Diffuse Reflectance Method Research Articles

Arsenate and Chromate Removal with Cationic Surfactant-Loaded and Cation-Exchanged Clinoptilolite-Rich Tuff vs Montmorillonite

Using a laboratory set-up, sorption of chromate and arsenate from aqueous solutions with the octadecylammonium acetate (ODA)-modified clinoptilolite was examined. In the experiments, a natural montmorillonite was compared with organically, i.e. surfactant-loaded clinoptilolite and with some inorganically substituted (Ag, Pb)-monoforms. The arrangements of the surface-attached ODA chains have been an important factor for the difference in the adsorption states of the guest species (oxyanions). A novel nanostructure inorganic-organic composite prepared has been investigated using SEM, thermogravimetry, UV-VIS diffuse reflectance and powder XRD spectral analytical methods. Finally, adsorption isotherms for the system studied have been measured. An approach for regeneration of exhausted surfactant-immobilized clinoptilolite with inorganic salt solutions under dynamic regime has been proposed.

Prediction of Tablet Hardness and Porosity Using Near‐Infrared Diffuse Reflectance Spectroscopy as a Nondestructive Method

The main objective of this research is to use the near‐infrared diffuse reflectance method to evaluate and quantify the effects of hardness and porosity on the near‐infrared spectras of tablets. To develop a model equation, validate the model and test the model predictive ability. Seven theophylline tablet formulations of the same composition but with seven different hardness values (3 kp, 6, 8, 10, 12, 15, and 17 kp) were prepared. Another seven theophylline tablets formulation with seven different porosity values (57.4, 50.3, 41.9, 40.3, 39.9, 37.3, and 35.1%) were prepared. Five placebo tablets formulation with different hardness and porosity values were also prepared. Laboratory hardness and porosity values were compared to near‐infrared diffuse reflectance data. Linear regression, quadratic, cubic and partial least square techniques were used to determine the relationship between hardness, porosity and the near‐infrared spectras. The results demonstrated that an increase in tablet hardness and a decrease in tablets porosity produced an increase in near‐infrared absorbance. Series of model equations depending on the mathematical technique used for regression were developed from the calibration of hardness and porosity data using laboratory equipment vs. the near‐infrared diffuse reflectance for each formulations. The results of near‐infrared hardness and porosity predictions were very similar to laboratory hardness and porosity tests. The near‐infrared diffuse reflectance spectroscopy method is an alternative nondestructive method for measurement of hardness and porosity of tablets.

ＩＳＯ白色度及び色の試験方法

Currently, there are two methods of brightness determination in JIS. One is JIS P 8123 (Testing method for brightness by Hunter of paper and pulp) and one is JIS P 8148 (Paper, board and pulps measurement of diffuse blue reflectance factor (ISO brightness)). JIS P 8123 was commonly used in Japan but was not popular in the world. In order to globalize the standard, JIS P 8148 : 1993 was prepared based on ISO 2470 : 1977 and revised at 2001 to adapt ISO 2470 : 1999. It is important to popularize this method in the Japanese pulp and paper industry.There is no method of color determination in P sector of JIS. At present, ISO 5631 (Paper and board-Determination of colour (C/ 2°)-Diffuse reflectance method) is under translation to JIS by JAPAN TAPPI. In this paper, the outline of JIS P 8148 : 2001 the determination of ISO brightness and ISO 5631 the determination of color are described.

Drift study of the products formed by radiolysis and photolysis of alkaline nitrates

The products of the radiolysis and photolysis of crystalline sodium, potassium, rubidium, cesium nitrates have been investigated by the diffuse reflectance infrared Fourier transform spectroscopy. The bands in the 1260-1220 and 804-809 cm−1 regions observed after the n -irradiation and photolysis by a light with the wave length 253.7 nm of crystalline alkali nitrates were identified as the vibrational modes of NO− 2 x 3 and x 2, respectively. The frequency of the x 3 oscillation of nitrite ions decreases from 1260 cm−1 up to 1220 cm−1 with the increase of the atomic weight or polarizability of a cation. The detection limit of the nitrite ions (1 ‐ 10−7 mol g−1) for the diffuse reflection method has been determined. The bands observed in KNO3, RbNO3 and CsNO3 spectra in the 947-940 and 722-737 cm−1 regions appearing only after photolysis are due to stretch oscillations of the peroxide bond O-O and wagging oscillations of the -ON=O group of peroxynitrite accordingly.

