浅议灵敏度、检出限和测定限

针对化学书籍及刊物中出现的不能正确理解和区别应用灵敏度、检出限和测定限的现象,对它们进行详细的分析比较,并给出正确使用的方法。     

分析化学中检出限和测定下限的探讨

分析化学中灵敏度是分析方法的主要参数,检出限为具体量度指标,特别是在痕量分析中,检出限的确定对于分析方法的选择具有重要意义。分析仪器在测定过程中存在着与噪音相区别的小信号检出问题,同时也存在分析方法能可靠测定物质最低含量的界限问题,这两个概念有着本质的不同。在实际应用中,仪器检出限、方法检出限及测定下限的概念经常混乱,笔者分类阐述了检出限及测定下限的含义和计算方法,以指导实际应用中的理解和计算。     

小波分形分析重叠峰信号

用连续小波变换与分形理论相结合的小波分形峰位法对含噪重叠信号峰位置的提取进行了研究, 同时考察了信噪比和分离度对该法提取峰位置的影响; 结果表明 该法是一种提取含噪重叠信号中各单独峰峰位置的有效工具, 即使对于重叠程度和噪声干扰严重的信号也能得到较好的结果; 将其用于 Cd(Ⅱ )和 In(Ⅲ )重叠伏安信号的处理, 峰位置提取的相对误差小于± 1%; 该法具有准确、快捷、简便易行等特点, 发展前景广阔.     

化学蒸气发生-原子荧光光谱法测定水中痕量Hg的影响因素探讨

化学蒸气发生-原子荧光光谱法(CVG-AFS)是一种痕量和超痕量的分析方法,具有测定灵敏度高、检出限低的特点。测汞时由于汞离子可以与硼氢化钾(钠)生成原子态的汞,在“冷”条件下可被激发出汞的原子荧光,一般也被称为冷原子蒸气法。笔者以海光AFS-2202型双道原子荧光光度计为例,就分析过程中可能出现的几种影响因素进行分析,并提出消除办法。1试剂空白的影响试剂空白值对分析方法的检出限和测定结果的准确度、精密度有着较大的影响。要求检测汞的量通常都是痕量级,空白值过高,所出现的荧光信号要比正常情况高出许多,这将直接影响到样品(特…     

Enhanced Nebulization Efficiency of Electrospray Mass Spectrometry: Improved Sensitivity and Detection Limit

A novel electrospray nebulizer has been designed, which includes an additional nebulization gas capillary inside the liquid capillary. This design offers significantly enhanced ionization efficiency compared with the classic nebulizer design and leads to improved sensitivity (by three to 10 times) and decreases the detection limit, on an average 10 times. We see these results as the first step in the design of ESI nebulizers offering improved sensitivity and higher robustness. Possible future developments would include optimization of the dimensions of the capillaries as well as testing the nebulizer for other matrices and analytes.     

提高Nb2O5中Ta2O5光谱分析的灵敏度

由于Ｎｂ２Ｏ５与Ｔａ２Ｏ５物理、化学性质相似，主体Ｎｂ２Ｏ５对Ｔａ分析线强度干扰很大。因此，Ｎｂ２Ｏ５中光谱测定Ｔａ２Ｏ５的灵敏度很差，为了提高Ｔａ分析线强度，通常的光谱条件选择是无效的。实验表明在旋流气室中，采用高含量Ａｒ的（Ａｒ、Ｏ２）控制气氛电弧激发，提高了Ｎｂ２Ｏ５中Ｔａ２Ｏ５的光谱分析灵敏度。然而，由于Ｎｂ２Ｏ５在高温下易于被碳还原，虽然用Ｓｔａｌｌｗｏｏｄ喷咀可以改善蒸发，减慢样品还原     

Active Junctions to Improve Sensitivity and Detection Limit of a Microdevice Based on Coulometry Coupled with Silver Metallization

For achieving miniaturization and coupling with microfluidics, electrochemical devices are advantageous. In particular, coulometry is an effective tool to analyze components in solutions of very small volumes. The sensitivity and detection limit of coulometry can be improved remarkably by converting an analyte into Ag on the same Pt electrode separated in two flow channels and measuring the amount of Ag using coulometry. We demonstrate that the cathodic and anodic potentials of both parts of the Pt electrode can be shifted and reactions can be accelerated by replacing the liquid junction connecting the two flow channels by a metal wire with redox active ends. This in turn improves the sensitivity and detection limit of the device. This effect can also be observed by directly applying a voltage to the solutions in the flow channels. The achieved detection limit for hydrogen peroxide (H₂O₂) was 2.4 nM.     

