Thermal degradation of polyesters by simultaneous TG-DTA/FT-IR analysis

A combination system of thermogravimetric/differential thermal analysis (TG-DTA) and Fourier-transform infrared absorption spectroscopy (FT-IR) was described. This simultaneous TG-DTA/FT-IR technique gave spectroscopic and weight loss information about the thermal degradation process of engineering polyesters; poly(ethylene terephthalate)(PET) and poly(butylene terephthalate)(PBT). The evolved gases from PET were benzoic acid, carbon dioxide and carbon monoxide, while those from PBT were terephthalic acid esters and benzoic acid esters.

---

Zusammenfassung Es wird ein kombiniertes System aus TG-DTA und FT-IR beschrieben. Mit dieser simultanen TG-DTA/FT-IR-Technik wurden spektroskopische und Massenverlustangaben über die thermische Zersetzung technisch wichtiger Polyester, namentlich von Poly(ethylenterephthalat) (PET) und Poly(Butylenterephthalat) (PBT) ermittelt. Die aus PET freigesetzten Gase waren Benzoesäure, Kohlendioxid und Kohlenmonoxid, die aus PBT freigesetzten Gase hingegen Terephthalsäureester und Benzoesäureester.

     

Applications of FT-IR/microscopy in forensic analysis

The technique of FT-IR/microscopy is applied to a variety of problems faced by the forensics chemist. These are as varied as the identification of drugs and fibers to the assignment of the origin of a paint sample. Our efforts in the effective utilization of FT-IR/microscopy in this area and usage of new data bases to aid in identifications are discussed.     

GC/FT-IR: A unique choice for solvent analysis

The analysis of solvents for both purity and component identifications is routinely performed by gas chromatography (GC). Coupling it with the latest FT-IR systems results in a technique which yields ppm sensitivity and excellent library search results.     

The differentiation and identification of pathogenic bacteria using FT-IR and multivariate statistical analysis

Correspondence analysis was used to classify the pattern-like FT-IR spectra of intact bacteria. The analysis was performed on a data set of approximately 80 normalized spectral derivatives of a selection of pathogenic bacteria. The correspondence analysis proved that the various different bacterial species were clustering in distinct regions of the correspondence maps suggesting that there do exist correlations between spectral data and biochemical/microbiological classification.     

DTA and FT-IR analysis of the rehydration of basic magnesium carbonate

The rehydration characteristics of a commercially produced hydromagnesite and two basic magnesium carbonates synthetically produced from Mg(OH)₂, are presented. The products were dehydrated and dehydroxylated at 325°C before rehydration was attempted. DTA and FT-IR were used to follow the structural changes that occurred during the rehydration processes. The results obtained for the commercially and synthetically produced hydromagnesite products indicated that the original symmetry of the groups was reclaimed during rehydration. This was not observed for the synthetically produced unidentified basic magnesium carbonate product. This investigation provides insight into the rehydration characteristics of a select group of basic magnesium carbonates. This revised version was published online in July 2006 with corrections to the Cover Date.     

Interaction of soybean agglutinin with leukemic T-cells and its use for their in vitro separation from normal lymphocytes by lectin-affinity chromatography

A procedure for separation of leukemic T-cells from normal lymphocytes, using lectin-affinity column chromatography, is described. CNBr-activated Sepharose 6MB was used as a non-mobile phase. The gel was covalently coupled with soybean agglutinin (SBA), then served as an affinity probe for fractionation of mixture of normal lymphocytes and leukemic cells. Leukemic cell lines, derived from acute lymphoblastic leukemia (Jurkat, MOLT-4, RPMI-8402), were tested. The elution of normal lymphocytes was carried out by PBS(-). The leukemic T-cells, interacting with SBA, were removed by N-acetyl-D-galactosamine or low-concentration acetic acid. The type and viability of the separated cell fractions were analyzed by flow cytometry and fluorescent microscopy, using adequate fluorescent antibodies. The interaction of leukemic T-cells with free SBA, as well as with SBA-conjugated Sepharose beads, was examined fluorimetrically and visualized by fluorescent microscopy, using FITC-SBA as a marker. The rate of cell elution on SBA-affinity column decreased in order: normal > leukemic T-cells. Both normal lymphocytes and leukemic T-cells were removed in a mixture from SBA-free Sepharose 6MB by PBS(-) and were not fractionated discretely. The leukemic T-cells specifically interacted with SBA as well as with SBA-affinity adsorbent. In contrast, the normal lymphocytes did not interact with free SBA as well as with SBA-conjugated Sepharose beads in the concentrations applied. The method potentially combines a discrete cell fractionation with manifestation of a specific target cytotoxicity of SBA against leukemic T-cells, without any influence on normal lymphocytes.     

