Etsuo Nishio

Determination of Methamphetamine and Its Related Compounds Using Fourier Transform Raman Spectroscopy

Fourier transform Raman spectroscopy (FT-Raman) is investigated as a simple and rapid method for the determination of the abused drug methamphetamine and its related compounds. Compounds can be reliably identified by using measurements made nondestructively and without the need for any sample preparation in around 1 min. The Raman spectrum of methamphetamine hydrochloride (MA) shows clear differences in spectra from a range of its related compounds such as amphetamine sulfate and ephedrine hydrochloride. These differences are adequate for spectral differentiation of the compounds. With the use of the FT-Raman technique, MA is also reliably identifiable to a detection limit of 1% (w/w) diluted in sodium chloride or water. FT-Raman spectra of MA were recorded through plastic packaging (polyethylene or polypropylene bags) typical of that used either by criminals for transportation or by law enforcement for containing and sealing evidence. Measurements could be made directly without removing the drug from the bag; excellent-quality spectra could be obtained with very little perturbation by the plastic bag.

Diffuse reflectance infrared Fourier transform spectral study of the thermal and adsorbed-water effects of a 3-aminopropyltriethoxysilane layer modified onto the surface of silica gel

Abstract Infrared absorption spectra of some polyaminopropylsiloxane (poly-APS) samples with different degrees of polymerization have been examined. The results show that this difference results in a marked variation in the environment of the NH 2 groups. The thermal and adsorbed-water effects on the silane-coated layer of silica gel samples, modified with 3-aminopropyltriethoxysilane (APTS), have also been investigated using a diffuse reflectance infrared Fourier transform (DRIFT) spectroscopic method. The results are summarized as follows. For the silica gel samples, the DRIFT spectral features in the CH stretch and NH 2 bend modes are almost independent of temperature within the range 303–373 K, indicating stable environments for the aminopropylsilyl segments of the silane-coated layer. For a sample which was treated with a higher APTS concentration, the spectral features were little affected by adsorption of water, while the effect of adsorbed water on a sample treated with a small APTS concentration led to observation of pronounced spectral features. These results have been ascribed to the difference in the degree of polymerization of the silane-coated layer between the samples.

Evaluation of interfacial properties in glass fibre-epoxy resin composites — reconsideration of an embedded single filament shear-strength test

An embedded single-filament shear-strength test was employed to explore the effect of the reinforced interface on the fracture of single filaments in glass fibre-epoxy resin composites. The interfacial effect was evaluated not only by critical fibre length but also by the fracture process of an embedded single filament observed by applying tensile load to the composites. The mean fragment length, measured at different tensile stresses, decreased with an increase in stress and finally reached a value correlated with critical fragment length. Interfacial reinforcement by silane treatment affects the fracture process rather than the critical fibre length. The behaviour was examined in several factors, such as filament diameter, the tension of filament on the moulding of composites, and the scatter of the composites in mechanical properties. A useful method was proposed to exclude such scatter: specimens treated on a half-length of embedded filament were subjected to this test. The present method leads us to confirm that the reinforced interface has no effect on the critical fibre length, while it does promote the progress of the fracture.

Kinetics of interaction of 3-aminopropyltriethoxysilane on asilica gel surface using elemental analysis and diffuse reflectanceinfrared Fourier transform spectra

In order to study the kinetics of interaction of 3-aminopropyltriethoxysilane (APTS) on silica gel, silica gel samples reacted with APTS were prepared by sampling the reaction mixture from the reactor at various time intervals, and the concentrations of 3-aminopropylsilyl (APS) groups modified on the silica gel surface were determined by elemental analysis. From the reaction time dependence of the APS concentration, it has been found that, after an initial fast reaction of APTS and silica gel, a slower second reaction and a much slower third reaction subsequently occur. For the three processes, the reaction rate constants (k obs /s -1 ) have been estimated and found to be k obs i =1.00×10 -1 s -1 for the initial reaction, k obs s =6.91×10 -3 s -1 for the second reaction and k obs t =4.20×10 -4 s -1 for the third reaction. The diffuse reflectance infrared Fourier transform (DRIFT) spectra were measured for the same samples. Bands at 3734–3739 cm -1 were observed in the OH stretch mode region, and were found to decrease in intensity with reaction time, reflecting the rate of reaction of APTS on the silica gel. Analysis of an OH stretching band has also furnished reaction rate constants that are very similar to those obtained from the time dependence of the APS concentration. A mechanism for the three reaction processes is postulated.

