Mabel Tudino

Seaweeds in the assessment of heavy metal pollution in the Gulf San Jorge, Argentina

Abstract The content of cadmium, lead, chromium, copper and zinc in algal samples from the Southern Atlantic coasts was determined by atomic absorption spectrometry. Algal population samples of Ulva lactuca , Enteromorpha prolifera and Porphyra columbina from Gulf San Jorge, Argentina, were collected, composited and pooled. Two stations with different exposure degree to human activities, Punta Borja and Punta Maqueda, were selected as sampling points. Freeze-dried algal powders of entire plants were digested in a microwave oven before spectroscopic analysis. This sample preparation program allowed the detection of lower levels of metals than the conventional wet digestion procedure. The content of total cadmium, lead, chromium, copper and zinc in filtered seawater from the collection sites was also determined in order to study metal concentration and distribution in the different algal species. Taking into account their toxicities, operational speciation of cadmium and lead was also carried out in order to compare metal accumulation in seaweeds under different environmental conditions.

Determination of As(III) and total inorganic As in water samples using an on-line solid phase extraction and flow injection hydride generation atomic absorption spectrometry

A simple and robust on-line sequential injection system based on solid phase extraction (SPE) coupled to a flow injection hydride generation atomic absorption spectrometer (FI-HGAAS) with a heated quartz tube atomizer (QTA) was developed and optimized for the determination of As(III) in groundwater without any kind of sample pretreatment. The method was based on the selective retention of inorganic As(V) that was carried out by passing the filtered original sample through a cartridge containing a chloride-form strong anion exchanger. Thus the most toxic form, inorganic As(III), was determined fast and directly by AsH(3) generation using 3.5 mol L(-1) HCl as carrier solution and 0.35% (m/v) NaBH(4) in 0.025% NaOH as the reductant. Since the uptake of As(V) should be interfered by several anions of natural occurrence in waters, the effect of Cl(-), SO(4)(2-), NO(3)(-), HPO(4)(2-), HCO(3)(-) on retention was evaluated and discussed. The total soluble inorganic arsenic concentration was determined on aliquots of filtered samples acidified with concentrated HCl and pre-reduced with 5% KI-5% C(6)H(8)O(6) solution. The concentration of As(V) was calculated by difference between the total soluble inorganic arsenic and As(III) concentrations. Detection limits (LODs) of 0.5 μg L(-1) and 0.6 μg L(-1) for As(III) and inorganic total As, respectively, were obtained for a 500 μL sample volume. The obtained limits of detection allowed testing the water quality according to the national and international regulations. The analytical recovery for water samples spiked with As(III) ranged between 98% and 106%. The sampling throughput for As(III) determination was 60 samplesh(-1). The device for groundwater sampling was especially designed for the authors. Metallic components were avoided and the contact between the sample and the atmospheric oxygen was carried to a minimum. On-field arsenic species separation was performed through the employ of a serial connection of membrane filters and anion-exchange cartridges. Advantages derived from this approach were evaluated. HPLC-ICPMS was employed to study the consistency of the analytical results.

Cd, Cu and Zn concentrations in sediments and the invasive bivalves Limnoperna fortunei and Corbicula fluminea at the Río de la Plata basin, Argentina

Cd, Cu and Zn content in sediments and bivalves (Limnoperna fortunei and Corbicula fluminea) were studied in the lower 500 km stretch of the Paraná River and in the right margin of the Río de la Plata Estuary. Both bivalves species showed higher metal contents at the Paraná River, possibly related to water chemistry. The Paraná water is circumneutral and soft, while the Río de la Plata coastal water is alkaline, hard, with a higher organic content. Bivalves sampled at the thermal effluent of the Atucha Nuclear Power Plant, at the Paraná River, showed the highest metal content, either from increased absorption at the higher water temperatures (12 °C higher than the river water) or from metal corrosion of the power plant cooling system. L. fortunei and C. fluminea appeared to be successful biomonitor organisms for Cd pollution in the basin, while Cu and Zn content in bivalve tissues was apparently not related to metal load.

On-line copper and iron removal and selenium(VI) pre-reduction for the determination of total selenium by flow-injection hydride generation-inductively coupled plasma optical emission spectrometry

Abstract Selenium was determined in samples with high copper and iron contents by hydride generation-inductively coupled plasma optical emission spectrometry (HG-ICP-OES) after flow-injection (FI) on-line copper and iron removal and selenium(VI) reduction. A Dowex 1X-8 anion-exchange microcolumn was used for the separation of selenium from copper and iron as their chloro-complexes. Se(VI) was then reduced on-line by heating a PTFE coiled reactor (150 cm long, 0.7 mm i.d.) in a 100°C water bath. After reduction of Se(VI), a 900-μl sample was injected into the carrier stream containing hydrochloric acid and sodium tetrahydroborate to generate the hydride. A limit of detection of 0.4 μg l −1 (RSD 2.3% for 20 μg l −1 selenium) was obtained. The application of the method to Geochemical Standard Reference Samples and copper metal reference materials (MBH) demonstrated that results were in good statistical accordance with certified values.