Trans-bis(dicyanamido)nickel(II) complexes with polyaza macrocyclic ligands

Two new trans-bis(dicyanamido)nickel(II) macrocyclic complexes, [Ni(II)(L1){N(CN)2}2] · H2O (1) and [Ni(II)-(L3){N(CN)2}2] (2), where L1 is 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane and L3 is 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane, have been synthesized and structurally characterized by spectroscopic and X-ray crystallographic methods. In (1) and (2), each central nickel(II) ion possesses a distorted octahedral geometry with four equatorial nitrogen atoms from the macrocycle and two axial nitrogen atoms from dicyanamide anions, which are terminally bonded to the central nickel atom. The solid state electronic spectra of (1) and (2) using the diffuse reflectance method show a characteristic high-spin d8 nickel(II) ion in a distorted octahedral environment.

Infrared Absorption Spectra of High Temperature Proton Conducting Ca2 + -Doped La2Zr2 O 7

Infrared (IR) absorption spectra of pyrochlore-type -doped proton conductors, i.e., and systems, were studied by the diffuse reflection method. The O-H stretching vibrations due to the protons dissolved in the crystal with negligible effects of adhesion and/or adsorption water could be detected by improvement of the sample preparation and the diffuse reflection technique. The bands, due to protons dissolved in the crystal, were distinctly different between the and the systems; three bands at 3517, 3401, and 3323 cm−1 for the system and six bands at 3517, 3430, 3414, 3371, 3341, and 3289 cm−1 for the system were observed. The stable sites for dissolved protons were distinctly different between the two systems. The wave numbers and the widths of the bands were higher and much sharper than those reported for the well-known perovskite-related-type proton conductors. It was concluded that the O-H bonds in -doped crystal are tight compared with perovskite-related-type proton conductors, and that definite stable sites for protons exist in -doped crystal. In the IR spectra of samples with various water vapor pressures, of proton dissolution treatment, the preferred dissolution of protons into the specific site was observed under low atmosphere. The details of the dissolution environment of protons are also discussed. © 2001 The Electrochemical Society. All rights reserved.

Spectroscopic Studies of Colloidal Solutions of Nanocrystalline Ru(bpy)32+−Zeolite Y

Preparation of suspensions of Ru(bpy)32+−zeolite Y has made it possible to use conventional optical transmission spectroscopic methods to examine the entrapped Ru(bpy)32+ species within the zeolite. To prepare the suspensions, the surface hydroxyl groups of nanocrystalline zeolite Y were silylated using n-octadecyltrichlorosilane. The hydrocarbon sheath on the surface of the zeolites prevented agglomeration of the particles and made the surface hydrophobic enough for dispersion in toluene. The spectroscopic properties of the entrapped Ru(bpy)32+ were measured via transmission techniques. For low levels of zeolite in the suspension (1 mg/10 mL), the scattering was low, and the absorption and fluorescence spectra of Ru(bpy)32+-entrapped zeolite Y were quantitatively identical to the solution spectra with comparable Ru(bpy)32+ concentrations. This suggests that all of the Ru(bpy)32+ inside the zeolite is being sampled and the extinction coefficient of the complex is not altered upon incorporation inside the zeolite. The nature of the quenching mechanism in the Ru(bpy)32+−viologen−zeolite Y system was studied by steady-state fluorescence and lifetime measurements, and it was determined to be mostly due to static quenching. Intrazeolitic electron transfer from the photogenerated viologen radical to Ru(bpy)33+ was followed by flash photolysis, and information about the dynamics of the electron-transfer process was obtained. Comparison of the electron-transfer and quenching data with previous studies on zeolite samples examined by diffuse reflectance methods led to the conclusion that, in reflectance measurements, mostly the surface of the zeolite is sampled. The suspensions, on the other hand, provide a method to examine molecules inside the crystal. Overall, this study demonstrates that zeolite-entrapped complexes can be examined using transmission spectroscopic techniques by using nanocrystalline zeolites with modified surfaces.

