Quantitative analysis of pharmaceutical products by laser-induced breakdown spectroscopy

In this paper, the capabilities of laser-induced breakdown spectroscopy (LIBS) for rapid analysis of multi-component pharmaceutical tablets are illustrated using several examples. The atomic line emission from an element present only in a particular component of the tablet (for instance, emission of phosphorus from the drug, or of magnesium from the lubricant) enables the quantitative analysis of that component. It is also demonstrated that simple schemes can significantly improve the analytical performance of LIBS in this context. In particular, internal standardization with a carbon line was found to enable the correction of a matrix effect, apart from improving the precision of measurement. Furthermore, an improvement in the linearity of calibration was observed when the plasma continuum emission was used as internal standard. Finally, in the case of drugs containing halogen species (e.g. F or Cl), producing the plasma in a helium atmosphere caused a seven to eight-fold increase of the signal-to-background ratio, thus improving sensitivity. These data illustrate the strengths of LIBS for fast at-line assessment of the reliability of pharmaceutical manufacturing processes.