叠加内标法色谱定量分析

 叠加内标法是指在色谱定量分析中将内标法与叠加法结合的一种新的定量方法。叙述了叠加内标法定量的理论依据 ,规定了其操作步骤 ,并详细说明了这种方法的适用条件和优缺点。     

Contributions to accuracy improvement of simultaneous ICP atomic emission spectrometry using multi-line measurements of analyte and internal standard elements Applications for the analysis of permalloy

For successful application of simultaneous ICP atomic emission spectrometry for major component determinations in multi-component materials the accuracy of the method has to be improved. As a contribution to solve this problem a combined procedure for multi-component standard sample preparation, optimum calibration and different variations of internal standard corrections is described. Variance-weighted multi-line calibrations give most accurate results. Internal standard corrections are effective, if the time-dependent spectral line intensity fluctuations of the standard and the analyte elements are well correlated. Their sensitivities against some responsible device parameter variations are investigated. On the basis of multi-line measurements of the analyte and internal standard elements a “group-selected internal standard correction” (GS-ISC) method is applied and results in relative errors of less than 1% even for extreme fluctuations of the raw intensities. For rapid routine determination methods of materials with variable element compositions the added line intensities of the internal standard element can be used to correct the added analyte line raw intensities (“intensity addition internal standard correction” (IA-ISC) method). These accuracy optimization procedures are applied for the analysis of the soft magnetic material permalloy using the internal standard element In.     

Relative matrix effects: A step forward using standard line slopes and ANOVA analysis

One of the alternative methods to identify and study the matrix effect is by determination of “relative” matrix effect. In this experiment % coefficient of variance of standard line slopes are calculated. First, six standard lines are prepared from single plasma lot. In another experiment standard line slopes are compared from six different lots of plasma. All these standard curves are prepared by using three different types of IS (internal standard). From all these experiments it is observed that using SIL-IS (stable isotope labeled-internal standard) is one of the best approach in methods having matrix effects. Alternatively, analog IS is a cost effective approach. After comparing a large number of calibration curve slopes, it can be recommended that during every bioanalytical method validation, where the sample size is >50, scientist should perform the “relative” matrix effect experiment by standard line slope method. In selected cases, the precision of standard line slopes in six different lots of a biofluid was compared with precision values determined six times in a single lot. The results of these studies indicated that the variability of standard line slopes in different lots of a biofluid [precision of standard line slopes expressed as coefficient of variation, CV (%)] may serve as a good indicator of a relative matrix effect and, it is suggested, this precision value should not exceed 5% for the method to be considered reliable and free from the relative matrix effect liability.     

Internal Standard Correction of Results Obtained by Atmospheric Pressure Chemical Ionization Mass Spectrometry

An internal standard system has been developed for a mass spectrometer equipped with an atmospheric pressure chemical ionization source. The system has been used to overcome sensitivity drift problems that are commonly encountered when the spectrometer is used for long-term environmental monitoring. Additionally, the internal standard has been used to correct sensitivity changes induced by the matrix being analyzed. Principal components of the system are a low concentration internal standard source and a flow-delivery system for introducing the standard to the reagent gas delivery stream of the spectrometer. Following an experiment, real-time data are downloaded to a personal computer where internal standard correction and data analysis are performed. Application of the internal standard to the measurement of nicotine and pyridine is demonstrated.     

Heats of solution of gaseous hydrocarbons in water at 25°C

The heats of solution at 25°C for a number of hydrocarbon gases are reported as measured by a calorimetric method. There is excellent agreement between the standard enthalpy changes of solution measured calorimetrically and those derived from high precision temperature dependent solubility measurements. However the calorimetrically determined standard enthalpies of solution of a number of gases are greatly improved over values obtained from low precision temperature dependent solubility measurements. A method is presented to readily estimate the standard errors in the standard enthalpy change for any process derived from the temperature dependence of the equilibrium constant for the process. Comparison of the standard enthalpies and entropies of solution of hydrocarbon gases in water shows that the standard free energies of solution for all hydrocarbon gases investigated are dominated by unfavorable entropy contributions. A strong linear correlation between the standard entropy of solution and the number of hydrogens in the hydrocarbon molecule is found. This correlation suggests that the hydrocarbon hydrophobic effect is regulated by the number of allowable configurations of a water molecule in contact with each C–H group.     

