Calcium determination in biochar-based fertilizers by laser-induced breakdown spectroscopy using sodium as internal standard

Abstract

Biochar has gained agricultural importance as a soil amendment because of its important agricultural properties such as water retention, plant nutrient supplier, promoter of microorganism growth, sequestration action of atmospheric CO 2 , etc. Further, it is a low cost material being produced by recycling. Due to its active sites, biochar can adsorb nutrients so acting as a soil fertilizer. Thus the rapid assessment of nutrients in these materials is essential to ensure quality control for agricultural purposes. This work aimed to develop a simple analytical method based on Laser-Induced Breakdown Spectroscopy (LIBS) to determine Ca in biochar-based fertilizers. In particular, biochar samples enriched with Ca were prepared from peanut shells, residues of eucalyptus and banana fibers. The calibration standards were prepared by matrix matching using a biochar from eucalyptus residues. Different spectral preprocessing were evaluated to enhance the precision and accuracy of the method. However, the matrix effects demanded the use of internal standardization as the appropriate methodology to obtain the best accuracy. A linear correlation coefficient of 0.989 and a linear work range of 1.51-11.23% Ca were obtained using the proposed method, which yielded limits of detection and quantification of 0.45% e 1.51%, respectively. Calcium contents determined by LIBS in biochar-based fertilizers were in good agreement (paired t-test at 95% confidence level) with those determined by using High-Resolution Continuous Source Atomic Absorption Spectrometry (HR-CS FAAS) as the reference technique. Thus, the importance of internal standardization was demonstrated to be successful for the quantitative analysis of Ca in complex matrices like biochar-based fertilizers.

Laser-induced breakdown spectroscopy determination of K in biochar-based fertilizers in the presence of easily ionizable element

“…Results showed no significant effect of Li + addition on LIBS signals sensitivity for unroasted coffee and orange leaves, whereas an apparent increase was observed for all biochars and roasted coffee samples. Previous thermal analysis results [30] have shown that in mixtures of eucalyptus biochar and Ca 2+ , the thermal decomposition of CaCO 3 occurred at temperatures higher than those measured for the eucalyptus biochar itself, which suggested the occurrence of incorporation of Ca by the biochar, so changing its thermal properties. These results suggested that the increase of emission signals in burned samples could be explained by salt cation incorporation to biochar, which yielded the simultaneous breakdown processes for both the analyte and Li + .…”

“…Among several other applications, LIBS has been shown to be a promising analytical tool for biochar elemental analysis [30]. However, low emission signal intensities were obtained due to the matrix complexity (high C content) of these materials, which rendered difficult the excitation of the species of interest.…”

Traditional Calibration Methods in Atomic Spectrometry and New Calibration Strategies for Inductively Coupled Plasma Mass Spectrometry

“…Lucena et al ( 1998 ), for example, used Ti as IS to compensate for pulse-by-pulse variation and matrix effects in V determination in a catalyst of TiO 2 supported on silica (2TiO 2 – SiO 2 ). In another work, Na was used as IS for Ca determination in biochar-based fertilizer for minimizing differences between the sample and the calibration standards, which were built using eucalyptus biochar as a matrix match (Morais et al, 2017 ). In this same context, Fe has been used as IS to determine several elements in complex-matrix samples such as soil (Kwak et al, 2009 ; Kim et al, 2013 ), steam generator tubes (Whitehouse et al, 2001 ), and industrial alloys (Latkoczy and Ghislain, 2006 ).…”

Laser Induced-Breakdown Spectroscopy (Libs): Histórico, Fundamentos, Aplicações E Potencialidades

“…121,133 A padronização interna é uma alternativa de calibração para minimizar as flutuações do sinal analítico, devido às condições instrumentais operacionais, aos erros de amostragem e, em um menor grau, aos efeitos de matriz. [134][135][136] Bons resultados têm sido obtidos com esta estratégia de calibração para análise de amostras geológicas e alimentícias complexas. No entanto, a escolha de um elemento como padrão interno apropriado não é tarefa fácil, uma vez que o padrão interno deve sofrer os processos temporais do plasma semelhantes aos dos analitos e possuir propriedades físico-químicas semelhantes, o que geralmente é desafiador em LIBS.…”