Temperature dependence of kinetics of triplet formation in phenazine: analysis by analogue computer

The temperature dependence of kinetic parameters of triplet phenazine have been determined by analysis of transient response to photoexcitation. The analogue computer used in the analysis is described.     

Der Mechanismus der Hydrolyse von Chlortriazinen in protischen Lösungsmitteln. II. Mitteilung Über nukleophile uromatische Substitutionen

The complex kinetics found for the hydrolysis of 1, 3, 5-trichloro-s-triazine in 9/91% (v) acetone/water at 10.0°C have been evaluated as a function of the hydroxyl ion and the acetate ion concentration using an analogue computer. The kinetics are consistent with a nonsteady state mechanism in which the primary intermediate anion is protonated giving a neutral species whose concentration goes through a maximum during the course of the reaction. This secondary intermediate forms the final product by deprotonation and release of a chloride ion. The product itself can undergo a second (reversible) deprotonation. In dimethylsulfoxide the analogous intermediate of the hydrolysis of 1, 3-dimethoxy-5-chloro-s-triazine can be identified by analysis of the NMR. and UV. spectra.     

Simulation techniques in analytical chemistry. Microcomputer-controlled simulation of the chromatographie process with an analogue computer

An analogue/digital hybrid interface is presented that allows the support of simulations on an analogue computer EAI 380 by a microcomputer PDP 11/34. On this simulation system the peak spreading process of a Chromatographie column was implemented as an example for a simulation of a dynamic process in analytical chemistry. To implement the Chromatographie mass balance equations on the analogue part of the simulation system, only one hardwired stage of a cascade of reactors is necessary. The output values of one analogue simulation step were stored by the microcomputer as intermediate results and were given back as input values during the next analogue simulation step. The simulation process can be seen on a screen and is easily modified by online variation of the simulation parameters.     

同位素稀释质谱法测定多肽含量

利用Leu-Phe作为模型肽,建立了水解后同位素稀释质谱测定多肽含量的方法。在实验中优化了酸水解的时间,采用高效液相色谱法和质谱法证明模型肽已完全水解。水解后的氨基酸经过HPLC分离,质谱检测采用选择离子监测模式,分别检测苯丙氨酸(m/z=166)和标记苯丙氨酸(m/z=174)的离子。根据苯丙氨酸的含量计算模型肽的含量,并评定了测定结果的不确定度。     

Trace quantitation of 4-hydroxy-2-nonenal in biological samples as its oxime-bis-tert.-butyldimethylsilyl derivative using 3-hydroxynonanal as an internal standard.

A gas chromatographic-mass spectrometric method for the determination of the lipid aldehyde 4-hydroxy-2-nonenal (4HNE) in trace quantities is described. The method utilizes the reaction of aldehydes with hydroxylamine leading to the formation of the oxime derivative. The aldehydes are recovered by octadecylsilyl solid-phase extraction and converted to the bis-tert.-butyldimethylsilyl derivatives for analysis using electron ionization. A novel 4HNE analogue, 3-hydroxynonanal, has been synthesized and is used as an internal standard. A limit of detection of approximately 1 pmol of 4 HNE in preparations of approximately 2.10(6) cells or 0.5 ml of whole blood, plasma or serum was observed. Standard addition analysis indicates that the method is accurate at these levels. Replicate analysis of the National Institutes of Standards and Technology Standard Reference Material SRM 909 indicates an average in-run precision of 8.1% and a between-run precision of 13.5% at an average concentration of 82.1 pmol/ml of reconstituted material.     

Qualitative and quantitative interpretation of gamma-ray spectra in activation analysis

A method is presented for the automatic identification of the elements present in a sample and the calculation of the corresponding concentrations from the energies and peak areas determined by a spectrum analysis computer program. A preliminary interpretation list is produced in which the possible isotopes are given for each peak in the spectrum. This list is based only on the gamma-ray energies and half-lives of the isotopes. A careful analysis of this list yields groups of identified elements at four different significance levels. The determination of the corresponding concentration is based on the single-comparator method. The procedure is included in an automatic activation analysis system but can also be used separately.     

Automated two-dimensional liquid chromatographic system for mapping proteins in highly complex mixtures.

An automated two-dimensional liquid chromatographic system was developed for systematic protein separations which could serve for analytical mapping and preparative separations of proteins. The system applies the principles of the column-switching technique, and consists of two different columns connected in tandem through an electrical column switching valve, two pumping systems to operate each column independently and a system controller to perform sequential chromatography on the two columns. A protein mixture is applied to the first-dimensional anion-exchange column and is separated by stepwise elution with an increasing sodium chloride concentration. The eluent is introduced directly to the second-dimensional reversed-phase column, and is further separated by gradient elution with an increasing acetonitrile concentration. The two elution stages are synchronized by a computer program. By this system, very complex protein mixtures such as crude cerebellar extracts were resolved reproducibly into ca. 200 peaks within 12 h. The method can be used for the total analysis of proteins in various tissues and cells without complicated premanupulation of samples, and allows the simultaneous analysis of a protein isolated by chromatography. The isolated protein is most suitable for use in the strategy of protein and gene sequence analysis.     

