Fourier Transform Infrared Absorption Spectroscopy Research Articles

Spectroscopic investigations of high-energy-density plasma transformations in a simulated early reducing atmosphere containing methane, nitrogen and water.

Large-scale plasma was created in gas mixtures containing methane using high-power laser-induced dielectric breakdown (LIDB). The composition of the mixtures corresponded to a cometary and/or meteoritic impact into the early atmosphere of either Titan or Earth. A multiple-centimeter-sized fireball was created by focusing a single 100 J, 450 ps near-infrared laser pulse into the center of a 15 L gas cell. The excited reaction intermediates formed during the various stages of the LIDB plasma chemical evolution were investigated using optical emission spectroscopy (OES) with temporal resolution. The chemical consequences of laser-produced plasma generation in a CH4-N2-H2O mixture were investigated using high resolution Fourier-transform infrared absorption spectroscopy (FTIR) and gas selected ion flow tube spectrometry (SIFT). Several simple inorganic and organic compounds were identified in the reaction mixture exposed to ten laser sparks. Deuterated water (D2O) in a gas mixture was used to separate several of the produced isotopomers of acetylene, which were then quantified using the FTIR technique.

Spectroscopy and Formation of Carbon Nitride by Pulse Laser Ablation in Liquid of Graphite Target

In this work carbon nitride was synthesized by pulsed laser ablation of graphite in ammonium solution. Fourier Transform Infrared Spectroscopy (FTIR), UV-Visible Spectrophotometer and Transmission Electron Microscopy (TEM) were used to study the bonding, absorption, size and morphology of the carbon nitride nanoparticles. The FTIR absorption peak at 2121.6, 1631.7, 1384 cm-1 stretching vibration bond, it is inferred that the C ≡ N, C = N and C-N, respectively. Bonds suggested the formation carbon nitride nanoparticles. UV absorption peaks coincide with the electronic transitions corresponding to formation carbon nitride C3N4 and monocyanopolyynes. The TEM image showed the aggregation of the carbon nitride nanoparticles with size ranges from (4 to 83.3 nm); the Leaf- like structure is shown in the structure of carbon nitride suspension.

Kinetic study of the OH, NO 3 radicals and Cl atom initiated atmospheric photo-oxidation of iso-propenyl methyl ether

Abstract Rate coefficients at room temperature and atmospheric pressure for the reaction of isopropenyl methyl ether ( i -PME) (CH 2 C(CH 3 )OCH 3 ), with OH and NO 3 radicals and with Cl atoms have been determined in a 50 L Pyrex glass reaction chamber in conjunction with Fourier Transform Infrared absorption spectroscopy (FTIR) as a detection technique. The chamber is equipped with a White-type multiple-reflection mirror system with a total optical path length of ≈200 m. Additional experiments were carried out using evacuable Teflon-coated bags (volume 150 L) and a gas chromatography/mass spectrometry-time of flight (GC-TOF MS) detection system. This is the first kinetic study carried out to date for these reactions. The rate coefficients k (in units of cm 3 molecule −1 s −1 ) obtained are: (1.14 ± 0.10) × 10 −10 for the OH reaction, (2.41 ± 0.50) × 10 −11 , for the NO 3 reaction and (7.03 ± 0.67) × 10 −10 for the Cl reaction. A mechanism is proposed from the observed reaction products. The atmospheric lifetimes of the studied ether is estimated considering the rate coefficients of the reactions with OH and NO 3 radicals and Cl atom. Calculated atmospheric lifetimes reveal that the dominant loss process for i -PME is clearly the night-time reaction with the NO 3 radical. The radiative efficiency (RE) is obtained from the infrared spectra of the ether and the global warming potential (GWP) is then estimated. Atmospheric implications of the ether emission are discussed.

