Quantitative analysis of nitrogen and sulfur through lines and bands of molecular emission with the LIBS technique.

• Grant number: 24/05207-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: July 01, 2024
• End date: June 30, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics - Atomic and Molecular Physics
• Principal Investigator: Paulino Ribeiro Villas Boas
• Grantee: Mariane Brunelli dos Santos
• Host Institution: Embrapa Instrumentação Agropecuária. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA). Ministério da Agricultura, Pecuária e Abastecimento (Brasil). São Carlos , SP, Brazil
• Associated research grant: 23/02444-5 - Understanding intensified and integrated production systems: from the quantum world to low-carbon agriculture, AP.PFPMCG.TEM

Abstract

Laser-induced plasma emission spectroscopy (LIBS) is a promising alternative for the detection of possible nutritional imbalances and the presence of potentially toxic elements in plants. It requires little sample preparation, is a fast method, does not generate waste and has a low cost analysis. However, despite its advantages, the LIBS technique has limitations, such as the high detection limit (LOD) for some elements, for example, nitrogen (N), sulfur (S), fluorine (F) and chlorine (Cl), which can compromise its effectiveness in certain applications. In this work, we propose to improve the LOD of N and S, exploring new forms of sample preparation (e.g., addition of signal potentiating element, such as alkaline metals), new experimental configurations of the LIBS system (e.g., vacuum, magnetic entrapment) and measurement of molecular bands with these elements. In this proposal, synthetic samples will be used to test models and methods under controlled and known conditions. Samples of plant materials with varied characteristics will also be used to verify the effectiveness of the technique in more complex situations. Methods of spectrum treatment, such as baseline correction and peak adjustment methods will be used to calculate the intensity of atomic or ionic emission lines. The analysis of the results will be performed based on the bands identified, using concepts of numerical integration for evaluation of the areas. For the peaks, adjustments of Gaussian, Lorentzian and Voigtian functions will be used to determine the areas. The effectiveness of the proposed methods will be evaluated through the signal-to-noise ratio, the LOD, the square root of the mean square error (RMSE), and ratio between performance and interquartile distance (RPIQ) of the calibration curves obtained.