Application of Orthogonal Functions to Pharmaceutical Analysis, Generation of Derivative Curves

Application of orthogonal functions to certain instrumental methods of analysis depends upon the expansion of an experimental curve in terms of orthogonal polynomials. The theoretical principle of the method is discussed. The method eliminates the effect of interferences during analysis. Thus, in the ultraviolet-visible region, the method has been successfully applied to the determination of many pharmaceutical compounds in different formulations. Dissolution methods of analysis, stability-indicating assays and dissociation constant determinations have been developed using orthogonal functions. Other applications to include spectrofluorometry , spectropolarimetry, atomic emission spectroscopy and electrochemical analysis have been reported. Ratios of orthogonal function coefficients have been used to test for purity of pharmaceutical compounds and also for pKa determination. Difference spectrophotometry using the A pj method has been developed to overcome the restrictions of the AA method. A combined polynomial, Pw , method solved certain difficulties met with during the application of the direct orthogonal function method. The expansion of an experimental curve in terms of Fourier functions and its application to pharmaceutical analysis is also discussed. Derivative curves have been generated using orthogonal functions. Thus, the convolution of a Gaussian band using the linear, quadratic etc. orthogonal polynomials by means of a visual BASIC program, was found to give the first, second,etc.- order derivative curves of the band, respectively