No abstract

The measurement of nuclear magnetic resonance absorption of hydrogen nuclei in water provides a rapid method for the determination of the water content of potato tissue without reference to other standard moisture procedures. In the case of apple tissue, the same procedure can be used, provided correction is made for soluble solids. Using the method previously applied to starch suspensions, the results obtained on water content of potatoes

Investigation of conformational changes of organic molecules sorbed in zeolites by proton magnetic resonance spectroscopy

An investigation was made of the applicability of the modulation method of magnetic resonance absorption for the determination of hydrogen in various liquids and in aqueous suspensions of starch. The materials investigated contained from (1.1 to 6.7) X loz2 hydrogen atoms per cc. in the liquid phase. The thermal relaxation time, TI, ranged from 0.3 to 3.7 seconds. The influence of TI on the measurements through radiofrequency saturation was eliminated by an extrapolation to zero radio-frequency magnetic field of a series of measurements at radio-frequency intensities in the range 10-4 to gauss. The precision of the measurements was limited to about 20/, by electrical noise in the spectrometer employed. The application of the magnetic absorption method for the determination of the water content of biological tissues on an absolute basis is briefly discussed.ITH the development of techniques suitable for liquids W and solids, the quantitative analytical aspects of magnetic resonance absorption spectroscopy have become of great interest. Cnfortunately, of the various methods for measurement of magnetic absorption, none appears uniquely adapted for routine analysis. One method, widely used for the observation of nuclear magnetic resonance absorption, utilizes small amplitude sinusoidal modulation ( I ) , with the detector followed by a narrow-band amplifier and lock-in amplifier. A small modulation of amplitude, H,, and angular frequency, w,, is applied to the static field, Ha, as the frequency of the radiofrequency magnetic field is slowly varied through the resonance region. For a simple absorption line the observed signal, D, proportional to the slope of the absorption line, passes through the extreme values D,,, and D,,,, corresponding to the inflection points of the absorption line. It is of interest in the analytical applications of magnetic absorption to consider the usefulness of the quantity D,,, as a measure of No, the number per cubic centimeters of sample of magnetic nuclei of the species of interest. In the present paper the application of D, , is considered for the determination of hydrogen nuclei in liquids and in mixtures (suspensions) of liquids and solids in which the hydrogen nuclei of interest are contained in the liquid phase. A primary object was to determine whether N O can be determined accurately via Dmay in SJ stems in which radio-frequency saturation is appreciable under the conditions of measurement, and the extent of saturation is both unknown and variable with No. I t -as not the object of the present work to determine the ultimate precision of the method, but rather to explore the general performance in an analytical procedure in order to determine whether fundamental limitations exist. THEORYFor a simple absorption line described by a shape function g(r), the signal D observed in the absence of radio-frequency saturation effects (3) may be expressed as Here C is a constant for an appropriate choice of instrument 1 Present address. Southwest Research Institute, San ilntonio, Tex. parame...

We describe a software system and a hardware interface between a laser Raman spectrometer and a time-shared computer. This data acquisition system controls the wavelength drive of the spectrometer and the analyzer orientation using stepping motors and position sensors. With this method accurate depolarization ratios can be determined at every wavelength increment. Digitized photon counting gives good signal/noise ratios and a wide dynamic range for Raman intensity measurements. The software design permits automatic separation of isotropic and anisotropic spectra, repetitive counting periods, instant scope display of raw, reduced or integrated data, and numerous data refinement options.