New background correction method for liquid chromatography with diode array detection, infrared spectroscopic detection and Raman spectroscopic detection

A new method to eliminate the background spectrum (EBS) during analyte elution in column liquid chromatography (LC) coupled to spectroscopic techniques is proposed. This method takes into account the shape and also intensity differences of the background eluent spectrum. This allows the EBS method to make a better estimation of the background eluent spectrum during analyte elution. This is an advantage for quantification as well as for identification of analytes. The EBS method uses a two-step procedure. First, the baseline spectra are modeled using a limited number of principal components (PCs). Subsequently, an asymmetric least squares (asLS) regression method is applied using these principal components to correct the measured spectra during elution for the background contribution. The asymmetric least squares regression needs one parameter, the asymmetry factor p. This asymmetry factor determines relative weight of positive and negative residuals. Simulations are performed to test the EBS method in well-defined situations. The effect of spectral noise on the performance and the sensitivity of the EBS method for the value of the asymmetry factorp is tested. Two applications of the EBS method are discussed. In the first application, the goal is to extract the analyte spectrum from an LC-Raman analysis. In this case, the EBS method facilitates easy identification of unknown analytes using spectral libraries. In a second application, the EBS method is used for baseline correction in LC-diode array detection (DAD) analysis of polymeric standards during a gradient elution separation. It is shown that the EBS method yields a good baseline correction, without the need to perform a blank chromatographic run.     

Method for the detection of diethylamine, a metabolite of disulfiram, in urine.

Disulfiram is a drug used in the treatment of chronic alcoholism in man. Accurate assessment of patient compliance is important in this treatment. This paper describes a method for the detection and quantitative analysis of diethylamine, a metabolite of disulfiram, in urine. The method involves conversion of the water-soluble diethylamine in the urine to a derivative, N,N-diethyl-3,5-dinitrobenzamide, that is soluble in an organic solvent. This derivative is extracted from urine with diethyl ether and then subjected to thin-layer chromatography. A spectrophotometric procedure is used for quantification. This method provides a means of determining whether or not a patient is taking his prescribed disulfiram.     

微波加热快速测定腐植酸总量

利用微波加热技术，在密闭容器内通过压力浸提、消解试样、能大大加快分析速度，本实验测定了不同煤样中的腐植酸总量，讨论了功率、时间、酸度等因素对分析结果的影响，并与标准方法相对照，用ｔ－检验法及Ｆ－检验法检验，没有明显差异，结果令人满意，该法具有省时、省力、经济、不污染环境，宜于批量分析，便于普及推广等优点。     

A novel piecewise multivariate function approximation method via universal matrix representation

Multivariance in science and engineering causes problematic situations even for continous and discrete cases. One way to overcome this situation is to decrease the multivariance level of the problem by using a divide—and—conquer based method. In this sense, Enhanced Multivariance Product Representation (EMPR) plays a part in the considered scenario and acts successfully. This method brings up a finite expansion to represent a multivariate function in terms of less-variate functions with the assistance of univariate support functions. This work aims to propose a new EMPR based algorithm which has two new features that improves the determination process of each expansion component through Fluctuation Free Integration method, which is an efficient method in evaluating multiple integrals through a universal matrix representation, and increases the approximation quality through inserting a piecewise structure into the standard EMPR algorithm. This new method is called Fluctuation Free Integration based piecewise EMPR. Some numerical implementations are also given to examine the performance of this proposed method.     

Use of the o-phenylenediamine fluorescence system in the enzymatic assay of serum uric acid.

A manual enzymatic method is described for sensitive fluorometric determination of uric acid in human serum. This method is based on an enzymatic reaction with uricase to form hydrogen peroxide from uric acid and the following oxidation of o-phenylenediamine with peroxidase and hydrogen peroxide for the production of a fluorescence compound. The specificity and the selectivity in the method are due to the uricase reaction and the fluorometry, respectively. The formed fluorescence in the reaction mixture is measured at 410 nm (an excitation) and 550 nm (an emission). This enzymatic method can determine uric acid at 30-1000 microM, with a between-assay relative standard deviation of 4.35% or less. A good correlation is obtained between the present method and the colorimetric kit method.     

