Analytical recovery of chromium from diet and faeces determined by colorimetry and atomic absorption spectrophotometry

The present study examined whether differences in mineral content of the diet or faecal samples contribute to variation in analytical recovery of marker chromium from these samples. Three corn/soya bean diets containing various levels of Ca, P and Mg, and the corresponding faeces of swine fed these diets were used. Diet and faecal samples were analysed by colorimetry and atomic absorption spectrophotometry with increments of Cr added to samples either preceding or following the acid digestion procedure. Results indicated significant differences (P <0·05) in analytical recovery of Cr between diets and corresponding faeces, between individual diets and faeces, and between methods of determination. The acid digestion step leads to the lower recovery of Cr (diets, P <0·05; faeces, P <0·01) whereas no significant differences were found in post‐digestion procedure by either method of determination, indicating that marker‐chromium loss due to the acid digestion procedure was not higher than the apparent loss due to the acid analytical method. Results suggest that the analytical recovery factors should be considered when estimating faecal recovery of marker chromium or digestibility of nutrients.