Synthesis and catalytic property of poly(styrene- co-divinylbenzene) supported ruthenium(III)-2-aminopyridyl complexes

Chloromethylated styrene-divinylbenzene copolymer beads with 8 and 14% cross-link were chemically modified by a reaction with 2-aminopyridine leading to the incorporation of nitrogen ligating sites on the surface of the polymer. These polymeric ligands, on treatment with a solution of ruthenium(III) chloride, gave the corresponding metal complex. The polymer supported Ru(III) complexes were characterized by elemental analysis, FT-IR, diffuse reflectance, SEM and DTA-TGA methods. The epoxidation of cis-cyclooctene, cyclohexene and styrene was investigated using the supported metal catalysts in presence of tert-butyl hydroperoxide as the terminal oxidant. Cis-cyclooctene gave the corresponding epoxide in a maximum yield of 51% whereas in case of styrene both styrene oxide and secondary oxidation product benzaldehyde were obtained in a combined yield of 95% under similar conditions. Surprisingly with cyclohexene as substrate the major product was 2-cyclohexene-1-one (64%) compared to the epoxide (2 %).

Solvatochromic Characterization of Organic−Inorganic Polymer Hybrids with Pyridinium N-Phenolate Betaine Dyes

We have estimated the local polarity in organic−inorganic polymer hybrids by employing solvatochromic pyridinium N-phenolate betaine dyes. Solvatochromic polymer was prepared by introducing Reichardt's betaine dye in the side chain of poly(2-methyl-2-oxazoline), and the model compound for the dye unit was also prepared. Polymer hybrids were prepared from these compounds and mixtures of various proportions of tetramethoxysilane (TMOS) and methyltrimethoxysilane (MeTMOS). The electronic absorption spectra were measured by the diffuse reflectance method. It was found that the local polarity in the polymer hybrids was affected by both the TMOS:MeTMOS ratio and the presence of the organic polymer. In addition, it was suggested that the dye molecules are preferentially surrounded by the organic polymer rather than the siloxane network in the polymer hybrids.

Simple Determination Method of Degree of Substitution for Starch Acetate

Abstract To develop a simple method to determine the degree of substitution (dS) for starch ester, we prepared starch acetate with various dS values (0—3) and examined the mode of starch-iodine complex formation for the starch acetate by monitoring the ultraviolet-visible (UV-vis) spectra and their Fourier-transform infrared (FT-IR) spectral changes. The effect of acetylation on the formation of the starch-iodine complex was investigated by monitoring the decrease in absorbance at 680 nm (blue value). The blue value decreased by increasing the standard dS value determined by NMR for starch acetate, but two different correlations between the blue values and the dS values were observed for the low- and highly-substituted starch acetate. The FT-IR spectra for starch acetate particles were measured using a diffuse reflection method. The peak areas and absorbances of the bands assigned to the acetyl group showed a poor correlation with standard dS values from the NMR. On the other hand, the FT-IR peaks assigned to sodium acetate produced by saponification of the starch acetate could be detected using the ATR (attenuated total reflection) method; they showed a good correlation with the standard dS values from the NMR. From these results, it was concluded that the ATR method should be available for the dS determination of starch acetate.

REDOX POTENTIAL IN THE TISSUE OF COLD-STORED APPLES AS AN INDICATOR OF ENZYMATIC ACTIVITY AND BROWNING

Under conditions of oxygen deficiency and lack of substrate of enzymatic browning that can develop inside apple flesh damaged by a redox electrode, a chemical balance appears. Redox measurements allow the determination of the kinetics of biochemical reaction lasting up to ten minutes within apple tissue, and of the redox potential distribution in apple tissue - the parameters specific for every cultivar. Redox potential can also be used to assess the susceptibility of apple flesh to enzymatic browning, quantified by means of the diffuse reflectance method. Moreover, the biochemical examination of apple varieties for the content of chlorogenic acid, epicatechin and phloretin glucoside shows that this group of phenolic compounds is responsible for establishment of redox potential values. Redox measurements have a potential value as a means to evaluate freshness and quality of minimally processed product.

