EFFECT OF SURFACTANTS IN FLAME ATOMIC-ABSORPTION SPECTROMETRY WITH PNEUMATIC NEBULIZATION - INFLUENCE OF HYDROPHOBIC CHAIN-LENGTH

The behaviour of surfactants of different natures and chain lengths was studied in relation to the improvement in sensitivity that their use affords in flame atomic absorption spectrometry. The results show that when present, the improvement in sensitivity is a consequence of a decrease in the aerosol mean drop size. For a given surfactant, the decrease in drop size is caused by the decrease in surface tension in the solutions as the surfactant concentration increases. The shorter the surfactant chain length, the greater is the efficiency of surface tension in diminishing the drop size, to the point that the longest surfactants do not modify drop-size distribution at all and hence do not improve the sensitivity, even though they exhibit the greatest capability to lower the surface tension of the solutions.