Computer techniques for three-dimensional analysis in atomic-absorption flame photometry

Flame methods, specifically in atomic-absorption work, have been augmented and enhanced by computer techniques for data reduction and mathematical analysis. Three-dimensional graphic display of experimental results allows for both a realistic and comprehensive approach to atomic-absorption analysis. The computer procedures and the mathematical techniques are described. Their coordination establishes quick, reliable, easily interpreted and useful results. The various equipment used is also described. The use of the remote scope (basically a cathode-ray tube) for immediate on-line display of three-dimensional data representation is explored. Several typical problems and their resulting solutions are presented in detail. Variations of absorbance are studied as a function of analyte concentration and a second variable: height of selection zone, concentration of interferent components, feed rate, slit width, or pressure of combustion gases. Variations of absorbance values are closely related to variations of percentual sensitivity.     

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.     

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.     

A computer controlled photon counting flame emission spectrometer

An automated emission spectrometer has been developed around a simple commercial instrument. The manner in which a computer is used for control and the way data are acquired and assimilated are discussed. The interfacing to the computer is described, sample programs are illustrated and methods of analyses are given. Sensing is achieved through photon counting. The linearity of the system has been examined and it was found that, for lithium, quantitative results can be obtained with an accuracy of 1 per cent for a concentration range of four orders of magnitude. The time required for analysis is discussed and, although the spectrometer is serial in nature, the increased information rate obtained through photon counting results in high speed data acquisition.     

Systematic drug receptor mapping: A new approach to the analysis of conformational energy calculations of flexible molecules with application to dopaminergic and adrenergic agonists

The computer program PRODIS is used to find low energy conformations of flexible molecules by searching the potential energy surface(s) of one or more torsion angles via rigid rotation. The n-dimensional grid of energy versus torsion angles is then converted to a Boltzman probability distribution, with the probability being represented not as a function of torsion angle, but rather a distance between two atoms. These atoms are chosen by comparison with a known, active analogue in which certain atoms have previously been determined as requirements for drug activity. PRODIS produces a list of low energy conformations, their corresponding interatomic distances and the Boltzman probability for each distance ±0.125, as well as the total probability for each conformation. The user also specifies a target interatomic distance and range (usually derived from a more rigid analogue) for which PRODIS lists all conformations and their Boltzman probability that meet this distance.     

Development of an improved method for trace analysis of chloramphenicol using molecularly imprinted polymers

A confirmatory method is described for the determination of the illegal antibiotic chloramphenicol using a specifically developed molecularly imprinted polymer (MIP) as the sample clean-up technique. The newly developed MIP was produced using an analogue to chloramphenicol as the template molecule. Using an analogue of the analyte as the template avoids a major traditional drawback associated with MIPs of residual template leeching or bleeding. The MIP described was used as a solid-phase extraction phase for the extraction of chloramphenicol from various sample matrices including honey, urine, milk and plasma. A full analytical method with quantification by LC-MS/MS is described. The method was fully validated according to the European Union (EU) criteria for the analysis of veterinary drug residues.     

Evaluation of the interaction of propranolol with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes: the partitioning model

The sorption behavior of the amine containing beta-receptor blocking agent propranolol (Ppn) in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) vesicles was investigated. Both protonated and unprotonated Ppn were measured in the continuous phase after removal of the vesicles containing sorbed Ppn by centrifugation. In contrast, by analyzing the surface charge density, deduced from electrophoretic mobility measurements, only the sorbed protonated Ppn was determined. A partitioning model was used to describe the sorption behavior. Sensitivity analysis revealed that sufficiently reliable and independent parameters were obtained. The partition coefficient of the unprotonated Ppn was about 22 times higher than that of the protonated analogue. Statistical analysis revealed a significant increase in the intrinsic partition coefficients of both Ppn analogues with an increase in the salt concentration.     

The line adsorption equation: the one-dimensional counterpart of the Gibbs adsorption equation

The thermodynamic development for multiphase contact lines is analogous to that for surfaces or interfaces. However, for one of the most important equations in surface thermodynamics, the Gibbs adsorption equation, the one-dimensional analogue is missing. This paper derives such an analogue, the line adsorption equation. Similarly to the Gibbs adsorption equation, the line adsorption equation is derived from Gibbsian thermodynamics. For a three-phase, three-component contact line system (e.g. an oil lens on the surface of an aqueous solution), the line concentrations (excesses) of two immiscible solvents can be made vanish by appropriately placing the dividing line. Consequently, the line concentration of the solute can be evaluated through the line tension change with the volume concentration of the solute. Such an evaluation provides information about molecular adsorption at the contact line, which is important in physical chemistry of lines, but difficult to obtain by any other means.     

