Area under Absorbance Curve Vs. Concentration for UV-Spectrophotometric Analysis of Insulin in Different PH Conditions

UV-Spectrophotometric method of analysis for zinc insulin in different pH conditions has been standardised. As the absorbance maxima (α_max) for insulin changes in different pH conditions and dilutions, the normal absorbance vs. concentration approach is replaced by area under absorbance curve (AUAC) vs. concentration approach. The models or equations (acceptable to FDA) for standard plots in each pH condition are determined instead of relying on conventional, simple, linear relationships. Two curves in each wavelength scan made it essential to carry out curve and range selection. Other simple parameters like inter/intra day variations and precisions are also determined. The relationship between AUAC and concentrations were found to be linear (model 2/or equation iii) in solution of pH 1.2, buffers of pH 5.8, 7.0; non-linear (model 3/or equation iv) in buffers of pH 6.0, 6.6 and log based (model 4/or equation v) in pH 7.5. The concentration range of 0.0-1.0 IU/ml was acceptable statistically (p-level 5.0%) in all pH conditions alongwith relative standard deviation (RSD) within 5.0% for all AUAC values. Therefore, UV-spectrophotometric method based on AUAC vs concentration may be used satisfactorily for analysis of zinc insulin.