Rice Labeling according to Grain Quality Features Using Laser-Induced Breakdown Spectroscopy.

Rice is an important source of nutrition and energy consumed around the world. Thus, quality inspection is crucial for protecting consumers and increasing the rice's value in the productive chain. Currently, methods for rice labeling depending on grain quality features are based on image and/or visual inspection. These methods have shown subjectivity and inefficiency for large-scale analyses. Laser-induced breakdown spectroscopy (LIBS) is an analytical technique showing attractive features due to how quick the analysis can be carried out and its capability of providing spectra that are true fingerprints of the sample's elemental composition. In this work, LIBS performance was evaluated for labeling rice according to grain quality features. The LIBS spectra of samples with their grain quality numerically described as Type 1, 2, and 3 were measured. Several spectral processing methods were evaluated when modeling a k-nearest neighbors (k-NN) classifier. Variable selection was also carried out by principal component analysis (PCA), and then the optimal k-value was selected. The best result was obtained by applying spectrum smoothing followed by normalization by using the first fifteen principal components (PCs) as input variables and k = 9. Under these conditions, the method showed excellent performance, achieving sample classification with 94% overall prediction accuracy. The sensitivities ranged from 90 to 100%, and specificities were in the range of 92-100%. The proposed method has remarkable characteristics, e.g., analytical speed and analysis guided by chemical responses; therefore, the method is not susceptible to subjectivity errors.

Characterization and predictive modeling potential of aging time of roasted coffee using infrared spectroscopy.

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, Fourier transform infrared spectroscopy was evaluated as a provider of relevant regressors, chemically explainable, aiming for predictive models for estimating the aging of roasted and packaged coffees during their shelf life. Spectra of two Coffea arabica varieties (Bourbon and Obatã) were periodically acquired during eleven months of storage. The most relevant absorption bands were selected, which showed a moderate correlation with the storage time. They were identified as responses from lipids, phenolic compounds, and carbohydrates. From those responsive bands, logistic regression (sigmoid functions) models were fitted for each coffee variety, as well as for both together. Predictive models for Bourbon and Obatã showed high performances in validation data, with r (Pearson correlation) above 0.92 and root mean square error (RMSE) below 43 days. For both varieties, the logistic model showed r greater than 0.83 and RMSE equal to 56 days. Results corroborate the methodological approach efficacy towards agile technological innovations in the coffee value chain, as well as opening new application fronts for estimating the aging of other foods.

Synthesis, characterization and application of a novel ion hybrid imprinted polymer to adsorb Cd(II) in different samples.

Two new ionic imprinted hybrid polymers (IIHP) and their corresponding non imprinted hybrid polymers (NIHP) were synthesized. The prepared IIHP was highly selective to Cd2+. To prepare the IIHP, 1-vinylimidazole (VIN) was used as the functional monomer, (3-mercaptopropyl) trimethoxysilane (MP) or (3-aminopropyl) trimethoxysilane (AMP) was used as the functional organosilane, trimethylolpropane (TRIM) was used as the crosslinking agent, AIBN was used as a radical initiator and TEOS was used as a functional precursor. The functional monomer was selected considering calculations based on the density functional theory (DFT). The fabricated materials were characterized via field emission gun scanning electron microscopy (FEG-SEM), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA). The maximum adsorption capacity of Cd2+ was achieved at a pH of 7.2 in the tris-HCl medium. The adsorption test indicated that the reaction followed pseudo second order kinetics, and the equilibrium sorption data fitted well into the Langmuir isotherm model. The relative selectivity coefficients of polymers IIHP-VIN-AMP and IIHP-VIN-MP, as evaluated in binary mixtures of Cd2+ and interferent cations (Pb2+, Zn2+, Hg2+, Cu2+, Ni2+, Ca2+, Mg2+, and Na+) at different molar ratios, were greater than one due to the presence of specific recognition sites for Cd2+ ions. Moreover, the selective materials exhibited a high reusability and reproducibility in the context of Cd2+ adsorption. These adsorbent materials, specifically IIHP-VIN-MP, exhibited a % removal efficiency of more than 90% for the Cd2+ in river water samples.

