The same investigation was carried out for C measurement,
which was used as the internal standard for K and Mg measurement.
The use of internal standard calibration in LIBS is a good
alternative to minimizing the standard deviation of the results,
caused especially by the variations of the laser energy and by the
heterogeneity in the density of material [13], which changes
the amount of ablated material and consequently the precision of
the results. The use of C as an internal standard in wood analysis