Determination of ruthenium and chromium by X-ray fluorescence spectrometry and the use of inert ruthenium (II) phenanthroline as a solid phase marker in sheep digestion studies

Abstract

SummaryThe quantitative estimation of ruthenium and chromium in faeces and digesta from sheep by X-ray fluorescence spectrometry is described. Estimates of calibration parameters, established by regression analysis, were applicable to a range of matrices. Lower limits of detection of 2·4 mg Ru/kg (solid), 1·8 mg Ru/1 (liquid), 1·6 mg Cr/kg (solid) and 1·1 mg Cr/1 (liquid) and precisions, expressed as coefficients of variation, of 5·4% at 17·7 mg Ru/kg (solid), 5·1% at 182·7 mg Cr/kg (solid) and 1·1% at 152 mg Cr/1 (liquid) were acceptable for the routine analysis of Ru and Cr.The use of inert ruthenium phenanthroline (Ru-P) and inert chromium ethylenediamine tetra-acetic acid (Cr-EDTA) as solid:liquid dual phase markers in digestive physiological studies was evaluated. The specificity of Ru-P for the particulate phase of digesta, established by both in vitro and in vivo experiments, was found to be 92–98%, and in vivo recovery of intraruminally administered Ru-P in faeces was 97–101%. In vitro incubation of rumen liquor showed that concentrations of Ru-P up to 10−4 M had little effect on volatile fatty acid production rates but at 10−3 M there was virtually complete inhibition of acetate and propionate production.Advantages of using inert Ru-P as a solid phase marker are discussed.