title: Use of microwave digestion and atomic absorption spectrophotometry to determine chromic oxide as a digestibility marker in feed, feces, and ileal content.
abstract: Most conventional digestion procedures, such as dry ashing and wet ashing, are tedious and labor intensive. Microwave digestion is a good alternative, because microwave dissolution is faster, safer, and simpler, and provides more controlled reproducible conditions than conventional methods. The purpose of this study was to develop a microwave digestion method for mineralizing meat and bone meal diets, feces, and ileal contents. Each sample was heated on a hot plate for 10 min, dry ashed at 65 degrees C for 4 h, and transferred into microwave vessels. Then, 10 mL 70% HNO3 was added. Samples were digested for 7, 10, and 20 min at 95, 90, and 85% power, respectively. After the heating cycle, 6 mL 30% H2O2 was added, and samples were returned to the microwave for a second heating cycle of 1 and 7 min at 95% and 90% power, respectively. Finally, chromium concentration was determined by flame atomic absorption spectrophotometry. The digestion method was validated by using a standard reference material, SRM domestic sludge 2781, with a certified chromium value of 195 +/- 9 micrograms/g. The value obtained in this study was 178 +/- 11 micrograms/g, for a difference of 17 micrograms/g. Spike recovery experiments resulted in 103.16 and 100.35% recoveries of chromium from diet and feces samples, respectively. Coefficients of variation were 10.8 and 7.8%, respectively.
authors.affiliation: Centro de Investigación en Alimentación y Desarrollo, A.C., Division of Food Science and Nutrition, Hermosillo, Sonora, México.
authors.forename: L
authors.initials: L
authors.lastname: García-Rico
authors.forename: R E
authors.initials: RE
authors.lastname: Ramos Ruiz
authors.forename: L
authors.initials: L
authors.lastname: Gutiérrez Coronado
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D015415:Biomarkers; D001842:Bone and Bones; D017608:Chromium Compounds / Q000032:analysis*; D004032:Diet; D004063:Digestion; D005243:Feces / Q000737:chemistry; D006358:Hot Temperature; D006861:Hydrogen Peroxide; D007082:Ileum / Q000737:chemistry; D008297:Male; D008460:Meat; D008872:Microwaves; D017942:Nitric Acid; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D013054:Spectrophotometry, Atomic
chemical_list: D015415:Biomarkers; D017608:Chromium Compounds; D017942:Nitric Acid; D006861:Hydrogen Peroxide; C023600:chromic oxide