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Made available in DSpace on 2022-05-01T09:31:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Additive manufacturing (AM) is gaining considerable interest due to the inherent capacity of fast and low-cost prototyping of customized devices and parts. In this work, seventeen commercial thermoplastic polymer filaments (PLA, TPU, and ABS) and one PLA pellet for fused deposition modeling (FDM) were characterized and evaluated to develop a disposable sample holder to be used as a solid sampling platform in graphite furnace atomic absorption spectroscopy (GFAAS). For GFAAS application, the selection of polymer filaments took into account no or minimal mass residue, decomposition profile, the lowest thermal decomposition temperatures, and colorless filament (preferably). These conditions are essential for the rapid and complete elimination of polymeric matrix without generating residues inside the graphite tube atomizer and lower analytical blanks. Thus, the filaments and pellets were characterized by thermogravimetry, derivative thermogravimetry, differential thermal analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy and scanning electron microscopy/energy-dispersive X-ray spectroscopy. It is desirable that the sample holder can be entirely decomposed at the lowest possible temperature. The PLA pellet material was chosen because it presented glass transition 71.7 ∘C, melting temperature at 182.7 ∘C, and showed single decomposition step in the 245–325 ∘C range (with peak temperature at 304.4 ∘C), without generating mass residue. The printed sample holder was tested in a commercial spectrometer. As “proof-of-concept, the calibration curve for cobalt (0–9.0 ng) was built up with a correlation coefficient of 0.9987. The RSD was < 10%, and the quantification limit was 1.18 ng. Recoveries of Co added to water samples varied from 96–102%. Analytical Inorganic and Physical-Chemistry Department UNESP-São Paulo State University, Professor Francisco Degni Street 55 UNIARA-Biopolymers and Biomaterials Laboratory, Carlos Gomes Street 1217 Analytical Inorganic and Physical-Chemistry Department UNESP-São Paulo State University, Professor Francisco Degni Street 55

Repackaging and tampering with labels of foods to extend their shelf life is an illegal practice, increasingly common in some Brazilian coffee retail markets. Fast, easy-to-use, and low-cost analytical techniques for the large-scale screening of aging time have been demanded lately to fight the growth of these frauds in retail coffee markets. In this work

Made available in DSpace on 2021-06-25T11:05:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Limited sensitivities of some laser-induced breakdown spectroscopy (LIBS) instruments may impair some applications. Although this drawback can be minimized by instrumental improvements, the complexity of operations and cost increases. In this work the principle of conventional dry ashing for sample preparation was evaluated as a simple and low-cost alternative to improve the sensitivity of LIBS analysis. Botanical, agronomic and industrial samples were analyzed. Samples were dry heated and their LIBS emission signals were evaluated. The results suggest the dry heating caused structural changes in samples providing greater availability of the analyte, which resulted in the enhancement of the signals. As proof of concept, the strategy was applied for Sr determination in plant leaves. Two Sr emission lines, enhanced after sample dry ashing were used. The developed methods showed similar performance featuring a good linear range (10 to 70 μg g−1) with coefficient of correlations higher than 0.99. Additionally, the accurate determination of Sr in apple and peach leaves standard materials was achieved. Department of Analytical Physical-Chemical and Inorganic Chemistry São Paulo State University - UNESP Istituto per la Scienza e Tecnologia dei Plasmi (ISTP) Sede di Bari CNR Exact and Earth Sciences Department Federal University of São Paulo - UNIFESP Department of Analytical Physical-Chemical and Inorganic Chemistry São Paulo State University - UNESP

One of the most important factors that interfere negatively in coffee global quality has been blends with defective beans, especially those called Black, Immature and Sour (BIS). The methods based on visual-manual estimation of defective beans have shown their inefficiency in coffee value chain for large-scale analysis. The lack of fast, accurate and robust analytical methods for BIS determination is still a research gap. Laser-Induced Breakdown Spectroscopy (LIBS) is a fast, low-cost and residue-free technique capable of performing multielemental determination and investigating organic composition of samples. In the present work, LIBS together with spectral processing and variable selection were evaluated to fit linear regression models for predicting BIS in blends. Models showed high capacity of prediction with RMSEP smaller than 3.8% and R2 higher than 80%. Most importantly, measurements are guided by chemical responses, which make LIBS-based methods less susceptible to the visual indistinguishability that occurs in manual inspections.

Honey is a natural food that is valued worldwide for its nutritional and therapeutic values. Therefore, authentication of honey according to the geographical origin is a guarantee of the genuine properties. In this article, an evaluation of spark discharge-assisted laser-induced breakdown spectroscopy (SD-LIBS) for certification of the geographical origin of honey is reported. Forty-nine samples of multifloral honey produced in four Argentine provinces were considered. The results showed the best classification performance was obtained using smoothing, generalized least squares weighting (GLSW) and mean centering for spectral preprocessing, added to the k-nearest neighbor (kNN) or Support Vector Machine (SVM) classification algorithms, which provided 100% of correct classification. More importantly, the results of Partial Least Squares – Discriminant Analysis (PLS-DA) pointed to N, Ca, K, Cu, Fe and Mn as key elements for the certification of geographical origin. In addition, the greatest potential of N stands out for the discrimination of the origin of honey. These findings confirm SD-LIBS as a promising tool for authentication of honey quality, providing a simple, fast and environmentally friendly solution. The method can be useful for industry, the market and others related to food authenticity. Fil: Fechner, Diana Corina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; Argentina Fil: Silva, Tiago Varão. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Nespeca, Maurilio Gustavo. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Vieira, Alan Lima. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Neto, Joséanchieta Gomes. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Júnior, Dário Santos. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Pellerano, Roberto Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; Argentina Fil: Ferreira, Edilene Cristina. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil

Made available in DSpace on 2022-04-29T08:37:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) 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 re-gard, 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. Department of Analytical Chemistry Institute of Araraquara Physical-Chemical and Inorganic Chemistry São Paulo State University (UNESP), P.O. Box 355 CNR Istituto per la Scienza e Tecnologia dei Plasmi (ISTP) Sede di Bari, Via Amendola 122/D Department of Analytical Chemistry Institute of Araraquara Physical-Chemical and Inorganic Chemistry São Paulo State University (UNESP), P.O. Box 355 FAPESP: 2015/24757-9 CNPq: 308200/2018-7

