Multivariate standard addition method solved by net analyte signal calculation and rank annihilation factor analysis

This article describes the use of the net analyte signal (NAS) concept and rank annihilation factor analysis (RAFA) for building two different multivariate standard addition models called “SANAS” and “SARAF.” In the former, by the definition of a new subspace, the NAS vector of the analyte of interest in an unknown sample as well as the NAS vectors of samples spiked with various amounts of the standard solutions are calculated and then their Euclidean norms are plotted against the concentration of added standard. In this way, a simple linear standard addition graph similar to that in univariate calibration is obtained, from which the concentration of the analyte in the unknown sample and the analytical figures of merit are readily calculated. In the SARAF method, the concentration of the analyte in the unknown sample is varied iteratively until the contribution of the analyte in the response data matrix is completely annihilated. The proposed methods were evaluated by analyzing simulated absorbance data as well as by the analysis of two indicators in synthetic matrices as experimental data. The resultant predicted concentrations of unknown samples showed that the SANAS and SARAF methods both produced accurate results with relative errors of prediction lower than 5% in most cases.     

Modular Breath Analyzer (MBA): Introduction of a Breath Analyzer Platform Based on an Innovative and Unique,Modular eNose Concept for Breath Diagnostics and Utilization of Calibration Transfer Methods in Breath Analysis Studies

Exhaled breath analysis for early disease detection may provide a convenient method for painless and non-invasive diagnosis. In this work, a novel, compact and easy-to-use breath analyzer platform with a modular sensing chamber and direct breath sampling unit is presented. The developed analyzer system comprises a compact, low volume, temperature-controlled sensing chamber in three modules that can host any type of resistive gas sensor arrays. Furthermore, in this study three modular breath analyzers are explicitly tested for reproducibility in a real-life breath analysis experiment with several calibration transfer (CT) techniques using transfer samples from the experiment. The experiment consists of classifying breath samples from 15 subjects before and after eating a specific meal using three instruments. We investigate the possibility to transfer calibration models across instruments using transfer samples from the experiment under study, since representative samples of human breath at some conditions are difficult to simulate in a laboratory. For example, exhaled breath from subjects suffering from a disease for which the biomarkers are mostly unknown. Results show that many transfer samples of all the classes under study (in our case meal/no meal) are needed, although some CT methods present reasonably good results with only one class.     

Significance of absolute energy scale for physics at BESⅢ

The effects of absolute energy calibration on BESⅢ physics are discussed in detail,which mainly involve the effects on τ mass measurement,cross section scan measurement,and generic error determination in other measurements.     

Variable selection for multivariate calibration using a genetic algorithm: prediction of additive concentrations in polymer films from Fourier transform-infrared spectral data

Variable selection using a genetic algorithm is combined with partial least squares (PLS) for the prediction of additive concentrations in polymer films using Fourier transform-infrared (FT-IR) spectral data. An approach using an iterative application of the genetic algorithm is proposed. This approach allows for all variables to be considered and at the same time minimizes the risk of overfitting. We demonstrate that the variables selected by the genetic algorithm are consistent with expert knowledge. This very exciting result is a convincing application that the algorithm can select correct variables in an automated fashion.     

Monochromator Wavelength Calibration Standards Extending into the Near-Infrared Using Second- and Third-Order Emission Lines from Mercury Vapor Lamps

The emission spectra of four mercury vapor lamps are used to obtain wavelength calibration curves for the double-grating emission monochromator of a spectrofluorimeter. The use of second- and third-order diffraction lines and emission lines from the argon carrier gas provides a rich spectrum, which extends well into the near-infrared spectral region and produces an improved calibration curve. More than 60 emission lines are listed between 250 and 900 nm, which is sufficient to produce an extremely accurate monochromator calibration. Additional second- and third-order lines can be used to even longer wavelengths (>1200 nm). The effectiveness of three scattering surfaces is compared.     

