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。     

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。     

十五种稀土元素的ICP-AES摄谱法的检出限和工作曲线的线性范围

本工作以去溶剂方法进样,在一套用正交试验设计法得到的折衷条件下测定了15种稀土元素的161条主要灵敏线的检出限及工作曲线的线性范围,并就多元素同时分析时条件优化试验的考察指标及检出限的计算进行了讨论。     

硫化学发光气相色谱法在气体分析中应用研究

本文建立了硫化学发光气相色谱仪测定气体中痕量硫化物的分析方法。通过对不同材质管线的考察,优化了该方法的进样系统。对氮中12组分含硫化合物气体标准物质在硫化学发光检测器上响应开展了研究,验证了硫化学发光检测器等摩尔响应的特性,计算得出各含硫化合物的响应因子,建立硫化学发光气相色谱法的校正因子,并对其机理进行了简单探讨。实验研究了硫化学发光气相色谱法的线性及检出限,结果表明该方法线性良好,方法检出限低至0.03μmol·mol~(-1)。该方法相比于其他测定硫化物方法,具有检出限更低,线性范围更宽,等摩尔响应等特性。     

空白批内标准偏差和方法检出限的计算

环境分析化学中,尤其痕量分析时,方法检出限对于监测结果的报出很重要。检出限的确定常会涉及空白标准偏差的计算。通过对一典型案例剖析,指出一部分新制修订环境标准方法采用空白批间标准偏差计算检出限是不合理的。在求算检出限时应先判断批间是否存在显著性差异。     

热解析法测汞仪的校准

建立了热解析法测汞仪的校准方法。比较了传统冷原子吸收测汞仪和热解析法测汞仪的测量原理及计算方式,指出了JJG 548–2004 《测汞仪检定规程》不适用于热解析法测汞仪的原因。选取固体和液体两种标准物质,对热解析法测汞仪的示值误差、检出限、重复性等主要计量特性及技术指标进行校准。选用DMA–80型热解析法测汞仪对该校准方法进行了验证,其示值误差为5.3%,检出限为0.007 ng,重复性为1.4%。经验证,上述结果均未超出设定指标,各计量特性符合方法要求。该方法校准后的计量特性及技术指标较为合理,校准方法切实可行,适用于热解析法测汞仪的校准。     

分析化学中的检出限和测定下限

检出限和测定下限是分析化学中的两个重要概念,是评价一个分析方法的重要度量特征。多年来,国外不少学者,包括一些国际学术组织,曾对这两个概念作过讨论和规定,但均未得到普遍承认。由于表达得不统一,使不同的分析方法难以对比。在国内,对原子吸收和离子选择电极领域中的检出限概念也进行过讨论。本文拟在数理统计的基础上,对检出限和测定下限的定义和计算作一评述和讨论。一、检出限(Limit of Detection) 检出限的一般定义是:“在一定的置信水     

检出限概念问题讨论—IUPAC及其它检出限定义的综合探讨和实验论证

讨论文以大量实验数据为依据，查证了光分析法中影响检出限的诸多因素，用设计实验获得数据与理论结合，对几种推荐的检出限计算方法予以归纳、论证，阐明以检出限做为分析主、分析仪器的比较标准时，应正确理解的有关问题和使用检出限的注意事项。     

X-射线荧光光谱法测定锌铝铜合金中的铝、铜、铁、硅、镍、铅和镉

建立了X射线荧光光谱法测定锌铝铜合金ZnAl6Cu1中铝、铜、铁、硅、镍、铅和镉的分析方法。探讨了各元素的分析条件,比较了不同制样方式及不同放置时间对铝强度的影响。在最佳的仪器分析条件下,测定了微量元素的检出限及主、次元素的精密度和准确度。检出限结果表明:各微量元素的检出限均满足标准要求,Cd和Pb元素的定量限稍高。精密度和准确度结果表明,铝、铜、铁元素的测量相对标准偏差在2.1%~5.9%,分析结果与国家标准方法一致。     

十三种利尿剂的高效液相色谱测定方法

对近几年国际奥委会医学委员会公布的禁用表中新增药物及一系列利尿剂的相关化合物进行了研究，比较了不同的提取方法及回收率，研究了几种药物的排泄情况；建立了同时分析13种利尿剂的高效液相色谱测定方法，检出限小于5ng。     