Made available in DSpace on 2021-06-25T10:15:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Dried Blood Spot (DBS) was evaluated as a solid sampling (SS) strategy for the simultaneous determination of Fe and Zn in blood samples by Solid Sampling High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry (SS HR-CS GF AAS). The alternative lines of Fe and Zn at 307.572 and 307.589 nm, respectively, were evaluated. A good correlation between the area of DBS (in mm2) and volume of blood (in µL) was observed up to 200 µL of blood. A 3.4 mm diameter paper disk, equivalent 3.86 ± 0.13 µL, was punched from the DBS and employed for blood analysis. Random sampling through the area of the paper circle produced by 50 μL blood samples showed no chromatographic effects. The upside of the solid sampling 'boat type' graphite platform was coated with a W-based film. This coating allowed around 350 firings. The use of 3 µL of 15% v/v H2O2 solution as chemical modifier improved both the thermal stability and peak profile of Zn for aqueous medium (standard solution deposited onto Whatman paper), possibly because of the weakening of Zn-paper interactions or even by the formation of thermally more stable Zn oxides. Solid standards used for calibration in the 0.1–3.0 µg Fe and 5.0–50.0 ng Zn ranges were prepared with Whatman 903® paper discs impregnated with standard solutions of the analytes. Results for Fe and Zn determined by the proposed SS HR-CS GF AAS method were in agreement at a 95% confidence level (paired t-test) with those obtained by the comparative method (except for one sample) based on microwave-assisted acid digestion of blood and High-Resolution Continuum Source Flame Atomic Absorption Spectrometry (HR-CS F AAS). The limits of quantification were 10.2 mg/L (0.04 µg) for Fe and 1.2 mg/L (4.6 ng) for Zn. The relative standard deviation was < 10% (n = 12) for a sample containing 516 mg/L Fe and 8.7 mg/L Zn, and the sample throughput was equivalent to ca. 90 s per measurement. São Paulo State University – UNESP Faculdade de Ciências Farmacêuticas de Ribeirão Preto Universidade de São Paulo São Paulo State University – UNESP FAPESP: 2018/24069-3 FAPESP: 2019/07537-6

Made available in DSpace on 2021-06-25T11:11:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Spark discharge (SD) laser-induced breakdown spectroscopy (LIBS) is a technique suitable to overcome the low energies of lasers by reheating the plasma, increasing the emission intensities and to perform single-standard calibration. A calibration method called one-point and multi-voltage calibration (OP-MVC), which requires two different voltages applied to both the standard and the sample, is proposed for use with SD-LIBS. The performance of this method was compared to that of the one-point and multi-lines calibration (OP-MLC) and the slope ratio calibration (SRC) methods for LIBS determination of Al in certified reference plant leaves and P in commercial fertilizers. No statistical differences at the 95% confidence level were observed between the Al and P concentrations determined by OP-MVC LIBS for the Al certified values and the P values measured by high-resolution continuum-source flame atomic absorption spectrometry (HR-CS FAAS). The limit of detection (LOD) for P was 0.60 wt% P2O5 and 35.1 mg kg-1 for Al. The relative standard deviation (n=3) was typically 7% for Al and in the 4-10% range for P. São Paulo State University-UNESP Analytical Chemistry Department, P.O. Box 355 Federal University of São Paulo-UNIFESP Chemistry Department CNR-Istituto per la Scienza e Tecnologia dei Plasmi (ISTP) sede di Bari, Via Amendola, 122/D São Paulo State University-UNESP Analytical Chemistry Department, P.O. Box 355 CNPq: 141977/2016-7 FAPESP: 2019/07537-6 CNPq: 302414/2017-7 CNPq: 308200/2018-7

Made available in DSpace on 2020-12-12T02:43:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The determination of N is an important demand for several sectors and the analytical features of laser-induced breakdown spectroscopy (LIBS) are very attractive to accomplish this task. In this work, a novel proposal for nitrogen determination was explored considering molecular diatomic emission lines of CN measured by LIBS. As a proof of concept, a method was developed to determine N in biochar-based fertilizers, a highly recalcitrant matrix. The fertilizers were prepared from biochar of eucalyptus pruning residues, peanut skin and fibers of banana tree and the calibration standards were prepared by matrix matching using eucalyptus biochar. Diatomic emission signals of CN at 388.3 nm showed high correlation with the levels of N in standards and samples, suggesting the molecular emission of CN is little affected by the matrix effect. The developed method is accurate since the N levels determined in the samples do not differ statistically from the expected level, with a 95% confidence level. Furthermore, the method using molecular emission is simple and highlights the potential of LIBS for N determination in complex matrices (e.g. biochar). Department of Analytical Chemistry São Paulo State University – UNESP Department of Chemistry Federal University of São Paulo – UNIFESP Department of Analytical Chemistry São Paulo State University – UNESP FAPESP: 2015/24757-9 FAPESP: 2019/18873-7 CNPq: 302414/2017-7 CNPq: 308200/2018-7

Spectra of diatomic molecules are rich in fine structures which may be used for different analytical applications in high-resolution continuum source molecular absorption spectrometry (HR-CS MAS). If several bands of a given diatomic molecule are simultaneously measured, they may be used in multi-energy calibration (MEC), a method based on the use of several wavelengths of the same absorbing/emitting entity to improve the accuracy in analytical atomic spectrometry. In this work, MEC is used for the first time as a calibration method for HR-CS MAS using flame (F) and graphite furnace (GF) atomizers. Methods were developed and applied for the determination of N, P and S in fertilizers by HR-CS F MAS and Cl in milk by HR-CS GF MAS. Chlorine, N, P and S were measured via CaCl (10 band heads), NO (13 band heads), PO (13 band heads) and CS (14 band heads), respectively. No statistically significant differences were observed between Cl, N, P and S concentrations determined by MEC and by the conventional external standard calibration (paired t-test at a 95% confidence level, n = 3). Recoveries were in the 97–109% (Cl), 97–103% (P), 99–109% (S) and 98–99% (N) intervals, and the relative standard deviations (n = 12) for Cl, N, P, and S were typically 6%, 3%, 2% and 2%, respectively.

In this work, an improved conductively heated digestion system (CHDS) with closed vessels, which provides simpler, easier and safer digestion of raw chicken, beef and pork meat samples aiming at Ca, Cu, Fe, K, Mg, Mn, Na, P, S, and Zn determinations by ICP OES and As, Cd, Cr, Mo, Pb and Se by ICP-MS/MS was evaluated. For purposes of safety, easy operation, and analytical performance, a novel polytetrafluoroethylene lid with a screw valve which enables pressure relief without touching the pressurized vessel at the end of the digestion was developed for the CHDS vessels. The accuracy was checked by the analysis of three meat certified reference materials (CRMs) and the results obtained for the CHDS were compared to those of microwave-assisted digestion (MW). Blank values and carbon contents in digested samples using the CHDS were comparable to those of MW, being adequate for ICP OES and ICP-MS techniques. The recoveries for the analytes in the three CRMs varied from 85 to 110% when using the CHDS. The results found by the proposed CHDS were in agreement with those obtained by the MW comparative procedure. The limit of quantification (LOQ) values for the CHDS may be considered comparable to those of MW and adequate for raw meat analysis. The CHDS is an interesting alternative for macronutrients, micronutrients, and contaminants, and highlighted mainly the volatile elements (As, Cd, Pb and Se), which could be easily lost with open-vessel digestion systems.