Syntheses and structures of nickel(II) and copper(II) complexes with a 14-membered tetraaza macrocyclic ligand

Nickel(II) and copper(II) complexes of 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0 7.12]docosane ( L) were prepared, isolated and characterized as trans-[Ni(CH 3CN) 2( L)][PF 6] 2 ( 1) and trans-[Cu(CH 3CN) 2( L)][PF 6] 2 ( 2) by UV–Vis, IR and X-ray crystallography. In complex 1 the coordination geometry about the nickel atom is close to octahedral with four equatorial nitrogen atoms from the macrocycle and two axial nitrogen atoms from acetonitrile. The solid-state electronic spectrum of 1 using the diffuse reflectance method shows a characteristic high-spin d 8 nickel(II) ion in a distorted octahedral environment. However, the spectrum of 1 dissolved in acetonitrile indicates that the square-planar species is predominant over the octahedral species. The copper ion environment in 2 is similar to that of nickel complex 1, but the great tetragonal distortion in 2 is observed with much longer Cu–N (acetonitrile) distances than Ni–N (acetonitrile) distances in 1. The electronic spectrum of square-planar [Cu( L)][PF 6] 2 in acetonitrile or the spectrum of 2 dissolved in acetonitrile in the visible region is basically similar to that of the Nujol mull solid-state diffuse reflectance spectrum of 2, indicating that the square-planar [Cu( L)][PF 6] 2 coordinates to acetonitrile molecules to form 2.

Scattering dilution method in Fourier transform infrared spectrometry

For the measurement methods of powder samples or muddy samples using infrared spectrometry, we proposed the scattering dilution method and scattering filter method. In our methods, the fabricating pellets are made by pressing mixed alkali halide powders (KBr/CsI). That is why the dilution powder's (KBr/CsI powders') packing ratio becomes almost 100%, thus giving the pellets a sufficient scattering effect. These methods have novel advantages versus transmission or diffuse reflectance methods although our proposal has much criticism and negative comments.

Tritium release from Li 2O studied by infrared absorption spectroscopy

Desorption of a surface hydroxyl group of -OD on Li 2O into the sweep gas of dry Ar, Ar+H 2 or Ar+H 2O was studied by using a diffuse reflectance method with Fourier transform infrared absorption spectroscopy under controlled H 2O (D 2O) or H 2 (D 2) partial pressure. Under a D 2O containing atmosphere, multiple peaks due to surface -ODs were observed in the O-D stretching vibration region and they showed different dependencies on temperature or D 2O vapor pressure. The surface -OD observed at 2660 and 2520 cm −1 was removed by drying under Ar gas at 833 K. However, surface -OD at 2900, 2540 and 2490 cm −1 stayed on the Li 2O surface up to 973 K. In order to remove these -ODs at 833 K, addition of H 2 to the sweep gas was needed. It was also found that desorption of surface -OD was affected by the oxygen partial pressure near the surface. We also compared the observed results with those of in situ tritium release experiments (TTTEx).

In-Situ Observation of Surface Hydroxyl Group on Lithium Ceramics at High Temperature by Infrared Absorption Spectroscopy

Hydroxyl groups on the surface of Li 2 O were studied by using a diffuse reflectance method with Fourier transform infrared spectroscopy at high temperature up to 833K under controlled D2O or D 2 partial pressure. Multiple peaks due to the stretching vibration of O-D were observed at 2748, 2717, 2660, 2620, 2540, 2520, 2490cm -1 showing a different behavior with temperature or atmosphere. When D 2 was added to the sweep gas, peak intensity of 2660 and 2620cm -1 decreased. This result indicates that the surface nature is influenced by oxygen potential. Assignment of observed peaks to the surface nature was also discussed.

