Raman Spectroscopic Determination of the Degree of Cationic Modification in Waxy Maize Starches

ABSTRACT

Waxy (essentially amylose-free) maize starch was chemically modified to varying degrees by treatment with 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (CHPTAC), and the degree of cationic modification was determined by a standard wet chemistry method. FT-Raman spectra of the modified starches were taken, and a characteristic Raman band ～761 cm^?1 was found. This 761 cm^?1 Raman band's intensity depended on the level of cationic modification of the starch. The ratio of intensity of the ～761 cm^?1 band to a ～715 cm^?1 C-C stretch Raman band (used as an internal standard) was plotted versus the amount of cationic modification derived by titration analysis, and a linear fit was obtained with a correlation of 0.998. The FT-Raman spectroscopy method presented here demonstrates a rapid non-destructive way to determine the level of cationic modification of waxy maize starch, and should be suitable for use with cationic modified starches of any amylose content.     

Raman Spectroscopic Determination of the Percent of Acetylation in Modified Wheat Starch

Abstract

Raman spectroscopy was developed as an analytical method for rapid determination of the degree of acetylation in chemically modified wheat starches. The carbon oxygen double bond stretch Raman peak (～1732 cm^?1) of the modified wheat starches showed a linear relationship with acetylation over the range of 0 to 3.5% as determined from calibration plots with the standard titrimetric method currently used to measure acetylation of modified starches. The Raman spectroscopic method allows much faster determination of the degree of acetylation, is nondestructive, and has less problems with interference from impurities than currently used methods.

Corresponding authors.     

Determination of amylose content in starch using Raman spectroscopy and multivariate calibration analysis

Fourier transform Raman spectroscopy and chemometric tools have been used for exploratory analysis of pure corn and cassava starch samples and mixtures of both starches, as well as for the quantification of amylose content in corn and cassava starch samples. The exploratory analysis using principal component analysis shows that two natural groups of similar samples can be obtained, according to the amylose content, and consequently the botanical origins. The Raman band at 480 cm^?1, assigned to the ring vibration of starches, has the major contribution to the separation of the corn and cassava starch samples. This region was used as a marker to identify the presence of starch in different samples, as well as to characterize amylose and amylopectin. Two calibration models were developed based on partial least squares regression involving pure corn and cassava, and a third model with both starch samples was also built; the results were compared with the results of the standard colorimetric method. The samples were separated into two groups of calibration and validation by employing the Kennard-Stone algorithm and the optimum number of latent variables was chosen by the root mean square error of cross-validation obtained from the calibration set by internal validation (leave one out). The performance of each model was evaluated by the root mean square errors of calibration and prediction, and the results obtained indicate that Fourier transform Raman spectroscopy can be used for rapid determination of apparent amylose in starch samples with prediction errors similar to those of the standard method.

Vibrational spectrum and conformation of cyclopropyldichloroborane

The infrared (3500-40 cm^?1) and Raman spectra (3200-0 cm^?1) have been recorded for cyclopropyldichloroborane in both the gaseous and solid states. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values obtained. Only one conformation has been found in all three physical states and, on the basis of the polarized nature of the Raman band assigned as the BCl₂ antisymmetric stretch, this conformer has been identified as being the bisected structure with C_s molecular symmetry. A complete vibrational assignment is proposed based on Raman depolarization data, infrared gas phase band contours, and group frequencies. These results are compared with the corresponding data in other organoboranes.     

Near infrared fourier transform Raman spectroscopy of human artery

We report the first near IR FT-Raman spectroscopy of normal diseased human artery. In normal human aorta, two bands at 1669 cm⁻¹ and 1452 cm⁻¹ dominate the spectrum and can be assigned to protein amide I and C-H in-plane bending vibrations, respectively. Weaker bands are also observed between 1250 and 1350 cm⁻¹. Non-calcified atherosclerotic lesions with a large amount of necrotic debris below the tissue surface show a relative increase in the intensity of the 1452 cm⁻¹ band. In atherosclerotic aortas which contain calcified deposits several hundred microns below the tissue surface, a strong 961 cm⁻¹ band is observed due to the symmetric stretch of phosphate groups in the calcified salts. The results show that this method provides the capability to probe biological substituents several hundred microns below the tissue surface.     

