Introduction

The uniform distribution of pharmaceutical materials such as drugs, lubricants, and other components used in the formulation of pharmaceutical powder blends and tablet dosage forms is critical in order to achieve optimal product performance. Ideally, each of the several million tablets produced during the manufacture of a batch should contain the same amount of each component. In practice, however, this goal is difficult to achieve because the pharmaceutical solids that are blended together generally have wide particle-size distributions as well as dissimilar bulk properties, such as density, shape, specific surface area, and energy. The analytical technologies that are currently available for the determination of the components in these tablet dosage forms are time consuming, i.e. 10–30 min per sample, can be laborious, and are not readily amenable to at-line or on-line process monitoring. About 70% of the marketed drug products are formulated as tablet or capsule dosage forms where the drug molecules contain one or more chlorine, sulfur, fluorine, sodium, potassium, magnesium, phosphorus, or calcium elements as integral parts of their structure. Laser-induced breakdown spectroscopy (LIBS) was found to be a good analytical technique to measure quickly the surface and internal distribution of many pharmaceutical materials, i.e. drugs and excipients, used in the formulation of solid dosage forms. The determination of this distribution is valuable to pharmaceutical research and development since it leads to a better understanding of formulations and manufacturing processes as well as improvements in at-line process monitoring.