CN diatomic emission for N determination by LIBS

Abstract

The determination of N is an important demand for several sectors and the analytical features of laser-induced breakdown spectroscopy (LIBS) are very attractive to accomplish this task. In this work, a novel proposal for nitrogen determination was explored considering molecular diatomic emission lines of CN measured by LIBS. As a proof of concept, a method was developed to determine N in biochar-based fertilizers, a highly recalcitrant matrix. The fertilizers were prepared from biochar of eucalyptus pruning residues, peanut skin and fibers of banana tree and the calibration standards were prepared by matrix matching using eucalyptus biochar. Diatomic emission signals of CN at 388.3 nm showed high correlation with the levels of N in standards and samples, suggesting the molecular emission of CN is little affected by the matrix effect. The developed method is accurate since the N levels determined in the samples do not differ statistically from the expected level, with a 95% confidence level. Furthermore, the method using molecular emission is simple and highlights the potential of LIBS for N determination in complex matrices (e.g. biochar).