Raman Spectroscopic Determination of the Degree of Succinate in Modified Waxy Maize Starches

ABSTRACT

Waxy (essentially amylose-free) maize starch was chemically modified to varying degrees by treatment with succinic anhydride, and the degree of substitution was determined by a standard wet chemistry method. FT-Raman spectra of the modified starches were obtained, and indicated a characteristic ～1730 cm^?1 C=O stretch Raman band whose intensity was dependent on the degree of succinylation. The ratio of intensity of the ～1730 cm^?1 band to a ～940 cm^?1 C-C stretch Raman band (used as an internal standard) was plotted against the degree of succinylation determined by titration, and a linear fit was obtained with a correlation of 0.998. Hence FT-Raman spectroscopy represents a rapid non-destructive method to determine the degree of succinylation of modified waxy maize starch, and should be suitable for use with succinylated 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.

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Xylenol Orange,Zirconium(IV) and Fluoride Color Reaction in Mixed Micelles of N-Hexadecylpyridinium Chloride and Brij 35, and Its Analytical Application1

Abstract

The color reaction between Xylenol orange (XO), zirconium (IV) and fluoride ions in the presence of various surfactants alone or in combination was studied at various pH. The XO -zirconium)IV)-fluoride ion ternary complex in mixed micellar media containing a low concentration of N-hexadecylpyridinium chloride (HPC) as a cationic surfactant and large amounts of (poly{oxyethylene)dodecyl ether (Brij 35) as a nonionic surfactant at weakly acidic media was found to be the most stable, and showed a remarkable bathochromic shift and clear contrast against a reagent blank. The maximum absorbance was at 600 nm in the mixed micellar media at pH 3.5, and the apparent molar absorptivities at 600 nm were 7.0 × 10⁴ 1 mol^?1 cm^?1 for zirconium(IV) and 1.4 × 10⁴ 1 mol^?1 cm^?1 for fluoride ion. The calibration curves covered the ranges of 0.5 ～ 20.0 μg/10 ml zirconium! IV) and 0 ～ 20.0 μg/10 ml fluoride ion with the Sandell sensitivities being 0.0013 μg/cm² for zirconium(IV) and 0.0016 μg/cm² for fluoride ion.     

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.     

4-Hydroxycoumarin/2-hydroxychromone tautomerism: Infrared spectra of 2-13c and 3-D labeled 4-hydroxycoumarin and its anion

Bands with primarily v (C=O) and v (C=O) character in the spectra of 4-hydroxycoumarin and its anion were identified by isotopic substitution with either ¹³C or deuterium. Two bands of each type were found for spectra of 4-hydroxycoumarin in solution in chloroform, dioxane, or dimethylsulfoxide, with v (C=O) at 1704–1733 cm^?1 and ～ 1567 cm^?1. Two bands, at 1618 and 1559 cm^?1, are associated with v (C=C) in the spectrum of crystalline 4-hydroxycoumarin monohydrate, but only a single v (C=O) band at ～ 1655 cm^?1 was observed. Anhydrous 4-hydroxycoumarin has v (C=O) bands at ～ 1700 cm^?1 and a shoulder at ～ 1670 cm^?1. The strong band at 1660 cm^?1 in the spectrum of 4-hydroxycommarin anion in dimethylsulfoxide solution is due to a delocalized v (O = C = O) vibration, whereas the band at 1555 cm^?1 has partial v (C=C) character and involves C(3) but not C(2), supporting a fully delocalized char structure for the anion. No evidence for the existence of the 2-hydroxychromone tautomer was found, except in the case of anhydrous 4-hydroxycoumarin in the solid state.     