Analysis of tetrahydrofuran and methanol in distillation residue samples by automated headspace solid-phase microextraction-gas chromatography with flame ionization detection

Automated headspace solid-phase microextraction (SPME) coupled with gas chromatography and flame ionization detection is used to determine the amounts of methanol and tetrahydrofuran (THF) in distillation residue samples from a proprietary chemical reaction. A 65-micron polydimethylsiloxane/divinylbenzene SPME fiber is used to perform the extractions. Optimized extraction conditions for each analyte are determined using a parts-per-million-level methanol in water standard and a parts-per-billion-level THF in water standard. The amount of methanol and THF in distillation residue samples is quantitated by both standard addition and external standard calibration curve. The two methods of quantitation are compared.     

A spectral and polarographic study of potassium chlorazepate.

Two new types of solid standards are described for the direct determination of trace impurities in metals by flameless atomic absorption. One of these, a primary standard, has a metal matrix and can be tailor-made to the required size and concentration by the technique of ion implantation. The other, a secondary standard, has a urea matrix into which trace elements are introduced by dissolution. Upper concentration limits are in the 100–1000 p.p.m. range. Both types of standard, the secondary in particular, are suitable for application in other methods of trace analysis.     

Enthalpies of the formation and dissolution of D-asparagine monohydrate in water and aqueous solutions of potassium hydroxide

The internal energy of combustion of D-asparagine monohydrate is determined by bomb calorimetry, and its standard enthalpies of combustion and formation in the crystal state are calculated. The enthalpies of dissolution of this compound in water and aqueous solutions of potassium hydroxide are measured by standard calorimetric methods. The standard enthalpies of formation of the amino acid and of the products produced as a result of its protonation and dissociation in an aqueous solution are evaluated.     

Standardization in the determination of red blood cell polyamines by high-performance liquid chromatography.

The choice of the standardization method in the high-performance liquid chromatographic determination of dansyl polyamines (spermidine and spermine) in red blood cell extracts is discussed. 1,6-Hexanediamine, commonly used as an internal standard, is unsuitable for the quantification of spermidine and spermine in red blood cells because their percentage recoveries are significantly different (100% for 1,6-hexanediamine, and 70% for spermidine and spermine). The external standard method and the standard addition method are better suited. The procedure for the preparation of the standard mixture before dansylation has an influence on the values of red blood cell polyamines. Two procedures are compared and the corresponding percentages of variation were found to be high for spermidine and spermine. Thus the procedure in which the standard is treated in a strictly similar way as the red blood cells is certainly the most appropriate one for the quantification.     

Thermodynamic Properties of a First-Generation Carbosilane Dendrimer with Terminal Phenylethyl Groups

The heat capacity of a first-generation carbosilane dendrimer with terminal phenylethyl groups as a function of temperature in the range from 6 to 520 K is studied for the first time via precision adiabatic vacuum calorimetry and differential scanning calorimetry. Physical transformations, such as low-temperature structural anomaly and glass transition are detected in the above-mentioned range of temperatures, and their standard thermodynamic characteristics are determined and analyzed. The standard thermodynamic functions of the studied dendrimer in the range of T → 0 to 520 K are calculated from the experimental data, as is the standard entropy in the devitrified state at T = 298.15 K. The standard thermodynamic characteristics of the carbosilane dendrimers studied in this work and earlier are compared.     

