Synthesis of an insulated molecular wire by click polymerization

We developed a new method for the synthesis of an organic-soluble insulated molecular wire (IMW) with permethylated cyclodextrin (PMCD); this method involves click polymerization of linked [2]rotaxane containing azide and alkynyl groups at both ends of a π-conjugated guest.     

Infrared laser spectroscopy of imidazole complexes in helium nanodroplets: monomer, dimer, and binary water complexes

Infrared laser spectroscopy has been used to characterize imidazole (IM), imidazole dimer (IMD), and imidazole-water (IMW) binary systems formed in helium nanodroplets. The experimental results are compared with ab initio calculations reported here. Vibrational transition moment angles provide conclusive assignments for the various complexes studied here, including IM, one isomer of IMD, and two isomers of the IMW binary complexes.     

Synthesis of Highly Insulated Molecular Wires by Polymerization of Organic-Soluble Symmetrical Linked Inclusion Complex Monomers

Summary: We developed a new method for synthesizing an organic-soluble permethylated cyclodextrin-based insulated molecular wire (IMW); this method involves the polymerization of a symmetrical linked inclusion complex as a monomer. This monomer was synthesized by dimerization of linked inclusion complexes at the terminal alkynyl groups by Glaser coupling. The polyrotaxane thus obtained is highly soluble in a variety of organic solvents and has a high covering ratio, regioregularity, and photoluminescence efficiency.     

Mass Spectrometry Parameters Optimization for the 46 Multiclass Pesticides Determination in Strawberries with Gas Chromatography Ion-Trap Tandem Mass Spectrometry

Multiclass analysis method was optimized in order to analyze pesticides traces by gas chromatography with ion-trap and tandem mass spectrometry (GC-MS/MS). The influence of some analytical parameters on pesticide signal response was explored. Five ion trap mass spectrometry (IT-MS) operating parameters, including isolation time (IT), excitation voltage (EV), excitation time (ET), maximum excitation energy or ??q?? value (q), and isolation mass window (IMW) were numerically tested in order to maximize the instrument analytical signal response. For this, multiple linear regression was used in data analysis to evaluate the influence of the five parameters on the analytical response in the ion trap mass spectrometer and to predict its response. The assessment of the five parameters based on the regression equations substantially increased the sensitivity of IT-MS/MS in the MS/MS mode. The results obtained show that for most of the pesticides, these parameters have a strong influence on both signal response and detection limit. Using the optimized method, a multiclass pesticide analysis was performed for 46 pesticides in a strawberry matrix. Levels higher than the limit established for strawberries by the European Union were found in some samples.     

Insulated molecular wires

An astonishing assortment of structures have been described as "insulated molecular wires" (IMWs), thus illustrating the diversity of approaches to molecular-scale insulation. These systems demonstrate the scope of encapsulation in the molecular engineering of optoelectronic materials and organic semiconductors. This Review surveys the synthesis and structural characterization of IMWs, and highlights emerging structure-property relationships to determine how insulation can enhance the behavior of a molecular wire. We focus mainly on three IMW architectures: polyrotaxanes, polymer-wrapped pi systems, and dendronized polymers, and compare the properties of these systems with those of conjugated polymers threaded through mesoporous frameworks and zeolites. Encapsulation of molecular wires can enhance properties as diverse as luminescence, electrical transport, and chemical stability, which points to applications in electroluminescent displays, sensors, and the photochemical generation of hydrogen.     

Influence of peak-broadening and interdetector volume error on size-exclusive chromatographic analysis with dual viscometric-concentration detection using the universal calibration method