分析化学中“检出限”的物理意义及测定方法探究

阐述了分析化学中各类分析方法的检出限的物理意义、测定方法及可能存在的问题,并论述了经典的检出限定义的局限性。在利用凝血酶适配体与凝血酶的特异性结合抑制Pt纳米颗粒对量子点荧光猝灭检测凝血酶和基于CuGeO_3纳米线和葡萄糖氧化酶(GOx)修饰的玻碳电极(GCE)生物传感器测定葡萄糖的分析方法中,由于测定信号与被检测物质浓度或浓度的对数成负相关关系,导致分析方法的检出限与经典的检出限测定产生一定的冲突,出现了测定精密度越高,检出限越差的异常情况。     

检出限的涵义和计算方法

介绍仪器检出限、方法检出限及样品检出限的基本定义及涵义,以气相色谱法测定海水中的十氯酮为例,进行不同方法的检出限计算,讨论了不同方法计算检出限引起的差异及计算方法中所选取参数的合理性,对如何科学使用检出限进行实验室质量控制提出了建议.     

Studying Systematic Errors on Estimation Decision, Detection, and Quantification Limit on Micro-TLC

The decision limit (CCα), capability of detection (CCβ) and quantification limit (QL) are importance performance characteristics in method validation. The TLC-Scanner 3 from Camag provides the possibility to choose the slit dimension of light to determine the peak chromatogram of a substance. The influence of the slit dimension for determination of CCα, CCβ and QL of paracetamol has been carried out. Paracetamol was spotted onto plates of AL-TLC Si G 60 F254 by linomat 4 in the range of 50–400 ng/spot and 10–400 ng/band, then on twin chambers eluted with TAEA (toluene:acetone-ethanol:conc.ammonia, 45 + 45 + 7 + 3 v/v) for 45 mm. Eluted spots were scanned in different slit dimensions at 248 nm. The CCα, CCβ and QL of paracetamol were estimated through the linear regression (LRM) and signal-to-noise (S/N) methods. Slit lengths between 50 and 133 % of the band width of the spots, and with the noise factor of the slit under 2.6, produced good precision measurements of TLC-densitometry between plates, while slit lengths between 50 and 83 % of the band width of the spots introduced a higher sensitivity response of the detector. The estimated CCα, CCβ and QL were determined by how the data were collected, the analytical optical setting, and the usage method for the estimation of both validation parameters.     

Enhancing Detection Sensitivity in Capillary Electrophoresis

A simple technique was proposed for improving detection sensitivity in capillary electrophoresis by the chemical etching of the interior surface of a fused-silica capillary in the detection region. This technique was applied to the electrophoresis of proteins. The sensitivity was found to increase, on the average, by a factor of 4 to 5 after etching a 75-m i.d. capillary with an HF solution for 7 min.     

Slope Sensitivity Analysis Using Spencer's Method in Comparison with General Limit Equilibrium Method

This paper analyses the sensitivity analysis of a natural-unreinforced slope in Kepong, Kuala Lumpur. In order to conduct a sensitivity analysis, several ranges of data, based on borehole information and figures and also typical range of earth materials geotechnical values are used to set the minimum and maximum value of parameters in Slide 6.0 software. Under Mohr-Coulomb failure criterion, Spencer's and General Limit Equilibrium methods of slices were used in the analysis to determine the influence of varying parameters values towards the change in safety factor. In addition, the percentage differences in safety factors obtained by both methods based on General Limit Equilibrium method are also determined in the analysis. In the analysis, water table location has the highest influence to the change in safety factors of the slope. Besides, the percentage differences in safety factors obtained by both methods are very nominal and showed a good agreement to each other.     

DNA电泳芯片快速检测系统的设计与实现

引　　言近年来 ,出现了基于微电子机械技术 (ＭＥＭＳ)的电泳芯片技术 ,已经被应用于蛋白质等生物大分子的分离分析、ＤＮＡ测序、药物分析等领域。由于芯片中分析的样品量仅有几十皮升 ,电泳时间的缩短至几分钟 ,必须采用高灵敏度、快速的检测方法。本文提出了一种激光激发的荧光快速检测方法。检测限已达到 1 0 -19ｍｏｌ。2　系统设计2 .1　仪器与设备　 367型 1 0ｍＷ氩离子激光器 (南京电子管厂 ) ;半反半透镜 ( 50 5ＤＲＬＰ ,545ＤＲＬＰ ,570ＤＲＬＰ ,590ＤＲＬＰ ,ＯｍｅｇａＯｐｔｉｃａｌ公司 ) ;单色滤光片 ( 52 5ＤＦ30 ,5…     

方法检出限三个评估方法标准解读与比较

文献中有多项方法检出限评估标准,如何正确理解和运用这些标准得到可比较的参数对基层实验室具有指导意义。对目前国内外方法检出限评估方法标准进行了系统总结和梳理,介绍了不同方法的特点、适用范围和注意事项。利用实验室实例和文献数据,比较了三种代表性方法计算结果。基于科学性和可操作性的原则,针对不同需求,提出了检出限评估改进建议及实施方案。