The mid‐IR Absorption Cross Sections of α‐ and β‐NAT (HNO3 · 3H2O) in the range 170 to 185 K and of metastable NAD (HNO3 · 2H2O) in the range 172 to 182 K

AbstractGrowth and Fourier transform infrared (FTIR) absorption in transmission of the title nitric acid hydrates have been performed in a stirred flow reactor (SFR) under tight control of the H2O and HNO3 deposition conditions affording a closed mass balance of the binary mixture. The gas and condensed phases have been simultaneously monitored using residual gas mass spectrometry and FTIR absorption spectroscopy, respectively. Barrierless nucleation of the metastable phases of both α‐NAT (nitric acid trihydrate) and NAD (nitric acid dihydrate) has been observed when HNO3 was admitted to the SFR in the presence of a macroscopic thin film of pure H2O ice of typically 1 µm thickness. The stable β‐NAT phase was spontaneously formed from the precursor α‐NAT phase through irreversible thermal rearrangement beginning at 185 K. This facile growth scheme of nitric acid hydrates requires the presence of H2O ice at thicknesses in excess of approximately hundred nanometers. Absolute absorption cross sections in the mid‐IR spectral range (700–4000 cm−1) of all three title compounds have been obtained after spectral subtraction of excess pure ice at temperatures characteristic of the upper troposphere/lower stratosphere. Prominent IR absorption frequencies correspond to the antisymmetric nitrate stretch vibration (ν3(NO3−)) in the range 1300 to 1420 cm−1 and the bands of hydrated protons in the range 1670 to 1850 cm−1 in addition to the antisymmetric O–H stretch vibration of bound H2O in the range 3380 to 3430 cm−1 for NAT.

Utilization of oriented crystal growth for screening of aromatic carboxylic acids cocrystallization with urea

The possibility of molecular complex formation in the solid state of urea with benzoic acid analogues was measured directly on the crystallite films deposited on the glass surface using powder X-ray diffractometry (PXRD). Obtained solid mixtures were also analyzed using Fourier transform infrared spectroscopy (FTIR). The simple droplet evaporation method was found to be efficient, robust, fast and cost-preserving approach for first stage cocrystal screening. Additionally, the application of orientation effect to cocrystal screening simplifies the analysis due to damping of majority of diffraction signals coming from coformers. During validation phase the proposed approach successfully reproduced both positive cases of cocrystallization (urea:salicylic acid and urea:4-hydroxy benzoic acid) as well as pairs of co-formers immiscible in the solid state (urea:benzoic acid and urea:acetylsalicylic acids). Based on validated approach new cocrystals of urea were identified in complexes with 3-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid and 3,5-dihydroxybenzoic acid. In all cases formation of multicomponent crystal phase was confirmed by the appearance of new reflexes on the diffraction patterns and FTIR absorption band shifts of O–H and N–H groups.

Reaction products and mechanisms for the reaction of n-butyl vinyl ether with the oxidants OH and Cl: Atmospheric implications

Abstract A reaction product study for the degradation of butyl vinyl ether (CH3(CH2)3OCH CH2) by reaction with chlorine atoms (Cl) and hydroxyl radicals (OH) has been carried out using Fourier Transform Infrared absorption spectroscopy (FTIR) and/or Gas Chromatography-Mass Spectrometry with a Time of Flight analyzer (GC-TOFMS). The rate coefficient for the reaction of butyl vinyl ether (BVE) with chlorine atoms has also been evaluated for the first time at room temperature (298 ± 2) K and atmospheric pressure (708 ± 8) Torr. The rate coefficient obtained was (9.9 ± 1.5) × 10−10 cm3 molecule−1 s−1 and this indicates the high reactivity of butyl vinyl ether with Cl atoms. However, this value may be affected by the dark reaction of BVE with Cl2. The results of a qualitative study of the Cl reaction show that the main oxidation products are butyl formate (CH3(CH2)3OC(O)H), butyl chloroacetate (CH3(CH2)3OC(O)CH2Cl and formyl chloride (HCOCl). Individual yields in the ranges ∼16–40% and 30–70% in the absence and presence of NOx, respectively, have been estimated for these products. In the OH reaction, butyl formate and formic acid were identified as the main products, with yields of around 50 and 20%, respectively. Based on the results of this work and a literature survey, the addition of OH radicals and Cl atoms at the terminal C atom of the double bond in CH3(CH2)3OCH CH2 has been proposed as the first step in the reaction mechanism for both of the studied oxidants. The tropospheric lifetime of butyl vinyl ether is very short and, as a consequence, it will be rapidly degraded and will only be involved in tropospheric chemistry at a local level. The degradation products of these reactions should be considered when evaluating the atmospheric impact.