The effect of peak-broadening and error in interdetector volume on the local calibration curve and experimental molecular-mass averages obtained by size-exclusion chromatography (SEC) with dual concentration/viscosity detection, and determination of molecular mass using the universal calibration (UC) method, is theoretically examined using a polymer sample with a molecular-mass distribution (MMD) approximated by the log-normal function. Although peak-broadening is often neglected, its effect on the slope of the local calibration curve and, consequently, on the experimentally obtained values of the weight-to-number average ratio is large. To obtain the right values of these parameters, a numerical correction is usually recommended. While using the UC method, the relationships between the extent of peak broadening, calibration slopes and interdetector volume are complex and can contribute to the occurrence of undiscovered errors. For this reason, an understanding of this problem, using a model, is necessary. The results of the UC method are compared with those obtained using dual-detection with known Mark-Houwink-Kuhn-Sakurada parameters (MHKS method), light-scattering (LS)/concentration detection as well as with the results obtained using conventional calibration. Due to peak-broadening, the slope of a local calibration curve and the weight-to-number average ratio, (Mw/Mn)", obtained using the UC method, increase compared to the theoretical values, whereas they decrease using the MHKS or LS methods. The increase when using the UC method is even larger compared to evaluation using conventional calibration. The effect of the error in interdetector volume on the slopes of local calibrations and the weight-to-number average ratios is opposite in the UC method to that found using the MHKS and LS methods.     

Extraction of uranium from simulated ore by the supercritical carbon dioxide fluid extraction method with nitric acid-TBP complex.

The supercritical fluid extraction (SFE) method using CO(2) as a medium with an extractant of HNO(3)-tri-n-butyl phosphate (TBP) complex was applied to extract uranium from several uranyl phosphate compounds and simulated uranium ores. An extraction method consisting of a static extraction process and a dynamic one was established, and the effects of the experimental conditions, such as pressure, temperature, and extraction time, on the extraction of uranium were ascertained. It was found that uranium could be efficiently extracted from both the uranyl phosphates and simulated ores by the SFE method using CO(2). It was thus demonstrated that the SFE method using CO(2) is useful as a pretreatment method for the analysis of uranium in ores.     

Direct detection method of oligosaccharides by high-performance liquid chromatography with charged aerosol detection

A simple and rapid detection method of oligosaccharides using high-performance liquid chromatography with a charged aerosol detection (HPLC-CAD) was studied. The direct detection of a sialylglycopeptide (SGP) derived from egg yolk was accomplished by HPLC-CAD using an amido-silica column, and its limit of detection was 0.40 pmol [signal-to-noise ratio (S/N) = 3]. The sensitivity of this method was lower than that of the fluorescence detection; however, the method showed approximately 5 times higher sensitivity than that using the conventional UV absorbance detection. Furthermore, this method was used for the analysis of the acid hydrolysis products of SGP. Monosialo- and asialo-oligosaccharides as well as free sialic acid were detected without using fluorescent derivatization. These results indicate that the present method is a new tool for the analysis of oligosaccharides.     

Pretilt angle generation by UV exposure during imidization of polyimide

We investigated pretilt angle generation and liquid crystal (LC) alignment by ultraviolet exposure during the imidization of polyimide (PI). The generated pretilt angle of a nematic (N) LC using an in situ photo-alignment method is smaller than that using a conventional photo-alignment method on a surface of PI having side chains. The NLC pretilt angles using an in situ photo-alignment method injected at isotropic phase increased with annealing were observed.     

Analysis of the Heterocyclic Aromatic Amines in Cigarette Smoke by Liquid Chromatography–Tandem Mass Spectrometry

In this paper, a sensitive accurate method for the determination of heterocyclic aromatic amines (HAAs) in cigarette smoke has been developed and validated using solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry. A calibration curve was obtained with representative cigarette smoke using the standard addition method to compensate for matrix effects because the smoke of different cigarettes shows similar matrix effects. With this method, the accuracy of the method can be improved using a common analog of HAAs, which will greatly reduce the expense of using an isotope-labeled internal standard. Validation results showed that the method has high sensitivity (quantification limits of 0.08–0.56 ng cig^?1), good reproducibility (RSD 6.37–9.31 %) and satisfactory recoveries (81.0–111 %). With this method, the emissions of HAAs in 30 commercial cigarette samples were analyzed and compared.     

Analysis of the Heterocyclic Aromatic Amines in Cigarette Smoke by Liquid Chromatography–Tandem Mass Spectrometry

In this paper, a sensitive accurate method for the determination of heterocyclic aromatic amines (HAAs) in cigarette smoke has been developed and validated using solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry. A calibration curve was obtained with representative cigarette smoke using the standard addition method to compensate for matrix effects because the smoke of different cigarettes shows similar matrix effects. With this method, the accuracy of the method can be improved using a common analog of HAAs, which will greatly reduce the expense of using an isotope-labeled internal standard. Validation results showed that the method has high sensitivity (quantification limits of 0.08–0.56 ng cig⁻¹), good reproducibility (RSD 6.37–9.31 %) and satisfactory recoveries (81.0–111 %). With this method, the emissions of HAAs in 30 commercial cigarette samples were analyzed and compared.