DSC Calibration During Cooling. A survey of possible compounds

A number of compounds is investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions and can be applied both for temperature and for heat calibrations. A third compound, namely 4,4’-azoxyanisole, has a liquid crystal to isotropic liquid transition at 409K. This compound can be used for temperature calibration. Heat calibration with this compound is more problematic because of the small heat effect and the construction of the baseline. Other compounds like NaNO₃, In, Hg and Pb, show a slight supercooling. Nevertheless they can be used for heat calibration. The use of large samples of NaNO₃ and In gives the possibility to construct the equilibrium onset temperatures of the cooling peaks, so these two compounds are also appropriate for temperature calibration on cooling. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of robustness based on n-way models in the spectrofluorimetric determination of tetracyclines in milk when quenching exists

An important step in the validation of an analytical procedure is the study of its robustness. In the case of spectrofluorimetric determinations, quenching introduces specific problems which are approached in this paper for the particular case of tetracyclines determination in milk. Quenching can be detected with excitation emission matrices (EEM) signals and a three-way Parallel Factor (PARAFAC) decomposition and modelled by means of a four-way PARAFAC decomposition which reproduces the physical model of this effect.The robustness of the method is evaluated by including changes in seven experimental variables: trichloroacetic acid (TCA) volume solution used in the precipitation of milk proteins, revolutions per minute, time and temperature in the centrifugation step, pH and emission-excitation slit width in the fluorimetric analyte determination and the analyst. The robustness analysis is carried out by means of a Plackett-Burman experimental design as it is suggested by European Decision 2002/657/EC (European Decision (EC) No. 2002/657/EC of 12 August 2002, implementing Council Directive 96/23/EC, concerning the performance of analytical methods and the interpretation of results, Off. J.L 221, 17/8/2002, 8). The analyte concentration will be taken as response in the Plackett-Burman experimental design instead of the signal as it is habitual in these cases. Therefore, a three-way Partial Least Squares (3-PLS) calibration models with EEM signal is needed.When an analogous study is carried out for tetracycline (TC) in the absence of chlorotetracycline (CTC) as interferent, univariate calibration is employed, being able to conclude that in the robustness analysis, different factors are significantly active when quenching exists.     

X光CCD响应特性研究

 在北京同步辐射源上建立了X光CCD(Charge-Coupled Device)量子效率实验标定方法，获得了150eV至1500eV能区范围多个X光能点的量子效率实验结果，发展了X光CCD量子效率简化计算模型，并对X光CCD表面油沾污对量子效率的影响进行了实验研究和修正。结果表明经过油沾污修正后的简化理论模型计算结果与实验标定结果符合较好。     

HLS新研制的束流位置探测器定标和误差分析

介绍了NSRL二期工程中,为存储环上注入段真空盒改造而新研制的8组束流位置探测器的定标和数据处理过程及其探头定标电场的拟合和误差计算结果.介绍了专门用于BPM信号处理模块的电子学系统以及它的运行性能.     

Assay of free captopril in human plasma as monobromobimane derivative,using RPLC/(+)ESI/MS/MS: validation aspects and bioequivalence evaluation

A sensitive method for determination of free captopril as monobromobimane derivative in plasma samples is discussed. The internal standard (IS) was 5‐methoxy‐1H‐benzimidazole‐2‐thiol. Derivatization with monobromobimane immediately after blood collection and plasma preparation prevents oxidation of captopril to the corresponding disulfide compound and enhances the ionization yield. Consequently, derivatization enhances sample stability and detection sensitivity. Addition of the internal standard was made immediately after plasma preparation. The internal standard was also derivatized by monobromobimane, as it contains a thiol functional group. Preparation of plasma samples containing captopril and IS derivatives was based upon protein precipitation through addition of acetonitrile, in a volumetric ratio 1:2. The reversed‐phase liquid chromatographic separation was achieved on a rapid resolution cartridge Zorbax SB‐C₁₈, monitored through positive electrospray ionization and tandem MS detection using the multiple‐reaction monitoring mode. Transitions were 408–362 amu for the captopril derivative and 371–260 amu for the internal standard derivative. The kinetics of captopril oxidation to the corresponding disulfide compound in plasma matrix was also studied using the proposed method. A linear log–log calibration was obtained over the concentration interval 2.5–750 ng/mL. A low limit of quantitation in the 2.5 ng/mL range was obtained. The analytical method was fully validated and successfully applied in a three‐way, three‐period, single‐dose (50 mg), block‐randomized bioequivalence study for two pharmaceutical formulations (captopril LPH 25 and 50 mg) against the comparator Capoten 50 mg. Copyright © 2009 John Wiley & Sons, Ltd.