An integrated GC/FT-IR system for the analysis of environmental pollutants

An integrated gas chromatography/Fourier transform infrared spectrometry (GC/FT-IR) system developed for the analysis of environmental pollutants is described. The versatility of the system allows the utilization of many different techniques of sample introduction and manipulation during analysis. The sample can be introduced by direct injection or thermal desorption from an adsorbent cartridge, and can then be separated on one of two capillary columns and detected by FT-IR or an FID. Cold traps and collection cartridges incorporated in the system permit recovery and additional fractionation of samples. Recovered sample and sample fractions can then be re-analyzed by GC/FT-IR or subsequently analyzed by GC/MS or other methods.     

FT-IR差谱法测定改性聚苯乙烯组成

本实验利用NICOLET 7199 FT-IR仪器,采用二次扣减法完成了低含量聚丁二烯改性的聚苯乙烯样品组成的定量分析。当苯乙烯含量在90～95%范围以内,标准误差小于±0.3%时,苯乙烯含量相对误差小于1%,丁二烯含量相对误差小于10%。     

Quantitative analysis of synthetic calcium carbonate polymorphs using FT-IR spectroscopy

Fourier Transform Infrared Spectroscopy (FT-IR) was used successfully for the simultaneous quantitative analysis of calcium carbonate phases (calcite, aragonite, vaterite) in ternary mixtures. From the FT-IR spectra of pure calcite, aragonite and vaterite powders with KBr, the absorptivities, α, of the absorption bands at 713 cm⁻¹ for calcite, 745 cm⁻¹ for vaterite, 713 and 700 cm⁻¹ for aragonite, were determined. In order to overcome the absorption band overlapping a set of equations based on Beer's law was developed. The detection limits were also established and found to be 1.1×10⁻⁴ mg calcite per mm² of pellet at 713 cm⁻¹, 3.6×10⁻⁴ mg aragonite per mm² of pellet at 700 cm⁻¹, 1.8×10⁻⁴ mg aragonite per mm² of pellet at 713 cm⁻¹ and 3.1×10⁻⁴ mg vaterite per mm² of pellet at 745 cm⁻¹. Analysis of a known ternary mixture of calcium carbonate polymorphs tested the validity of the method.     

FT-IR/PAS investigation of solid fuels and catalysts

Coal and catalysts are examples of substances of great technical importance, whose knowledge has advanced for many years empirically. They are considered as disordered and complex materials. FT-IR/PAS suggests models closer to the real systems as the samples can be examined as they are: coal with the same sampling procedure as for ASTM analysis and catalysts during catalysis without manipulation. Some examples are reported.     

Selection of modulation frequency of FT-IR equipped with an MCT detector for thin-film analysis

Optimal modulation frequency (scan rate) of an FT-IR equipped with a mercury–cadmium–telluride (MCT) detector has been investigated for obtaining high quality spectra of a monolayer-level thin film. Since an MCT detector is a semiconductor light device, it does not respond to modulation frequency significantly in comparison to a pyroelectric detector. A very thin film, however, requires high-throughput measurements to have high signal-to-noise ratio. In this study, a balance of throughput and measurement time has been investigated by varying modulation frequency by using two spectrometers that have different sampling frequencies. In this study, the stability of the baseline of absorbance spectra was also investigated depending on modulation frequencies, which suggested that 60 kHz was most suitable for quantitatively reliable transmission measurements of Langmuir–Blodgett films.     

Preparation and FT-IR spectra of calcium bilirubinate

In this investigation two calcium bilirubinates compounds, Ca(HBR)₂·H₂O and Ca(BR)·2H₂O, were prepared. Their Fourier transform infrared spectra were measured in KBr discs and in fluorolube and nujol mulls, respectively. The results suggest that it is better to identify the Ca(HBR)₂·H₂O and Ca(BR)·2H₂O with fluorolube and/or nujol mulls when examining mixtures (e.g. gallstone).     

水合硼氧酸盐结晶过程中液相的红外光谱

使用差示红外光谱的方法记录了MgB4O7.9H2O,NaB5O8.5H2O,MgB6O10.7H2O和MgB6O10.7.5H2O过饱和水溶液结晶析出相应固相时液相中多聚硼氧配阴离子的变化。结果得出,硼氧酸盐水溶液的红外光谱在800－1000cm^-1波数范围内,存在多种多聚硼氧配阴离子的特征峰,并对振动光谱频率进行了归属。870,810cm^-1为三硼氧配阴离子特征峰;844cm^-1为四硼氧配阴离子特征峰;929cm^-1为五硼氧配阴离子特征峰;959cm^-1为六硼氧配阴离子的特征峰。     

Improvement and application of two extrapolation methods to FT-IR data

The applicability of two non-parametric extrapolation methods to FT-IR absorptance spectra is investigated. The first method minimizes those parts of the spectrum which do not satisfy a given constraint, while the second one changes them in each iteration through the true values.     