Made available in DSpace on 2018-12-11T17:33:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-09-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) 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. São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355 Federal University of São Paulo UNIFESP Chemistry Department, Rua São Nicolau, n° 210 - Centro - CEP CNR NANOTEC - PlasMI Lab, Via Amendola 122/D São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355 FAPESP: 2015/24757-9

Analytical Chemistry Department UNESP - Univ. Estadual Paulista, 55 Rua Prof. Francisco Degni

Made available in DSpace on 2018-12-11T16:45:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-05-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The use of a new molecule the calcium mono-chloride (CaCl) with absorption band head at 621.145 nm was evaluated in the development of a method for Cl determination in cement by high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GFMAS) employing direct solid sample analysis. Calcium compounds present in cement samples acted as CaCl-forming reagent. Pyrolysis and vaporization curves were established to optimize the atomizer temperature program. The optimum pyrolysis and vaporization temperatures were 1000 °C and 2200 °C, respectively. These values provided higher thermal stability of the CaCl molecule which allows reducing matrix effects and the calibration with aqueous standard solutions in the range of 10–200 ng Cl. Correlation coefficient of 0.995 and a slope of 0.00159 s ng− 1 were obtained, with a calculated limit of detection of 1.4 ng Cl. Sample masses in the range 0.65–1.05 mg can be accurately weighed and assayed. Commercial cement samples were analyzed by the proposed method and the concentrations of Cl were in the 159–540 μg g− 1 concentration range. Samples were also analyzed by the Brazilian Association of Technical Norms (ABNT) and results were in agreement at a 95% confidence level (paired t-test). Recoveries of Cl added to samples were in the range 101–118% and the relative standard deviations (n = 12) were in the 3.4–11.2% interval. São Paulo State University - Unesp Analytical Chemistry Department, P.O. Box 355 São Paulo State University - Unesp Analytical Chemistry Department, P.O. Box 355 CNPq: #303255/2013-7 FAPESP: 2014/12595-1

Made available in DSpace on 2020-12-12T01:49:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The present work proposes methods for detection and quantification of honey adulterants using laser-induced breakdown spectroscopy (LIBS). The sample set consisted of 6 pure honey from different botanical sources, 2 sweetener syrups and 228 fortified samples. The spectra acquired using a spark discharge coupled to the LIBS system were used for the development of the PLS-DA (classification) and PLS (calibration) models. Several data preprocessing and variable selection methods were evaluated to obtain the best fit. The detection of adulterants was performed with 100% of accuracy. The quantification of adulterants was possible through a PLS model with the variables selected by iPLS. The PLS model was validated with external samples and presented good accuracy, selectivity, sensitivity, and linearity. The proposed methods highlighted the potential of the LIBS technique for honey authenticity certification, providing fast, simple, and clean determinations since no sample pretreatment was required. Analytical Chemistry Department Institute of Chemistry São Paulo State University – UNESP, Prof. Francisco Degni 55 Department of Chemistry Federal University of São Paulo – UNIFESP, R. São Nicolau 210 Analytical Chemistry Department Institute of Chemistry São Paulo State University – UNESP, Prof. Francisco Degni 55 CNPq: 141977/2016-7 CNPq: 308200/2018-7

Made available in DSpace on 2018-12-11T17:05:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-12-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Different precursors were evaluated for the generation of reference spectra and correction of the background caused by SiO molecules in the determination of Sb in facial cosmetics by high-resolution continuum source graphite furnace atomic absorption spectrometry employing direct solid sample analysis. Zeolite and mica were the most effective precursors for background correction during Sb determination using the 217.581 nm and 231.147 nm lines. Full 23 factorial design and central composite design were used to optimize the atomizer temperature program. The optimum pyrolysis and atomization temperatures were 1500 and 2100 °C, respectively. A Pd(NO3)2/Mg(NO3)2 mixture was employed as the chemical modifier, and calibration was performed at 217.581 nm with aqueous standards containing Sb in the range 0.5–2.25 ng, resulting in a correlation coefficient of 0.9995 and a slope of 0.1548 s ng−1. The sample mass was in the range 0.15–0.25 mg. The accuracy of the method was determined by analysis of Montana Soil (II) certified reference material, together with addition/recovery tests. The Sb concentration found was in agreement with the certified value, at a 95% confidence level (paired t-test). Recoveries of Sb added to the samples were in the range 82–108%. The limit of quantification was 0.9 mg kg−1 and the relative standard deviation (n=3) ranged from 0.5% to 7.1%. From thirteen analyzed samples, Sb was not detected in ten samples (blush, eye shadow and compact powder); three samples (two blush and one eye shadow) presented Sb concentration in the 9.1−14.5 mg kg−1 range. Univ. EstadualPaulista - Unesp Departamento de Química Analítica, P.O. Box 355, 14800-060, Araraquara - SP Univ. EstadualPaulista - Unesp Departamento de Química Analítica, P.O. Box 355, 14800-060, Araraquara - SP CNPq: #147166/2012-8 FAPESP: #2014/12595-1 CAPES: 33004030072P8

Made available in DSpace on 2018-12-11T17:27:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-05-15 A new method is proposed for the simultaneous determination of Mo and Ni in plant materials by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS), employing direct solid sample analysis (DSS) and internal standardization (IS). Cobalt was used as internal standard to minimize matrix effects during Ni determinations, enabling the use of aqueous standards for calibration. Correlation coefficients for the calibration curves were typically better than 0.9937. The performance of the method was checked by analysis of six plant certified reference materials, and the results for Mo and Ni were in agreement with the certified values (95% confidence level, t-test). Analysis was made of different types of plant materials used as renewable sources of energy, including sugarcane leaves, banana tree fiber, soybean straw, coffee pods, orange bagasse, peanut hulls, and sugarcane bagasse. The concentrations found for Mo and Ni ranged from 0.08 to 0.63 ng mg-1 and from 0.41 to 6.92 ng mg-1, respectively. Precision (RSD) varied from 2.1% to 11% for Mo and from 3.7% to 10% for Ni. Limits of quantification of 0.055 and 0.074 ng were obtained for Mo and Ni, respectively. São Paulo State University Unesp Analytical Chemistry Department, P.O. Box 355 University of São Paulo USP FFCLRP Department of Chemistry São Paulo State University Unesp Analytical Chemistry Department, P.O. Box 355

