Phosphorous Determination in Biochar-Based Fertilizers by Spark Discharge-Laser-Induced Breakdown Spectroscopy

Biochar-based fertilizers are a new attractive alternative to P supplementation for crops, as they can gradually release the nutrient, avoiding losses and improving soil quality. In this regard, the evaluation of the P amount in biochar-based fertilizers is extremely important for their quality control. Analytical techniques that require sample solubilization are not very efficient for this task, as biochar is difficult to solubilize. Laser-induced breakdown spectroscopy (LIBS) is a promising technique to respond to this demand, as it enables a direct analysis of solid samples, avoiding the complicated process of sample solubilization. In this work, a novel method based on spark discharge (SD) coupled to LIBS was evaluated for P determination in biochar-based fertilizers prepared from three different biomasses. To overcome calibration problems in LIBS analysis, a matrix-matching procedure accomplished by the addition of eucalyptus biochar to calibration standards was used in experiments. This procedure minimized matrix effects and allowed us to achieve a satisfactory accuracy even when applied to similar but different matrices. Furthermore, the developed method is simple, fast, direct, does not generate post-analysis residues and appears appropriate for the quality control of sustainable biochar-based fertilizers and other biochar products

Use of sugar cane bagasse as solid phase extractor for cadmium determination by FAAS

The present paper describes the use of sugar cane bagasse as solid phase extractor for cadmium determination after complexation of the analyte with ammonium diethyldithiophosphate (ADDP) and sorption of the Cd-DDP complexes on the solid support. The concomitants were separated using a flow injection analysis (FIA) system coupled to flame atomic absorption spectrometry (FAAS) for determination. The main parameters such as ADDP concentration, acid medium, flow rate, reaction coil length, and reaction time were investigated.The results obtained with HNO3 showed good accuracy and precision. The enhancement factor was 20.5 times for a 120-second preconcentration time, and the analytical frequency was 25 determinations per hour. The calibration curve was linear over the concentration range of 1-40 mu g L-1 Cd with a LOD of 0.697 mu g L-1 Cd and a relative standard deviation of 0.96% after 12 successive measurements of 30 mu g L-1 Cd.The proposed method was evaluated for the FIA-FAAS analysis of certified reference materials (tomato leaves, spinach leaves, and bovine liver) and Cd-spiked foods (shrimp, sardine, tuna, chicken liver and bovine liver). Good recoveries (80.0-97.1%) for the Cd-spiked samples and certified reference materials were obtained. The results of bagasse-packed minicolumns were compared with Si-C,8 packed minicolumns. The F-test was applied between Si-C-18/Bagasse minicolumns, Si-C-18/certified values, and bagasse/certified values. It was found that the results were in agreement with the certified values at a 95% confidence level

Direct and Simultaneous Determination of Cd Cu, and Se in Blood Samples by Graphite Furnace Atomic Absorption Spectrometry

A graphite furnace atomic absorption spectrometric method is proposed for the direct and simultaneous determination of Cd, Cu, and Se in human blood. Samples were diluted 1:10 (v/v) in 0.5% (v/v) HNO(3) + 0.5% (v/v) Triton X-100 solution. For 12 mu L injected sample volume + 5 mu L, of 1000 mg L(-1) Pd(NO(3))(2) + 3 mu L of 1000 mg L(-1) Mg(NO(3))(2), the calculated characteristic masses (mo) were 0.9 pg Cd, 16 pg Cu, and 39 pg Se, which are close to those mo values for single-element conditions for THGA furnace (1.3 pg Cd, 17 pg Cu, and 45 pg Se). Calibration curves with linear correlations better than 0.999 were obtained. The limits of detection (LOD) were 0.03 mu g L(-1) Cd, 0.075 mu g L(-1) Cu and 0.3 mu g L(-1) Se, and the relative standard deviations (n= 12) were 2.5%, 0.3%, and 1.5%, respectively. The method was applied for Cd, Cu, and Se determination in 10 human blood samples and the results were in agreement at the 95% confidence level with those obtained by inductively coupled plasma mass spectrometry. Concentrations of analytes in the selected blood samples varied from 1.7 to 3.2 mu g L(-1) Cd, 700 to 921.7 mu g L(-1) Cu, and from 68.6 to 350 mu g L(-1) Se. The accuracy of the proposed method was also evaluated by an addition-recovery experiment and recoveries of Cd, Cu, and Se added to blood samples ranged from 99-109%, 91-103%,and 93-103%, respectively.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Evaluation of Ir and Pd(NO3)(2)/Mg(NO3)(2) as Modifiers for the Simultaneous Determination of Mn, Ni, Pb, and Sb in Fuel Ethanol by Graphite Furnace MS