Comparison of photoacoustic, diffuse reflectance and transmission infrared spectroscopy for the study of carbon fibres

Three infrared spectroscopic methods—photoacoustic, diffuse reflectance and transmission—were evaluated for the qualitative analysis of carbon fibres. Transmission spectra of a potassium bromide (KBr) pellet detect the bulk of a carbon fibre, and are subject to interference by water in the KBr pellet. Extensive dehydration of a KBr pellet at elevated temperatures may cause chemical changes. In contrast, photoacoustic and diffuse reflectance methods are free of water interference. Both methods differentiate the near-surface region of a carbon fibre from its bulk, thus providing information about chemical structures in the near-surface. The photoacoustic, diffuse reflectance and transmission infrared spectra of a carbon fibre have similar band frequencies. Therefore diffuse reflectance and photoacoustic methods can be used for reliable qualitative analysis of carbon fibres.

In situ observation of surface -OH and -OD on lithium oxide

To elucidate the tritium release mechanism from the surface of solid breeding materials, surface -OH and -OD on Li 2O were studied at high temperature up to 400°C and under controlled H 2O (D 2O) vapor pressure or H 2(D 2) partial pressure by using a diffuse reflectance method of FTIR (Fourier transform infrared absorption spectroscopy). During the drying process of Li 2O, a large peak of precipitated LiOH was observed at 3662 cm −1. When D 2O vapor was added to a concentration higher than the precipitation limit, the O-D peak from LiOD was observed at 2696 cm −1. Below the limit D 2O vapor pressure, absorption peaks of isolated -OD on the surface were found at least at two positions: 2748 cm −1 and 2717 cm −1. This experimental fact shows that the surface is not homogeneous for D 2O adsorption. The peaks shifted to the lower wave numbers with the precipitation of LiOD at lower temperature. When D 2 was added to He + D 2O sweep gas, the intensity of the peak from isolated -OD became higher, indicating D 2 is dissociatively adsorbed on the Li 2O surface to produce -OD.

Fourier-transform infrared photoacoustic studies of hydrogenated diamond surfaces

Fourier-transform infrared photoacoustic spectroscopy (FTIR-PAS) is shown to be a useful tool for structural studies of hydrogen and/or oxygen chemisorption on the surface of diamond powders. As compared with the diffuse reflectance method or the KBr pellet method, it has become clear that PAS has an advantage in terms of surface sensitivity. The possibility of quantitative analysis of chemisorbed hydrogen has also been demonstrated.

UV-visible and near-IR spectra of heat-treated pitches during mesophase formation

Heat-treatment processes of various pitches have been monitored by the UV-visible and near-IR spectra measured with the diffuse reflectance method. The shape and intensity of the observed absorption bands changed with the heat treatment of the pitches, reflecting the size of the aromatic molecules and the degree of the intermolecular interactions. For pitches exhibiting spherical mesophase and flow optical texture, some parts of the isolated aromatic hydrocarbons are converted into the agglomerates with lamellar structure by the heat treatment and both fractions are present in a considerable amount with proper ratio. On the other hand, in the case of pitch exhibiting the mosaic optical texture, the isolated aromatic hydrocarbons are unstable, converting to the disordered carbon.

Complex formation of ruthenium(IV) and osmium(VIII) with 1,10-phenanthroline on the surface of silica sorbents

A study was made of the sorption of ruthenium(IV) and osmium(VIII) by silica and silica with chemically grafted sulpho groups from solutions containing 1,10-phenanthroline. Using diffuse reflection, luminescence and x-ray photoelectron spectroscopic methods, it was found that during sorption at pH 6–7 and room temperature on the surface of silica sorbents phenanthrolinate complexes of various composition are formed, bis- and tris(1,10-phenanthroline)metal (II, III), the Os(II) to Os(III) mole ratio being 2:1. A quantitative yield of tris(1,10-phenanthroline)metal(II) complex is obtained at 98 /+- 2 °C. The rate of complex formation on the surface of the sorbents considerably exceeds the rate of formation of the corresponding complexes in solution. It is suggested that silica sorbents have a catalytic action on the process of formation of complexes of ruthenium and osmium with 1,10-phenanthroline on the sorbent surface. A rapid sorption-luminescence method for determining ruthenium and osmium is proposed. The detection limit is 7 × 10 −4 μg ml −1 for ruthenium and 1 × 10 −3 μg ml −1 for osmium.