Made available in DSpace on 2021-06-25T10:12:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-02-05 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Raman spectroscopy is emerging and powerful technique for identifying oxyanions of phosphorus, but it still is not straightforward applied to identify and quantify simultaneously phosphite and phosphate species in solution. Herein, simultaneous determination of phosphate (PO4) and phosphite (PO3) in fertilizer were evaluated by Raman spectroscopy. The influence of pH on Raman spectra of species was evaluated at various solution pH values, and the results showed accurate and selective analysis for phosphate and phosphite by using pH = 10.0 and bands located at 874 cm−1 and 2321 cm−1, respectively. Linear working range in the 0.15%–6.20% (w/v) P concentration was consistently obtained with regression coefficients (r) of 0.9953 (PO4) and 0.9945 (PO3). The limits of detection were 0.10% (w/v) P (PO4) and 0.05% (w/v) P (PO3). Relative standard deviations were lower than 6% for samples containing 10% P2O5 (PO4) and 31% P2O5 (PO3). Commercial fertilizers were analyzed by the proposed method using external calibration and found concentrations of P were in agreement with those obtained by the comparative spectrophotometric method at the 95% confidence level (paired t-test). Recoveries of spiked samples were in the 92–110% range. Institute of Chemistry São Paulo State University (UNESP) Institute of Chemistry São Paulo State University (UNESP) FAPESP: 2019/04586-6 FAPESP: 2019/07537-6 CNPq: 302414/2017-7 CNPq: 308200/2018-7

Made available in DSpace on 2021-06-25T10:45:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Discrimination of genetically modified organisms is increasingly required by legislation and consumers worldwide. Currently the most commonly used detection methods for identification of transgenic crops are high cost, destructive and time-consuming, so not suitable for fast and extensive application. Raman is a noninvasive and nondestructive spectroscopic technique capable of extracting sample fingerprints. In this paper, Raman spectroscopy and chemometric tools were evaluated for discrimination of transgenic corn. Different spectral preprocessing as well as algorithms for variables selection were evaluated to fit a classifier model based on linear discriminant analysis (LDA). Results showed spectral bands assigned to carbohydrates and carotenoids responsible for classes discrimination. The best classifier achieved 87.5 % of predictive accuracy. These results suggest that genetic differences between evaluated classes are also expressed in their chemical composition, which could be detected using Raman spectroscopy. The developed method is clean, fast and can contribute for establishing normative about genetically modified foods. São Paulo State University – UNESP Chemistry Institute Dep. of Analytical Physical-Chemical and Inorganic Chemistry Rua Prof. Francisco Degni, 55, Quitandinha, P.O. Box 355 Embrapa Maize & Sorghum, Rodovia MG-424, Km 45, P.O. Box: 285 or 151 Embrapa Instrumentation Rua XV de Novembro, 1.452, Centro, P.O. Box 741 São Paulo State University – UNESP Chemistry Institute Dep. of Analytical Physical-Chemical and Inorganic Chemistry Rua Prof. Francisco Degni, 55, Quitandinha, P.O. Box 355

Made available in DSpace on 2020-12-12T02:44:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-30 A simple, fast, and efficient spark discharge-laser-induced breakdown spectroscopy (SD-LIBS) method was developed for determining rice botanic origin using predictive modeling based on support vector machine (SVM). Seventy-two samples from four rice varieties (Guri, Irga 424, Puitá, and Taim) were analyzed by SD-LIBS. Spectral lines of C, Ca, Fe, Mg, N and Na were selected as input variables for prediction model fitting. The SVM algorithm parameters were optimized using a central composite design (CCD) to find the better classification performance. The optimum model for discriminating rice samples according to their botanical variety was obtained using C = 5.25 and γ = 0.119. This model achieved 96.4% of correct predictions in test samples and showed sensitivities and specificities per class within the range of 92–100%. The developed method is robust and eco-friendly for rice botanic identification since its prediction results are consistent and reproducible and its application does not generate chemical waste. Institute of Basic and Applied Chemistry of the Northeast of Argentina (IQUIBA-NEA) National Scientific and Technical Research Council (CONICET) Faculty of Exact and Natural Science and Surveying National University of the Northeast – UNNE, Av. Libertad 5470 Chemistry Institute of Araraquara São Paulo State University – UNESP, R. Prof. Francisco Degni 55 Faculty of Agricultural Sciences UNNE, Sgto. Cabral, 1213 Chemistry Institute of Araraquara São Paulo State University – UNESP, R. Prof. Francisco Degni 55

Made available in DSpace on 2018-12-11T17:36:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-06-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A spark discharge system was coupled to laser-induced breakdown spectroscopy (SD-LIBS) to improve sensitivity in the determination of P in fertilizers. A LIBS system consisting of a Q-switched Nd:YAG laser operating at 1064 nm and emitting pulses at 50 mJ with a fluence of 70 J cm−2 at the focal point was used. Results of preliminary experiments suggested that the most appropriate wavelength to measure P was the P (I) line at 214.9 nm, which did not show interferences by Fe, Cu and Zn. The electrical discharge was provided by a homemade high-voltage electronic circuit consisting of two cylindrical tungsten electrodes at the optimized output voltage of 4.5 kV, with tips arranged at the optimal distances of 4 mm between them and 2 mm above the sample surface. To minimize the expected matrix effects calibration standards of P2O5 in the range of 4.8 and 33.3% were prepared by mixing various amounts of a phosphate rock reference material (SRM-120c) with a mixture of CaCO3, CaSO4, (NH2)2CO and KCl at a 1:1:1:1 mass ratio. The calibration curves obtained at a 4.5 kV SD-LIBS output voltage showed correlation coefficients ≥0.993, RSD ≤8% and LOQ 5.3% (m/m) P2O5. Data obtained by analyzing commercial samples by the proposed system were in good agreement, at 95% confidence level, with those obtained by using high-resolution continuum-source flame atomic absorption spectroscopy. São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355 University of São Paulo – USP Department of Electrical and Computer Engineering CNR-Istituto di Nanotecnologia (NANOTEC) – PLasMI Lab, Via Amendola 122/D Federal University of São Paulo - UNIFESP Exact and Earth Sciences Department São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355 CNPq: 141977/2016-7 FAPESP: 2004/14212-0 CNPq: 2015/24757-9 CNPq: 303255/2013-7 CNPq: 311085/2014-8

Made available in DSpace on 2018-12-11T17:37:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Laser-induced breakdown spectroscopy is an optical emission technique quite suitable for the analysis of recalcitrant materials as it eliminates complex procedures of sample preparation. However, for some simple LIBS instrumentation the detection limits are still higher compared to those of consolidated spectroscopic techniques. The aim of the present work was to develop a method for the determination of K in new biochar-based fertilizer samples using a simple single pulse LIBS arrangement. Due to the low K detectability, which made impossible to obtain calibration curves, an exploratory qualitative study was performed aiming to evaluate the influence of the addition of easily ionizable elements (EIE) on the sensitivity. To this aim different salts containing EIE (K, Li and Na) and other cations (Cu and Mg) have been evaluated. Results obtained showed that salts containing EIE cations increased the spectral emission signals of some elements in samples previously submitted to charring. In particular, the strategy of using Li+ was applied to the determination of K in biochar-based fertilizers. The addition of Li+ allowed to develop an analytical method for K determination featuring a linear dynamic range from 0.8% to 21.56% K, and limits of detection and quantification of 0.2% and 0.8%, respectively. São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355 Federal University of São Paulo UNIFESP Chemistry Department, Rua São Nicolau, no 210 - Centro CNR-Istituto di Nanotecnologia (NANOTEC) - PLasMI Lab, Via Amendola 122/D São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355 CAPES: 1490630 FAPESP: 2015/24757-9 CNPq: 302414/2017–7 CNPq: 311085/2014–8