Temperature dependent Raman study of SB → SC transition in liquid crystalline compound N-(4-n-pentyloxybenzylidene)-4′-heptylaniline (5O.7)

Temperature dependent Raman study of C–H in-plane bending mode (～1163 cm^?1 and ～1190 cm^?1) and C–C stretching mode of phenyl ring (～1571 cm^?1 and ～1594 cm^?1) of N-(4-n-pentyloxybenzylidene)-4′-heptylaniline (5O.7) has been done. Vibrational assignment and potential energy distribution (PED) of individual modes have been calculated employing density functional theory (DFT) for the first time. The S_B → S_C transition is nicely depicted in the variation of the linewidth of the ～1163 cm^?1 band and the peak position of ～1594 cm^?1 band with temperature. Because of a small amount of charge density transfer from the core part to the alkyl chain region, the ～1163 cm^?1 band shifts towards lower wavenumber side whereas the ～1190 cm^?1 band towards higher wavenumber side at S_B → S_C transition. The ～1571 cm^?1 and ～1594 cm^?1 bands are assigned as 8a and 8b modes, whose relative intensity variation with temperature gives the evidence of increased possibility of C–H bending motion of the linking group and the C–C stretching of the alkyl chain in S_C phase.     

Structure of 4‐biphenylthiolate on Au nanoparticle surfaces studied by UV‐Vis absorption spectroscopy,transmission electron microscopy and surface‐enhanced Raman scattering

Structure of 4‐biphenylthiolate on Au nanoparticle surfaces has been studied by UV‐Vis absorption spectroscopy, transmission electron microscopy and surface‐enhanced Raman scattering (SERS). 4‐Biphenylthiolate is found to have a standing geometry on Au from the presence of the benzene ring CH stretching band identified at ～3060 cm^?1. The ν_8a band at 1597 cm^?1 in the ordinary Raman spectrum was found to split clearly into two features at 1599 and 1585 cm^?1. This result suggests that orientation of the phenyl rings in 4‐biphenylthiolate may be quite different and should not lie in the same plane on Au nanoparticle surfaces. On the basis of the electromagnetic enhancement factor, the dihedral angle could be estimated with a reported value of the tilt angle. Copyright © 2004 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the antimonate mineral roméite

Raman spectroscopy has been sued to study the antimony containing mineral roméite Ca₂Sb₂O₆(OH,F,O) from three different origins. Roméite is a calcium antimonate mineral of the pyrochlore group. An intense Raman band at ～518 cm^?1 for roméite is assigned to the SbO ν₁ symmetric stretching mode and the band at 466 cm^?1 to the SbO ν₃ antisymmetric stretching mode. The Raman band at 303 cm^?1 is attributed to the OSbO bending mode. Some variation in band positions is observed and is attributed to the variation in composition between the three mineral samples.     

Realtime Monitoring of Xylitol Fermentation by Micro-Raman Spectroscopy

The fermentation of xylitol is a promising alternative to conventional chemical processes. Micro-Raman spectroscopy was used to monitor the process involving Candida tropicalis, including the medium and yeast cells during xylitol fermentation. The spectra of the fermentation medium showed that the characteristic xylitol peak at 866 cm^?1 was enhanced from 18 h and that the characteristic xylose peak at 901 cm^?1 gradually diminished as the reaction progressed. The characteristic ethanol peak at 880 cm^?1 indicated the production of by-products. Intracellular biological macromolecules, such as nucleic acids, proteins, lipids, and carbohydrates, were identified in the spectra of yeast cells. The intensity of nucleic acids at 783 cm^?1 reached the highest value after 3 h. The xylose band at 901 cm^?1 and the peaks in the carbohydrate region reached a maximum in the logarithmic phase, indicating the carbohydrate metabolism was the most active. The amide I band located at 1658 cm^?1 indicated the major secondary structure of proteins was α-helix; its intensity gradually reduced during the fermentation. The 853 cm^?1 band due to buried tyrosine was predominant at 21 h. In addition, the 1275 cm^?1 band corresponded to the presence of a random coil only at 27 h. These results provided a perspective to understand fermentation and verified the applicability of Raman spectroscopy in xylitol fermentation.     