Laser-induced breakdown spectroscopy determination of K in biochar-based fertilizers in the presence of easily ionizable element.

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.

Effect of different precursors on generation of reference spectra for structural molecular background correction by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry: Determination of antimony in cosmetics.

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 217.581nm and 231.147nm 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 217.581nm with aqueous standards containing Sb in the range 0.5-2.25ng, resulting in a correlation coefficient of 0.9995 and a slope of 0.1548s ng-1. The sample mass was in the range 0.15-0.25mg. 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 0.9mgkg-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 9.1-14.5mgkg-1 range.

Cobalt internal standard for Ni to assist the simultaneous determination of Mo and Ni in plant materials by high-resolution continuum source graphite furnace atomic absorption spectrometry employing direct solid sample analysis.

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.

Internal standardization combined with dilute-and-shoot preparation of distilled alcoholic beverages for Cu determination by high-resolution continuum source flame atomic absorption spectrometry.

Internal standardization (IS) and dilute-and-shoot preparation of distilled alcoholic beverages were evaluated for the direct determination of Cu by high-resolution continuum source flame atomic absorption spectrometry. Among Bi, In, Sn and Te evaluated as internal standards, Bi and Te furnished best results. Calibration curves were built up by plotting A(Cu)/A(Bi) and A(Cu)/A(Te)versus Cu concentration (0.05-4.0 mg L(-1)) and linear correlation coefficients were 0.9994 and 0.9990, respectively. Contents of Cu in 22 commercial distilled beverages analyzed by the proposed method varied in the 0.029-3.608 mg L(-1) interval. These results were in agreement (paired t-test) at 95% confidence level with those obtained by line source FAAS using standard addition calibration. Recoveries improved from 77-83% (without IS) to 99-101% (with IS) intervals. The relative standard deviation (n=12) was 0.8-3.7% (IS-Bi), 0.4-4.4% (IS-Te), and 0.5-9.1% (without IS) and the limit of detection was ca. 5 µg L(-1) using Bi or Te.

Rugged, portable tungsten coil atomic emission spectrometer.

Tungsten coil atomic emission spectrometry is an ideal technique for field applications because of its simplicity, low cost, low power requirement, and independence from cooling systems. A new, portable, compact design is reported here. The tungsten coil is extracted from an inexpensive 24 V, 250 W commercial light bulb. The coil is housed in a small, aluminum cell. The emission signal exits from a small aperture in the cell, while the bulk of the blackbody emission from the tungsten coil is blocked. The resulting spectra exhibit extremely low background signals. The atomization cell, a single lens, and a hand-held charge coupled device (CCD) spectrometer are fixed on a 1 × 6 × 30 cm ceramic base. The resulting system is robust and easily transported. A programmable, miniature 400 W solid-state constant current power supply controls the temperature of the coil. Fifteen elements are determined with the system (Ba, Cs, Li, Rb, Cr, Sr, Eu, Yb, Mn, Fe, Cu, Mg, V, Al, and Ga). The precision ranges from 4.3% to 8.4% relative standard deviation for repetitive measurements of the same solution. Detection limits are in the 0.04 to 1500 µg/L range. Accuracy is tested using standard reference materials for polluted water, peach leaves, and tomato leaves. For those elements present above the detection limit, recoveries range from 72% to 147%.

Feasibility of internal standardization in the direct and simultaneous determination of As, Cu and Pb in sugar-cane spirits by graphite furnace atomic absorption spectrometry.