New applications of integral equations methods for solvation continuum models: ionic solutions and liquid crystals

We present a new method for solving numerically the equations associated with solvation continuum models, which also works when the solvent is an anisotropic dielectric or an ionic solution. This method is based on the integral equation formalism. Its theoretical background is set up and some numerical results for simple systems are given. This method is much more effective than three‐dimensional methods used so far, like finite elements or finite differences, in terms of both numerical accuracy and computational costs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Label-free quantitation: A new glycoproteomics approach

We demonstrate herein a method for quantifying glycosylation changes on glycoproteins. This novel method uses MS data of characterized glycopeptides to analyze glycosylation profiles, and several quality control tests were done to demonstrate that the method is reproducible, robust, applicable to different types of glycoproteins, and tolerant of instrumental variability during ionization of the analytes. This method is unique in that it is the first label-free quantitative method specifically designed for glycopeptide analysis. It can be used to monitor changes in glycosylation in a glycosylation site-specific manner on a single glycoprotein, or it can be used to quantify glycosylation in a glycoprotein mixture. During mixture analysis, the method can discriminate between changes in glycosylation of a given protein, and changes in the glycoprotein’s concentration in the mixture. This method is useful for quantitative analyses in biochemical studies of glycoproteins, where changes in glycosylation composition can be linked to functional differences; it could also be implemented in the pharmaceutical industry, where glycosylation profiles of glycoprotein-based therapeutics must be quantified. Finally, quantification of glycopeptides is an important aspect of glycopeptide-based biomarker discovery, and our quantitative approach could be a valuable asset to this field as well, provided the compositions of the glycopeptides to be quantified are identifiable using other methods.     

A new method to test the effectiveness of sunscreen ingredients in a novel nano-surface skin cell mimic

Photophysical properties of sunscreens are commonly studied in solvent media, which do not mimic the skin, or in complex artificial skin systems, which are difficult to handle. In an earlier study, we showed that polystyrene nanosphere suspensions mimic the mixed polarity environment of skin cell systems. This paper presents a new method to quantify the effectiveness of sunscreens in the polystyrene nanosphere environment. This method utilizes the intrinsic UV-B fluorescence of polystyrene nanospheres. We studied three UV-B sunscreens by this new method and compared their extinction coefficients with observed values in solvent. The values follow the trend observed in solvents, but the ratio of their extinction coefficient in solvent to the value obtained by this new method is 1.3-1.8 instead of 1. This difference might be caused by the mixed polarity or the microgeometry of the nanosphere system. Regardless of the difference in the extinction coefficients, this new system can be used to test hundreds of chemicals for their sunscreening potential in a cost-effective way. One marked advantage of this new method is its ability to test both hydrophobic and hydrophilic sunscreening chemicals in the same environment. This is virtually impossible for current solvent-based models, which require different solvents for hydrophobic and hydrophilic chemicals. The new method also allows the simultaneous evaluation of a host of photophysical properties of sunscreening chemicals.     

Label dilution method: a novel tool for bioligand interaction studies using bead injection in the lab-on-valve format

This work introduces a novel method, label dilution, which is analogous to the well-established isotope dilution method. The principle is tested on a model system of commercially available antibodies and protein-coated Sepharose beads and implemented using micro-bead injection in the lab-on-valve format. This micro-scale method uses a labeled form of the target molecule as an internal standard. Label dilution employs ratiometric measurements using the absorbance signals from the label and the target molecules for quantitative determination of an analyte. The label dilution method is shown to discriminate between selective and non-selective binding and provides a means for monitoring bioligand interactions in real time. With a detection limit of 470 ng of IgG, this method provides a sensitive, automated technique for the determination of low-level analytes in complex samples. This technique has been developed with the aim of using it to facilitate diabetes research in which the interactions between autoantibodies and the molecules they target are a central focus.     

