Approaches to quantitative structure-enantioselectivity relationship modeling of chiral separations using capillary electrophoresis

Quantitative structure-enantioselectivity relationships (QSERs) have been developed to describe the resolution of a series of chiral arylpropionic acids using capillary electrophoresis. Native beta-cyclodextrin and two derivatized forms are used as the chiral resolving agents. The QSER models are developed using the results of molecular mechanics calculations as input to multivariate linear regression and also to neural networks. Single models are developed to predict the optimum cyclodextrin to resolve a given analyte, the migration order, and the magnitude of the separation. Models are also developed to predict only the optimum cyclodextrin.     

Recent advances in automobile exhaust catalyst

Catalysts that were recently developed by Toyota for the control of automobile exhaust are reviewed. (1) A system combining a close-coupled catalyst with high heat resistance and an under-floor catalyst with high oxygen storage capacity were developed for low emission vehicles. (2) Based on a new concept, a three-way catalyst having the ability to store NOx at oxidizing atmosphere and to reduce stored NOx at stoichiometric or reducing atmosphere was developed for automotive lean burn engines. (3) A thin wall ceramic substrate was developed for better catalyst performance.     

Copolymerization at high conversion when the concentration of one monomer does not change

Exact equations and several computer programs were developed for use in studies on copolymerizations carried to high conversion when the concentration of one of the monomers (A) remains constant. Simple ACSL® and DESIRE® programs are described for simulating such copolymerizations, and their output was used to test programs and procedures that were developed to evaluate monomer reactivity ratios for such copolymerization systems. Based on an integrated form of the copolymer equation, Excel® and Fortran programs were developed for evaluating monomer reactivity ratios from information about initial monomer compositions, copolymer compositions, and the fractions of the second monomer (B) that reacted. A graphical procedure for evaluating monomer reactivity ratios from such data was also developed. A previous program developed for calculating information about monomer sequence distributions in copolymers was modified so that it would apply to copolymerization at high conversion when the concentration of one monomer remains constant. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1118–1128, 2000     

Miniature surface-plasmon resonance immunosensors – rapid and repetitive procedure

Miniaturized immunosensors based on surface-plasmon resonance (SPR) have been developed by using the sensor recently developed by Texas Instruments. By using this sensor for human immunoglobulin G (IgG) rapid and repetitive measurements could be performed by alternate injection of sample and glycine-HCl buffer. A sensor for human serum albumin (HSA) could also be developed similarly. One difficulty in immunosensor development is dissociation of the strongly bound antigen-antibody complex. A "regenerable" immunosensor has also been developed for this reason.     

Development of a portable survey meter system for the studies of uranium discovery

In this study, a portable radiation measurement system which has a microprocessor-controller was developed for uranium discovery. The developed system has the feature of saving the counting data from a Geiger–Mueller detector and position data from a global positioning system. The pulses obtained from the detector were transferred into a counting input of a microprocessor via a pulse shaper. Evaluation of the pulses has been performed by microprocessor’s software. The results obtained from the developed radiation detection system were compared with those of a calibrated reference detector system. The developed system has some important features such as low current consumption, low cost, small size and lightness.     

Quantitative analysis of the cholesterol-lowering drugs ezetimibe and simvastatin in pure powder, binary mixtures, and a combined dosage form by spectrophotometry, chemometry, and high-performance column liquid chromatography

Simple, accurate, sensitive, and precise UV spectrophotometric, chemometric, and HPLC methods were developed for simultaneous determination of a two-component drug mixture of ezetimibe (EZ) and simvastatin (SM) in laboratory-prepared mixtures and a combined tablet dosage form. Four spectrophotometric methods were developed, namely, ratio spectra derivative, ratio subtraction, isosbestic point, and mean centering of ratio spectra. The developed chemometric-assisted spectrophotometric method was the concentration residual augmented classical least-squares method; its prediction ability was assessed and compared to the conventional partial least-squares method. The developed HPLC method used an RP ZORBAX C18 column (5 microm particle size, 250 x 4.6 mm id) with isocratic elution. The mobile phase was acetonitrile-pH 3.5 phosphate buffer (40 + 60, v/v) at a flow rate of 1.0 mL/min, with UV detection at 230 nm. The accuracy, precision, and linearity ranges of the developed methods were determined. The developed methods were successfully applied for determination of EZ and SM in bulk powder, laboratory-prepared mixtures, and a combined dosage form. The results obtained were compared statistically with each other and to those of a reported HPLC method; there was no significant difference between the proposed methods and the reported method regarding both accuracy and precision.     

