John R. Loofbourow

Bio: John R. Loofbourow is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 12 citations.

Physical methods for the identification and assay of vitamins and hormones.

Abstract: Publisher Summary Physical methods that have been employed in vitamin and hormone studies include: visible- and ultraviolet-absorption spectrophotometry, photochemical techniques, colorimetry, fluorescence spectroscopy, fluorophotometry, infrared and Raman spectroscopy, x-ray diffraction studies, manometric techniques, polarography, and isotopic tracer methods. Of these techniques, some have had limited application and others are not universally regarded as physical. As this chapter is limited to methods that are both essentially physical, and of broad application in the vitamin and hormone field, only the following topics are included: visible- and ultraviolet-absorption spectrophotometry, colorimetry, fluorescence spectroscopy, and fluorophotometry. It has not been practicable to consider all aspects of these techniques. In discussing colorimetry, for example, it has been necessary to omit reference to the many chemical problems concerned with the devising of color reactions and of procedures for eliminating interfering substances. In deciding what material to include and what to exclude, preference has been given to the quantitative and physical aspects of the methods discussed.

Spectrophotometric Method for Determination of 2,4-Dichlorophenoxyacetic Acid

Abstract: 1. A simple and accurate spectrophotometric method for the determination of 2,4-dichlorophenoxyacetic acid in aqueous and ether solutions is described. 2. The extinction coefficients for the acid in water at 2835 A and at 2300 A, and in ether at 2845 A, have been determined. 3. Certain chemical and instrumental precautions essential to quantitative results are discussed.

Hormone Assays in Obstetrics and Gynecology

Abstract: Publisher Summary This chapter reviews the pertinent information on hormone assays in women in such conditions as the gynecologist and the obstetrician are likely to encounter in clinical practice. It examines evidence in favor of, or against, the use of hormone determinations as a tool that may help the physician to determine his diagnosis, to establish a prognosis, and to decide on the therapy. Morphological changes due to hormonal activity may occur or persist some time after the release or withdrawal of the hormones responsible. This time-lag may give rise to apparent discrepancies between the result of a hormone assay and the clinical and histologic findings noted at the same time. Moreover, it should be remembered that the level of hormones and hormone metabolites in body fluids does not depend exclusively on the rate of secretion. Blood-levels, except for chorionic gonadotropin and estrogens in pregnancy, must be considered at best as they are very much less informative than excretion values. The latter should be calculated in weight or biologic units per excretion time, and they should be obtained from complete twenty-four hour collections.