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Neutron Activation Analysis of Dysprosium (A Potential Inert Marker) in Hay and Feces^{1, 2,}

University of Arizona, Tucson 85721

Abstract

Neutron activation analysis of dysprosium in forage and fecal samples using a mass irradiation technique was accomplished without wet-ashing the sample. Samples were placed in a rotary specimen rack or "lazy-susan" surrounding the core of the reactor and irradiated with the "lazy-susan" under continuous rotation. Thus, all samples and appropriate standards were irradiated under identical conditions. The X-ray and gamma peaks of ¹⁶⁵Dy, 47 and 95 kev, respectively, were counted using a multi-channel analyzer. Differences in neutron flux due to tier (vertical position) in the "lazy-susan" were quantified. A tier correction factor was effective in the calculation of tier 2 sample concentrations from a tier 1 standard curve. The coefficients of variation (C.V.) among quadruplicate standards of each concentration averaged .9 and 1.1% for hay and feces, respectively. Triplicate subsamples of hay sprayed with Dy, and feces recovered from cattle fed the sprayed hay had mean C.V.'s of 5.0 and 1.5%, respectively. Since Dy has been shown in previous digestion studies to be highly recoverable, the development of a simplified, dependable Dy analysis procedure enhances the feasibility of using this rare earth as a reliable inert marker.

¹ Arizona Agricultural Experiment Station Technical Paper 2257.

² This paper is part of a dissertation prepared by the senior author in partial fulfillment for the Ph.D. degree in Agricultural Biochemistry and Nutrition.

³ Department of Watershed Management.

⁴ Department of Animal Science.

⁵ Department of Nuclear Engineering.

⁶ Present address: Bechtel Power Corporation, Ann Arbor, Michigan.

⁷ The authors gratefully acknowledge the technical assistance of George W. Nelson and Thomas E. Caffarella in the half-life determinations.