Identical flow injection spectrophotometric manifold for determination of protein, phosphorus, calcium, chloride, copper, manganese, iron, and zinc in feeds or premixes

A simple procedure using an identical manifold was developed for determinat ion of nitrogen (protein) phosphorus, calcium, chloride, copper, manganese, iron, and zinc in feeds and feedstuffs. By changing appropriate reagents a nd detection wavelength, these 8 elements were determined successively with a simple identical double-line flow injection (FI) manifold. FI spectropho tometric determinations were made by the blue indophenol reaction for ammon ium, the molybdenum blue method for phosphate, the cresolphthalein complexo ne procedure for calcium, and the mercuric thiocyanate procedure for chlori de. The chromogenic reagents for copper, iron, manganese, and zinc determin ation were bis(cyclohexanone)oxalydihydrazone (Cuprizone), 1,10-phenanthrol ine, formaldoxime, and xylenol orange, respectively. Sample digestion catal yst, Fl manifold, and some chemical parameters were optimized. The proposed procedure had a sampling rate of 90/h for each analyte. The determination ranges (mg/L) were 10-60 for N, 1-15 for P and Ca, 5-40 for Cl, and 0.5-15 for Cu, Fe, Mn, and Zn, respectively. Results of the analyses of animal fee d and feedstuff samples by this procedure did not differ significantly from those obtained by proven manual methods.