The mixture Pd(NO3)(2)/Mg(NO3)(2) and an Ir-coated platform co-injected with Pd(NO3)(2)/Mg(NO3)(2) were evaluated as modifiers for the direct and simultaneous determination of Mn, Ni, Pb, and Sb in fuel ethanol by graphite furnace atomic absorption spectrometry. For a 20-mu L diluted sample dispensed onto the platform of graphite tube in the presence of 5 mu g Pd and 3 mu g Mg, analytical curves in the 0 - 50.0 mu g L-1 range were built up resulting in linear correlation coefficients better than 0.99. The calculated characteristic masses were 6 pg Mn, 25 pg Ni, 67 pg Pb, and 50 pg Sb. The limits of detection CLOD) were 013 mu g L-1 Mn, 1.2 mu g L-1 Ni, 1.2 mu g L-1 Pb, and 0.10 mu g L-1 Sb.Accuracy was checked after the analysis of 10 commercial fuel ethanol samples. The results were in agreement at a 95% confidence level (paired Rest) with those obtained by inductively coupled plasma mass spectrometry. The recovery of Mn, Ni, Pb, and Sb in fuel ethanol samples was within the 97-104%, 86-116%, 83-119%, and 92-104% intervals, respectively, and the relative standard deviation (n = 12) was typically 4%, 7%, 6%, and 5%, respectively. The useful lifetime of the THGA atomizer was around 300 firings.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Simultaneous Determination of Ba, Cr, Mo (Group 1), and Cu, Fe, Ni, and Pb (Group 2) in Commercial Fuel Ethanol by Graphite Furnace AAS

The direct and simultaneous determination of Ba, Cr, and Mo (group 1) and of Cu, Fe, Ni, and Pb (group 2) in commercial fuel ethanol by graphite furnace atomic absorption spectrometry is proposed employing no chemical modifier (group 1) and W permanent modifier together with Pd(NO(3))(2) + Mg(NO(3))(2) conventional modifiers (group 2). For 20 mu l, injected volume, the calculated characteristic masses were 65 pg Ba, 3 pg Cr, 13 pg Cu, 10 pg Fe, 43 pg Mo, 50 pg Ni, and 35 pg Pb. The limits of detection (LOD) were 0.6 mu g L(-1) Ba, 0.1 mu g L(-1) Cr, 0.6 mu g L(-1) Cu, 1.8 mu g L(-1) Fe, 0.2 mu g L(-1) Mo, 0.4 mu g L(-1) Ni, and 0.6 mu g L(-1) Pb. Accuracy was checked after the analysis of 10 commercial fuel ethanol samples. The recoveries of Ba, Cr, Cu, Fe, Mo, Ni, and Pb added to the fuel ethanol samples ranged from 100-123%, 84-123%, 85-99%, 90-117%, 81-102%, 89-119%, and 84-114%, and the relative standard deviations (n = 12) were 1.8%, 0.9%, 4.2%, 7.6%, 3.8%, 1.7%, and 2.0%, respectively. The useful lifetimes of the untreated and pretreated tubes were around 300 and 600 firings, respectively.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

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

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 CO2, 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. (C) 2017 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e TecnológicoSão Paulo State Univ UNESP, Analyt Chem Dept, POB 355, BR-14801970 Araraquara, SP, BrazilUniv Fed São Paulo, UNIFESP, Chem Dept, Rua Sao Nicolau 210, BR-09913030 Diadema, SP, BrazilCNR, NANOTEC PlasMI Lab, Via Amendola 122-D, I-70126 Bari, ItalyUniv Fed São Paulo, UNIFESP, Chem Dept, Rua Sao Nicolau 210, BR-09913030 Diadema, SP, BrazilFAPESP: 2015/24757-9Web of Scienc