Calibration and quantitative measurement is a difficult task
with LIBS analysis. This paper identifies a useful approach, which
is direct quantitative K and Mg measurement in plant samples by
LIBS. Instead of analyte addition to the sample matrix to make
the calibration, we propose a variety of calibrating standards by
spiking of increasing concentrations of K and Mg into wood, filter
paper or babassu mesocarp to be used as calibrating material in
LIBS. The use of C as the internal standard was imperative since
it corrected the interferences, which were probably the differences
of the ablation process between matrices. Choosing the best emission
wavelengths, which were K(I) 766.490 and 769.896 nm, Mg(II)
279.553 and 280.270 nm and C(I) 247.856 nm, for use in the quantitative
measurement associated with the optimization of the
instrumental parameters was decisive in allowing the analyte
quantification.
This is an initial investigation of the production of a synthetic
calibrating standard for direct solid sampling microanalysis. The
preliminary study suggests this material can be employed in other
solid sampling analytical methods such as LA-ICP-MS, LA-ICP OES
or in other analytes and matrices; our intention is to apply these
in the near future.