On-line coupling of solid-phase extraction with mass spectrometry for the analysis of biological samples. I. Determination of clenbuterol in urine

The potential of the direct coupling of solid-phase extraction (SPE) with mass spectrometry (MS) for the analysis of biological samples is demonstrated. For SPE a cartridge exchanger is used and the eluate is directly introduced into the mass spectrometer. This system has been investigated for the determination of clenbuterol in urine. With mixed-mode cartridges, a considerable ion suppression has been obtained. The mass spectrum at the elution time of clenbuterol is dominated by that of creatinine and adduct formation of clenbuterol and creatinine has been observed. The whole procedure including injection of 1 ml urine, washing and desorption has been developed with cartridges containing 8-microm C18-bonded silica. If only a single MS step is used, the selectivity and, therefore, the sensitivity are insufficient. The detection limit is about 100 ng/ml. However, with atmospheric pressure chemical ionisation and the tandem MS mode the detection limit has been decreased to about 2 ng/ml and the ion suppression is only about 10%. For the electrospray ionisation the detection limit is about 10-times higher and the ion suppression is less favourable. The repeatability for the SPE-MS-MS procedure was 6.5% at 10 ng/ml (n=5) and the difference between the response factors at 10 ng/ml and 100 ng/ml was only 2.5%. The MS behaviour of clenbuterol and the matrix under the present conditions is discussed.     

Determination of Oltipraz in serum by high-performance liquid chromatography with optical absorbance and mass spectrometric detection.

Three methods have been developed for the analysis of Oltipraz in serum. A method suitable for routine use employs spiking with a homologous internal standard, off-line solid-phase extraction, high-performance liquid chromatographic separation, and optical absorbance detection at 450 nm. Method detection limit is about 1 ng/ml. A second method, less susceptible to bias from co-eluting interferences, uses a stable isotope-labeled internal standard, similar extraction and separation, and detection by thermospray mass spectrometry. Method detection limit is about 0.2 ng/ml. A third method was developed which can be used without specially synthesized internal standards. It uses on-line solid-phase extraction, with quantification by comparison with external standards. Method detection limit is about 3 ng/ml. Good agreement was observed between these methods and with similar and different methods run in other laboratories. Calibration curves were linear over the entire range which was investigated, i.e., up to 500 ng/ml. Coefficients of variation were similar for all three methods, being about 5%.     

Field-amplified sample injection and in-capillary derivatization for sensitivity improvement of the electrophoretic determination of histamine

The feasibility of the combination of field-amplified sample injection (FASI) and in-capillary derivatization was explored for improving sensitivity of histamine in capillary electrophoresis (CE). Naphthalene-2,3-dicarboxaldehyde (NDA) was used as derivatization reagent. The reagent and sample was introduced by tandem mode. The derivatization was accomplished by at-inlet mode with standing time of 1.5 min. The combination of FASI and in-capillary derivatization was successfully achieved with about 400-fold concentration sensitivity enhancement compared to pre-capillary derivatization at the same set-up. The detection limit of concentration for histamine reached 1.25 x 10(-11) M by CE and fluorescence detection with S/N = 3. Parameters affecting FASI and in-capillary derivatization process including sample matrix, buffer concentration and reagent injection amount, were investigated.     

The application of strongly reducing agents in flow injection analysis : Part 3. Vanadium(II)

The application of vanadium(II) as a powerful reducing reagent in flow injection analysis is described. Results are presented for the determination of various organic and inorganic substances. With spectrophotometric detection, based on the absorption by vanadium(II)-EDTA at 350 nm, limits of determination were about 5 X 10^?5 mol 1^?1. Nitrate, nitrite and hydroxylamine were measured with amperometric detection. The limit of determination was about the same as with spectrophotometric detection. In a slightly acidic medium, hydrazine could be determined with the amperometric detector, with a limit of determination of about 10^?4 mol l^?1. By coupling an ammonia detection device to the reduction system, the percentage conversions of nitrate, nitrite and hydroxylamine to ammonia were shown to be 26%, 54% and 47%, respectively.     

