Optimization and validation of a LIBS method for the determination of macro and micronutrients in sugar cane leaves

Abstract

Laser induced breakdown spectrometry (LIBS) was applied for the determination of macro (P, K, Ca, Mg) and micronutrients (B, Cu, Fe, Mn and Zn) in sugar cane leaves, which is one of the most economically important crops in Brazil. Operational conditions were previously optimized by a neuro-genetic approach, by using a laser Nd:YAG at 1064 nm with 110 mJ per pulse focused on a pellet surface prepared with ground plant samples. Emission intensities were measured after 2.0 ms delay time, with 4.5 ms integration time gate and 25 accumulated laser pulses. Measurements of LIBS spectra were based on triplicate and each replicate consisted of an average of ten spectra collected in different sites (craters) of the pellet. Quantitative determinations were carried out by using univariate calibration and chemometric methods, such as PLSR and iPLS. The calibration models were obtained by using 26 laboratory samples and the validation was carried out by using 15 test samples. For comparative purpose, these samples were also microwave-assisted digested and further analyzed by ICP OES. In general, most results obtained by LIBS did not differ significantly from ICP OES data by applying a t-test at 95% confidence level. Both LIBS multivariate and univariate calibration methods produced similar results, except for Fe where better results were achieved by the multivariate approach. Repeatability precision varied from 0.7 to 15% and 1.3 to 20% from measurements obtained by multivariate and univariate calibration, respectively. It is demonstrated that LIBS is a powerful tool for analysis of pellets of plant materials for determination of macro and micronutrients by choosing calibration and validation samples with similar matrix composition.

A spectrum standardization approach for laser-induced breakdown spectroscopy measurements

“…One common method to reduce LIBS signal uncertainties is through repeated measurements and averaging of the LIBS spectra [4][5][6][7][8]. However, because of the non-linear relationship between spectral line intensity and plasma temperature and electron density, the linear averaging method has some limitations.…”

Expeditious prediction of fiber content in sugar cane: An analytical possibility with LIBS and chemometrics

“…Sugar cane leaves were also investigated by LIBS for the determination of macro (P, K, Ca and Mg) and micronutrients (B, Cu, Fe, Mn and Zn), however the samples were prepared using cryogenic mill and pressed as pellets to perform LIBS mapping [6]. This procedure improves the sensitivity of the data, but it is not attractive to in loco measurements, for instance.…”

Определение отношения Mn/Fe в железомарганцевых конкрециях с помощью безэталонной лазерно-искровой эмиссионной спектроскопии

“…Лазерно-искровая эмиссионная спектрометрия (ЛИЭС) является одним из наиболее перспективных методов прямого экспресс-анализа твердых, жидких и газообразных образцов [1]: металлов [2], включая легкие сплавы [3], метеоритов [4], почв и руд [5,6], растительных образцов [7]. Применение экспрессных методов элементного анализа исключительно актуально для оптимизации процедуры поиска и отбора проб пелагических отложений во время морских экспедиций.…”