2011年约稿： 电感耦合等离子体原子发射光谱法测定铜合金中锆量的不确定度评定

讨论了采用电感耦合等离子体发射光谱法测定铜合金中锆量分析结果不确定度产生的原因。建立了数学模型,对测量重复性,标准溶液,标准曲线变动性,试液体积,试样称量,数字修约等引起的不确定分量进行评定,计算了合成标准不确定度和扩展不确定度,并给出铜合金中锆量测定结果的报告。评定结果表明：测量重复性,标准曲线线性回归引起的不确定度对总不确定度影响最大。所以,在测定中应进行多次平行测定,特别注意标准曲线的校正和绘制校准曲线所用标准样品的选择。     

Transport efficiencies and analytical determinations with electrothermal vaporization employing electrostatic precipitation and electrothermal atomic spectroscopy

Analyte transport efficiencies of solid as well as liquid samples were determined for electrothermal vaporization (ETV). A graphite furnace of the boat-in-tube type was employed for ETV. The generated aerosol was transported by an argon flow via a tubing into an external precipitator and deposited on a L’vov platform with a corona-like discharge. The sample on the secondary platform was analysed with a laboratory-constructed coherent forward scattering multielement spectrometer. For determining the analyte transport efficiencies, the comparative measurements were carried out with standard solutions dosed directly on the platform in the spectrometer furnace. The simultaneously investigated elements were Cu, Fe and Mn in the standard reference material BCR CRM 189 wholemeal flour and in a multielement standard solution containing approximately the same element ratio as certified for the solid sample. ETV boat-to-L’vov platform transport efficiencies of approximately 19% for Cu, 24% for Fe and 19% for Mn were calculated for both solid samples and multielement standard solutions. Cu, Fe and Mn in wholemeal flour were determined simultaneously by calibrating against aqueous multielement standard solutions injected into the boat as well as by the standard addition method. The results agree satisfactorily, the deviations from the certified values are below 10% and the relative standard deviations are typically 5–8%. The limits of detection are 250 pg for Cu (λ=324.8 nm), 230 pg for Fe (λ=248.3 nm) and 90 pg for Mn (λ=279.8 nm), loaded into the ETV boat.     

The micro determination of copper(II) with a solid-state copper-selective electrode

The standard addition and standard subtraction methods are discussed briefly. Both methods are applied to the determination of copper(II) in very small sample volumes. A microcell (25 μl) and a copper-selective micro-electrode are described for this purpose; a nanoliter burette was constructed for the addition of very small increments. The results are compared with those obtained in a 10-ml cell.     

Flow injection calibration methods for atomic absorption spectrometry

The use of an atomic absorption spectrometer as a detector in flow injection analysis is briefly reviewed. A new simplified model is described for the dispersion effects observed with such systems; the model is based on considering the dispersion to be due to a single hypothetical mixing chamber located immediately prior to the measurement stage. The utility of this approach is demonstrated for two methods of calibration commonly used in atomic absorption spectrometry, and it is shown that flow injection sample and standard handling techniques are comparable to manipulation with volumetric apparatus. The flow injection method has a number of advantages for the analogue of the standard addition method. The use of an exponential concentration gradient is proposed as a novel method of calibration using a single concentrated standard. Results are presented for the determination of chromium in standard steels.     

电感耦合等离子体发射光谱(ICP-OES)法同时测定矿泉水界限指标中的4种元素

国家标准方法中,对矿泉水界限指标中的四种矿物质元素锌、锂、锶、偏硅酸(以H2SiO3计),需每种元素分别测定且步骤繁琐,采用电感耦合等离子体发射光谱(ICP-OES)法对矿泉水中这4种元素的含量进行同时测定,四种元素的检出限在0.01～0.10 mg/L,对市售矿泉水进行了检测,加标回收率在83％ ～100％,相对标准...     

