Selective determination of penicillamine by on-line vapor-phase generation combined with Fourier transform infrared spectrometry

In this work, an on-line system with vapor-phase generation (VPG) and Fourier transform infrared (FTIR) spectrometric detection has been developed as a direct and highly selective analytical technique for the assay of penicillamine (PA). Potassium iodate solution was injected into a reactor, heated at 75 °C, containing PA. The CO generated under these conditions was transported by means of N2 gas carrier stream to an infrared gas cell and corresponding FTIR spectra were acquired in a continuous mode. The maximum absorbance of CO band at 2170 cm−1, corrected by a baseline established between 2240 and 2000 cm−1 at a nominal resolution of 2 cm−1, was selected as a measurement criterion. Initially, the effect of different chemical, physical and spectroscopic parameters, such as concentration and volume of oxidant, pH, equilibrium time, reactor temperature, reactor volume, N2 carrier flow rate and number of scans on the analytical signals were evaluated by using a short path length (10 cm) IR gas cell. At optimum experimental conditions, the method provided a relatively broad linear dynamic range of 4–380 mg L−1, a limit of detection of 0.5 mg L−1, a sampling frequency of 15 h−1 and a relative standard deviation (R.S.D.) of 1.6%. Further, the method was successfully applied to the determination of PA in pharmaceutical formulations and results compared well with those obtained by a reference colorimetric method.