Comparison of different carbon nanostructures influence on potentiometric performance of carbon paste electrode

Recently, different carbon nanomaterials were introduced for construction of electrochemical sensors. In this study, the influence of carbon nanomaterial on performance of carbon paste potentiometric electrode was investigated. In this manner, different kinds of carbon nanomaterial, i.e., graphene, graphene oxide and carbon nanotube (CNT) were used as a conduction phase in carbon paste electrode. Then, potentiometric characteristics of the corresponding paste electrodes such as calibration slope, linear range, detection limit, response time and stability were compared with each other. The results appeared comprehensive findings about the role of electrode’s content in electrochemical performance.     

Visual and on-site detection of mercury(II) ions on lateral flow strips using DNA-functionalized gold nanoparticles

A test strip for detection of Hg(2+) in aqueous solution based on the DNA-functionalized gold nanoparticles (DNA-AuNPs) was developed and evaluated. When Hg(2+) ions were introduced, the biotinylated DNA(2) hybridized with thiolated DNA(1) functionalized on the AuNPs (DNA(1)-AuNPs) to form mismatch complexes through thymine-Hg(2+)-thymine (T-Hg(2+)-T) coordination. The formed mismatch complexes and excess DNA(1)-AuNPs could be captured on the test line formed by streptavidin and the control line formed by DNA(3)-BSA, respectively. Two red lines appeared due to the accumulation of AuNPs, enabling visual detection of Hg(2+) with a detection limit of about 6 nM. The assay results can be obtained within 5 min. The results show that the test strip has excellent sensitivity and selectivity for detection of Hg(2+); thus it holds a great potential for rapid, on-site and real time detection of Hg(2+).     

化学反应—气相色谱法测定蔬菜中杀虫双残留量

本文介绍了一种运用化学反应转化，气相色谱法快速测定蔬菜中杀虫双残留量的方法，其检测限为０．０１ｍｇ／ｋｇ。     

仪器定量分析中几个问题的探讨

详细介绍了分析方法的评价指标,包括检出限、测定限、灵敏度、精密度、准确度、动态范围和线性范围、抗干扰能力等,单因素优化方法与加标回收实验评定测定结果准确度的可靠性,并就分析工作中遇到的一些实际问题进行了讨论.     

宽离子能量检测范围垂直引入反射式飞行时间质谱仪的研制

本实验室研制了国内首台宽离子能量检测范围飞行时间质谱仪。仪器采用紧凑式电子轰击源设计,配合离子透镜系统有效的调制离子流,飞行时间质量分析器采用了离子垂直引入式,双场加速和双场反射以及大尺寸MCP检测装置设计。仪器单离子信号半峰宽约2 ns,仪器分辨率优于1600FWHM,检测实际样品质量范围为1~127 amu(仪器理论质量检测上限优于800 amu),可检测离子能量范围优于2个数量级(3~140 eV)。若该TOF质量分析器与短瞬高压脉冲放电离子源耦合联用,可广泛应用于高能离子束的快速检测,如真空阴极放电对制备薄膜、离子注入材料的表征,导电材料的离子电荷态分布以及离子扩散速度的测定等。     

Validation of chromatographic methods: evaluation of detection and quantification limits in the determination of impurities in omeprazole

To guarantee that an analytical procedure gives reliable, exact and interpretable information about a sample, it must be validated. Two ambiguous parameters are detection limit and quantification limit. The determination of these limits is still of great concern and there are still a variety of procedures described in the current literature. The fundamental objective of the present work is to apply the different recommendations suggested by official guidelines for the quantitative determination of omeprazole and its impurities (omeprazole sulphone and 5-hydroxy-omeprazole) in capsules and tablets using high performance liquid chromatography with UV detection. The importance of calibration linearity in the context of the quantification limit is considered, since one of the approaches, the estimated concentrations of this limit, are deduced from the regression line. The values of the detection limit and the quantification limit obtained show that, in chromatographic analyses, the best method is that based on the use of the parameters obtained from the analytical curve, which are statistically reliable. It was shown that smaller values of the detection limit and the quantification limit were obtained by the visual approach and by the method using the signal-to-noise ratio. However, these values may reflect a subjective evaluation, prone to error and large variations. This was confirmed by showing that these methods result in values that fall outside the linear range of the method.