Showing papers by "Peter R. Griffiths published in 1978"

Infrared analysis by diffuse reflectance spectrometry

Abstract: Measurements of the diffuse reflectance spectra of powdered materials in the ultraviolet and visible region of the spectrum have been performed for many years. Ultraviolet-visible reflection spectra have been used for colorimetry, and qualitative and quantitative analysis. Instruments for the accurate measurement of diffuse reflectance spectra in this region frequently incorporate a monochromator together with an integrating sphere for the collection of radiation diffusely reflected from the sample. Although an integrating sphere generally allows photometrically accurate results to be obtained, its efficiency is so low that the signal-to-noise ratio (SNR) of spectra measured this way may be more than two orders of magnitude lower than the SNR of spectra measured by direct transmittance.

Application of Fourier Transform Infrared Spectroscopy to the Identification of Trace Organics in Water

Abstract: The application of dual-beam Fourier transform infrared spectroscopy to the on-line identification of organic water pollutants separated by gas chromatography and high performance liquid chromatography is described. The materials are concentrated using neutral polystyrene resins, eluted with diethyl ether, and chromatographed. For GC-IR measurements, readily identifiable spectra from compounds originally present at a level of 2 ppb may be obtained, and if procedures are optimized an increase in sensitivity of at least an order of magnitude is predicted. HPLC-IR measurements using conventional flow-through cells are less sensitive, and a procedure for solvent elimination is suggested which will yield submicrogram detection limits.

Fourier Transform Infrared Spectrometry: Theory and Instrumentation

Abstract: Over the past decade Fourier transform infrared spectrometry (FT—IR) has become an important tool for vibrational spectroscopists and analytical chemists. In this chapter we will discuss the theory of FT—IR and show how it relates to instrumental design. The performance of FT—IR spectrometers will be compared to that of conventional grating spectrometers, and illustrated in the next chapter through descriptions of several applications where FT—IR has been used to advantage.

Fourier transform infrared spectroscopy: recent developments.

Abstract: The 1977 International Conference on Fourier Transform Infrared Spectroscopy was held 20-24 June 1977 at Columbia, S.C. The manuscripts of most of the invited speakers at this meeting follow this report. This paper summarizes the seven papers in this category which could not be submitted. These papers described the application of cryogenic interferometers to atmospheric sounding (Stair), to the measurement of cosmic background radiation (Richards), and to the study of chemical reaction dynamics (McDonald). The use of ultrasensitive far infrared detectors for studying the properties of solids was described by Sievers. Genzel and Griffiths described applications of the optical subtraction technique for far infrared and mid infrared measurements, respectively. Finally Wyntjes summarized his views on the present and future of interferometry.

Applications of the FFT in Electrochemistry

Abstract: Most modern electroanalytical techniques are basically electrochemical relaxation measurements (ERM), in which one observes a time-varying response from some type of electrochemical cell to an applied perturbation such as current, potential, or charge. The observed relationship between the response and the perturbation is known as the transfer function and provides analytical data, kinetic information, and/or mechanistic information on a variety of processes that can occur in the electrode, in the electrolyte bulk, or in the interfacial regions. Perhaps the most common experiment is one in which a cell voltage perturbation is created and the cell current response is measured. Typical techniques that fall into this category are DC, AC, and pulse polarography, linear sweep and triangular wave voltammetry, and potential step chronoamperometry.

Transform Techniques in Chemistry: Past, Present, and Future

Abstract: Although the use of transform techniques in analytical chemistry and applied spectroscopy has only become widespread in the past five years, the history of this subject can be traced back to the middle of the nineteenth century when the effect of the interference of light was first used to derive spectroscopic information In 1862, Fizeau(1) used Newton’s rings to show that the yellow sodium radiation was a doublet whose separation was 1/980 of their average wavelength At the end of the century Michelson designed the interferometer, which now bears his name(2,3) The initial uses of this instrument for spectroscopic purposes concerned the determination of spectral profiles through the use of the visibility technique,(4) which is essentially a study of the envelope of what we now call the interferogram Rayleigh(5) pointed out that a unique spectral distribution cannot be found from the visibility curve itself, and the Fourier transform of the interferogram is needed to calculate the spectrum unequivocally

Infrared Fourier Transform Spectrometry: Applications to Analytical Chemistry

Abstract: Before the applications can be discussed for which the use of FT—IR spectrometers give the greatest advantage over grating spectrometers, we will first discuss the various factors leading to differences in the performance of the two types of spectrometer Obviously the performance of any type of spectrometer is dependent on the nature of its components, but in this section we shall only compare typical commercially available mid-infrared spectrometers Thus for the purpose of illustration, the FT—IR spectrometer will contain a rapid-scanning Michelson interferometer with 2-in-diameter mirrors, a Ge: KBr beamsplitter and a TGS detector The grating spectrometer will be an optical null instrument with 52 × 52 cm interchangeable gratings and a thermocouple detector