Calibration standards for Laser-Induced Breakdown Spectroscopy analysis of asphalts

A simplified method of sulfur determination in asphalt with Laser-Induced Breakdown Spectroscopy on S I 921.29 nm line is presented. Helium at atmospheric pressure was employed in the interaction chamber. Calibration standards were prepared by hand mixing and homogenizing a cellulose or limestone powder with a precise amount of sodium sulfate. Calibration pellets were pressed out and used for quantitative bulk analysis of four asphalt samples. Sulfur content from Inductively Coupled Plasma triple Quadrupole Mass Spectrometry analysis was taken as a reference. The yielded results from the limestone calibration set should be empirically corrected to the microplasma emission which is different from that of cellulose. However, the use of cellulose pellets led directly to true results within experimental uncertainty. Despite evident differences between cellulose and asphalt, there are some hidden factors interconnecting organic matrices and setting mineral ones apart.