Determination of iprodione in agrochemicals by infrared and Raman spectrometry

Two methodologies based on vibrational spectrometry—making use of Fourier transform infrared absorption (FTIR) and Raman spectrometry—were developed for iprodione determination in solid pesticide formulations. The FTIR procedure involved the extraction of iprodione by CHCl₃, and the latter determination involved measuring the peak area between 1450 and 1440 cm⁻¹, corrected using a horizontal baseline defined at 1481 cm⁻¹. FT-Raman determination was performed directly on the powdered solid products, using standard chromatography glass vials as sample cells and measuring the Raman intensity between 1003 and 993 cm⁻¹, with a two-point baseline correction established between 1012 and 981 cm⁻¹. The sensitivities obtained were 0.319 area values g mg⁻¹ for FTIR determination and 5.58 area values g g⁻¹ for FT-Raman. The repeatabilities, taken to be the relative standard deviation of five independent measurements at 1.51 mg g⁻¹ and 10.98% w/w concentration levels, were equal to 0.16% and 0.9% for FTIR and FT-Raman, respectively, and the limits of detection were 0.3 and 0.2% w/w (higher than those obtained for HPLC, 0.016% w/w). FTIR determination provided a sample frequency of 60 h⁻¹, higher than those obtained for the Raman and reference chromatography methods (25 and 8.6 h⁻¹, respectively). On the other hand, the new FT-Raman method eliminates reagent consumption and waste generation, and reduces the need for sample handling and the contact of operator with the pesticide. In spite of their lack of sensitivity, vibrational procedures can therefore provide viable environmentally friendly alternatives to laborious, time- and solvent-consuming reference chromatography methods for quality control in commercially available pesticide formulations.     

Raman study of prereactional transformations in calcium hydroxide crystals during a thermal treatment leading to dehydration

The Raman spectroscopy study of Ca(OH)₂ single crystals shows that important modifications take place in the crystal structure far below the dehydration temperature. In particular, an intense and broad background scattering and a broad band centered at ～1650 cm^?1 evolve in the Raman spectra.     

Infrared and Raman spectra and normal coordinate calculations for methylisothiocyanate

The infrared spectra (3200-50 cm^?1) of gaseous and solid CH₃NCS and CD₃NCS and the Raman spectra (3200-10 cm^?1) of the liquids and solids have been recorded. The spectra have been interpreted on the basis of a “pseudo-symmetric top” with C_3v symmetry. An assignment of the fundamental vibrations in both molecules, based on their infrared band contours, depolarization values and group frequencies, is given and discussed. Particularly interesting is the low-frequency region where band maxima were observed at 152 and 80 cm^?1 for CH₃NCS and 139 and 71 cm^?1 for CD₃NCS in the infrared spectra of the gases. A normal coordinate analysis has also been carried out based on C_3v symmetry. Considerable mixing was found between the C_αN stretch and NCS symmetric stretch in both isotopic species. The other normal modes in CH₃NCS are reasonably pure but, for the CD₃NCS molecule, considerable mixing was found between the CD₃ stretches and NCS antisymmetric stretch. The proposed vibrational assignment and the results of the normal coordinate calculations are discussed and compared with the results obtained for similar molecules.     

The effect of apodization and finite resolution on Fourier transform Raman spectra

The effects that finite resolution and choice of apodization function have on Fourier transform (FT) Raman spectra are illustrated by the 839 cm⁻¹ (ν₁) and 914 cm⁻¹ bands of KMnO₄. FT-Raman spectra were recorded at 0.5, 1, 2, 4, 8, 16 and 32 cm⁻¹ resolution using boxcar, Norton—Beer (strong, medium and weak) and triangular apodization functions at each resolution. The results show the dramatic changes in bandshape that occur as the ratio (resolution/true full width at half height of band) increases. The changes were measured in terms of the full width at half height of the band, the height of the band, the area of the band and the bandshape (expressed as a sum of Lorentzian and Gaussian lines). At a given resolution the degree to which each of these characteristics is affected is strongly dependent on the choice of the apodization function.     

