Marcos Y. Kamogawa

A new strategy for preparation of hair slurries using cryogenic grinding and water-soluble tertiary-amines medium

Abstract The investigation of trace metal contents in hair can be used as an index of exposure to potentially toxic elements. Direct determination of Cd, Cu and Pb in slurries of hair samples was investigated using an atomic absorption spectrometer with Zeeman-effect background correction. The samples were pulverized in a freezer/mill for 13 min, and hair slurries with 1.0 g l −1 for the determination of Cu and Pb, and 5.0 g l −1 for the determination of Cd, respectively, were prepared in three different media: 0.1% v/v Triton X-100, 0.14 mol l −1 HNO 3 , and 0.1% v/v of CFA-C, a mixture of tertiary amines. The easiest way to manipulate the hair samples was in CFA-C medium. The optimum pyrolysis and atomization temperatures were established with hair sample slurries spiked with 10 μg l −1 Cd 2+ , 30 μg l −1 Pb 2+ , and 10 μg l −1 Cu 2+ . For Cd and Pb, Pd was used as a chemical modifier, and for Cu no modifier was needed. The analyte addition technique was used for quantification of Cd, Cu, and Pb in hair sample slurries. A reference material (GBW076901) was analyzed, and a paired t -test showed that the results for all elements obtained with the proposed slurry sampling procedure were in agreement at a 95% confidence level with the certified values. The cryogenic grinding was an effective strategy to efficiently pulverize hair samples.

Autoamostrador de baixo custo para análise por injeção em fluxo

This paper describes a homemade autosampler for flow injection analysis (FIA), constructed with two step motors from old floppy disk drives (5¼-inch). The autosampler was connected to a computer through the parallel port and the sampling process was controlled by software in Quick Basic. The performance of the system was assessed by the determination of ammonium, based on the gaseous diffusion into a bromocresol purple solution, following the spectrophotometric determination of change in absorbance. The easy and simple construction is the main characteristics of this equipment and analytical results with RSD lower than 1% were obtained.

Avaliação da reação foto-fenton na decomposição de resíduos de carrapaticida

Experimental procedures based on factorial design and surface response methodology were applied to establishe experimental conditions for the decomposition of a 1:400 (v/v) Supocade® (chlorfenvinphos 13.8% and cypermethrin 2.6%) solution, used to control cattle ticks. Experiments exploring photo-oxidative reactions were performed with and without UV radiation, fixing exposition time and pesticide volume, and varying the oxidant mixture. The use of 3.6 mmol L-1 Fe2+ plus 1.9 mol L-1 H2O2 plus UV radiation provided destruction of 94% of the original carbon content and reduction of aromatic, aliphatic and carbinolic compounds, evaluated by determination of residual carbon content by ICP OES and NMR analysis.

Absorption and Toxicity of Copper and Zinc in Bean Plants Cultivated in Soil Treated with Chicken Manure

The interaction between copper, zinc, and chicken manure, whenadded to soil, was studied in a greenhouse setting. Coppersulfate and of zinc chloride at concentrations of 0.5 to 2.0mmol kg-1 were added separately to pots containing 3.0 kgof dystrophic dark red latosoil (LEd) plus 1,0% (m/m) pH 4.2chicken manure. IAPAR 57 beans were used as test plant andcultivated in the experimental soils for 30 days. Plant growthin terms of dry weight and the concentrations of copper and zincin the aerial part of the plants were determined. Bean plantingswere repeated four times, at four-month intervals. A 20%decrease in dry weight was observed when amounts of copper orzinc equal to or geater than 1.0 or 2.0 mmol kg-1, respectively, were applied to the soil over an average of fourplantings. For these concentrations, the average amount of metalfound in the plant was 13.4 mg kg-1 for copper and 224.8 mgkg-1 for zinc. Chlorosis of the leaves in the bean plantswas also observed. The copper and zinc concentrations in thetreated soil were determined using different extractants. Amongthe solutions evaluated for the extraction of available zinc,1.0 M ammonium acetate, pH 4.8, showed a better correlation withthe metal concentration in the plant. As for copper, the bestcorrelation was found with the Mehlich-1 extractant.

A critical review on photochemical conversions in flow analysis.

Photochemical conversions are cost-effective and environmental friendly processes that require mild experimental conditions and avoid generation of highly acidic wastes. Treated samples are then compatible with most of the analytical techniques. These characteristics become more relevant when the photoconversions are accomplished to flow analysis, thus allowing exploitation of incomplete reactions, the effective use of the photogenerated unstable radicals and in-line sample treatment. Decreasing of reagent consumption and waste generation, sample processing in a closed environment, and improvement of efficiency of the photochemical processes are other inherent advantages. These aspects are critically reviewed in this article, which emphasizes applications to fractionation and speciation analysis, photo-induced luminescence, miniaturization, and in-line waste treatment. Design of flow-through photochemical cells, use of auxiliary reagents in homogeneous and heterogeneous media, and configurations of flow manifolds are also discussed.

