Fourier transform infrared photoacoustic spectroscopy of dental calculus

The mid and far FTIR spectra of supragingival and subgingival calculus were measured, respectively. From the subtraction spectra of the two types of calculus, the protein components of calculus have been obtained. The results of photoacoustic spectroscopy indicated the presence of protein layer on the surface of early calculus.     

涂石蜡大米傅立叶变换红外吸收光谱识别分析

针对11种未涂石蜡大米和18个涂不同量石蜡的大米样品,以石油醚提取的油脂为试样,采用傅立叶变换红外光谱仪,扫描样品的傅立叶变换红外吸收光谱,并对光谱进行预处理,提取红外特征信息,将2855与1746、1462与1163 cm-1处特征峰的面积比值为坐标,采用Origín 6.0软件作识别分类图.结果表明:特征峰的面积比值与所涂石蜡量成线性变化,大米油脂的特征峰面积比值在一定的区域分布,涂以0.05%以上石蜡的大米,其油脂特征峰面积比值与未涂石蜡米油脂的值有一定区别.     

Characterization of nano FeIII-tannic acid modified polyacrylate in controlled-release coated urea by Fourier transform infrared photoacoustic spectroscopy and laser-induced breakdown spectroscopy

Polyacrylate polymer (PA) has been widely applied in coating products for decades. Recently, it has been used in controlled-release fertilizers. Nano Fe^III-tannic acid modified PA (PA-Fe) provides a better nutrient controlled release performance than conventional PA. In this work, a preliminary database of molecular and elemental information about the polymer was obtained using FTIR-PAS (Fourier transform infrared photoacoustic spectroscopy) and LIBS (laser-induced breakdown spectroscopy), respectively. The PA-Fe polymer contained more hydrophobic groups (–CH₃) and fewer hydrophilic groups (–COOR, –COOH) than PA. More elements were detected for PA-Fe than PA. LIBS was useful to identify and classify PA and PA-Fe samples using principal component analysis. The combination of spectroscopic results and a film formation process model explained the lower nutrient release rate of PA-Fe. These results showed the strong analytical capabilities of FTIR-PAS combined with LIBS for identifying and characterizing modified PA.     

Characterisation of bhringaraj and guduchi herb by ICP-MS analysis, optical absorption, infrared and EPR spectroscopic methods

Leaves of bhringaraj and guduchi herb of Kadapa district of Andhra Pradesh, India, are dried and powdered. ICP-MS analysis of samples indicates that copper is present in both the samples. An EPR study of guduchi sample also confirms the presence of Fe(III) whereas Eclipta alba confirms the presence of Fe(III), Mn(II) and Cu(II). Optical absorption spectrum of guduchi indicates that Cu(II) is present in rhombically distorted octahedral environment. NIR and IR results are due to carbonate fundamentals.     

Continuous nondestructive monitoring of <Emphasis Type="Italic">Bordetella pertussis</Emphasis> biofilms by Fourier transform infrared spectroscopy and other corroborative techniques

This work describes the application of several analytical techniques to characterize the development of Bordetella pertussis biofilms and to examine, in particular, the contribution of virulence factors in this development. Growth of surface-attached virulent and avirulent B. pertussis strains was monitored in continuous-flow chambers by techniques such as the crystal violet method, and nondestructive methodologies like fluorescence microscopy and Fourier transform (FT) IR spectroscopy. Additionally, B. pertussis virulent and avirulent strains expressing green fluorescent protein were grown adhered to the base of a glass chamber of 1-μm thickness. Three-dimensional images of mature biofilms, acquired by confocal laser scanning microscopy, were quantitatively analysed by means of the computer program COMSTAT. Our results indicate that only the virulent (Bvg⁺) phase of B. pertussis is able to attach to surfaces and develop a mature biofilm. In the virulent phase these bacteria are capable of producing a biofilm consisting of microcolonies of approximately 200 μm in diameter and 24 μm in depth. FTIR spectroscopy allowed us not only to follow the dynamics of biofilm growth through specific biomass and biofilm marker absorption bands, but also to monitor the maturation of the biofilm by means of the increase of the carbohydrate-to-protein ratio.     

Polymorphism of phenylpyruvic acid studied by IR, Raman and solid state C NMR spectroscopy

Polymorphs I and II of phenylpyruvic acid are obtained as mixtures of both crystal forms or relatively pure crystals, from different solvents. Polymorph I is more stable than polymorph II at room temperature. Spectral characteristics of these polymorphs are discussed on the basis of IR, Raman and solid state ¹³C NMR spectra. Also, the assignment of the IR features observed in the 1600–1700 cm⁻¹ region is re-investigated by referring to the spectra of heavy-atom substituted derivatives. It is suggested that the C=O stretching band is split by the crystal field for both polymorphs.     