Made available in DSpace on 2018-12-11T17:25:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-06-23 Acid-base equilibria are involved in almost all the processes that occur in soil. The bioavailability of nutrients for plants, for instance, depends on the solubilization of mineral nutrients in the soil solution, which is a pH-dependent process. The determination of pH in soil solutions is usually carried out by potentiometry using a glass membrane electrode, after extracting some of the soil components with water or CaCl2 solution. The present work describes a simple method for determining the pH of soil, using laser-induced breakdown spectroscopy (LIBS). Sixty samples presenting different textural composition and pH (previously determined by potentiometry) were employed. The samples were divided into a calibration set with fifty samples and a validation set with ten samples. LIBS spectra were recorded for each pelleted sample using laser pulse energy of 115 mJ. The intensities of thirty-two emission lines for Al, Ca, H, and O were used to fit a partial least squares (PLS) model. The model was validated by prediction of the pH of the validation set samples, which showed good agreement with the reference values. The prediction mean absolute error was 0.3 pH units and the root mean square error of the prediction was 0.4. These results highlight the potential of LIBS for use in other applications beyond elemental composition determinations. For soil analysis, the proposed method offers the possibility of determining pH, in addition to nutrients and contaminants, using a single LIBS measurement. São Paulo State University - UNESP, Analytical Chemistry Department, Rua Prof. Francisco Degni 55 Embrapa Agricultural Instrumentation, Rua XV de Novembro 1452 Laser Laboratory and Environment, Faculty of Sciences, University of Zaragoza, C/. Pedro Cerbuna 12 São Paulo State University - UNESP, Analytical Chemistry Department, Rua Prof. Francisco Degni 55

Made available in DSpace on 2022-04-29T15:14:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-01-01 This paper describes the development of analytical procedures for the determination of cadmium in facial make-up based on line-source graphite furnace AAS (LS-GFAAS) and direct solid sampling (DSS) coupled to a high-resolution continuum source graphite furnace AAS (HR-CS-GFAAS). Eye shadow, blush, and compact powder samples were analyzed by LS-GFAAS after microwave-assisted digestion with an HNO3/H2O2/HF mixture. Use of boric acid to eliminate HF from the digests was not feasible due to precipitation. Ammonium hydroxide was then dispensed into the graphite platform to eliminate HF and reduce digest acidity. The DSS HR-CS GFAAS procedure did not require any previous treatment. Both proposed procedures were validated using a certified reference material. Then, cadmium was determined in six facial make-up samples by LS-GFAAS and DSS HR-CS GFAAS with calibration against aqueous standard solutions. A paired Mest at a 95% confidence level showed that the DSS HR-CS GFAAS procedure enabled the achievement of similar results as those obtained by LS-GFAAS after acid digestion. The precision, expressed as the relative standard deviation, varied from 2.0 to 9.1% (LS-GFAAS) and from 1.0 to 11.1% (DSS HR-CS GFAAS). The DSS HR-CS GFAAS procedure was then applied for the determination of cadmium in 30 blush samples and 130 eye shadow samples of different brands and colors. The cadmium concentration varied from 12 to 111 ug kg-1 in the blush samples and from 5.1 to 198 ug kg-1 in the eye shadow samples. São Paulo State University, Analytical Chemistry Department, P.O. Box 355 São Paulo State University, Analytical Chemistry Department, P.O. Box 355

Made available in DSpace on 2022-04-28T19:08:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-11-01 The use of incense has increased over the past years; however, few studies have been carried out concerning the quantification of toxic elements. This article describes the development of analytical methods for Pb determination in the rod and coating of incense sticks by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry (SS HR-CS GFAAS). For comparative purposes, samples were also analyzed by line source graphite furnace atomic absorption spectrometry (LS GFAAS) after acid microwave-assisted digestion. The concentration of lead varied from 0.06 a 2.17 μg g-1 in the rods and 1.06 to 6.60 μg g-1 for the coating. A paired West at a 95% confidence level showed that the SS HR-CS GFAAS results were in agreement with those obtained by LS GFAAS. The precision of measurements obtained by SS HR-CS GFAAS varied from 0.5 to 16% and 1.9 to 15% for rod and coating, respectively. Also, emission of lead generated when the incense stick samples were burning was evaluated by ash analysis and the mass balance applied for total lead in the whole samples and the remaining lead in the ashes. These findings showed that 25 to 80% of the total lead content in incense may be released to the air. These large variations may be related to the type of raw materials (chemical composition) employed in incense production. Sao Paulo State University Institute of Chemistry Departamento de Quimica Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto University of Sao Paulo (FFCLRP/USP) Sao Paulo State University Institute of Chemistry

Made available in DSpace on 2018-12-11T17:31:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-04-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) New methods are proposed for the determination of Mo, Ni, Co, and V in soils using high-resolution continuum source graphite furnace atomic absorption spectrometry with direct solid sampling. Cobalt and V were simultaneously determined, and different analytical lines of Ni and V were monitored to adjust sensitivity for each sample. Accuracy was checked by means of soil certified reference materials, and also by flame atomic absorption spectrometry as comparative technique. The results for Mo, Ni, Co, and V found by proposed methods were in agreement with certified values and with those obtained by the comparative technique at 95% confidence level. The concentrations found in different soil samples were in the ranges 0.19–1.84 mg kg− 1 (Mo), 9.2–22.7 mg kg− 1 (Ni), 1.1–10.7 mg kg− 1 (Co), and 35.6–426.1 mg kg− 1 (V). The relative standard deviations were in the ranges 3.2–10% (Mo), 2.8–9.8% (Ni), 4.0–9.2% (Co), and 1.2–8.0% (V). The limits of quantification for Mo, Ni, Co, and V were 0.027, 0.071, 0.15, and 1.43 ng, respectively. Univ. Estadual Paulista - UNESP Analytical Chemistry Department, P.O. Box 355 Univ. Estadual Paulista - UNESP Analytical Chemistry Department, P.O. Box 355 FAPESP: 2014/12595-1

The determination of N, P, and K in fertilizers by high-resolution continuum source flame atomic and molecular absorption spectrometry is proposed. Under optimized conditions, measurements of the diatomic molecules NO and PO at 215.360 and 247.620 nm, respectively, and K using the wing of the alternative line at 404.722 nm allowed calibration curves to be constructed in the ranges 500–5000 mg L− 1 N (r = 0.9994), 100–2000 mg L− 1 P (r = 0.9946), and 100–2500 mg L− 1 K (r = 0.9995). Commercial fertilizers were analyzed by the proposed method and the concentrations of N, P, and K were found to be in agreement with those obtained by Kjeldahl, spectrophotometric, and flame atomic emission spectrometry methods, respectively, at a 95% confidence level (paired t-test). A phosphate rock certified reference material (CRM) was analyzed and the results for P and K were in agreement with the reference values. Recoveries from spiked CRM were in the ranges 97–105% (NO3−-N), 95–103% (NH4+-N), 93–103% (urea-N), 99–108% (P), and 99–102% (K). The relative standard deviations (n = 12) for N, P, and K were 6, 4, and 2%, respectively.

