[Simultaneous determination of aspirin, phenacetin and caffeine in compound APC by derivative ratio UV adsorption spectrum method].

The principle of derivative spectrum is described, which is based on the simultaneous use of the first derivative of ratio spectra and measurements of zero-crossing wavelengths. The method can be used to analyze one of three components in ternary mixture and eliminate the interference of others. This method is used to determine the ternary mixture of aspirin, phenacetin and caffeine in APC simultaneous with satisfactory results. The regression coefficient is higher than 0.9992, the relative standard derivatives (RSD) is less than 3.2%, the recovery is between 93.3%-106.3%.