experimental design

The target of the present study is to use experimental design in screening and optimizing experimental variables to develop a spectrophotometric method for determination of Cefdinir (CFN) antibiotic. The proposed method is based on the oxidative coupling reaction of CFN with 3-methylbenzothiazolinone-2- hydrazone (MBTH) in presence of FeCl3 in acidic medium forming a green colored chromogen measured at λ max of 660 nm. A 25-2 fractional factorial design was utilized to screen the effect of FeCl3, HCl and MBTH concentrations, in addition to reaction time and nature of diluting solvent on the absorbance of the formed chromogen. One way ANOVA and Pareto ranking analyses have shown that all variables were statistically significant. Full factorial design was then utilized to evaluate the effects of the variables on the selected response. With the help of a response surface and contour plots the optimum value of each variable was determined and used for further experiments. These optimum values were 5mg/mL FeCl3, 0.06% HCl, 4mg/mL MBTH, reaction time of 10 min and methanol as diluting solvent. Beer’s law is obeyed in the range of 0.5-6.0 μg/mL. The proposed method was successfully applied for the determination of CFN in bulk powder and commercial dosage forms without interference from the commonly encountered excipients and additives. The mean recoveries of the analyte in pharmaceutical preparations were in agreement with those obtained from a comparison method, as revealed by statistical analysis of the obtained results using the Student's t-test and the variance ratio F-test.