Discriminação geográfica de águas minerais do Estado de São Paulo através da análise exploratória

The correlation and grouping of mineral waters from different regions of Sao Paulo state was carried out using exploratory analysis of pH values and Ba, Ca, K, Mg, Na and V contents. By using principal components analysis (PCA) and hierarchical cluster analysis (HCA) was possible to evaluate the similarity of mineral water samples through group formation that was directly correlated with their sources. Employing scores, loadings and dendogram graphics was possible to observe the formation of two groups and the separation of Ibira and Itu mineral water samples. The first group is composed by samples from Serra da Mantiqueira region (Aguas da Prata, Campos do Jordao and Lindoia) and the other one is formed by samples from cities located above the Guarani Aquifer (Aguas de Santa Barbara, Palmares Paulista, Presidente Prudente, Sao Carlos, Sao Simao e Santa Rosa do Viterbo). The segregation of Ibira samples was due to predominant presence of Na and V in their mineral composition, while for Itu samples it was observed higher contribution of Ba, Ca and Mg elements. The application of exploratory analysis enabled to correlate the chemical composition with the geographical source of the mineral water samples producing useful results for establishing of classification and prevision models.

Uso de scanner em espectrofotometria de absorção molecular: aplicação em experimento didático enfocando a determinação de ácido ascórbico

Quantitative analysis of colored substances is generally performed using a spectrophotometer for detection of radiation. However, the combination of digital images and mathematical conversion of colors is an alternative for quantitative procedures based on colored chemical reactions. This work proposes a didactic experiment using a scanner for determination of ascorbic acid in medicines based on the formation of the Prussian blue complex. Results were in good agreement with a conventional spectrophotometer method and the procedure is attractive for instrumental analysis undergraduate courses.

Determination of soil calcareous efficiency using flow system with pervaporative separation

A method is described for the conductimetric determination of CO 2 . The proposed system was constructed with a pervaporator chamber coupled to a flow system comprised of a six-way solenoid valve, a conductivity cell, a conductivimeter and a PC microcomputer for data acquisition and external controls. An amount of 2 g of dry soil samples were directly weighted in the donor compartment of the pervaporation chamber. The CO 2 was determined from an analytical curve within 5.0 x 10 -3 -5.0 x 10 -2 mol kg -1 CaCO 3 . This curve was constructed with the matrix matching approach and presented a linear regression of y = 13.58 + 584.77r (r = 0.9962). Soils with different lime amounts were analyzed by the proposed methodology and with the official method, that uses the calcium difference between the total, extracted with HCl 1 mol l -1 and exchangeable, extracted with the KCl 1 mol l -1 After paired t-test application, no significant difference between the methods was found at the 95% probability level. The proposed method presented sampling rate of 17 h -1 , detection limit of 8.0 x 10 -4 mol kg -1 CaCO 3 , and R.S.D. < 3%. The use of the pervaporator allowed the in situ soil pretreatment for the residual lime determination.

Temperature effect in potassium and nitrate ions in soil transport

When doing researches on solute dynamics in porous medium, the knowledge of medium characteristics and percolating liquids, as well as of external factors is very important. An important external factor is temperature and, in this sense, our purpose was determining potassium and nitrate transport parameters for different values of temperature, in miscible displacement experiments. Evaluated parameters were retardation factor (R), diffusion/dispersion coefficient (D) and dispersivity, at ambient temperature (25 up to 28 oC), 40 oC and 50 oC. Salts used were potassium nitrate and potassium chlorate, prepared in a solution made up of 5 ppm nitrate and 2.000 ppm potassium, with Red-Yellow Latosol porous medium. Temperature exhibited a positive influence upon porous medium solution and upon dispersion coefficient.

Use of a Digital Image in Flow Analysis: Determination of Nitrite and Nitrate in Natural Waters

A webcam is proposed as the detector in a flow system with multicommutation, and the feasibility of the approach is demonstrated in the determination of nitrate and nitrite in natural waters. The typical transient signal inherent to the flow system was obtained using a digital video and quantified by ImageJ software. The linear dynamics range for nitrite and nitrate determinations were 0.2 to 2.0 mg L-1 NO2− and 1.0 to 10.0 mg L-1 NO3−, with relative standard deviation < 2% for both analytes. The limits of detection were 0.01 and 0.04 mg L-1 for nitrite for nitrate, respectively, and the sampling rate were 80 and 103 h-1 for nitrite and nitrate, respectively. The use of webcams has a high potential for analysis in the visible region of the electromagnetic spectrum, and the proposed strategy constitutes a promising alternative to traditional absorbance measurements that depend on conventional equipment. The webcam detection system is attractive, especially in relation to field analysis.