IR spectra of toluene, ethylbenzene and styrene adsorbed on pressed discs of hematite between room temperature and 400°C are described. Mechanisms of adsorption and transformation are discussed and compared with those reported on the basis of kinetic measurements of ethylbenzene dehydrogenation on iron oxide catalysts. © 1985 Akadémiai Kiadó

No abstract

We discuss situations where thermogravimetric/Fourier transform infrared (TG/FT-IR) plots are obtained which differ substantially from the expected ones. The most common of these situations involves samples that release atmospheric components (H2O, CO2) at low temperatures. It is shown that the phenomena are mainly related to the purging action of the carrier gas, which strongly influences the spectroscopic portion of the TG/FT-IR plot. Such an influence, as well as the different situations originating from it, is discussed and explained on the basis of an analogy with the operational mode of a conventional dispersive spectrometer.

Sir: Some papers dealing with the ultraviolet and visible study of molecular vapors produced by electrothermal atomizers were recently published (1-5). Various instruments were proposed depending on the aim of the work, from conventional flameless atomic absorption spectrometers (1-4) to dedicated equipment (5).Recently also the infrared range has been investigated, coupling an FT-IR spectrometer with a heated graphite atomizer, thus introducing further analytical applications of this device (6). At the same time new techniques have been developed for simultaneous multielement determination by graphite furnace atomic absorption (GFAA) or emission spectrometry (7)(8)(9).Considering these different applications, it seems advisable to explore the capability and behavior of electrothermal atomizers in acquiring, with the same equipment, molecular and/or atomic spectra for qualitative and quantitative analysis. This work reports some results obtained by a single instrument, made up of a graphite furnace and a diode array detector, in the ultraviolet investigation of vaporization phenomena of organic and organometallic compounds previously studied (2,4, 6).EXPERIMENTAL SECTION Apparatus. The equipment consists of a graphite furnace atomizer, Perkin-Elmer HGA-76 B, and Jasco KS-1Q0 M multispectrometer modified to meet the requirements of this study.The atomizer is equipped with an AS-1 autosampler, while solids are sampled as previously described ( 6). The spectrometer includes a deuterium source, polychromator, data processor, and recorder. Deuterium lamp, atomizer, and polychromator are mounted on an optical rail. The diode array of the polychromator (512 elements 25 pm wide) is a Reticon 512 S. The wavelength range (190-355 nm) is focused on the detector diodes by a concave holographic grating (500 lines/mm) blazed at 230 nm. A baffle inserted in front of the entrance slit of the polychromator reduces the detection of light emitted by the graphite furnace tube walls.The calculated resolution of the polychromator is about 0.3 nm/diode and the stray light is evaluated below 0.3%.The data processor can acquire up to 16 spectra with collection times varying from 0.05 s to 1 s and interval times from 0.05 s to 25 s. The spectra are transferred by RS-232 C interface to a Perkin-Elmer 7500 professional computer for absorbance calculation, data storage, and representation.Reagents. Crude oils, pigments, and polymers are examined in this work. The oils are diluted 1 to 10 with pure grade toluene. Pigment Blue 15 (copper phthalocyanine), Pigment Yellow 1 (monoazo derivative of 2-nitro-p-toluidine and acetoacetanilide), and Pigment Red 48:4 (Mn salt of monoazo derivative of 6amino-4-chloro-3-methylbenzenesulfonic acid and 3-hydroxy-2-

No abstract