laser-induced breakdown spectroscopy; plasma modeling; calibration-free approach; quality control of drugs; multivitamin tablet;RELATIVE OSCILLATOR-STRENGTHS; PRECISION-MEASUREMENT; TRACE-ELEMENTS; TRANSITIONS; ARGON
The feasibility of the compositional analysis of drugs by calibration-free laser-induced breakdown spectroscopy (LIBS) was investigated using multivitamin tablets as a sample material. The plasma was produced by a frequency-quadrupled Nd: YAG laser delivering UV pulses with a duration of 5 ns and an energy of 12 mJ, operated at a repetition rate of 10 Hz. The relative fractions of the elements composing the multivitamin drug were determined by comparing the emission spectrum of the laser-produced plume with the spectral radiance computed for a plasma in a local thermodynamic equilibrium. Fair agreement of the measured fractions with those given by the manufacturer was observed for all elements mentioned in the leaflet of the drug. Additional elements such as Ca, Na, Sr, Al, Li, K, and Si were detected and quantified. The present investigations demonstrate that laser-induced breakdown spectroscopy is a viable technique for the quality control of drugs.