Simultaneous determination of nafcillin and methicillin by different fluorimetric techniques using partial least-squares calibration.

The simultaneous determination of nafcillin and methicillin was accomplished by constant wavelength synchronous fluorimetry, in combination with partial least-squares multivariate calibration. The total luminescence information of the compounds was used to optimize the spectral data set to perform the calibration. A calibration set of standard samples was designed by combination of a factorial design, with three levels for each factor, and a central composite design. A comparative study of the results obtained using the excitation, the emission, the constant wavelength synchronous and the constant energy synchronous spectral data as analytical signals was performed. The data, set composed of the constant wavelength synchronous spectra, was selected as the analytical signal. The method was successfully applied to the determination of nafcillin and methicillin in mixtures.