Structure of Alkali Lignins Fractionated from Ricinus communis and Bagasse. 3. IR Spectra

Abstract

The lignin fractions isolated by one- and multistage soda and sulfate cookings showed almost identical IR spectra, indicating the similarity of the lignin skeletal structure throughout the plant. However, the absorbances reveal some differences. Similarity of the spectra includes: 1) chelation and bonding of the hydroxyl groups. 2) Stretching vibration of C-H bonds in methyl, methoxyl, and methylene groups. 3) Stretching vibration of C≡N. 4) Carbonyl unconjugated β-ketone, conjugated acids, or esters at 1725 cm^?1. There is no change in the intensity of absorption at this band from that at 1515 cm^?1 with the cooking stage. 5) Aromatic skeletal vibration at 1610 and 1515 cm^?1, affected by ring substituents at 1425 cm^?1. 6) The band at 1465 cm^?1 showed a higher intensity for soda and soluble kraft lignins than for insoluble kraft ones. 7) The band at 1370 cm^?1, assigned to phenolic OH bending, is affected by the methoxyl group. 8) The absence of condensed guaiacyl and the presence of syringyl and uncondensed guaiacyl. Assignments for hardwood lignin are shown for soda and soluble kraft lignins of bagasse, while those for softwood lignin are shown for soda, soluble, and insoluble kraft lignins of Ricinus communis and for insoluble kraft lignin of bagasse. A relation exists between the carbohydrate's lignin and the band at 920 cm^?1. Lignins from Ricinus communis are of higher guaiacyl to syringyl ratios than those from bagasse. The presence of C—S vibration and the absence of thiol groups for kraft lignins are indicated.     

IR,Raman, and Surface‐enhanced Raman Spectroscopic Study on Triruthenium Dipyridylamide Diruthenium Nickel Dipyridylamide Family: Metal‐metal Bonding and Structures

We report the infrared, Raman, and surface‐enhanced Raman scattering (SERS) spectra of triruthenium dipyridylamido complexes and of diruthenium mixed nickel metal‐string complexes. From the results of analysis on the vibrational modes, we assigned their vibrational frequencies and structures. The infrared band at 323–326 cm^?1 is assigned to the Ru₃ asymmetric stretching mode for [Ru₃(dpa)₄Cl₂]^0–2+. In these complexes we observed no Raman band corresponding to the Ru₃ symmetric stretching mode although this mode is expected to have substantial Raman intensity. There is no frequency shift in the Ru₃ asymmetric stretching modes for the complexes with varied oxidational states. No splitting in Raman spectra for the pyridyl breathing line indicates similar bonding environment for both pyridyls in dpa^– , thus a delocalized structure in the [Ru₃]^6–8+ unit is proposed. For Ru₃(dpa)₄(CN)₂ complex series, we assign the infrared band at 302 cm^?1 to the Ru₃ asymmetric stretching mode and the weak Raman line at 285 cm^?1 to the Ru₃ symmetric stretching. Coordination to the strong axial ligand CN^– weakens the Ru‐Ru bonding. For the diruthenium nickel complex [Ru₂Ni(dpa)₄Cl₂]^0–1+, the diruthenium stretching mode ν_Ru‐Ru is assigned to the intense band at 327 and 333 cm^?1 in the Raman spectra for the neutral and oxidized forms, respectively. This implies a strong Ru‐Ru metal‐metal bonding.     

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.     

Matrix Raman studies of Bin(n ⩾ 2) molecules

Resonance Raman spectra of bismuth molecules reveal two progressions with ω_e = 172 and 152 cm^?1 The metal concentration dependence allows us to assign the 172 cm^?1 band to Bi₂ and the 152 cm^?1 band to a larger molecule, most likely Bi₄. Thus the existence of an X' ground state of Bi₂ ≈ 1500 cm^?1 below the X state can be excluded.     

Determination of crystallinity of swollen poly(vinyl alcohol) by laser Raman spectroscopy

Laser Raman spectra of atactic poly(vinyl alcohol) (PVA) after heat treatment and/or swelling in water have been obtained. An amorphous Raman band is observed at 1124 cm^?1, while a crystalline Raman band is found at 1147 cm^?1. A new method for crystallinity determination is proposed, in which the amorphous band is used instead of the crystalline band. The method is superior to others for water-swollen PVA samples. Laser Raman spectra of swollen PVA revealed that swelling causes destruction of a major fraction of the crystalline regions and the remaining intact crystalline part increases with increasing temperature of heat treatment.