Biosorption of anthocyanins from grape pomace extracts by waste yeast: kinetic and isotherm studies

The potential uses of two food industry by-products were analyzed in this study. The extraction optimization of anthocyanins from grape pomaces of different grape varieties and the application of waste brewery's yeast biomass as biosorbent of the anthocyanins in solution were evaluated. The biosorption capacity of the biomass was determined by pseudo-second order kinetic model and different isotherm models were used to describe the biosorption process. Fourier Transform Infrared Spectroscopy (FTIR) analysis was carried out to characterize the interaction of the biomass with anthocyanins. The biosorption process was also evaluated by HPLC analysis. Experimental data of the isotherm profile were adequately described by the Temkin model. The mean free energy (E) value from the model of Dubinin–Radushkevich suggested the occurrence of a chemical mechanism in the biosorption process. FTIR absorption spectrum of yeast biomass was complex. Significant changes in the intensity of yeast cell absorption bands and shifts of characteristic bands were observed after biosorption.

Fourier transform infrared spectroscopic study of rabbit glue/inorganic pigments mixtures in fresh and aged reference paint reconstructions

We studied the interactions of rabbit glue, a collagen-based proteinaceous binder, with azurite (Cu3(CO3)2(OH)2), calcium carbonate (CaCO3), hematite (Fe2O3·nH2O), red lead (Pb3O4) and cinnabar (HgS) by Fourier transform infrared spectroscopy (FT-IR). The research was carried out on a set of paint reconstructions, which were analysed before and after artificial light ageing. A deconvolution of the amide I FT-IR absorption peak was performed with a written-in-house LabVIEW program to study the secondary structure of the glue.The changes in the glue conformation highlighted that all the inorganic pigments interact with the proteinaceous binder. The conformational changes were correlated with a loss of stability of the collagen structure, especially after ageing, likely due to the interlayer coordination of metals salts and oxide with protein functional groups. These results were correlated with the lower thermal stability of the glue/pigment mixtures with respect to the pure glue, evidenced by thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses performed in a previous step of this work.

New Insights into Sequential Infiltration Synthesis

Sequential infiltration synthesis (SIS) is a process derived from ALD in which a polymer is infused with inorganic material using sequential, self-limiting exposures to gaseous precursors. During the initial SIS cycles, the organometallic precursor (e.g. trimethyl aluminum, TMA) reacts preferentially with specific functional groups within the polymer, while in later cycles growth occurs in an ALD-like fashion on the inorganic “seeds” that have been planted inside the polymer. Consequently, it is possible to start with a blend of two polymers, such as a diblock coplymer, and selectively infuse just one of the two components. As a result of this selective, step-wise infusion, SIS can create novel composites with intermediate or even unique properties compared to those of the pure polymeric and inorganic constituents. Alternatively, the organic component can be removed through oxidation leaving a purely inorganic material, but with a mesostructure that mimics that of the starting polymer. One particularly attractive application for SIS is lithography: SIS can harden polymer resists rendering them more robust towards subsequent etching, and this permits deeper and higher-resolution patterning of substrates such as silicon. With this objective in mind, we have performed a series of investigations using in-situ Fourier transform infrared absorption spectroscopy (FTIR), in-situ synchrotron grazing incidence small angle X-ray scattering (GISAXS), and high resolution scanning transmission electron microscope (STEM) tomography of a model system: Al2O3 SIS using TMA and H2O within the diblock copolymer, poly(styrene-block-methyl methacrylate) (PS-b-PMMA). While the picture is far from complete, these studies reveal some important details: 1) TMA adsorption on PMMA occurs through a weakly-bound intermediate; 2) the SIS kinetics are diffusion-limited, but desorption is 10x slower than adsorption; 3) dynamic structural changes occur during the individual precursor exposures. All of findings impact the resulting composite, and hence will dictate the success of the lithography. Figure 1