Use of Fourier transform infrared spectroscopy and chemometrics to discriminate clinical isolates of bacteria of the Burkholderia cepacia complex from different species and ribopatterns

A methodology for the discrimination of Burkholderia cepacia complex (Bcc) clinical isolates at the species level and at the ribopattern level using Fourier transform infrared (FTIR) spectroscopy and chemometrics analysis was assessed in this study. Different Bcc sequential isolates collected at the Santa Maria Hospital (HSM), in Portugal, from clinically infected cystic fibrosis (CF) patients were previously classified by established molecular methods at the species level and differentiated at the strain level, based on their ribopatterns. A set of 185 of these isolates, representing four different Bcc species (Burkholderia cepacia, Burkholderia cenocepacia (recA lineages III-A and III-B), Burkholderia multivorans and Burkholderia stabilis), was analyzed by FTIR and results were processed with chemometric methods. Ten reference strains of these species were used to test the FTIR method. The discrimination at the species level led to misclassification error rates of 10% and 32% for the HSM isolates and reference strains, respectively, clearly indicating that the FTIR classification method was unable to generalize results for the reference strains. Infrared spectra of HSM isolates were further analyzed in terms of the discrimination according to the ribopattern. Results showed misclassification error rates of 4%, 2%, and 8% for B. cepacia, B. cenocepacia III-A, and B. cenocepacia III-B ribopatterns, respectively. These results demonstrated good FTIR spectroscopy discrimination capacity at the ribopattern level, for the HSM isolates but showed difficulty at the species level, especially when the reference strains were included. Remarkably, this methodology was found to discriminate isolates belonging to the same species and ribopattern that were collected from the same patient during prolonged colonization, opening the door to the identification of chemical modifications resulting from adaptation strategies to the CF lung stressing environment, in particular to aggressive and prolonged antibiotic therapy. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

In situ scanning FTIR microscopy and IR imaging of Pt electrode surface towards CO adsorption

In situ scanning FTIR microscopy was built up for the first time in the present work, which consists of an FTIR apparatus, an IR microscope, an X-Y mapping stage, and the specially designed electrochemical IR cell and computer software. It has been demonstrated that this new space-resolvdin situ IR technique can be used to study vibration properties of micro-area, and to perform IR imaging of electrode surface. The chemical image obtained using this technique for CO adsorption on Pt electrode illustrated, at a space-resolution of 10^-2 cm, the inhomogeneity and the distribu-tion of reactivity of micro-area of electrode surface. Project supported by the National Natural Science Foundation of China (Grant No. 29525307).     

Determination of total <Emphasis Type="Italic">trans</Emphasis> fats and oils by infrared spectroscopy for regulatory compliance

The mandatory requirement in many countries to declare the amount of trans fat present in food products and dietary supplements has led to a need for sensitive and accurate methodologies for the rapid quantitation of total trans fats and oils. Capillary gas chromatography (GC) and infrared spectroscopy (IR) are the two methods most commonly used to identify and quantify trans fatty acids for food labeling purposes (see the article by Delmonte and Rader in this ABC issue for a detailed presentation of GC methodology). The present article provides a comprehensive review of the IR technique and the current attenuated total reflection (ATR) Fourier-transform (FT) IR methodologies for the rapid determination of total trans fats and oils. This review also addresses potential sources of interferences and inaccuracies in FTIR determinations, particularly those done at low trans levels. Recent observations have shown that the presence of saturated fats caused interferences in the FTIR spectra observed for trans triacylglycerols. The recognition and resolution of previously unresolved quantitative issues improved the accuracy and sensitivity of the FTIR methodology. Once validated, it is anticipated that the new negative second-derivative ATR-FTIR procedure will make IR spectroscopy more suitable than ever, and a rapid alternative and/or complementary method to GC, for the rapid determination of total trans fats for regulatory compliance. Figure Infrared light bouncing inside an internal reflection crystal     

Molecular and structural characteristics in toxic algae cultures of Ostreopsis ovata and Ostreopsis spp. evidenced by FTIR and FTNIR spectroscopy

In this article we investigated the compositional and structural characteristics of the principal biomolecules such as carbohydrates, proteins, lipids, nucleic acids and chlorophyll pigments present in biofilm cultures of Ostreopsis spp. and in batch cultures of Ostreopsis ovata. Our approach based on the use of infrared (FTIR) and near infrared (FTNIR) spectroscopy showed the marked differences existing between biofilm cultures and batch cultures. FTIR spectroscopy showed the higher contents of polysaccharides and chlorophyll pigments in O. ovata from batch cultures with respect to Ostreopsis spp. Second derivative FTIR spectroscopy showed different features concerning the secondary structure of proteins because in O. ovata samples the beta sheet and beta turn structures were observed whereas in Ostreopsis spp. samples the alpha helix structure was the most evident. FTNIR spectroscopy showed other structural differences observed existing between O. ovata and Ostreopsis spp. mainly related to hydrogen bond interactions determining more packed structures in the nucleus of O. ovata. In addition, the interpretation of FTIR and FTNIR spectral information was also supported by the application of two statistical methods, the independent component analysis (ICA) and the spectral cross correlation analysis (SCCA). ICA was used as spectral deconvolution technique to separate the effects of the interference bicarbonate ion from algal FTIR spectra so to verify the high similar qualitative composition of the three biofilm samples of Ostreopsis spp. At last, SCCA applied to FTIR and FTNIR spectra was useful to evidence some structural differences involving -CH and CH(2) groups of aliphatic chains in O. ovata and Ostreopsis spp. samples. Though preliminary, these results agree with some previous studies suggesting that the presence of different ecophysiological characteristics in O. ovata and Ostreopsis spp. depending on the parameters related to the condition growth.     