Substoichiometry in neutron activation analysis technique

Neutron activation analysis has become one of the most sensitive and selective analytical technique for the determination of trace elements in a wide variety of matrices. Neutron activation involves the irradiation of the test sample and a standard of the element to be determined with thermal neutrons in a reactor, followed by dissolution of the test sample in the presence of carrier of the element to be determined. The carrier and radioisotopes are separated from the bulk of other induced activities (employing precipitation, solvent extraction, ion exchange etc.) and then the activity induced in the sample is measured on a suitable detector. The standard is treated identically. From the ratios of the activity of the sample and standard and the weight of the standard irradiated, the concentration of element in the test sample is calculated. A rapid, selective and sensitive method of radiochemical separation is subtoichiometric extraction in which the same amount of carrier is added to the irradiated test sample and standard. Exactly the same amount of reagent is added to both the sample and standard but in substoichiometric amounts, followed by the separation of the species formed by extracting it with an organic solvent. The activities of the extracts are measured. The amount of element present in the sample is calculated with help of the ratio of the activities and the weight of the standard taken. The advantages of the method are discussed. Application of substoichiometry in neutron activation has been elucidated with reference to the determination of Au in various samples by substoichiometric neutron activation analysis.     

Evaluation and application of internal standardization in atomic absorption spectrometry with electrothermal atomization

A new dual-channel system developed for use in atomic absorption spectrometry is used to assess the internal standard technique for electrothermal atomization. Cobalt was found to be a suitable internal standard for iron determinations, and is used for determination of 7—330 ng Fe ml^-1 in water samples. With use of the internal standard technique, fluctuations caused by atomizer variables are reduced and interferences from many cations are also decreased.     

Mössbauer emission spectroscopy of an unsupported cobalt-molybdenum hydrodesulfurization catalyst

A new internal standard method coupled with the standard addition method for PIXE analysis has been developed. In its basic principle, this method is characterized by that a suitable element present initially in the sample is used as an internal standard, and further the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample contains W_a g of trace element A to be determined together with an element B which is usable as an internal standard, and when the comparative standard is prepared by adding an exactly known amount of element A, W _a ^* g, to the duplicated sample, the absolute concentration of W_a can easily be determined by the following equation even if the above sample and comparative standard are irradiated separately by a different number of protons W_a=W _a ^* /[(R^*/R)-1] where R and R^* are ratios of net photopeak counts due to the characteristic X-rays from the element A and B in the irradiated sample and comparative standard, respectively. The usefulness of the method was examined through determination of Cu, Zn, Rb and Sr in two biological materials, such as spinach and orchard leaves. As a result, this method was demonstrated to be sensitive, highly reproducible and reasonably accurate.     

Can the usual validation standard series for quantitative methods,ISO 5725, be also applied for qualitative methods?

Repeatability standard deviation, laboratory standard deviation, and reproducibility standard deviation for quantitative methods according to ISO 5725 series were recently proposed to estimate the precision of qualitative measurements, giving a presence/absence response. In this paper, it is shown that for qualitative methods, the reproducibility standard deviation across laboratories does not reflect the performance of the method as suggested. It is demonstrated that the benefit of the respective laboratory standard deviation is very limited. Alternative performance measures are introduced which are based on another approach also directly linked to ISO 5725. Thereby, meaningful information about the precision of qualitative test methods can be achieved.     

A new internal standard method for activation analysis and its application. Determination of Co,Ni, Rb,Sr in pepperbush by means of photon activation

A new internal standard method for activation analysis has been developed. This method is characterized by that a suitable element present originally in the sample is used as an internal standard and the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample under examination contains W_ag of trace element A to be determined together with a known amount of element B which is usable as an internal standard, and when the comparative standard is prepared by adding W _a ^* g of accurately known small amount of the element A to the duplicated sample, even if the sample and comparative standard are irradiated separately by particles with different fluxes, W_a can be determined, easily by using the following equation: W_a=W _a ^* /[(A _R ^* /A_R)-1] Where A_R and A _R ^* are counting ratios of gamma-rays emitted by two radioactive nuclides produced from the element A and B in the sample and comparative standard, respectively. Neither correction of the inhomogeneities of flux between the sample and comparative standard, nor that of, the self-shielding effects are necessary for the present method. The usefulness of the method was examined through the determination of Co, Ni, Rb and Sr in pepperbush by means of photon activation, and the precision and accuracy of the method were proved to be valid.