Effect of the 67Zn isotope on leukemic cells and normal lymphocytes

Porphyrinofullerene nanoparticles (NP) containing magnetic isotopes ²⁵Mg and ⁶⁷Zn (²⁵Mg-NP and ⁶⁷Zn-NP) and the natural isotopic composition of zinc (Zn) were tested on human leukemic cells of patients with acute leukemia and on lymphocytes of healthy donors. The fundamental differences in the cytotoxic effect of magnetic and nonmagnetic zinc isotopes on tumor cells were observed, as well as the complete absence of the influence of the magnetic magnesium isotope and pristine nanoparticles. The ⁶⁷Zn-NP manifested high cytotoxicity towards cells of acute B-lymphoblast leukemia with LD₅₀ almost three times lower than that of healthy donors and four times lower than that of the Zn-NP. Apoptosis was evaluated by cytofluorimetry for the drugs used.     

TGA/FT-IR: Thermogravimetric analysis with fourier transform infrared detection of evolved gases

Thermogravimetric analysis (TGA) is a widely employed technique for measuring the change in weight of a sample as a function of temperature or time in a controlled atmosphere. FT-IR has been utilized with success in the identification of gases [1]. The combination of these two techniques permits a complete characterization of materials in terms of thermal stability and decomposition mechanisms [2]. A complete integrated system for TGA/FT-IR analysis is described.     

FT-IR Study of Carbon Nanotube Supported Co-Mo Catalysts

In this paper, adsorption properties of dibenzothiophene (DBT) on carbon nanotube, carbonnanotube supported oxide state and sulfide state CoMo catalysts are studied by using thermal gravi-metric analysis (TGA) technique and FT-IR spectroscopy. Activated carbon support, 7-A1203 supportand supported CoMo catalysts are also subjected to studies for comparison. It was found that sulfidestate CoMoS/MWCNT, CoMoS/AC and CoMoS/γ-A12O3 catalysts adsorbed much more DBT moleculesthan their corresponding oxide state catalysts, as well as their corresponding supports. The chemicallyadsorbed DBT aromatic molecules did not undergo decomposition on the surface of supports, supportedoxide state CoMo catalysts and sulfide state CoMo catalysts when out-gassing at 373 K. FT-IR results indicated that DBT molecules mainly stand upright on the active sites (acid sites and/or transition active phases) of CoMoS/MWCNT catalyst. However, DBT aromatic molecules mainly lie flat on MWCNT and CoMoO/MWCNT.     

Surface oxidation of high-surface-area silicon carbide: FT-IR studies

The surface of ultrafine silicon carbide powders, prepared by a laser-driven gas-phase reaction was studied as a self-supporting disk by FT infrared spectrometry. After evacuation silicon and carbon atoms located at the surface give rise tovSiH andvCH bands. When heating in oxygen, subtraction spectra showed features which could be strictly correlated with a progressive growth of a silica layer: SiH and CH bands were replaced by new bands characteristic of amorphous silica and the typical band of surface silanol groups on silica (3745 cm^–1) simultaneously increased.     

On-line sample treatment and FT-IR determination of doxylamine succinate in pharmaceuticals

A low solvent consumption method for Fourier transform infrared spectroscopy (FT-IR) determination of doxylamine succinate in pharmaceuticals has been developed. The analyte was continuous and selectively extracted with a 13% (v/v) ethanol:chloroform solvent mixture, recirculating the solvent through the sample and monitoring the process by FT-IR. Doxylamine succinate was determined by on-line standard addition measuring the peak area in the regions 1730–1710 and 1485–1462 cm⁻¹ corrected with a two-point baseline established between 2000 and 1800 cm⁻¹. This new method implies low volumes of chloroformic solvent mixture, only 2.6 mL per sample, in front of classical batch FT-IR methods, improving analytical efficiency and reducing waste generation. The on-line extraction and standard addition determination of doxylamine succinate allowed a throughput of 10 h⁻¹.     

Flavor analysis by HRGC/FT-IR: Cherimoya (Annona cherimolia,mill.) fruit volatiles

The volatiles of fresh cherimoya (Annona cherimolia, Mill.) fruit pulp were separated by combined high-vacuum distillationliquid/liquid extraction (pentane/dichloromethane 2+1). After preseparation by liquid chromatography on silica gel three fractions (I-III) were obtained by eluting with pentane (I), pentane/diethyl ether (9+1) (II), and diethyl ether (III), and fractions II and III were subjected to HRGC/FT-IR analysis. 26 volatile compounds comprising nearly all the main components (range, 10–300 μg/kg fruit pulp) were identified by this technique for the first time in cherimoya fruit.