Separation of lanthanides using ion-interaction chromatography with HDEHP coated columns

A rapid and high resolution separation of lanthanides by HPLC technique has been developed using Di-(2-ethylhexyl) phosphoric acid (HDEHP) coated reverse phase column and a-hydroxy isobutyric acid as the complexing reagent for elution. A gradient elution technique has been developed for achieving the separation of the entire lanthanide series. Isocratic elution procedure has also been developed for the separation of lighter (La to Gd) as well heavier lanthanides (Lu to Tb). This paper describes the separation methods developed and their application for the determination of lanthanides in a fission product mixture.     

Design and performance of an automated single column sequential extraction chromatographic system

An automated extraction chromatographic system and its virtual instrument system based on LabVIEW platform have been developed and characterized to perform single column-based sequential radiochemical procedures. The developed system was characterized by its dead volume and memory effect pertinent to fluidic tubing, and the linearity of feeding pump speed. An automated sequential procedure was developed for the rapid and reproducible separation of strontium from calcium, barium and yttrium with strontium selective resin.

     

Comparison study of RNAA and ICP-MS for the determination of ultra-traces of Th and U in geological and cosmochemical samples

In order to determine thorium and uranium traces in geochemical and cosmochemical samples, we developed an ICP-MS procedure, in which an anion-exchange step was introduced after sample digestion to separate major matrix elements, leading to decrease the dilution factor and increase the sensitivity for Th and U. The ICP-MS procedure was compared to the RNAA procedure which we recently developed for the same purpose. Both ICP-MS and RNAA procedures developed were found to yield similar detection limits (sub ppb) for Th and U.     

Sequential simplex optimization and multichannel detection in HPLC: Application to method development

Summary The sequential simplex procedure for the optimisation of mobile phase composition in high-performance liquid chromatography (HPLC) is combined with multichannel detection. The operating software already available in a commercial LC system is exploited and extended to incorporate a number of new routines developed to facilitate HPLC method development. An efficient stop criterion for automated simplex procedures is proposed, based on continuous comparison of the chromatographic response function attained with that predicted. The theoretical basis is developed for a new peak homogeneity test, based on the wavelength sensitivity of the chromatographic peak maximum. An algorithm for assigning peak elution order, based on peak areas at multiple wavelengths, is developed for cases where multiple optima are recorded. The simplicity and practical utility of these techniques are demonstrated in the context of an HPLC separation method developed for a model system of six solutes.     

Cover Picture: Axis-Unfixed Biphenylphosphine-Oxazoline Ligands: Design and Applications in Asymmetric Catalytic Reactions (Chem. Rec. 10/2023)

The design and synthesis of chiral ligands plays an important role in asymmetric catalytic reactions. Over the past decades, various types of chiral phosphine-oxazolines (PHOX ligands) have been developed and have greatly advanced the field of asymmetric catalysis. Novel chiral PHOX ligand with an axis-unfixed biphenyl backbone, developed by our group, have shown interesting coordination behavior and excellent chiral inducing ability in various transition-metal-catalyzed asymmetric reactions. This personal account focuses on our developed axis-unfixed biphenylphosphine-oxazoline ligand (BiphPHOX), including an overview of its design and applications, which will provide inspiration for the exploration of novel ligands and related reactions.     

Immunochemical-based method for detection of hazelnut proteins in processed foods

A competitive enzyme-linked immunosorbent assay (ELISA) was developed to detect hazelnut by using polyclonal antibodies generated against a protein extract of roasted hazelnut. No cross-reactivity was observed in tests against 39 commodities, including many common allergens, tree nuts, and legumes. Hazelnut protein standard solutions at 0.45 ng/mL [inhibition concentration (IC80) of the competitive test] were clearly identified by the ELISA. An extraction and quantification method was developed and optimized for chocolate, cookies, breakfast cereals, and ice cream, major food commodities likely to be cross-contaminated with undeclared hazelnut during food processing. No sample cleanup was required when extracts were diluted 10-fold. Recovery results were generated with blank matrixes spiked at 4 levels from 1 to 10 microg/g hazelnut protein. With the developed extraction and sample handling procedure, hazelnut proteins were recovered at 64-83% from chocolate and at 78-97% from other matrixes. A confirmatory technique was developed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western transfer. The developed methods were applied to a small market survey of chocolate products and allowed the identification of undeclared hazelnut in these products.     