     

A simple method using on-line continuous leaching and ion exchange chromatography coupled to inductively coupled plasma mass spectrometry for the speciation analysis of bio-accessible arsenic in rice

A simple method for the speciation analysis of bio-accessible arsenic (As) in rice was developed using a continuous on-line leaching method to release the bio-accessible fraction. The continuous on-line leaching method has several advantages over commonly used batch methods including quicker and easier sample preparation, reduced risk of contamination and access to real time leaching data. The bio-accessibility of As in the samples was monitored using inductively coupled plasma mass spectrometry (ICP-MS). Results from a certified reference material as well as cooked and uncooked white rice showed that the majority of As was leached by saliva. Results obtained using the continuous on-line leaching method were comparable to those obtained using a batch method. Speciation analysis of the saliva leachate was performed using ion exchange chromatography coupled to ICP-MS. The four most toxic forms of As (As(III), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and As(V)) were clearly separated within 5 min in a single chromatographic run. Over 92% of bio-accessible As in the certified reference material and uncooked white rice sample was in the form of DMA and As(V), whereas it was present as DMA and As(III) in the cooked white rice.     

Studies on the RAST method using tray added disc

The radioallergosorbent test (RAST) provides a reliable method for detecting of specific IgE antibodies against a wide variety of antigens. The method using tube added disc for the estimation have been widely used in routine assay. In this study, the method using tray added disc has developed in our laboratory. The results were as follows; (1) The method using tray showed good correlation to the original method. (2) Characteristics of the method are rapidity, simplicity and economics. (3) The reaction well of tray is flat bottomed and is good for disc reaction. (4) Coefficients of variation for intra assay were; (d1): 9.40-9.68%, inter assay were 10.39-12.15% respectively. (5) The seasonal variation of positive allergens and the correlation of d to h, g1 to g3 were estimated. The method using tray seems to be one of the most useful routine methods of RAST assay and checking the seasonal variation of RAST will give good advantages to estimate the regional pollution of pollens allergy.     

Pretilt angle generation by UV exposure during imidization of polyimide

We investigated pretilt angle generation and liquid crystal (LC) alignment by ultraviolet exposure during the imidization of polyimide (PI). The generated pretilt angle of a nematic (N) LC using an in situ photo-alignment method is smaller than that using a conventional photo-alignment method on a surface of PI having side chains. The NLC pretilt angles using an in situ photo-alignment method injected at isotropic phase increased with annealing were observed.     

Flow-injection spectrophotometric determination of cyanate in bioremediation processes by use of immobilised inducible cyanase

A new flow injection (FI) method for photometric monitoring of cyanate in bioremediation processes using immobilised native cyanase is described. The method is based on the catalytic reaction between cyanate and bicarbonate to produce ammonia and carbon dioxide in the presence of an inducible native cyanase, immobilised in a reactor packed with glass beads. Two degrees of purification of the biocatalyst were used-heated cell-free extract and purified extract of cyanase from Pseudomonas pseudoalcaligenes CECT 5344. The ammonia produced by the enzymatic reaction is finally monitored photometrically at 700 nm using a modification of the conventional Berthelot method. The method furnishes different calibration curves depending on the degree of purification of the cyanase, with linear ranges between 1.23 and 616.50 micromol L(-1) ( r(2)=0.9979, n=7) and between 1.07 and 308.25 micro mol L(-1) ( r(2)= 0.9992, n=7) for the heated cell-free extract and the purified cyanase extract, respectively. No statistically significant differences between the samples were found in the precision study evaluated at two cyanate concentration levels using one-way analysis of variance. A sampling frequency of 15 h(-1) was achieved. The method was used to monitor cyanate consumption in a cyanate bioremediation tank inoculated with Pseudomonas pseudoalcaligenes CECT 5344 strain. The correlation between cyanate degradation and ammonia production was tested using a conventional method. Finally, the method was applied to different samples collected from the bioremediation tank using the standard addition method; recoveries between 85.9 and 97.4% were obtained.     