CHARACTERIZATION OF CARBON NITRIDE NANOPARTICLES PREPARED BY LASER ABLATION IN LIQUID FOR OPTOELECTRONIC APPLICATION

In this work, carbon nitride ( C 3 N 4) nanoparticles (NPs) were synthesized by pulse laser ablation of graphite in ammonium solution, and deposited on silicon substrates by spray. Fourier transform infrared spectroscopy (FTIR), UV-visible spectrophotometer and transmission electron microscopy (TEM) were used to study bonding, absorption, size and morphology of the produce NPs. The FTIR absorption peaks at 2121.6, 1631.7 and 1384 cm-1 stretching vibration bond, it is inferred for the C ≡ N , C = N and C – N , respectively. Bonds suggests the formation, C 3 N 4 NPs. UV absorption peaks coincide with the electronic transitions corresponding to the formation, C 3 N 4 NPs with 3.98 eV optical bandgap. The TEM show the aggregation of the C 3 N 4 NPs with size ranges from 4 to 83 nm, and also the leaf-like structure are shown in the structure of C 3 N 4 suspension. High performance rectifying C 3 N 4/ Si heterojunction with a rectifying ratio exceeding 345 at V = 5 V was obtained, with high photoresponsivity of 2.33 A/W at 600 nm.The results show that C 3 N 4 NPs on silicon substrates will act as very good candidates for making high efficiency photodiodes.

First Calibration Measurements of an FTIR Absorption Spectroscopy System for Liquid Hydrogen Isotopologues for the Isotope Separation System of Fusion Power Plants

Fusion facilities like ITER and DEMO will circulate huge amounts of deuterium and tritium in their fuel cycle with an estimated throughput of kg per hour. One important capability of these fuel cycles is to separate the hydrogen isotopologues. For this purpose the Isotope Separation System (ISS), using cryogenic distillation, as part of the TRitium Enrichment Test Assembly (TRENTA) is under development at Tritium Laboratory Karlsruhe. Fourier transform infrared absorption spectroscopy (FTIR) has been selected to prove its capability for inline monitoring of the tritium concentration in the liquid phase at the bottom of the distillation column of the ISS. The actual R&D work is focusing on the calibration of such a system. Two major issues are the identification of appropriate absorption lines and their dependence on the isotopic concentrations and composition. For this purpose the Tritium Absorption IR spectroscopy experiment has been set up as an extension of TRENTA. For calibration a Raman spectroscopy system is used. First measurements, with equilibrated mixtures of H2, D2 and HD demonstrate that FTIR can be used for quantitative analysis of liquid hydrogen isotopologues and reveal a nonlinear dependence of the integrated absorbance from the D2 concentration in the 2nd vibrational branch of D2 FTIR spectra.

Structural and electrical evolution of Barium Cerate catalyst for CO oxidation

Barium cerate BaCeO3 is obtained by a coprecipitation method. The crystallized samples are characterized by X-ray diffraction and electron microscopy. The structural and thermodynamic analyses revealed several transitions as a function of temperature according to the phase transformation. The electrical properties are studied using electrical impedance spectroscopy as a function of temperature. The Nyquist representations are semi-circles, characteristic of electron and ionic conduction. A series of electrical transitions are observed, which are in good agreement with structural transitions. The catalytic properties of these powdered materials in presence of air and 2500 ppm of carbon monoxide gas flows are studied by Fourier Transform Infrared spectroscopy (FTIR). The catalytic activity given rise to the total oxidation reaction and has been determined from the CO2 FTIR absorption band intensities. This activity reaches the complete transformation at 400°. The conversion rate of CO into CO2 is analyzed as a function of temperature and reaction time.

Superficial effects and catalytic activity of ZrO2–SO42− as a function of the crystal structure

As assessment was made of the influence of the crystal structure on the activity of SO42−–ZrO2 catalysts for the acid-catalyzed reactions of sucrose inversion and the esterification of fatty acids with glycerol. Purely monoclinic or purely tetragonal SO42−–ZrO2 catalysts were synthesized by sulfation with 1M sulfuric acid of different ZrO2 starting materials of defined crystal phase. The final catalysts were obtained by calcination at 400°C, a relatively mild temperature for this kind of materials. Structural and morphological characterization tests showed that the crystal phase of zirconia had an influence on the properties of the sulfated zirconia catalysts. Monoclinic and tetragonal catalysts had different acidities and also different levels of activity in the reactions. Better results in the sucrose inversion tests were obtained using tetragonal phase catalysts while monoclinic phase materials were better catalysts for glycerol esterification.The catalysts were further characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and nitrogen physisorption. The acidity was measured by amine titration using Hammett indicators and FT-IR absorption of adsorbed pyridine.