Soil organic matter (SOM) constitutes an important reservoir of terrestrial carbon and can be considered an alternative for atmospheric carbon storage, contributing to global warming mitigation. Soil management can favor atmospheric carbon incorporation into SOM or its release from SOM to atmosphere. Thus, the evaluation of the humification degree (HD), which is an indication of the recalcitrance of SOM, can provide an estimation of the capacity of carbon sequestration by soils under various managements. The HD of SOM can be estimated by using various analytical techniques including fluorescence spectroscopy. In the present work, the potential of laser-induced breakdown spectroscopy (LIBS) to estimate the HD of SOM was evaluated for the first time. Intensities of emission lines of Al, Mg and Ca from LIBS spectra showing correlation with fluorescence emissions determined by laser-induced fluorescence spectroscopy (LIFS) reference technique were used to obtain a multivaried calibration model based on the k-nearest neighbor (k-NN) method. The values predicted by the proposed model (A-LIBS) showed strong correlation with LIFS results with a Pearson's coefficient of 0.87. The HD of SOM obtained after normalizing A-LIBS by total carbon in the sample showed a strong correlation to that determined by LIFS (0.94), thus suggesting the great potential of LIBS for this novel application.

Bismuth was evaluated as internal standard for Pb determination by line source flame atomic absorption spectrometry (LS FAAS), high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and line source graphite furnace atomic absorption spectrometry (LS GFAAS). Analysis of samples containing different matrices indicated close relationship between Pb and Bi absorbances. Correlation coefficients of calibration curves built up by plotting A(Pb)/A(Bi)versus Pb concentration were higher than 0.9953 (FAAS) and higher than 0.9993 (GFAAS). Recoveries of Pb improved from 52-118% (without IS) to 97-109% (IS, LS FAAS); 74-231% (without IS) to 96-109% (IS, HR-CS FAAS); and 36-125% (without IS) to 96-110% (IS, LS GFAAS). The relative standard deviations (n=12) were reduced from 0.6-9.2% (without IS) to 0.3-4.3% (IS, LS FAAS); 0.7-7.7% (without IS) to 0.1-4.0% (IS, HR-CS FAAS); and 2.1-13% (without IS) to 0.4-5.9% (IS, LS GFAAS).

Rice is the most consumed food worldwide, therefore its designation of origin (PDO) is very useful. Laserinduced breakdown spectroscopy (LIBS) is an interesting analytical technique for PDO certification, since it provides fast multielemental analysis requiring minimal sample treatment. In this work LIBS spectral data from rice analysis were evaluated for PDO certification of Argentine brown rice. Samples from two PDOs were analyzed by LIBS coupled to spark discharge. The selection of spectral data was accomplished by extreme gradient boosting (XGBoost), an algorithm currently used in machine learning, but rarely applied in chemical issues. Emission lines of C, Ca, Fe, Mg and Na were selected, and the best performance of classification were obtained using k-nearest neighbor (k-NN) algorithm. The developed method provided 84% of accuracy, 100% of sensitivity and 78% of specificity in classification of test samples. Furthermore, it is simple, clean and can be easily applied for rice certification. Fil: Pérez Rodríguez, Michael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; Argentina Fil: Dirchwolf, Pamela Maia. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Silva, Tiago Varão. Universidade Estadual Paulista; Brasil Fil: Villafañe, Roxana Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; Argentina Fil: Neto, José Anchieta Gomes. Universidade Estadual Paulista; Brasil Fil: Pellerano, Roberto Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; Argentina Fil: Ferreira, Edilene Cristina. Universidade Estadual Paulista; Brasil

Made available in DSpace on 2020-12-12T02:26:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-11-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) A user-friendly interface was developed in Excel (Microsoft Office) to deal with spectroscopic and chromatographic data. The Excel spreadsheet includes baseline correction, area and height determination, and identification of variables that represent the maximum height. In addition, the user can quickly evaluate standardization methods and create databases by adding information to the library, where up to 300 peaks can be saved. In the present work, the application of the Excel spreadsheet is exemplified by analytical curves developed with gas chromatography, Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) data. The analytical parameters obtained by the Excel spreadsheet were compared with the results generated in different software, such as MATLAB (routine), Origin and ChromQuest. The coefficient of determination (R2) and root-mean-square error (RMSE) obtained from Excel spreadsheet were very similar to those from other software. The analytical curves were also submitted to analysis of variance (ANOVA) and, regarding the F-test, all presented values of Fcalculated greater than Fcritical. The relationship between the analytical responses from the Excel spreadsheet and other software showed a coefficient of correlation close to 1. Therefore, the proposed Excel interface is an attractive alternative to expensive software and provides easy handling for LIBS data. The spreadsheet and a short tutorial video are available in the electronic supplementary material (or in the link https://1drv.ms/f/s!AjTI1LyRsk35lYtYOvj6EGyXvFgWlQ). São Paulo State University - UNESP Institute of Chemistry, P.O. Box 355 São Paulo State University - UNESP Institute of Chemistry, P.O. Box 355 CNPq: 141977/2016-7 CNPq: 302414/2017-7

Made available in DSpace on 2018-12-11T17:32:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-09-01 Coffee is an important commodity and a very popular beverage around the world. Its economic value as well as beverage quality are strongly dependent of the quality of beans. The presence of defective beans in coffee blends has caused a negative impact on the beverage Global Quality (GQ) assessed by cupping tests. The main defective beans observed in the productive chain has been those Blacks, Greens and Sours (BGS). Chemical composition of BGS has a damaging impact on beverage GQ. That is why analytical tools are needed for monitoring and controlling the GQ in coffee agro-industry. Near Infrared Spectroscopy (NIRS) has been successfully applied for assessment of coffee quality. Another potential technique for direct, clean and fast measurement of coffee GQ is Laser Induced Breakdown Spectroscopy (LIBS). Elements and diatomic molecules commonly present in organic compounds (structure) can be assessed by using LIBS. In this article is reported an evaluation of LIBS for the main interferents of GQ (BGS defects). Results confirm the great potential of LIBS for discriminating good beans from those with BGS defects by using emission lines of C, CN, C2 and N. Most importantly, some emission lines presented strong linear correlation (r > 0.9) with NIRS absorption bands assigned to proteins, lipids, sugar and carboxylic acids, suggesting LIBS potential to estimate these compounds in unroasted and ground coffee samples. São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355 Embrapa Instrumentation, P.O. Box 741 São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355

