The chemical and sorptive characteristics of mineral coals extracted from a mine in Lebu (Biobío Región, Chile) and its derivatives were studied. These derivatives were obtained by applying a thermal treatment in an environment with N2 and CO2 at different experimental conditions, in order to increase their specific surface. In addition, coals were characterized by using proximal analysis, elementary analysis and petrographic analysis. In order to know their structureand surface, Boehm titration analysis, FTIR infrared spectroscopy, X-ray diffraction and scanning electron microscopy were performed. The surface of the selectedcarbons was modified by selectively oxidizing it with (NH^S^O and with H2O2 e impregnating with an iron solution for the study with H2O2 In the oxidation ofH2O2, the work was carried out at different pH. The results show a moderate homogeneity between different types of seams studied, whereas when coals are treatedwith heat or strong oxidants, increases its surface and can be used with analytical applications (v.g. electroanalytical sensors).

An analytical testing study of interference standard method (IFS) for metals in wines with low and high residual sugar by inductively coupled plasma mass spectrometry (ICP-MS) was evaluated. Selection of IFS probes was based on the ions formed in the argon plasma, such as natural 38Ar+ or contaminant like 83Kr+ or also ions provided from the matrix sample (for instance, 13C+). The analytical signal was obtained from ratio between the original signals of the analyte and those of the IFS probe species. The accuracy was confirmed using a t-test statistic for comparison between the concentrations obtained by Flame Atomic Absorption Spectrometry (FAAS) and ICP-MS. In a first study, the IFS effect was analyzed by comparing the correlation coefficients obtained with or without dividing the analytical signal by the IFS. Using the 83Kr+ IFS probe provide always better results in the determination of Fe, Mn and Zn compared to 13C+ and 38Ar+.

Oxygen is an important element for plant growth. Reducing its concentration in the soil affects plant physiological processes such as nutrient and water uptake as well as respiration, the redox potential of soil elements and the activity of microorganisms. The main mechanism of oxygen transport in the soil is by diffusion, a dynamic process greatly influenced by soil physical properties such as texture and structure, conditioning, pore size distribution, tortuosity and connectivity. Organic matter is a modifying agent of the soil’s chemical and physical properties, affecting its structure and the porous matrix, which are determinants of oxygen transport. This study reviews the theory of soil gas diffusion and the effect of soil organic matter on the soil’s physical properties and transport of gases. It also reviews gas diffusion models, particularly those including the effect of soil organic matter.

A flow system coupled to a tungsten coil atomizer in an atomic absorption spectrometer (TCA-AAS) was developed for As(III) determination in waters, by extraction with sodium diethyldithiocarbamate (NaDDTC) as complexing agent, and by sorption of the As(III)-DDTC complex in a micro-column filled with 5 mg C18 reversed phase (10 µL dry sorbent), followed by elution with ethanol. A complete pre-concentration/elution cycle took 208 s, with 30 s sample load time (1.7 mL) and 4 s elution time (71 µL). The interface and software for the synchronous control of two peristaltic pumps (RUN/ STOP), an autosampler arm, seven solenoid valves, one injection valve, the electrothermal atomizer and the spectrometer Read function were constructed. The system was characterized and validated by analytical recovery studies performed both in synthetic solutions and in natural waters. Using a 30 s pre-concentration period, the working curve was linear between 0.25 and 6.0 µg L-1 (r = 0.9976), the retention efficiency was 94±1% (6.0 µg L-1), and the pre-concentration coefficient was 28.9. The characteristic mass was 58 pg, the mean repeatability (expressed as the variation coefficient) was 3.4% (n=5), the detection limit was 0.058 µg L-1 (4.1 pg in 71 µL of eluate injected into the coil), and the mean analytical recovery in natural waters was 92.6 ± 9.5 % (n=15). The procedure is simple, economic, less prone to sample loss and contamination and the useful lifetime of the micro-column was between 200-300 pre-concentration cycles.

Thermospray flame furnace Atomic Absorption Spectrometry (TS-FF-AAS) was used for the total determination of Cd, Pb and Zn in fresh water and seawater samples at µg L-1 levels, and in marine sediment samples at µg g-1 levels. Using a sample loop of 50 µL and a peristaltic pump the samples were transported into the metallic tube placed over an air/acetylene flame, through a ceramic capillary (o.d. = 3.2 mm) containing two parallel internal orifices (i.d = 0.5 mm). The detection limits determined for Cd, Pb and Zn using a synthetic water matrix (2.5% m/v NaCl, 0.5% m/v MgCl2 and 0.8% m/v CaCl2) were 0.32 µg L-1; 2.6 µg L-1 and 0.21 µg L-1 respectively. The methodology by TS-FF-AAS was validated by determination of Cd, Pb and Zn in certified reference materials of water and marine sediment, and the t-test for differences between means was applied. No statistically significant differences were established in fresh water and seawater (p>0.05), whereas differences became apparent in marine sediment (p<0.03).