Bismuth and Sb were evaluated as internal standards (IS) to minimize matrix effects on the direct and simultaneous determination of As, Cu, and Pb in cachaça by graphite furnace atomic absorption spectrometry using W-coated platform plus Pd-Mg(NO(3))(2) as modifier. For 20microL injected sample, calibration within the 0.5-10microg L(-1) As, 100-1000microg L(-1) Cu and 0.5-30microg L(-1) Pb intervals were established using the ratios As absorbance to Sb absorbance, Cu absorbance to Bi absorbance and Pb absorbance to Bi absorbance versus analytes concentration, respectively. Typical linear correlations of 0.998, 0.999 and 0.999 were, respectively, obtained. The proposed method was applied for direct determination of As, Cu and Pb in 10 commercial cachaça samples and results were in agreement with those obtained by inductively coupled plasma mass spectrometry at 95% confidence level. The found characteristic masses were 30pg As, 274pg Cu and 39pg Pb. The useful lifetime of the graphite tube was around 760 firings. Recoveries of As, Cu and Pb added to cachaça samples varied, respectively, from 98% to 109%, 97% to 108% and 98% to 104% with internal standards and from 48% to 54%, 53% to 92% and 62% to 97% without internal standards. The limits of detection were 0.13microg L(-1) As, 22microg L(-1) Cu and 0.05microg L(-1) Pb. The relative standard deviations (n=12) for a spiked sample containing 20microg L(-1) As, Pb and 500microg L(-1) Cu were 1.6%, 1.0%, and 1.8% with IS and 4.3%, 5.2%, and 5.5% without IS.

Evaluation of lubricating oil preparation procedures for the determination of Al, Ba, Mo, Si and V by high-resolution continuum source FAAS.

Microwave-assisted acid decomposition and oil-in-water emulsification were evaluated as sample pretreatment procedures to determine Al, Ba, Mo, Si and V in lubricating oils by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Average recoveries of Al, Ba and V in oil digests (107, 103 and 101%) were close to those obtained for emulsions prepared in kerosene medium (94, 113 and 95%). Average recoveries for Mo were close to 105 and 46% for emulsions and digests, respectively. Improved average recoveries (101%) were obtained for Mo in digests using the analyte addition technique. Silicon was successfully quantified only in digested samples. Limits of quantification for Al, Ba, Mo and V were 1.4, 31.5, 1.5 and 11.4-fold lower than those obtained by line-source FAAS. Enhanced sensitivity, multi-elemental capability, and high sample throughput are among the main advantages of HR-CS FAAS in comparison with the line-source FAAS technique.

Phosphite determination in fertilizers after online sequential sample preparation in a flow injection system.

A flow injection spectrophotometric system is proposed for phosphite determination in fertilizers by the molybdenum blue method after the processing of each sample two times on-line without and with an oxidizing step. The flow system was designed to add sulfuric acid or permanganate solutions alternately into the system by simply displacing the injector-commutator from one resting position to another, allowing the determination of phosphate and total phosphate, respectively. The concentration of phosphite is obtained then by difference between the two measurents. The influence of flow rates, sample volume, and dimension of flow line connecting the injector-commutator to the main analytical channel was evaluated. The proposed method was applied to phosphite determination in commercial liquid fertilizers. Results obtained with the proposed FIA system were not statistically different from those obtained by titrimetry at the 95% confidence level. In addition, recoveries within 94 and 100% of spiked fertilizers were found. The relative standard deviation (n = 12) related to the phosphite-converted-phosphate peak alone was

Tungsten permanent chemical modifier for fast estimation of Se contents in soil by graphite furnace atomic absorption spectrometry.

A tungsten carbide coating on the integrated platform of a transversely heated graphite atomizer was used as a modifier for the direct determination of Se in soil extracts by graphite furnace atomic absorption spectrometry. Diethylenetriaminepentaacetic acid (0.0050 mol L(-1)) plus ammonium hydrogencarbonate (1.0 mol L(-1)) extracted predominantly available inorganic selenate from soil. The formation of a large amount of carbonaceous residue inside the atomizer was avoided with a first pyrolysis step at 600 degrees C assisted by air during 30 s. For 20 microL of soil extracts delivered to the atomizer and calibration by matrix matching, an analytical curve (10.0-100 microgram of L(-1)) with good linear correlation (r = 0.999) between integrated absorbance and analyte concentration was established. The characteristic mass was approximately 63 pg of Se, and the lifetime of the tube was approximately 750 firings. The limit of detection was 1.6 microgram L(-1), and the relative standard deviations (n = 12) were typically <4% for a soil extract containing 50 microgram of L(-1). The accuracy of the determination of Se was checked for soil samples by means of addition/recovery tests. Recovery data of Se added to four enriched soil samples varied from 80 to 90% and indicated an accurate method.