Mechanically exfoliated ultra-thin WO3 nanostructures: study of their enhanced electrical properties

Ultra-thin orthorhombic β-WO3 nanoflakes were prepared by two-step sol-gel-exfoliation method and sintered at 550 and 650 °C, respectively. Their morphology and electrical properties were investigated by the following material characterisation techniques: energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), current sensing force spectroscopy atomic force microscopy (CSFS-AFM, or PeakForce TUNA™), Fourier transform infra-red absorption spectroscopy (FTIR), linear sweep voltammetry (LSV) and Raman spectroscopy. CSFS-AFM analysis exhibited good correlation between the topography of the developed nanostructures and various features of WO3 nanoflakes. It was found that β-WO3 nanoflakes annealed at 550 °C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, microstructured and nanostructured WO3 synthesized at alternative temperatures.

Characterization of New Categories of Bioactive Based Tellurite and Silicate Glasses

New types of tellurite glass ceramics were prepared and studied from the viewpoint of bioactivity. The obtained results were compared with those of silicate glass ceramics. The crystallization behaviors of both silicate and tellurite glass ceramics with equal ratio of CaO/P2O5 were investigated. The silicate glass samples were transformed to glass ceramics by a thermal treatment process. While the tellurite glass ceramics were directly obtained without any thermal treatment. The microstructure of these materials was characterized by X-ray diffraction (XRD), Fourier transform infrared absorption spectroscopy (FTIR) and a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (SEM/EDX). The results revealed clear proof that TeO2 promoted the nucleation and crystallization processes which led to the formation of different crystalline bio-phases. While the silicate glasses showed a much lower degree of crystallinity than that presented by the tellurite glass ceramics. The crystals of tellurite containing glass were needle- like morphology, which is attributed to the one-dimensional rapid growth of the apatite-tellurite phase. On the other hand, a particle-like morphology is shown in the silicate glass matrix. Bioactivity of the glasses in simulated body fluids (SBF) was investigated. Tellurite containing glass ceramics showed a better bioactivity during the in vitro test than that of the silicate one. This was attributed to a great analogous between the morphology of crystals of tellurite glass and the morphology of hydroxyapatite in human bone, since both possess a needle-like morphology.

Enhanced electrical properties in sub-10-nm WO3 nanoflakes prepared via a two-step sol-gel-exfoliation method.

The morphology and electrical properties of orthorhombic β-WO3 nanoflakes with thickness of ~7 to 9 nm were investigated at the nanoscale with a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), current sensing force spectroscopy atomic force microscopy (CSFS-AFM, or PeakForce TUNA™), Fourier transform infra-red absorption spectroscopy (FTIR), linear sweep voltammetry (LSV) and Raman spectroscopy techniques. CSFS-AFM analysis established good correlation between the topography of the developed nanostructures and various features of WO3 nanoflakes synthesized via a two-step sol-gel-exfoliation method. It was determined that β-WO3 nanoflakes annealed at 550°C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, micro and nanostructured WO3 synthesized at alternative temperatures.

Fabrication of SDBS intercalated-reduced graphene oxide/polypyrrole nanocomposites for supercapacitors

PPy (polypyrrole)/SDBS (sodium dodecyl benzenesulfonate) intercalated reduced graphene oxide (rGO) nanocomposites (PPy/GSR) were prepared via in situ oxidative polymerization of pyrrole on the SDBS interposed graphene. FE-SEM (field emission scanning microscopy), TEM (transmitting electron microscopy), UV–vis (ultraviolet and visible) absorption spectroscopy, FT-IR (Fourier transform infrared) spectroscopy, XRD (X-ray diffraction) analyzer and TGA (thermogravimetric analysis) instrument were used to characterize the morphology and structure of the samples. The results showed the disordered GSR (SDBS organo modified-rGO) disappeared and rGO existed in the form of individual graphene sheet or stacked layers in PPy matrix. The rGO serves as a support material for nano-sized PPy particles. In addition, CV (cyclic voltammetry), GCD (galvanostatic charge-discharge) and EIS (electrochemical impedance spectroscopy) techniques were used to measure the electrochemical properties with a three-electrode cell measurement. The specific capacitance of the PPy/GSR nanocomposite achieved 277F/g for the PPy/GSR 9:1 sample.