Zinc speciation in marine shallow sediments from Aysen fjord was analyzed using a differential attack. This treatment was used in order to identify the dominance of the different Zn species. Samples were collected in two stations, one of them in the fjord mouth, and the other in the fjord head, november 2001. The Zn total results were: 168.0 ± 15 <IMG SRC="http:/fbpe/img/imar/v32n1/figura7.jpg" WIDTH=12 HEIGHT=18>g·g-1 at the fjord head (corresponding to enriched sediments) and, 83.6 ± 6 <IMG SRC="http:/fbpe/img/imar/v32n1/figura7.jpg" WIDTH=12 HEIGHT=18>g·g-1 at the fjord mouth (concentration close to base line value in this area). These results were consistent with the Zn total concentration from the samples obtained in 1995, in stations placed at the same geographic location. The study of speciation of Zn showed that at Stn. 82-a the metals, in order of abundance, were associated with the residual fraction > oxyhydroxides > interchangeables > organic matter > carbonates. In contrast, at Stn. 78-a, in order of abundance the residual fraction > oxyhydroxides <IMG SRC="http:/fbpe/img/imar/v32n1/figura8.jpg" WIDTH=20 HEIGHT=12>interchangeables > carbonates > carbonates > organic material. The resultant relationship among the species of the interchangeable sites were: carbonates : oxyhydroxides : organic material : residuals = 2.7 : 0.44 : 11.2 : 7.5 : 1.4. The percentages of all the species were interchangeable: carbonates : oxyhydroxides : organic material : residuals = 1.37 : 0.21 : 5.73 : 3.9 : 0.71. These results showed that the absolute values for concentrations were independent of percentages of the species. The relationship between, concentration in the sediments showed that Puerto Chacabuco (shipment site of concentrate minerals), had twice the Zn concentrations shown by samples from the mouth of Aysén Fjord

Se analiza la especiación de zinc presente en los sedimentos superficiales del fiordo Aysén mediante un ataque diferencial para identificar la dominancia de las diferentes especies de Zn. Las muestras se obtuvieron en dos estaciones, una en la boca y la otra en la cabeza del fiordo, en noviembre de 2001. Los resultados de zinc total fueron de 168,0 ± 15 <IMG SRC="http:/fbpe/img/imar/v32n1/figura7.jpg" WIDTH=12 HEIGHT=18>g·g-1en la cabeza (correspondiendo a sedimentos enriquecidos en Zn) y 83,6 ± 6 <IMG SRC="http:/fbpe/img/imar/v32n1/figura7.jpg" WIDTH=12 HEIGHT=18>g·g-1 en la boca del fiordo (concentración levemente inferior al valor de la línea de base). Estos resultados fueron consistentes con las concentraciones de zinc total determinados en 1995, en estaciones de similar ubicación geográfica. El estudio de especiación de Zn, mostró que en la cabeza del fiordo, dominan en abundancia las concentraciones de las fracciones: residual > oxihidróxidos > intercambiables > materia orgánica > carbonatos. En cambio, en la boca, dominan la fracción residual > oxihidróxidos <IMG SRC="http:/fbpe/img/imar/v32n1/figura8.jpg" WIDTH=20 HEIGHT=12>intercambiables > carbonatos > materia orgánica. Respecto del análisis de las concentración, entre los valores absolutos de las especies de Zn en los sedimentos, estas resultaron ser el doble en Puerto Chacabuco (puerto de embarque de concentrado de mineral), en relación a la boca de fiordo Aysén. Las proporciones de cada una de las fracciones entre los sitios estudiados fueron: intercambiables : carbonatos : oxihidróxidos : materia orgánica : residuales = 2,7 : 0,4 : 11,2 : 7,5 : 1,4. No obstante, si se toman los porcentajes de las diferentes especies sobre la concentración total, para cada uno de los sitios, se observó que el mayor porcentaje de la fracción residual ocurre en la boca del fiordo

This article describes the combination of low- and high-pressure flow systems for the determination of Magnesium, Calcium and Strontium by flame atomic absorption spectrometry (FAAS). In the low-pressure system a short C-18 RP column (length 0,5 cm) was utilized for the preconcentration/matrix separation step, xylenol orange was used as chelating agent and tetrabutylamonium acetate for ion pair formation. The hydraulic high pressure nebulization (HHPN) was used for sample transport and sample introduction in the high pressure system. The repeatabilities and detection limits for Mg, Ca and Sr were determined and compared with those obtained by pneumatic nebulization (PN). The results show that the detection limits obtained using the HHPN for Mg, Ca and Sr are between 1.5 to 2 times better than those obtained by PN when the signal transient was measured in area. The system presented a sampling frequency of 130 h-1 for direct determination of Mg, Ca or Sr in samples of saturated sodium chloride used in the production of chlorine and sodium hydroxide.