  Successful quantitative measurement of carbon content in coal using
laser-induced breakdown spectroscopy (LIBS) is suffered from relatively low
precision and accuracy. In the present work, the spectrum standardization
method was combined with the dominant factor based partial least square (PLS)
method to improve the measurement accuracy of carbon content in coal by LIBS.
The combination model employed the spectrum standardization method to convert
the carbon line intensity into standard state for more accurately calculating
the dominant carbon concentration, and then applied PLS with full spectrum
information to correct the residual errors. The combination model was applied
to the measurement of carbon content for 24 bituminous coal samples. The
results demonstrated that the combination model could further improve the
measurement accuracy compared with both our previously established spectrum
standardization model and dominant factor based PLS model using spectral area
normalized intensity for the dominant factor model. For example, the
coefficient of determination (R2), the root-mean-square error of prediction
(RMSEP), and the average relative error (ARE) for the combination model were
0.99, 1.75%, and 2.39%, respectively; while those values for the spectrum
standardization method were 0.83, 2.71%, and 3.40%, respectively; and those
values for the dominant factor based PLS model were 0.99, 2.66%, and 3.64%,
respectively.