A cheap gas-liquid-solid method for nanodeposition of iron on the surface of flaky graphite powder

A cheap gas-liquid-solid method to prepare a nanodeposition of iron on the surface of a micrometer-size flaky graphite powder is described. This method is suited not only for spherical, but also nonspherical small substrates. The method is only a one-step process, in which decomposition of iron pentacarbonyl is induced by nitrogen gas in a 90 degrees C reactor. This synthetic route simplifies the operation procedure and manufacturing equipment, and decreases the reaction temperature, compared with conventional liquid-solid-phase methods and gas-solid-phase methods.     

Improved HPLC determination of urinary neopterin

In order to improve the urinary neopterin measurement, the reversed-phase HPLC method has been reevaluated. The parameters which influence the chromatographic behavior of 12 pteridines were studied: nature of buffer, pH, ionic strength, addition of organic modifier to the mobile phase. Accordingly, an isocratic HPLC method is described which offers a good compromise between specificity and analysis time. This method is well-suited to automation in routine clinical laboratory use. Using this HPLC method, urinary neopterin related to creatinine was determined in lung diseases (neoplasm, sarco?dosis and bronchial asthma) and in kidney allografts. This method was shown to be useful in the diagnosis and in the monitoring of treatment of rejection episodes.     

Application of MALDI TOF/TOF mass spectrometry and collision-induced dissociation for the identification of disulfide-bonded peptides

This paper describes a method for the fast identification and composition of disulfide-bonded peptides. A unique fragmentation signature of inter-disulfide-bonded peptides is detected using matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF)/TOF mass spectrometry and high-energy collision-induced dissociation (CID). This fragmentation pattern identifies peptides with an interconnected disulfide bond and provides information regarding the composition of the peptides involved in the pairing. The distinctive signature produced using CID is a triplet of ions resulting from the cleavage of the disulfide bond to produce dehydroalanine, cysteine or thiocysteine product ions. This method is not applicable to intra-peptide disulfide bonds, as the cleavage mechanism is not the same and a triplet pattern is not observed. This method has been successfully applied to identifying disulfide-bonded peptides in a number of control digestions, as well as study samples where disulfide bond networks were postulated and/or unknown.     

New Measuring Method in Isothermal Titration Calorimetry Based on a Proportional-Integral Controlled System

This paper introduces a new measuring method in Isothermal Titration Calorimetry (ITC). This method, based on a proportional-integral control system, offers many important advantages when compared to the frequently used proportional control: higher signal-to-noise ratio, improved stability of baseline, increased static and dynamic sensitivity, similar or smaller time constants and calibration constant independent of the control parameters. Here an experimental proof of this method is detailed and full theoretical foundation will be discussed in a next paper. This revised version was published online in July 2006 with corrections to the Cover Date.     

火焰原子吸收光谱法快速测定水性漆中镉

研究了水性漆中镉的原子吸收法分析。采用干灰化法处理漆片试样,硝酸消解,ＦＡＡＳ测定,加标回 在８７．８￣９６．４％     

Conjugate addition of sodium methanesulfinate to vinyl pyridines and diazines for the synthesis of aliphatic sulfones

A convenient method to introduce a sulfone group to pyridines and diazines is described. This efficient method involves the conjugate addition of sodium methanesulfinate to vinyl heterocycles. This process tolerates a wide variety of functional groups and is performed in the presence of acetic or trifluoroacetic acid. A one-pot, two-step synthesis of sulfones starting from the corresponding heteroaryl halide is also described.     

