Least squares method in matrix form which is K-matrix representation of Beer's law is presented for simultaneous determination of ibuprofen and paracetamol in tablets without prior separation from each other. The concentration of each component in the mixture was determined spectrophotometrically from absorbances of the mixture measured at 225, 226, 228, 232, 230, 234, and 235 nm. Mixtures of known composition were used as standards to minimise errors due to presence of both compounds in the same solution. Excellent results were obtained by this method.
Basu, D., Mahalanabis, K. K., & Roy, B. (1998). Application of least squares method in matrix form: Simultaneous determination of ibuprofen and paracetamol in tablets. Journal of Pharmaceutical and Biomedical Analysis, 16(5), 809–812. https://doi.org/10.1016/S0731-7085(97)00111-8