Determination of Catecholamines by Resonance Raman Spectroscopy of Their Aminochromes

Abstract

Catecholamines are oxidized by ferricyanide to the corresponding aminochromes. The band intensities of the resonance-enhanced Raman active C=N⁺ stretches of the aminochromes (1400–1500 cm^?1) are used to determine the catecholamines at the 10^?5 M level without prior separation.     

Darstellung,Eigenschaften und elektronische Raman-Spektren von Bis(chloro)phthalocyaninatoferrat(III), -ruthenat(III) und -osmat(III)

Preparation, Properties and Electronic Raman Spectra of Bis(chloro)-phthalocyaninatoferrate(III), -ruthenate(III) and -osmate(III) Bis(chloro)phthalocyaninatometalates of Fe^III, Ru^III and Os^III [MCl₂Pc(2-)]^?, with an electronic low spin ground state are formed by the reaction of [FeClPc(2-)] resp. H[MX₂Pc(2?)] (M = Ru, Os; X = Cl, I) with excess chloride in weakly coordinating solvents (DMF, THF) and are isolated as (n-Bu₄N) salts. The asym. M? Cl stretch (ν_as(MCl)) is observed in the f.i.r. at 288 cm^?1 (Fe), 295 cm^?1 (Ru), 298 cm^?1 (Os), ν_as(MN) at 330 cm^?1 (Fe), 327 cm^?1 (Ru), and 317 cm^?1 (Os); only ν_s(OsCl) at 311 cm^?1 is resonance Raman (r.r.) enhanced with blue excitation. The m.i.r. and FT-Raman spectra are typical for hexacoordinated phthalocyanines of tervalent metal ions. The UV-vis spectra show besides the characteristic π-π* transitions (B, Q, N, L band) of the Pc ligand a number of extra bands at 12–15 kK and 18–24 kK due to trip-doublet and (Pc→M)CT transitions. The effect of metal substitution is discussed. The r.r. spectra obtained by excitation between the B and Q band (λ₀ = 476.5 nm) are dominated by the intraconfigurational transition Γ₇ Γ ₈ arrising from the spin-orbit splitting of the electronic ground state for Fe^III at 536 cm^?1, for Ru^III at 961 cm^?1 and Os^III at 3 028 cm^?1. Thus the spin-orbit coupling constant increases very greatly down the iron group: Fe^III (357 cm^?1)< Ru^III (641 cm^?1)< Os^III (2 019 cm^?1). The Γ₇ Γ ₈-transition is followed by a very pronounced vibrational finestructure being composed in the r.r. spectra by the coupling with ν_s(MCl), δ(MClN) and the most intense fundamental vibrations of the Pc ligand. In absorption only vibronically induced transitions are observed for the Ru and Os complex at 1 700-2800 rsp. 3100-5800 em^?1 instead of the 0-0 phonon transitions. The most intense lines are attributed to combinations of the intense odd vibrational mo-des at ≈ 740 and 1120 cm^?1 with ν₅(MCI), δ(MClN).     

Resonanzramanspektrum von matrixisoliertem Se3

Resonance Raman Spectrum of Matrixisolated Se₃ By the application of a double furnace it is possible to get a gas mixture of 90% Se₂ molecules and 10% Se atoms. By condensing this mixture in an inertgas matrix at 15 K followed by annealing to nearly 25 K we got Se₃ molecules by a matrix reaction In the resonance Raman spectrum of this molecule we observed 14 overtones of the symmetric stretching vibration. So we can calculate the following values of ω₁ an x₁₁ for ⁸⁰Se₃: 312.15 ± 0.2 cm^?1 and 0.53 ± 0.02 cm^?1. Using a mixture of 62% ⁷⁶Se and 38% ⁸²Se we got band structures in which the intensity of the bands and their frequency shift can only be explained by a bent Se₃ molecule (～115°). The value of the force constant f_r + f_rr is 310 ± 20 Nm^?1. — By a new construction it is possible to get the Raman and IR reflection spectrum of the same matrix.     