Gem quality and archeological green ‘jadeite jade’ versus ‘omphacite jade’

Raman spectroscopy was used for the characterization of seven gem quality green ‘jade’ samples and three green ‘jade’ samples of archaeological importance. The results were also compared with those acquired by other nondestructive techniques such as classical gemology, energy‐dispersive X‐ray fluorescence (EDXRF), ultraviolet‐visible‐near infrared (UV‐Vis‐NIR) in absorption, Fourier transform infrared spectroscopy (FTIR) in absorption and micro‐FTIR in reflectance. Five samples of gem quality and two samples of archaeological interest were found to be ‘jadeite jade’, whereas two samples of gem quality and one sample of archaeological interest were ‘omphacite jade’. Raman spectroscopy is found to be the most efficient method for their characterization. The results were confirmed with EDXRF and micro‐FTIR in reflectance. Data acquired using classical gemology, UV‐Vis‐NIR absorption and FTIR absorption spectroscopy were similar on ‘omphacite jade’ and ‘jadeite jade’. Copyright © 2014 John Wiley & Sons, Ltd.

H<sub>2</sub>O and HCl trace gas kinetics on crystalline HCl hydrates and amorphous HCl / H<sub>2</sub>O in the range 170 to 205 K: the HCl / H<sub>2</sub>O phase diagram revisited

Abstract. In this laboratory study, H2O ice films of 1 to 2 μm thickness have been used as surrogates for ice particles at atmospherically relevant conditions in a stirred flow reactor (SFR) to measure the kinetics of evaporation and condensation of HCl and H2O on crystalline and amorphous HCl hydrates. A multidiagnostic approach has been employed using Fourier transform infrared spectroscopy (FTIR) absorption in transmission to monitor the condensed phase and residual gas mass spectrometry (MS) for the gas phase. An average stoichiometric ratio of H2O : HCl = 5.8 ± 0.7 has been measured for HCl · 6H2O, and a mass balance ratio between HCl adsorbed onto ice and the quantity of HCl measured using FTIR absorption (Nin – Nesc – Nads) / NFTIR = 1.18 ± 0.12 has been obtained. The rate of evaporation Rev(HCl) for crystalline HCl hexahydrate (HCl · 6H2O) films and amorphous HCl / H2O mixtures has been found to be lower by a factor of 10 to 250 compared to Rev(H2O) in the overlapping temperature range 175 to 190 K. Variations of the accommodation coefficient α(HCl) on pure HCl · 6H2O up to a factor of 10 at nominally identical conditions have been observed. The kinetics (α, Rev) are thermochemically consistent with the corresponding equilibrium vapour pressure. In addition, we propose an extension of the HCl / H2O phase diagram of crystalline HCl · 6H2O based on the analysis of deconvoluted FTIR spectra of samples outside its known existence area. A brief evaluation of the atmospheric importance of both condensed phases – amorphous HCl / H2O and crystalline HCl · 6H2O – is performed in favour of the amorphous phase.

Rapid Differentiation and Identification of <i>Shigella sonnei </i>and <i>Escherichia coli </i>O157: H7 by Fourier Transform Infrared Spectroscopy and Multivariate Statistical Analysis

Fourier transform infrared spectroscopy (FTIR) combined with multivariate statistical analysis was applied to differentiate and identify Shigella sonnei and Escherichiacoli O157: H7. FTIR absorption spectra from 4000-600 cm-1 were collected from sampling 10 μL of bacterial suspention. The spectra between 1800 and 900 cm-1 highlighted the most distinctive variations and were the most useful for characterizing the selected microorganisms. Spectra of the two bacteria were noticeably segregated with distinct clustering by principal component analysis (PCA). Further more, another cluster model of hierarchical cluster analysis (HCA) was established and could also gave a good separation between the two bacteria. These results demonstrate that FTIR technology has considerable potential as a rapid, accurate and simple method for differentiating and identifying bacteria.