Calibration of laser-induced breakdown spectroscopy

A non-transitory computer readable medium storing instructions that when executed by a computer causes the computer to perform a method comprising

• receiving a LIBS spectrum comprising resonance peaks corresponding to the constituents in the composition, the resonance peaks comprising spectral amplitudes indicative of the unknown concentrations of the constituents;
• determining a first spectral amplitude in the LIBS spectrum corresponding to the unknown concentration of a first constituent to be determined;
• determining a second spectral amplitude corresponding to a maximum value of a self-reversed resonance peak of the first or another constituents in the LIBS spectrum, wherein the maximum value of the self-reversed resonance peak is limited by self-absorption reduction during the LIBS measurement;
• calculating an amplitude ratio between the first spectral amplitude and the second spectral amplitude;
• accessing calibration data to match the calculated amplitude ratio with a predetermined calibration amplitude ratio as function of a known concentration of the first constituent;
• and
• using the known concentration of the matched calibration amplitude ratio to calculate the unknown concentration of the first constituent in the composition.

A LIBS system for determining unknown concentrations of constituents in a composition, the system comprising

• a sample holder configured to hold the composition;
• a light source and/or optics configured to cause Laser Induced Breakdown in a sample region of the composition;
• a spectrometer configured to receive and spectrally resolve light from the sample region resulting from the Laser Induced Breakdown;
• a light sensor configured to measure the spectrally resolved light for determining a LIBS spectrum of the composition;
• and
• a controller configured to
• receive the LIBS spectrum comprising resonance peaks corresponding to the constituents in the composition, the resonance peaks comprising spectral amplitudes indicative of the unknown concentrations of the constituents;
• determine a first spectral amplitude in the LIBS spectrum corresponding to the unknown concentration of a first constituent to be determined;
• determine a second spectral amplitude corresponding to a maximum value of a self-reversed resonance peak of the first or another constituents in the LIBS spectrum, wherein the maximum value of the self-reversed resonance peak is limited by self-absorption reduction during the LIBS measurement;
• calculate an amplitude ratio between the first spectral amplitude and the second spectral amplitude;
• access calibration data to match the calculated amplitude ratio with a predetermined calibration amplitude ratio as function of a known concentration of the first constituent;
• and
• use the known concentration of the matched calibration amplitude ratio to calculate the unknown concentration of the first constituent in the composition.