A comparative study of structure,thermal degradation,and combustion behavior of starch from different plant sources

The present study investigated the structure, degradation properties, and combustion behavior of starch from maize, sweet potato, lotus root, and tobacco. Compared with other plant starches, tobacco starch had the smallest size, the highest amylose content and the least crystallinity. Microscale combustion calorimetry (MCC) experiment demonstrated that sweet potato starch showed the maximum peak heat release rate value (888.0 W g^?1) while tobacco starch showed the minimum value (316.0 W g^?1) and thermogravimetric analysis coupled with Fourier transform infrared spectrometer (TG-FTIR) results showed tobacco starch had good char formability (residue mass: 15.6%) and released more incombustible gaseous products, such as H₂O and CO₂. These results suggest that the thermal properties of plant starches were mainly influenced by the structural features and amylose content, especially the amylose ratio, and tobacco starch was very promising for application in green flame-retardant material.     

Surface enhanced Raman spectra of nucleic acid components adsorbed at a silver electrode

High-resolution vibrational spectra of nucleic acid components adsorbed on a silver electrode were obtained using a spectroelectrochemical method based on the large-intensity enhancement for Raman scattering at electrode surfaces.The laser surface Raman spectra of purine, adenine, adenosine, deoxyadenosine, adenine mononucleotides, adenylyl-3′, 5′-adenosine and polyriboadenylic acid were recorded in the range of 150–3500 cm^?1. The intensities of the vibrational bands were highly dependent upon the electrochemical preparation of the electrode, the applied potential and the nature of the adsorbate species. High-intensity spectra in rather dilute bulk solutions were obtained.The phosphate derivatives of adenosine exhibited strongly enhanced Raman scattering. Spectral band frequencies corresponded closely with normal Raman spectra of these molecules in solution. The adenine ring breathing mode at 740 cm^?1 and the adenine ring skeletal vibration at 1335 cm^?1 produced prominent Raman scattering. A strong band at about 240 cm^?1 for the adenine mononucleotides was attributed to silver/adsorbed phosphate group vibrations.     

Multilayer graphene/amorphous carbon hybrid films prepared by microwave surface‐wave plasma CVD: synthesis and characterization

Hybrid films of multilayer graphene (MG) containing amorphous carbon (a‐C) were synthesized on Al substrates by microwave surface‐wave plasma chemical vapor deposition. Raman scattering and surface transmission electron microscopy showed that the carbon films contained a large quantity of MG when a radio frequency (RF) substrate bias was not applied. Amorphization of graphene in the carbon film was promoted by applying an RF bias, which generated Ar⁺ in the plasma. The bandgaps of the films were found to increase as the Raman intensity ratios between the 2D‐band (at 2700 cm^?1) and D‐band (at 1350 cm^?1) decreased, indicating the formation of a‐C. The MG/a‐C all‐sp² phase of carbon hybrid films exhibited an increase in current density under 5 mW/cm² of AM1.5G solar simulated irradiation as the RF bias increased because of Ar⁺‐induced amorphization of the graphene. Copyright © 2016 John Wiley & Sons, Ltd.     

1‐allyloxy‐2‐hydroxy‐propyl‐starch: Synthesis and characterization

New reactive unsaturated starch derivatives, 1‐allyloxy‐2‐hydroxy‐propyl‐starches (AHP‐starches), were synthesized by the reaction of waxy maize starch (WMS) and amylose‐enriched maize starch (AEMS) with allyl glycidyl ether in a heterogeneous alkaline suspension containing NaOH and Na₂SO₄. The degree of substitution (DS) was determined by ¹H NMR spectroscopy, and a DS of 0.20 ± 0.01 was found for both AHP‐WMS and AHP‐AEMS, respectively. The AHP derivatives of WMS and AEMS were further characterized with ¹H and ¹³C NMR. It was shown that the AHP substitution was located on the C‐6 hydroxyl group of the glucose residues in the starch. The substitution pattern of the AHP groups along the polymer chain was randomly clustered, as determined by enzymatic digestion using pullulanase, α‐amylase, and amyloglucosidase, followed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis of the digestion products. With X‐ray diffraction and scanning electron microscopy, no changes in the granular morphology and crystallinity between the unmodified starches and AHP‐starches were detected. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2734–2744, 2007