Detection of recombinant hirudin using capillary electrophoresis with laser-induced fluorescence detection

Hirudin, a thrombin inhibitor, is a polypeptide of 65 amino acids. To check purity levels and perform pharmacokinetic studies of recombinant hirudin (r-hirudin), a specific and reproducible analysis method is required. Capillary electrophoresis (CE) is rapidly becoming an important procedure for the analysis of biological molecules. Recently, CE combined with immunoassay has emerged as a new analytical technique. CE-based immunoassay (CEIA) is a sensitive and specific method combining laser-induced fluorescence (LIF) and immunoassay. Therefore, in this study, we specifically investigated fluorescence labeling and determination of r-hirudin by CEIA with a LIF detector using labeled r-hirudin and polyclonal antibody. r-Hirudin was labeled with fluorescein isothiocyanate (FITC). FITC-labeled r-hirudin was purified using high-performance liquid chromatography (HPLC). The method is based on preincubation of r-hirudin and antibody for 20 min, followed by CE analysis using an uncoated capillary. Free and bound r-hirudin were separated within 5 min using CE with high reproducibility. This study demonstrated that the CEIA method could be applied to quantitative analysis of r-hirudin in biological fluids.     

Synthesis of radioiodinated labeled peptides

This report covers optimization of radioiodination of peptides by both a direct method in which a constituent tyrosine residue is labeled and indirect method by using an iodinated derivative (SIB) of N succinimidyl 3-(tri-n-butylstannyl) benzoate (ATE) as the intermediate. Radioiodination of IgG and FMLF were performed by direct method using Chloramine-T as an oxidant but since Formyl-Methyl-Leucyl-Phenylalanine, FMLF, does not lend itself for direct radioiodination we performed labeling of FMLF by indirect method via radioiodined SIB at different pH.     

Comparison between amperometric and true potentiometric end-point detection in the determination of water by the Karl Fischer method

A rapid and sensitive method using true potentiometric end-point detection has been developed and compared with the conventional amperometric method for Karl Fischer determination of water. The effect of the sulphur dioxide concentration on the shape of the titration curve is shown. By using kinetic data it was possible to calculate the course of titrations and make comparisons with those found experimentally. The results prove that the main reaction is the slow step, both in the amperometric and the potentiometric method. Results obtained in the standardization of the Karl Fischer reagent showed that the potentiometric method, including titration to a preselected potential, gave a standard deviation of 0.001(1) mg of water per ml, the amperometric method using extrapolation 0.002(4) mg of water per ml and the amperometric titration to a pre-selected diffusion current 0.004(7) mg of water per ml. Theories and results dealing with dilution effects are presented. The time of analysis was 1-1.5 min for the potentiometric and 4-5 min for the amperometric method using extrapolation.     

A comparative study of the degradation of different starches using thermal analysis

Four starches obtained from different sources were treated to thermal analysis and their mechanisms of degradation were deciphered using a rising temperature method of evaluation. A comparison of the solid state reactivity between the four starches was made, using a method known as the alpha(s)-alpha(r) method. By this method, it was possible to differentiate between four starches of completely different plant origin. Potato starch and rice starch were found to have the highest reactivity.     

Thiocyanate and nitrite analysis using miniaturised isotachophoresis on a planar polymer chip

A new method has been developed to improve the determination of thiocyanate using isotachophoresis. This method uses complexation with copper(II) as a mechanism for improving the separation of thiocyanate from chlorate and perchlorate. By using a pH of 3.25 the method can also be used to analyse nitrite. Separations were carried out using a miniaturised poly(methyl methacrylate) (PMMA) separation device. Linearity was observed from 1.25 to 75 mg dm(-3) with a correlation coefficient of 0.998 for both thiocyanate and nitrite. Limits of detection for these two species were calculated to be 0.8 mg dm(-3) and 0.9 mg dm(-3) respectively. The method was successfully applied to the analysis of these anions in a range of samples including explosive residues.