极,采用恒电位沉积法在碳布上修饰纳米Au-Cu复合粒子(Au-Cu NPs),以四环素(TC)为模板分子,邻苯二胺为功能单体,采用循环伏安法在修饰了纳米粒子的活化碳布上电聚合分子印迹膜,制备了四环素分子印迹柔性传感器(Cu-Au NPs/PANI/TC/CC),通过循环伏安法(CV)、差分脉冲伏安法(DPV)研究了其电化学性能。结果显示,在优化实验条件下,TC的DPV峰值电流与其浓度在1.0×10~(-7)～3.0×10~(-5) mol/L范围内成良好的线性关系,相关系数为0.9996,检出限为2.57×10~(-11) mol/L,实际样品的加标回收率为97.3%～105%。该传感器柔软稳定,灵敏度高,抗干扰性和重复性好,可应用于柔性可穿戴传感器的设计。     

结合密度泛函理论的橙皮素及其包合物的红外和拉曼光谱研究

本文通过密度泛函理论(DFT)结合实验研究了橙皮素的红外和拉曼光谱,采用B3LYP/6-311+G(d,p)基组对其红外和拉曼光谱进行了计算,计算结果和实验结果基本一致。本文还利用红外及拉曼光谱对橙皮素与β-环糊精(β-CD)形成的包合物进行了分析,证明了橙皮素通过氢键作用嵌入β-CD的疏水空腔中而形成包合物,从而验证了拉曼光谱可以作为一种新型的验证包合物形成的方法。该研究为橙皮素及其包合物的鉴定提供了一种简单、快捷、无损测量的优良方法。     

Quantitation of femtomolar protein levels via direct readout with the electrochemical proximity assay

We have developed a separation-free, electrochemical assay format with direct readout that is amenable to highly sensitive and selective quantitation of a wide variety of target proteins. Our first generation of the electrochemical proximity assay (ECPA) is composed of two thrombin aptamers which form a cooperative complex only in the presence of target molecules, moving a methylene blue (MB)-conjugated oligonucleotide close to a gold electrode. Without washing steps, electrical current is increased in proportion to the concentration of a specific target protein. By employing a DNA-based experimental model with the aptamer system, we show that addition of a short DNA competitor can reduce background current of the MB peak to baseline levels. As such, the detection limit of aptamer-based ECPA for human thrombin was 50 pM via direct readout. The dual-probe nature of ECPA gave high selectivity and 93% recovery of signal from 2.5 nM thrombin in 2% bovine serum albumin (BSA). To greatly improve the flexibility of ECPA, we then proved the system functional with antibody-oligonucleotide conjugates as probes; the insulin detection limit was 128 fM with a dynamic range of over 4 orders of magnitude in concentration, again with high assay selectivity. ECPA thus allows separation-free, highly sensitive, and highly selective protein detection with a direct electrochemical readout. This method is extremely flexible, capable of detecting a wide variety of protein targets, and is amenable to point-of-care protein measurement, since any target with two aptamers or antibodies could be assayed via direct electrochemical readout.     

514— Oxidase-cofactor electrodes aimed at the quantitative measure of substrate concentrations

Two approaches are described briefly for utilizing oxidase enzymes in electrochemical sensors. In one approach an oxidase enzyme flavin cofactor was covalently coupled to the electrode surface with the anticipated readout being a current proportional to the concentration of enzyme substrate. In the second approach enzyme glocose oxidase was immobilized on platinum such that the potential of the platinum varied with the concentration of glucose in a solution buffered at pH 7.4. The status of the two projects is described.     

A dual ion-selective electrode detector for the simultaneous detection of bromine- and chlorine- containing compounds in gas chromatography

A dual ion-selective electrode gas chromatographic detector which allows the simultaneous detection of chlorine- and bromine-containing compounds through two-channel operation is described. Components eluted from the g.c. column are hydrogenated, the hydrogen chloride and hydrogen bromide produced being absorbed in a standard solution of halide; the ion concentrations in the resulting solution are monitored by chloride- and bromide-selective electrodes. The dual electrode detector gives two chromatograms simultaneously, one selective for chlorine- and bromine-containing compounds and the other for bromine-containing compounds. The response ratio, i.e., the peak area of the readout from the chloride channel divided by that from the bromide channel for the same compound, gives valuable information. The Cl/Br ratio in an eluted molecule can be determined accurately from the response ratio if a standard reference compound is injected simultaneously.     

The processing of gas-chromatographic data

Summary Methods of data processing for gas chromatography other than the strip-chart recorder are reviewed. After an introductory discussion of the choice between measurement of peak height and peak area for quantitative analysis, the review deals briefly with the use of digital integrators, and more fully with current developments in the application of digital computers to GC.

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Zusammenfassung Es wird ein Überblick gegeben über die Methoden zur Datenverarbeitung in der Gas-Chromatographie (ausgenommen Bandschreiber). Nach einer einführenden Diskussion des Problems Peakshöhen- oder -flächenmessung bei der quantitativen Analyse wird kurz die Verwendung von Digitalintegration besprochen und so dann ausführlicher die neueren Entwicklungen bei der Anwendung von Digitalcomputern behandelt.

