Flow injection spectrophotometric determination of copper, iron, manganese, and zinc in animal feeds using a common manifold

A rapid and simple procedure was developed for the determination of copper, iron, manganese, and zinc in animal feeds using an identical flow injection spectrophotometric manifold but different chromogenic reagents and different detection wavelengths. Bis(cyclohexanone)oxalydihydrazone, formaldoxime, 1,10-phenanthroline, and xylenol orange were adopted as chromogenic reagents for Cu, Mn, Fe, and Zn, respectively. Detection conditions such as manifold parameters, buffer pH, reagent concentration, temperature, and acidity of sample solution were optimized. Analytical characteristics of the method and interference of metal ions commonly present in feeds were studied. By changing the reagents and detection wavelengths, which can be done quickly, the proposed low cost flow injection system can determine Cu, Fe, Mn, or Zn in the range of 0.5-10 mg/L with a sampling throughput of 120/h.