Multivariate data modelling through Piecewise generalized HDMR method

This work aims to develop a new High Dimensional Model Representation (HDMR) based method which can construct an analytical structure for a given multivariate data modelling problem. Modelling multivariate data through a divide-and-conquer method stands for multivariate data partitioning process in which we deal with a number of less variate data sets instead of a single N dimensional problem. Generalized HDMR is one of these methods used to model a multivariate data set which has a number of scattered nodes with associated function values. However, Generalized HDMR includes a linear equation system with huge number of unknowns and equations to be solved. This equation sometimes has linearly dependent equations in it and this is an undesirable situation. This work offers a new method named Piecewise Generalized HDMR method which bypasses this disadvantage as well as reducing the mathematical complexity and CPU time needed to complete the algorithm of the previous method. Our new method splits the given problem domain into subdomains, applies the Generalized HDMR philosophy to each subdomain and superpositions the information coming from these subdomains. The algorithm of this new method and a number of numerical implementations are given in this paper.     

Size distribution analysis of polymer latex systems by use of extrema in the angular scattering intensity

The angular position of the extrema of the vertically polarized scattering intensity has previously been utilized for a method of particle size analysis for systems of monodisperse, spherical, isotropic particles which conform to the Rayleigh-Gans-Debye theory. The consequences of a finite polydispersity, which is always present in real systems, was not assessed and the application of the method has resulted in erroneous characterization of some latex systems. This work is concerned with (1) reporting the effects of finite polydispersity on the method of analysis, (2) pointing out previous misuse of the method, and (3) introducing a method of analysis which is based on the position of the extrema but which also considers polydispersity and the exact Mie calculation. This method enables one to characterize a scattering system in terms of a modal diameter and a distribution-width parameter by utilizing prepared diagrams for a particular relative refractive index.     

用模糊数学评价中成药质量的方法研究

本研究应用模糊数学中ISODATA(Interactive Self-Organizing Data Analysis Technique A)聚类分析法,把不同厂家的同一品种中成药分成五个等级,即Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ级品。并根据此分级结果构造一个多元隶属函数,提出一种模糊模型的等级识别法,为制定各类中成药质量判别标准提供了依据。本文用十个厂家共三十个批号的冠心苏合丸验证,效果满意。     

Determination of the Concentrations of Metal Cations in Aqueous Solutions Using Proton NMR Spectral Area Integration of the EDTA Complexes

This paper introduces an alternative method to determine the concentrations of metal cations in aqueous solutions, using area integration of proton NMR spectra of EDTA (the disodium salt of ethylenediaminetetraacetic acid) metal complexes. Using this method, a certain volume of unknown metal cation solution is added to an excess amount of standard EDTA solution, and the ratio of the remaining free EDTA and the EDTA–metal complex in the solution can be calculated from the integration areas of the proton NMR spectra. Unlike the conventional complexometric titration, where indicators need to be used to determine the endpoint, this NMR method aims to provide a simple method to eliminate the need for using indicators. This method, when EDTA is used as the standard, is valid for determining the concentrations of nonparamagnetic transition and rare earth metal cations, and for the concentrations of group IIIA and IVA metal cations.     

A comprehensive two-dimensional gas chromatography method for analyzing extractable petroleum hydrocarbons in water and soil

A flow-switching two-dimensional gas chromatography (GCxGC) apparatus has been constructed that can operate at temperatures as high as 340 degrees C. This system is employed to analyze complex hydrocarbon mixtures such as diesel fuel, gas-oil, motor oil, and petroleum contaminated environmental samples. The GCxGC system generates two-dimensional chromatograms with minimal overlap between the aliphatic and aromatic regions This allows these compound classes to be independently quantitated without prior fractionation. The GCxGC system is used to analyze extracts of spiked water samples, wastewater, and soil. The accuracy of the method is compared to that of the Massachusetts Extractable Petroleum Hydrocarbons (MA EPH) method. The GCxGC system generates a quantitative accuracy similar to the MA EPH method for the analysis of spiked water samples. The GCxGC method and the MA EPH method generate comparable levels of total hydrocarbons when wastewater is analyzed, but the GCxGC method detects a significantly higher aromatic content and lower aliphatic content. Both the GCxGC method and MA EPH method measure comparable levels of aromatics in the soil samples.