Deconvolution of UV-VIS spectroelectrochemical thin-layer data for an EE electrochemical process

A deconvolution method, based on Fixed Size Window Evolving Factor Analysis (FSWEFA) has been developed to analyse the spectroelectrochemical sequence of spectra obtained in OTTLE electrodes for EE electrochemical processes. The analysis of the data permits to reconstruct the concentration profiles, the spectra of the intermediates and an optical analogue of the i vs E curve.     

Application of the least-squares method in the matrix form: simultaneous spectrophotometric determination of rifampicin and isoniazid in binary pharmaceutical formulations

A least-squares method in the matrix form is described for the simultaneous determination of rifampicin and isoniazid in a mixture. The method allows the rapid analysis of binary pharmaceutical formulations with minimum error. The concentration of each component in the mixture has been determined spectrophotometrically by measuring the absorbance of the mixture at 5-nm intervals from 230 to 290 nm. To calculate the matrix of the proportionality constant a standard mixture was used for each component. All data analyses were performed on a personal computer.     

基于3种非天然糖代谢标记的分泌蛋白质组分析性能对比

分泌蛋白质是调控细胞间信号转导的重要生物大分子。由于分泌蛋白的丰度相比于胞内蛋白以及培养基添加剂更低,因此分泌蛋白的高通量鉴定是目前蛋白质组学界研究的热点和难点。目前,基于生物质谱的分泌蛋白质组学分析一般均需要从无血清的条件培养基中获得分泌蛋白质,再对其进行富集和分析。该流程操作步骤繁琐,易造成分泌蛋白质的损失和降解。本工作采用基于生物正交化学生物学技术实现对分泌蛋白质的高选择性标记和高效富集。通过结合点击化学技术,综合评估了分泌蛋白质分析中用于代谢标记的不同糖类似物。采用3种最常用的商品化糖类似物,N-叠氮乙酰甘露糖胺(ManNAz)、N-叠氮乙酰半乳糖胺(GalNAz)和N-叠氮乙酰葡萄糖胺(GlcNAz)分别对HeLa细胞进行代谢标记,之后通过炔基生物素探针对条件培养基中的分泌蛋白进行富集,结合质谱分析来对比3种糖类似物对分泌蛋白的标记效率。最后通过无标定量蛋白质组学分析,系统评估了3种糖类似物用于分泌蛋白质组分析的性能。结果表明,基于ManNAz的分泌蛋白标记方法鉴定到了282个分泌蛋白、224个细胞质膜蛋白以及846个N-糖基化位点;对分泌蛋白的富集效率分别较GalNAz和GlcNAz提高了130%和67.2%;对细胞质膜蛋白的富集效率较GalNAz和GlcNAz分别提高了273.3%和148.7%,体现出了明显的优势。本研究的实验结果为分泌蛋白高选择性富集和系统分析提供了有益的对比分析和新技术策略。     

Determination of pesticides in waters by automatic on-line solid-phase extraction-capillary electrophoresis

The separation of seven pesticides by micellar electrokinetic capillary chromatography in spiked water samples is described, allowing the analysis of pesticides mixtures down to a concentration of 50 microg l(-1) in less than 13 min. Calibration, pre-concentration, elution and injection into the sample vial was carried out automatically by a continuous flow system (CFS) coupled to a capillary electrophoresis system via a programmable arm. The whole system was electronically coupled by a micro-processor and completely controlled by a computer. A C18 solid-phase mini-column was used for the pre-concentration, allowing a 12-fold enrichment (as an average value) of the pesticides from fortified water samples. Under the optimal extraction conditions, recoveries between 90 and 114% for most of the pesticides were obtained.     

Validation of a high-performance liquid chromatographic method for the enantiospecific quantitation of zopiclone in plasma

Zopiclone is a hypnosedative with clinical effects similar to benzodiazepines but thought to have less potential for rebound insomnia and withdrawal effects. Zopiclone is administered as a racemic mixture, and an enantiospecific method of analysis of zopiclone in plasma is desirable in the study of pharmacokinetic drug interactions. We report a modification of an HPLC method reported by Foster et al. using a closely related structural analogue of zopiclone as internal standard. Zopiclone was detected at 306 nm and linear calibration curves were constructed in the range of 1.0-250 ng/mL for each enantiomer. The % CV at 2.5 ng/mL was 12.0% for (-)-zopiclone and 14.3% for (+)-zopiclone, and the limit of quantification of each enantiomer was 2.5 ng/mL. At higher concentrations, the coefficient of variation was less than 10%. The nominal concentration of quality control samples was predicted with an accuracy within a range of +/-11.6%. The method was used in the analysis of plasma obtained from psychiatric patients. One sample obtained following a non-fatal overdose with zopiclone contained the metabolites (-)-N-oxide zopiclone and both enantiomers of desmethyl zopiclone. The metabolite enantiomers were resolved on the column with retention times similar to zopiclone. The N-oxide metabolite co-eluted with internal standard.