Standard solutions (0.20–1.20 μg/mL of Zn) were prepared by using a zinc working standard (1 mg/mL Zn) and aspired into the flame of an atomic absorption spectrophotometer. For each sample at least five readings were noted. System suitability parameters were evaluated and found to be within the limits. The purpose of the system suitability test was to ensure that the complete testing system (including instrument, reagents and analyst) is suitable for the intended application. The % relative standard deviation for absorbance from five readings of each zinc standard is presented in Table 1. This shows the suitability of atomic absorption spectrophotometer for the determination of zinc in insulin.