Copper (II) determination in fertilizer: Design of experiment (DoE) for method optimization and concomitants identification

This study is dedicated to the determination of Cu in fertilizer sample using a spectrophotometric (UV-Vis) method after reaction of the analyte with diethyldithiocarbamate (DDTC) at basic pH, and monitoring the absorbance in 456 nm. The method working conditions (samples volumes and time of reaction) were optimized using design of experiments (DoE) and the results compared with Photometrix and inductively coupled plasma optical emission spectrometry (ICP OES) reference method. A good concordance was observed among the results with 95% of confidence level. Elements as Co, Ni and Zn presented a high potential of interference during Cu spectrophotometric determination.