Molecular miscible blend of poly(2-cyano-1,4-phenyleneterephthalamide) and polyvinylpyrrolidone characterized by two-dimensional correlation FTIR and solid state C NMR spectroscopy

Miscibility of blends of poly(2-cyano-1,4-phenyleneterephthalamide/polyvinylpyrrolidone) (CN-PPTA/PVP) was investigated by dilute solution viscometry, two-dimensional (2D) correlation Fourier transformed infrared (FTIR) spectroscopy and solid state ¹³C NMR spectroscopy. It was shown that a large proportion of the PVP, the water-soluble component, could not be removed from CN-PPTA by extraction with water, and even with boiling water for blend films, suggesting that the flexible aliphatic PVP chain forms a blend with the rigid aromatic CN-PPTA chain through strong intermolecular interaction making it too difficult to dissolve even in boiling water. Viscometry on a polymer mixture of dilute solution showed that [η]_exp exhibited larger value than [η]_theo in all mixtures used in this experiment, suggesting occurrence of a strong attractive interaction between the two polymers. 2D correlation FTIR spectroscopy revealed that the carbonyl absorption band of PVP at 1675 cm⁻¹ shifted to a new low frequency absorption band at 1640 cm⁻¹ with a change of 35 cm⁻¹, suggesting strong hydrogen bonding with NH (amide II) proton of CN-PPTA. Another new absorption band at 1685 cm⁻¹ was due to the carbonyl absorption band of CN-PPTA shifting to a higher frequency than that at 1662 cm⁻¹, indicating that some of the carbonyl groups in the CN-PPTA components of the blends were in a free state or in a non-hydrogen bonded state as a consequence of the participation of NH proton of CN-PPTA in hydrogen bonding, resulting in the absorption bands of NH bend deformation of CN-PPTA at 1542 and 1313 cm⁻¹ being shifted to higher wavenumber of 1556 and 1324 cm⁻¹, respectively. Solid state ¹³C NMR spectroscopy revealed a chemical shift for CO of the PVP component in the blend fiber changing down-field (shift to left) at 177.346 ppm with a difference of 1.812 ppm; this was due to a lower electron density around the carbon atom of CO of lactam via hydrogen bonding with NH proton of amide in the CN-PPTA component, suggesting that a homogeneous blend of the CN-PPTA and PVP was produced on a molecular scale via hydrogen bonding.     

Production ofL-glutamate oxidase andin situ monitoring of oxygen uptake in solid state fermentation ofstreptomyces sp. Nl

Effects of water content and carbon and nitrogen sources on the production ofL-glutamate oxidase (GOD) by solid state fermentation (SSF) ofStreptomyces sp. N₁ were investigated in a 250-mL shake flask. The results show that in the solid medium containing wheat bran 98% (w/w), KCl 0.2% (w/w), and MgCl₂ 0.2% (w/w), addition of 2.0-mL water per gram solid medium and 0.4% (w/w) (NH₄)₂SO₄ was the best for GOD production. In this work, we also developed a simple technique forin situ measuring oxygen uptake rate (OUR) and carbon dioxide evolution rate (CER) in SSF in a shake flask based on the principle of Warburg manometer. The method was successfully applied to determine OUR and CER values in SSF ofStreptomyces sp. N₁. The results indicate that the largest OUR value was detected about one or two days ahead of the highest GOD activity reached depending on the fermentation conditions, and the OUR may be used as anin situ indicator of GOD production in the SSF process.     

Speciation and detection of arsenic in aqueous samples: A review of recent progress in non-atomic spectrometric methods

Inorganic arsenic (As) displays extreme toxicity and is a class A human carcinogen. It is of interest to both analytical chemists and environmental scientists. Facile and sensitive determination of As and knowledge of the speciation of forms of As in aqueous samples are vitally important. Nearly every nation has relevant official regulations on permissible limits of drinking water As content. The size of the literature on As is therefore formidable. The heart of this review consists of two tables: one is a compilation of principal official documents and major review articles, including the toxicology and chemistry of As. This includes comprehensive official compendia on As speciation, sample treatment, recommended procedures for the determination of As in specific sample matrices with specific analytical instrument(s), procedures for multi-element (including As) speciation and analysis, and prior comprehensive reviews on arsenic analysis. The second table focuses on the recent literature (2005–2013, the coverage for 2013 is incomplete) on As measurement in aqueous matrices. Recent As speciation and analysis methods based on spectrometric and electrochemical methods, inductively coupled plasma-mass spectrometry, neutron activation analysis and biosensors are summarized. We have deliberately excluded atomic optical spectrometric techniques (atomic absorption, atomic fluorescence, inductively coupled plasma-optical emission spectrometry) not because they are not important (in fact the majority of arsenic determinations are possibly carried out by one of these techniques) but because these methods are sufficiently mature and little meaningful innovation has been made beyond what is in the officially prescribed compendia (which are included) and recent reviews are available.