Arlene A. Garrison

Photochemical transformation of pyrene and benzo(a)pyrene vapor-deposited on eight coal stack ashes

The photochemical decomposition of pyrene and benzo(a)pyrene, as adsorbates deposited from the vapor phase, has been examined on eight coal stack ashes of diverse origin and properties. Similar studies using alumina, silica gel, controlled-porosity glass, and graphite adsorbents also have been performed. Phototransformation of the adsorbates proceeds more slowly on any of the ash substrates than on alumina, silica, or glass surfaces. Those ashes relatively high in carbon and/or iron content are especially effective at suppressing photodegradation of adsorbed pyrene or benzo(a)pyrene. This relationship appears, at least in part, to be associated with the relatively dark colors of those ashes. The apparent acidity of ash surfaces does not appear to be related to the rate of phototransformation of adsorbed polycyclic aromatic hydrocarbons. 40 references, 1 figure, 5 tables.

Analytical Applications of Matrix Isolation Fourier Transform Infrared Spectroscopy

A review of analytical applications of matrix isolation Fourier transform infrared spectroscopy is presented. The characteristics of matrix isolation spectroscopy are discussed along with practical techniques for obtaining analytically useful results. A few studies relating to matrix isolation used in conjunction with Raman and conventional IR spectroscopy are reviewed. The majority of analytical applications of matrix isolation vibrational spectroscopy has entailed the use of FT-IR techniques. Qualitative and quantitative results from a number of sample types are presented. The coupling of matrix isolation vibrational spectroscopy with chromatographic separations is reviewed.

Practical Aspects of Rapid Scanning Fourier Transform Time-Resolved Infrared Spectroscopy:

The results of experiments designed to study the infrared spectra of transient species produced by ultraviolet photolysis of acetaldehyde are reported and analyzed. Spectra obtained in similar work [A. W. Mantz, Appl. Opt. 17, 1347 (1978)] are critically reinterpreted. The evidence presented demonstrates that insufficient attention has been given to the necessary stringent control of experimental conditions. The consequences of poor control are described and a qualitative explanation is offered. This paper discusses, in particular, the production of spectral artifacts consisting of displaced (not folded) bands and their previous erroneous assignments. Other practical aspects of time resolved Fourier transform spectroscopy with a rapid scanning Michelson interferometer are outlined.

Analysis of Polycyclic Aromatic Compounds Containing Nitrogen and Oxygen by Matrix Isolation Fourier Transform Infrared Spectroscopy

Matrix isolation sampling techniques are used in the qualitative and quantitative analysis of polar aromatic hydrocarbons. Fourier transform infrared spectrometry is used to characterize pure compounds isolated in nitrogen matrices and subsequently to identify individual components in mixtures. Compounds studied are polycyclic aromatic hydrocarbons containing nitrogen and oxygen heteroatoms or amine substituent groups. These toxic substances are common to coal liquefaction products. The analytical method chosen, matrix isolation Fourier transform infrared spectrometry, is capable of distinguishing between isomers differing only in the position of the heteroatom. Beers law is obeyed in the range between 20 μg and 500 ng.

The effect of nitrogen dioxide on the photochemical and nonphotochemical degradation of pyrene and benzo[a]pyrene adsorbed on coal fly ash

Abstract Nitration by NO 2 of pyrene or benzo[a]pyrene adsorbed from the vapor phase onto six coal ashes, alumina, and silica substrates is not observed if the NO 2 is thoroughly purged of nitric acid. Also, the photochemical transformation of pyrene or benzo[a]pyrene adsorbed on these substrates is not detectably influenced by the presence of nitric acid-free NO 2 . Photochemical production of nitro derivatives of adsorbed polycyclic aromatic hydrocarbons in the presence of NO 2 does not appear to be a significant process unless appreciable concentrations of nitric acid, or perhaps strong oxidants such as ozone, also are present.

Recent advances in the development of a fiber-optic-based instrument for on-line Raman analysis

The measurement of composition of chemical process streams at multiple points is a critical problem in many industrial environments. We are developing an instrument, based on laboratory Raman spectroscopy, to measure composition of multiple components in a distillation column. A Nd:YAG laser is used to excite the sample and an interferometer is used to detect the Raman spectrum. The light from the laser is routed to the measurement points through a fiber optic probe which also gathers the light generated in the column by the Raman effect. A multiplexer is introduced to allow sharing of the expensive components of the system among several measurement points. The instrunient will initially be applied to distillation columns, but should be applicable to analysis of many liquid mixtures of commercial interest. The response time is approximately three minutes per measurement. The composition measurement range is from approximately 5% to 100% with an average error of less than 2% RMS. Progress in the implementation of the instrument will be discussed, with particular emphasis on losses due to optical fiber lengths up to 35 meters.

Fourier transform Raman spectroscopy-application to process control

A commercial FT-Raman instrument has been modified for use in on-line chemical composition analysis to control an industrial distillation column. Optical fibers are utilized to allow the placement of the instrument 35 meters from the process environment. Various process probes have been tested and compared. Computational algorithms are used to develop a mathematical model which correlates spectral characteristics to composition. Predictions from the model are presented at three minute intervals to allow statistical process control of a distillation column through operator intervention. Recent application studies and probe modifications are discussed.

On-line analysis of chemical composition using an FT-Raman spectrometer in the near-ir

Newly commercialized Fourier transform Raman spectroscopic instrumentation provides a simpler alternative for vibrational spectroscopic analysis. Instrument vendors currently design for laboratory use, but there are many potential process applications of these stable, easy to use instruments. Raman spectroscopy is highly suited to analysis of aqueous samples. Near infrared excitation minimized fluorescence interference and allows for remote operation via fiber optic probes. The Department of Energy has funded research at the Measurement and Control Center to establish the utility of this method for on-line composition analysis in distillation columns. Laboratory evaluation and instrument employs an air-cooled laser and a thermoelectrically cooled detector. The device is mounted on a three by three foot cart for convenient location in control rooms. Current fiber optic extension cables allow for analysis in a cell thirty five meters from the instrument. Application of the device to an acid recovery column at Tennessee Eastman Corporation in Kingsport, Tennessee will be discussed. Sensor placement is critical to optimal application of any on-line device. Potential energy savings and product throughput increase will be detailed.

Progress In Fourier Transform Time-Resolved Spectroscopy

The development of Fourier transform infrared spectroscopic studies of pulsed transient phenomena, using rapid scanning interferometers is described. Early results obtained using this technique have been shown to have been misinterpreted. Some problems that have been encountered are described and systems of interest discussed.

Use Of Matrix Isolation Fourier Transform Infrared (FTIR) In Gas Chromatographic Detection

Earlier work in this laboratory has shown matrix isolation Fourier transform infrared spectrometry (MI FTIR) to possess several advantages over conventional sampling techniques for the qualitative analysis of complex samples. The ability to obtain very sharp spectra using MI makes it possible to distinguish between very similar compounds, including isomers, present in a sample. Instrumentation to couple capillary column gas chromatography (GC) to MI FTIR has been developed as an alternative to on-the-fly gas-phase GC FTIR measurements. This technique allows leisurely study of chromatographic fractions at medium resolution (1 cm-1). A gold-plated disk is cooled to 15K with a closed-cycle helium refrigerator and used to collect compounds eluting from the GC. Nitrogen is used as both GC carrier gas and matrix material. Beam condensing optics and KRS-5 rods are used to reflect the IR beam from the individual sample deposition surfaces.