Made available in DSpace on 2018-11-26T16:34:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-07-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Establishing fast, simple, low-cost, and efficient sample preparation procedures to determine elements in foodstuffs is a relevant aspect for nutritional and health purposes. For this reason, the recently proposed closed-vessel conductively heated digestion system (CHDS) was evaluated for the digestion of milk powder, chocolate powder, and soluble coffee samples aiming for Ca, Cu, Fe, K, Mg, Mn, Na, and Zn determinations by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and Cd, Mo, and Se determinations by inductively coupled plasma mass spectrometry with tandem configuration (ICP-MS/MS). The accuracy was evaluated by analyzing two milk certified reference materials digested by the CHDS and a microwave oven for comparison. When using the CHDS, recoveries for the analytes varied from 91 to 104 %. For microwave digestions, recoveries within the 94-109 % intervals were obtained. The method was then applied to the samples. For comparative purposes, the analytes were also determined in the samples after microwave digestion, and the results between the two digestion systems showed no differences based on a paired t test at a 95 % confidence level. Similar analytical blanks were obtained because quartz digestion tubes were used in both digestion systems. The CHDS with quartz tubes is an interesting alternative for laboratories dedicated to large-scale routine analysis because volatile elements usually found in very low concentrations in food samples such as Cd and Se can also be determined. Sao Paulo State Univ, Dept Analyt Chem, POB 355, BR-14801970 Araraquara, SP, Brazil Univ Fed Sao Carlos, Dept Chem, POB 676, BR-13565905 Sao Carlos, SP, Brazil Sao Paulo State Univ, Dept Analyt Chem, POB 355, BR-14801970 Araraquara, SP, Brazil FAPESP: 2014/12595-1 FAPESP: 2012/02891-7 FAPESP: 2014/18393-1 FAPESP: 2012/23323-7 CNPq: 303255/2013-7 CNPq: 140934/2013-8

A method using Laser Induced Breakdown Spectroscopy (LIBS) for calcium (Ca) determination in breakfast cereals was evaluated. To perform the calibration curve, seven commercial cereals containing Ca in a range of 16.00–3734 mg kg −1 were considered. The Ca amounts provided by the manufacturers were evaluated by using inductively coupled plasma optical emission spectrometry (ICP OES). The precision of the LIBS measurements was of 8% and the accuracy, observed by using a corn bran standard reference material was higher than 99%. The method was successfully applied to predict the Ca concentration in a set of commercial samples dispensing the sample pre-treatment, with the potential to be used in production lines.

Laser-induced breakdown spectroscopy (LIBS) is an emerging analytical technique to perform elemental analysis in natural samples independent of their physical state (solid, liquid, or gaseous). Due to its instrumental features, LIBS shows promising potential to perform analysis in situ and in environments at risk. Since the analytical performance of LIBS strongly depends on the choice of experimental conditions, each particular application needs a specific instrumental adjustment. The present study evaluated three LIBS instrumental parameters regarding their influences on signal-to-noise ratio (SNR) of seven elements in soil samples: laser pulse energy, delay time, and integration time gate. A multivariate technique was used due to the significant interaction among the evaluated parameters. Subsequently, to optimize LIBS parameters for each individual element response, a method for multiple response optimization was used. With only one simple screening design, it was possible to obtain a good combination among the studied parameters in order to simultaneously increase the SNR for all analytes. Moreover, the analysis of individual response for elements is helpful to understand their physical behavior in the plasma and also how they are embedded in the sample matrix.

Laser Induced Breakdown Spectroscopy (LIBS) is an advanced analytical technique for elemental determination based on direct measurement of optical emission of excited species on a laser induced plasma. In the realm of elemental analysis, LIBS has great potential to accomplish direct analysis independently of physical sample state (solid, liquid or gas). Presently, LIBS has been easily employed for qualitative analysis, nevertheless, in order to perform quantitative analysis, some effort is still required since calibration represents a difficult issue. Artificial neural network (ANN) is a machine learning paradigm inspired on biological nervous systems. Recently, ANNs have been used in many applications and its classification and prediction capabilities are especially useful for spectral analysis. In this paper an ANN was used as calibration strategy for LIBS, aiming Cu determination in soil samples. Spectra of 59 samples from a heterogenic set of reference soil samples and their respective Cu concentration were used for calibration and validation. Simple linear regression (SLR) and wrapper approach were the two strategies employed to select a set of wavelengths for ANN learning. Cross validation was applied, following ANN training, for verification of prediction accuracy. The ANN showed good efficiency for Cu predictions although the features of portable instrumentation employed. The proposed method presented a limit of detection (LOD) of 2.3 mg dm− 3 of Cu and a mean squared error (MSE) of 0.5 for the predictions.

Soils are an important component in the biogeochemical cycle of carbon, storing about four times more carbon than biomass plants and nearly three times more than the atmosphere. Moreover, the carbon content is directly related on the capacity of water retention, fertility, among other properties. Thus, soil carbon quantification in field conditions is an important challenge related to carbon cycle and global climatic changes. Nowadays, Laser Induced Breakdown Spectroscopy (LIBS) can be used for qualitative elemental analyses without previous treatment of samples and the results are obtained quickly. New optical technologies made possible the portable LIBS systems and now, the great expectation is the development of methods that make possible quantitative measurements with LIBS. The goal of this work is to calibrate a portable LIBS system to carry out quantitative measures of carbon in whole tropical soil sample. For this, six samples from the Brazilian Cerrado region (Argisoil) were used. Tropical soils have large amounts of iron in their compositions, so the carbon line at 247.86 nm presents strong interference of this element (iron lines at 247.86 and 247.95). For this reason, in this work the carbon line at 193.03 nm was used. Using methods of statistical analysis as a simple linear regression, multivariate linear regression and cross-validation were possible to obtain correlation coefficients higher than 0.91. These results show the great potential of using portable LIBS systems for quantitative carbon measurements in tropical soils.

