A chemometric approach exploring Derringer's desirability function for the simultaneous determination of Cd, Cr, Ni and Pb in micronutrient fertilizers by laser-induced breakdown spectroscopy

Author(s)

Nunes, Lidiane Cristina ^[1] ; Pereira, Edenir Rodrigues ^[2] ; Bueno Guerra, Marcelo Braga ^[3] ; Krug, Francisco Jose ^[1]

Affiliation

^[1] Univ Sao Paulo, Ctr Energia Nucl Agr, Av Centenario 303, BR-13416000 Piracicaba, SP - Brazil

^[2] Univ Fed Sao Carlos, Dept Quim, Rodovia Washington Luis, Km 235, BR-13565905 Sao Carlos, SP - Brazil

^[3] Univ Fed Lavras, Dept Quim, Campus Univ, BR-37200000 Lavras, MG - Brazil

• Document type: Journal article
• Source: SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY; v. 154, p. 25-32, APR 2019.
• Web of Science Citations: 2

Abstract

Given the large variety of raw materials used in manufacturing micronutrient fertilizers, the quantitative determination of Cd, Cr, Ni and Pb in such complex matrices is challenging and often impairs the routine analysis even in modern laboratories. In the present work, a LIBS method for the direct analysis of pelletized test samples was developed to find a solution where the optimization relied on both analytical sensitivity and limit of detection by combining Doehlert experimental design with Derringer's desirability function. The test samples were analyzed in the form of pressed pellets prepared from a large variety of laboratory samples previously comminuted in a planetary ball mill. LIBS experiments were carried out with a Q-switched Nd:YAG laser at 1064 nm, and a spectrometer with Echelle optics and an intensified charged-coupled device. The optimized operating conditions were thus found with laser pulses of 25 J cm(-2) (750 mu m laser spot size), 30 accumulated laser pulses per site, 2.5 mu s gate delay, and 10.0 mu s integration time gate. Cd, Cr, Ni and Pb mass fractions, obtained by a validated reference method based on microwave-assisted acid digestion and ICP OES measurements, were used to build the calibration models. Linear correlation coefficients between the analyte mass fractions and the corresponding emission intensities ranged from 0.9980 for Pb to 0.9999 for Cr, and the limits of detection were 5mg kg(-1) Cd, 7 mg kg(-1) Cr, 15 mg kg(-1) Ni and 50 mg kg(-1) Pb. The coefficients of variation of measurements (n = 10 sites per pellet, 30 laser pulses per site) varied from 0.5% (Ni, Pb) to 15% (Cd, Cr). The proposed method simplifies the analytical sequence and complies with the purpose of fast and accurate assessment of inorganic contamination profiles in micronutrient fertilizers. (AU)

• FAPESP's process: 10/17158-8 - Evaluation of laser induced breakdown spectrometry (LIBS) for determination of inorganic contaminants in agricultural fertilizers
• Grantee: Lidiane Cristina Nunes
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/50951-4 - INCT 2014: Advanced Analytical Technologies
• Grantee: Celio Pasquini
• Support Opportunities: Research Projects - Thematic Grants