Fourier Transform Near-Infrared Attenuated Total Reflectance Spectroscopy of Silane Coupling Agents on Glass IRE

Attenuated total reflectance (ATR) has been shown to be highly sensitive for surface analysis. The major advantage of ATR is that the region of the specimen is restricted to a thin layer adjacent to the internal reflectance element (IRE). In an investigation of the surface reactions and interfacial effect of silane coupling agents on the surface of glass, a glass IRE was used in the near-infrared region (7000–4000 cm−1). This technique is useful for analyzing the near-surface of the glass IRE. By a comparison between each measured ATR spectrum and the transmission spectrum of the same glass IRE, it is possible to determine the mechanism of reaction of the silane coupling agent on the glass substrate. The process of dehydration was also investigated by calibration, with the use of the intensity of the band due to Si-OH groups. A condensation reaction occurs between molecules of the silane coupling agent in the bulk film. However, a small fraction of the agent reacts with the Si-OH groups of the glass at a lower rate. In this study, we show the transmission and ATR spectra of silane coupling agent reacted on a glass plate used for the IRE in the ATR method. With the use of the ATR method, the state of the dehydration condensation reaction, which involves hydrolyzing Si-OH at the surface, can be observed. Furthermore, the process of dehydration condensation reaction on the substrate of glass can also be compared with the bulk reactions measured by transmission.

Raman scattering study of the interaction of 3-aminopropyltriethoxy silane on silica gel. Time-dependent conformational change of aminopropylsilyl segments

Abstract Silica gel samples, modified with 3-aminopropyltriethoxy silane (APTS), have been prepared by sequentially sampling the substrate from the reaction vessel at various time intervals, and the Raman spectra of these samples have been measured. The CH stretch Raman bands at 2938 and 2981 cm −1 became more intense as the reaction proceeded. Kinetic analyses were then carried out, after making the assumption that the time dependence of relative Raman peak heights ( I 2938 / I 800 and I 2981 / I 800 ) is a pseudo-first order. The rate constants obtained are k =8.05×10 −4 s −1 for the 2938 cm −1 band and k =9.45×10 −4 s −1 for the 2981 cm −1 band. We may assume that the dependence of the change in intensity of the CH stretch Raman bands on time is a reflection of the change in conformation of the APS moieties.

Pyrolysis-GC/FT-IR Analysis for Silane Coupling Treatment of Glass Fibers

Pyrolysis gas chromatography coupled with FT-IR (Py-GC/FT-IR) has been applied to the study of silane treatment of E-glass fiber. The glass fiber treated with a silane coupling agent, γ-anilinopropyltrimethoxy-silane (AnPS), is pyrolyzed at 750°C. The pyrolysates are fractionated by GC and analyzed by FT-IR. The main fraction is assigned to the organofunctional group of the coupling agent. Thus, Py-GC/FT-IR enables us to identify the treated coupling agent qualitatively. A mixture of two different coupling agents, AnPS and γ-methacryloxypropyltrimethoxysilane on glass fiber, is separated and characterized from the spectra of fractions resulting from each coupling agent. Py-GC/FT-IR also provides quantitative information regarding the coupling agents on glass fiber. The total amount of the treated coupling agent is estimated according to the calibration curves, which are proportional to the amount of the coupling agent. Moreover, Py-GC/FT-IR enables us to evaluate the fixing ratio of the coupling agent to the total amount through washing the samples with methanol. The fixing ratio falls significantly above treatment concentration. This tendency is consistent with the results from nondestructive sampling preparation techniques in infrared spectroscopy. The above results indicate the usefulness of Py-GC/FT-IR for the evaluation of silane treatment.

An analytical investigation of silane coupling agents on glass fibres

Abstract Pyrolysis gas chromatography coupled with FTIR (Py-GC/FTIR) has been applied to the investigation of silane treatment of E-Glass fibres. The thermal decomposition products are fractionated organofunctional groups from the coupling agent. The fragments from the coupling agent can be identified by FTIR. Moreover, for a qualitative analysis, a mixture of structurally similar coupling agents can be analysed using Py-GC/FTIR. Thus this technique is useful for the qualitative identification of coupling agents or mixtures of coupling agents on treated fibres.

Vibrational Spectroscopic Evidence for the Associated-Anion Promotion of the Helical Structure of N-Acylglycine Oligomers

Vibrational spectroscopic evidence for conformational change of the anions of N-acylglycine oligomers (trimers, tetramers, and pentamers) in aqueous solution is reported. The infrared absorption spectra of sample solutions diluted below the critical micelle concentration (cmc) can be explained by the coexistence of several conformations containing the polyglycine I-like extended form and the polyglycine II-like helix. However, above the cmc the infrared bands arising from the polyglycine II-like helix are intensified. This result is due to preferential stabilization of the helical structure, promoted by intermolecular association of the anions. The helical structure is also stable in the hydrophobic environment of micelles.

Vibrational spectra of N-acylglycine oligomers and the long N-acyl chain effect

Trimers, tetramers and pentamers of N-acylglycine oligomer acid types with various acyl chains, their potassium or sodium salts, and their N-deuterated salts have been prepared. The vibrational spectra of these molecules have been measured and compared with those of polyglycine I (PGI; extended β form) and polyglycine II (PGII; helical form). Only a conformation similar to PGII exists in the solid state for these compounds. The long acyl chains induce a further PGII-like structure in the NH⋯OC and peptide skeletons. This effect is reflected markedly in the NH and ND stretching, amide I and II and low-frequency regions.