An infrared spectroscopic method for quantitative analysis of fatty alcohols and fatty acid esters in machinery oils

A new infrared spectroscopic method suitable for determining total fatty alcohol and fatty acid ester concentrations in industrial oils has been developed. Oil samples were diluted with toluene (1:3 w/w), the toxicity and volatility of which are relatively low compared with more commonly used IR solvents, like carbon tetrachloride or carbon disulfide. Mixture standards were prepared from dodecanol, tetradecanol, octadecanol, methyl stearate and methyl palmitate. Some analytical and statistical tests were performed on the developed method. The recoveries and the repeatability of the method proved to be sufficient for the quantitative determination of fatty alcohol and fatty acid ester additives in industrial oils. Reproducibility testing in another laboratory also produced satisfactory results. The developed method also proved to be relatively quick and simple. This method was developed to satisfy industry’s need to determine the concentrations of these oil additives, and it has already been applied successfully in machinery oil analysis.     

Atom-efficient Pd-catalyzed cross-couplings of chloroarenes with triarylbismuth reagents

Various Pd-catalyzed protocols have been developed for the atom-efficient cross-coupling of chloroarenes with triarylbismuth reagents. Using the developed protocols, an efficient synthesis of unsymmetrical biaryls in good to excellent yields was achieved by employing electron-deficient chloroarenes and a range of triarylbismuth reagents.     

Determination of Cefdinir by a stability-indicating liquid chromatographic method

A simple, fast, specific, stability-indicating, and precise reversed-phase liquid chromatographic method was developed for the determination of Cefdinir in its different dosage forms, i.e., capsules and suspensions. The method was developed and optimized by analyzing the placebo preparation, formulations, and degraded samples of the drug substance according to the International Conference on Harmonization. The proposed method can successfully separate the drug from degradation products formed under stress conditions along with pharmaceutical ingredients such as preservatives. The developed method was used successfully to determine Cefdinir in capsules and Insta-use suspensions. The developed method was found to be linear for a concentration range of 6-14 microg/mL. Average recoveries obtained with the method were 99.3 +/- 0.4 and 99.6 +/- 0.4% for Insta-use suspensions and capsules, respectively. The method was shown to be specific, precise, and robust.     

Computational techniques for vertex partitioning of graphs

A powerful vertex-partitioning algorithm is developed and applied for vertex partitioning of graphs of chemical and spectroscopic interest. The codes developed on the basis of these algorithms are tested and compared for performance with other methods based on the Morgan algorithm and the principal eigenvector algorithm based on the Givens-Householder method. The newly developed algorithm and codes appear to be more powerful than the Morgan and the principal eigenvector algorithms for vertex partitioning of graphs.     

On-line monitoring of granule growth in high shear granulation by an image processing system

A novel system has been developed to continuously monitor granule growth in a high shear granulation. The system consists of an image processing system and a particle image probe comprising a CCD camera, lighting unit and air purge system. Segregation during powder mixing was investigated experimentally and the optimal positioning of the probe was determined. High shear granulation was conducted using pharmaceutical powders, and granule size and product's yield of various size ranges were continuously measured by the developed system. Sieve analysis of the granulated products sampled out during the granulation was simultaneously conducted, and the obtained data was compared with that by the on-line image processing system. An extremely close relationship could be found between both data, proving that the developed system could monitor the granule growth accurately and continuously throughout the granulation. An on-off control system was developed to control the granulation process, and the performance of the system was confirmed.     

A modified approach to the phomoidrides: synthesis of a late-stage intermediate containing a key carbon quaternary stereocenter

A previously developed approach to the synthesis of the phomoidrides has been modified to incorporate all necessary carbon atoms prior to the key tandem carbonylation/Cope rearrangement reaction. This modification necessitated the synthesis of a challenging all-carbon quaternary stereocenter, which in turn rendered ineffective several reactions from the original synthesis. An oxidative radical cleavage of a spirocyclopropane ring system was developed that accomplishes the synthesis of the quaternary center, and a regioselective double hydroboration reaction was devised that provides an alternate approach to a key sequence of functional group interconversions, where the originally developed route was found to be ineffective.