     

Systematic and statistical errors in quantitative evaluation in TLC and HPTLC. 1. Evaluation by graphic methods

The paper discusses errors and error propagation in respect of graphic methods in quantitative in situ measurements in TLC. An error of 0.3% is possible by measuring only peak height if optimal conditions are chosen. This is in good agreement with analysis done practically which gives errors in the order of 0.3–0.6%. If the peak area is evaluated using the approximation peak height × half width, the error is in the order of 0.6%, but in real experiments only 1.5% had been found. Systematic errors in determining peak heights are introduced by the time constant of the amplifiers and the recorder.     

Evaluation of the temporal effect to the peak tailing in flow injection analysis

The deformation of a flow injection analysis peak from a Gaussian shape has two components: spatial and temporal. The former is mainly attributed to the Poisseulie effect in the tubular flow, whereas the latter is related to the observing position (of a fixed detector) at which signal is measured. The combination of the two makes a skewed peak track on the recorder chart. Therefore, an observed peak may imply a substantial fraction of a “false” tail due to the effect of non-simultaneous detection. An expanding-Gaussian model is proposed to simulate the purely temporal effect, and the asymmetric factors were compared with that of the experimental peak shapes. In most cases the peak deformation occurring in flow injection analysis should be regarded as “temporal”. The contribution of the spatial effects (Poisseulie profile and others) might not be as significant as it was thought previously.     

An electrochemical sensor for sodium dodecyl sulfate detection based on anion exchange using eosin Y/polyethyleneimine modified electrode

A simple and effective method for the detection of electrochemically inactive sodium dodecyl sulfate (SDS) has been designed, based on different binding affinity of polyethyleneimine (PEI) toward electrochemically active eosin Y and electrochemically inactive SDS. The stronger binding affinity of the PEI toward SDS than eosin Y results in the decrease of the redox peak current of surface confined eosin Y and provides a quantitative readout for the SDS. The difference in value of the cathodic peak current showed a linear relationship with SDS concentration in a concentration range from 1 to 40 μg mL⁻¹, and a detection limit of 0.9 μg mL⁻¹ for SDS was obtained. Furthermore, the method has been successfully applied to the detection of SDS in real samples. The developed approach provided a simple and reliable detection for SDS and might have potential applications in electrochemical methods for inactive molecules.     

Reusable conductimetric array of interdigitated microelectrodes for the readout of low-density microarrays

Low-density protein microarrays are emerging tools in diagnostics whose deployment could be primarily limited by the cost of fluorescence detection schemes. This paper describes an electrical readout system of microarrays comprising an array of gold interdigitated microelectrodes and an array of polydimethylsiloxane microwells, which enabled multiplexed detection of up to thirty six biological events on the same substrate. Similarly to fluorescent readout counterparts, the microarray can be developed on disposable glass slide substrates. However, unlike them, the presented approach is compact and requires a simple and inexpensive instrumentation. The system makes use of urease labeled affinity reagents for developing the microarrays and is based on detection of conductivity changes taking place when ionic species are generated in solution due to the catalytic hydrolysis of urea. The use of a polydimethylsiloxane microwell array facilitates the positioning of the measurement solution on every spot of the microarray. Also, it ensures the liquid tightness and isolation from the surrounding ones during the microarray readout process, thereby avoiding evaporation and chemical cross-talk effects that were shown to affect the sensitivity and reliability of the system. The performance of the system is demonstrated by carrying out the readout of a microarray for boldenone anabolic androgenic steroid hormone. Analytical results are comparable to those obtained by fluorescent scanner detection approaches. The estimated detection limit is 4.0 ng mL⁻¹, this being below the threshold value set by the World Anti-Doping Agency and the European Community.     

A pH‐Responsive MRI Agent that Can Be Activated Beyond the Tissue Magnetization Transfer Window

A terbium‐based complex that displays a water exchange CEST resonance well outside the normal magnetization transfer (MT) frequency range of tissues provides a direct readout of pH values by MRI. Deprotonation of the phenolic proton in this complex results in a frequency shift of 56 ppm in a bound water molecule exchange peak between pH 5 and 8. This allows direct imaging of pH without prior knowledge of the agent concentration and with essentially no interference from the tissue MT signal.     

MISER chromatography (multiple injections in a single experimental run): the chromatogram is the graph

An experimental approach for rapid analysis and convenient interpretation of multiparallel experiments is described. Conventional approaches use a series of individual chromatographic runs to produce integrated peak area data, which are stored in individual data files, then transferred to a spreadsheet program and graphed to allow interpretation of experimental results. A simpler and more direct approach utilizes multiple injections within a single chromatographic run to produce a continuous trace of chromatograms, which can often provide a direct visual readout of experimental outcome without the need for peak integration, data transfer, or graphing. In this approach, the chromatogram itself serves as the graph whereby the outcome of the multiparallel experiment can be discerned. The utility of the technique is greatly enhanced by the use of compound-specific detection technologies such as mass spectrometry or chiroptical spectroscopy, and can benefit from experimental designs that facilitate the direct interpretation of results.