Made available in DSpace on 2018-12-11T17:25:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-02-01 The analysis of soil texture is crucial for the proper management of agricultural systems and for environmental studies. Soil texture is important as it affects erosion potential, water retention capacity, organic matter complexation, and the retention of nutrients, among others. It is usually determined by pipette or hydrometer methods, but analysis requires a preparation with chemical reagents, which can take hours and hence is unfeasible for large number of samples. Here we propose the use of laser-induced breakdown spectroscopy (LIBS) to estimate the proportions of sand, silt, and clay in 60 Brazilian soil samples of varying composition. Two calibration models were developed with the partial least square regression method: one considering the spectral region from 188 to 980 nm and the other, emission lines of the elements Si, Na, Fe, Ti, Ca, K, Al, Co, Mg, V, Ba, and Be. The Pearson correlation coefficients for the estimated values were 0.89 and 0.90 on average for the first and second models, respectively. The uncertainties were 6% on average for both models. These results demonstrate the use of LIBS for rapid scanning of the texture of soil samples with distinct composition. The procedure presented here can be extended to other chemical and physical soil properties, which makes LIBS a universal tool for rapid soil analysis without preparation with chemical reagents. Embrapa Instrumentation, R. XV de Novembro 1452 Physics Institute of São Carlos University of São Paulo IFSC-USP, Av. Trabalhador Sancarlense, 400 Pq. Arnold Schimid Physics Department São Carlos Federal University, P.O. Box 676 São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355, R. Prof. Francisco Degni, 55 São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355, R. Prof. Francisco Degni, 55

Made available in DSpace on 2018-12-11T16:39:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-09-01. Added 1 bitstream(s) on 2019-10-09T18:28:16Z : No. of bitstreams: 1 S0103-50532015000901879.pdf: 238433 bytes, checksum: dd72dcca3d8eab9293ff8af186c9c8d5 (MD5) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Bismuth was evaluated as internal standard for Pb determinations and showed usefulness to minimize variations due to changes in the experimental conditions of the inductively coupled plasma optical emission spectrometry (ICP OES), inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). Thirty four samples were analyzed and the Pb contents obtained by ICP-MS and ETV-ICP-MS were in agreement at 95% confidence level. Plant, biological tissue and soil reference materials were also analyzed and the results were close to certified values upon the use of the internal standard. Recoveries for Pb spikes (ICP OES: 95-110%; ICP-MS: 95-106%; ETV-ICP-MS: 92-119%) were better than those obtained with external calibration (ICP OES: 56-91%; ICP-MS: 36-136%; ETV.ICP-MS: 5-123%). The relative standard deviations (n = 12) was improved from 1-9% to 0.2-6% (ICP OES), from 0.5-11% to 0.1-7% (ICP-MS) and from 0.4-7% to 0.1-4% (ETV.ICP.MS) by using external and internal standard calibrations, respectively. Departamento de Química Analítica, Universidade Estadual Paulista (UNESP), Rua Prof. Francisco Degni, 55 Departamento de Química, Universidade Federal de Santa Catarina (UFSC), Campus Trindade Departamento de Química Analítica, Universidade Estadual Paulista (UNESP), Rua Prof. Francisco Degni, 55 FAPESP: 2012/13500-9

A flow injection system was proposed to evaluate the transient product of a colorimetric reaction between hydrolysable tannin and potassium iodate (KIO 3 ) solution. The system optimization was accomplished by using statistical methods based on experimental design. Flow rate of KIO 3 solution, sample volume, carrier flow rate, and reaction coil were the selected factors for evaluation. On screening step, complete factorial 2 4 was used and two levels for each selected factor were studied. For the optimization phase, a centered face composite design 2 2 + star was employed to evaluate sample volume and flow rate of KIO 3 solution, which were the factors identified in the screening phase as having more influence on the absorbance signal. After optimization, the proposed system was compared with batch determination. Some characteristics, such as analytical frequency, reagent consumption and chemical residues generation presented better results by the use of the proposed system if compared with batch method. The system presented good repeatability with standard deviation lower than 3%, for n = 10, linearity ( R 2 = 0.9974) for tannic acid standard, analytical frequency of 15 injections h − 1 and limit of quantification of 24 mg L − 1 of tannic acid. Good results were obtained when the proposed system was applied to hydrolysable tannin determination in Stryphnodendron barbatimao , Eucalyptus citriodora and Phyllanthus niruri , samples of plants commonly used in popular medicine.

Total phenols and condensed tannins in Pigeon pea seeds were determined by flow injection spectrophotometry. Folin-Denis and vanillin assays were used for total phenol and condensed tannin, respectively. Three Pigeon pea accessions were cultivated in a greenhouse. After harvesting, one access was separated into two aliquots. One aliquot was freeze-dried (−196 °C), and the other was dried in a forced air oven at 50 °C, like the other access samples, to evaluate drying temperature interference. The seeds were initially analyzed and then stored at around −10 °C, 16 °C or at ambient temperature (25 ± 10 °C). The stored samples were analysed every 30 days, for a 90 day period. A significant difference ( P P

Laser induced breakdown spectroscopy (LIBS) is an atomic emission spectroscopy technique for simple, direct and clean analysis, with great application potential in environmental sustainability studies. In a single LIBS spectrum it is possible to obtain qualitative information on the sample composition. However, quantitative analysis requires a reliable model for analytical calibration. Multilayer perceptron (MLP), an artificial neural network, is a multivariate technique that is capable of learning to recognize features from examples. Therefore MLP can be used as a calibration model for analytical determinations. Accordingly, the present study proposes to evaluate the traditional linear fit and MLP models for LIBS calibration, in order to attain a quantitative multielemental method for contaminant determination in soil under sewage sludge application. Two sets of samples, both composed of two kinds of soils were used for calibration and validation, respectively. The analyte concentrations in these samples, used as reference, were determined by a reference analytical method using inductively coupled plasma optical emission spectrometry (ICP OES). The LIBS?MLP was compared to a LIBS?linear fit method. The values determined by LIBS?MLP showed lower prediction errors, correlation above 98% with values determined by ICP OES, higher accuracy and precision, lower limits of detection and great application potential in the analysis of different kinds of soils. Made available in DSpace on 2022-07-25T17:22:33Z (GMT). No. of bitstreams: 1 PROCI2011.00029.pdf: 310854 bytes, checksum: 0575835b7b288e9973531e5bf7682924 (MD5) Previous issue date: 2011

A flow system, coupled with flame atomic absorption spectrometry (FIA-FAAS), was developed for tannin determination in pigeon pea samples, exploring the precipitation reaction between tannins and proteins. Sample extracts obtained by sonication with a 50% (v/v) methanol solution were introduced into the system and induced to react with a hemoglobin solution. The precipitate produced was retained on a filter located in the analytical flow. A reversed flow of 1% (w/v) sodium dodecyl sulfate solution was used for solubilization of the precipitate from the filter and to conduct the tannin-hemoglobin complex to the FAAS, to quantify the iron ions present in the hemoglobin structure. A tannic acid solution was used to prepare the analytical curve. The proposed method allowed determination of 30 samples per hour, a standard deviation of 9.7% (n=10), and a quantification limit of 0.27 mg L-1 for tannic acid.