Fully Automatic On-line Separation Preconcentration System for Electrothermal Atomic Absorption Spectrometry: Determination of Cadmium and Lead in Sea-water

An automatic separation preconcentration system coupled to an electrothermal (graphite furnace) atomic absorption spectrometer is described. The preconcentration step is performed on a chelating resin microcolumn (Chelex-100) placed in the injection tip of the autosampler. A time based manifold with two- and three-way solenoid valves commanded by an eight channel microcomputer programmable controller is used for column conditioning, preconcentration and washing steps; no manual operations are involved. Elution is performed by the programmable graphite furnace autosampler and achieved in only one step. Operations involving complete and partial injection of the eluate into the graphite furnace are also discussed. The system was applied to the determination of Cd and Pb in near shore sea-water from Patagonia, Argentina. Detection limits of 1 and 8 ng l-1 were obtained for Cd and Pb respectively. Analysis of a certified reference material (CASS-3) showed good agreement with the certified values.

Multicomponent kinetic determination of Cu, Zn, Co, Ni and Fe at trace levels by first and second order multivariate calibration

A flow injection system coupled to a photodiode array spectrophotometer (FI-PDA) for the multicomponent kinetic determination of Cu, Zn, Co, Ni and Fe at trace levels is presented. The substitution reaction of metal-nitrilotriacetic complexes (M-NTA) by 4-(2-pyridilazo) resorcinol (PAR) instead of the direct complexation of the free ions with PAR is employed. In this way, the spectral differences between the colored complexes are combined with the different reaction rates of the ions producing a more specific λ-time region for each metal enhancing the selectivity. Since the NTA-M-PAR system is fast and the pure analyte profiles appear partially overlapped in the time and λ-axis, temporal and spectral information were added to PLS and PCR models to improve results and to increase the number of metals to be determined. The developed method provides the fast and cheap determination of the five metals at the sub-ppm range and demonstrates that the use of temporal and spectral information increases the number of analytes to be simultaneously determined, improving the analytical figures of merit as well.

A survey of some trace elements in seaweeds from Patagonia, Argentina

Cadmium and lead concentrations were determined in some common algal species living in the southernmost coasts of Argentina. Two different sampling areas were chosen: Gulf Nuevo, a locality being influenced by a developing industrial city, and Bay Camarones, a traditional harvest area for seaweed exploitation. Selected species of the genera Lessonia, Macrocystis and Gigartina, all of commercial interest, were collected from the harvest area, and analyses showed low levels of the metals in these species. Accumulation of Pb and Cd was also evident in other common brown seaweeds from the industrial site. Analysis of Al was included in this study due to an aluminum works near one of the sampling sites. High values of this metal ranging between 300 and 3000 mg Al/kg (dry basis) were recorded in the industrialized area. Amongst all of the species studied, Colpomenia sinuosa from Gulf Nuevo exhibited the highest values of aluminum. This preliminary survey showed that, except for Al, the levels of Cd and Pb were lower than those reported in same species of seaweeds from the polluted marine waters of the rest of the world.

Hybrid mesoporous materials for on-line preconcentration of Cr(VI) followed by one-step scheme for elution and colorimetric determination at ultratrace levels.

An hybrid mesoporous material synthesised in our laboratories for solid phase extraction (SPE) in flow through systems has been used for analytical purposes. The solid was obtained from mesoporous silica MCM-41 functionalized with 3-aminopropyltriethoxy silane by Sol-Gel methodology. In order to exploit the large sorption capacity of the material together with the possibility of modeling it for anions retention, a microcolumn (MC) filled with the solid was inserted in a flow system for preconcentration of Cr(VI) and its determination at ultratrace levels in natural waters. The analytical methodology involved a reverse flow injection system (rFI) holding a MC filled with the solid for the analyte extraction. Elution and colorimetric detection were carried out with 1-5 diphenylcarbazide (DPC) in sulfuric acid. DPC produced the reduction of Cr(VI) to Cr(III) together with the generation of a cationic red complex between Cr(III) and 1-5 diphenylcarbazone which was easily eluted and detected with a visible spectrophotometer. Moreover, the filling material got ready for the next sample loading remaining unspoiled for more than 300 cycles. The effect of several variables on the analytical signal as well as the influence of cationic and anionic interferences were discussed. Particular attention was given to sulfuric acid interference since it is the required media for the complex generation. Under optimal conditions, 99.8% of Cr(VI) recovery was obtained for a preconcentration time of 120s (sample and DPC flow rates=1 mL min(-1)) and an elution volume of 250 micro L. The limit of detection (3s) was found to be 0.09 microg L(-1) Cr(VI) with a relative standard deviation (n=10, 3 microg L(-1)) of 1.8. Since no Cr(III) was retained by the solid material and Cr(VI) was completely adsorbed, electrothermal atomic absorption spectrometry (ET AAS) determinations of Cr(III) were also performed by simply measuring its concentration at the end of the microcolumn after Cr(VI) retention by the mesoporous solid. Applications to the determination of Cr(VI) and Cr(III) in natural waters and the validation of the methodology were also studied.

Trace metal concentrations in coastal marshes of the Lower Paraná River and the Río de la Plata Estuary

Cu, Cr, Pb, Zn and Fe in water, sediment and tissue of the emergent macrophyte Schoenoplectus californicus were studied in three coastal environments differing in aquatic chemistry and tide amplitude: a deltaic floodplain marsh, a coastal vegetated strip of the river and a tidal marsh at the south margin of the Río de la Plata Estuary. Metal content in water was not significantly different between the river and the floodplain marsh. Metal content in sediments showed higher values in the marshes than in the river, suggesting a retention in the marsh. Except for Cu, the highest metal content in sediments and water was observed in the tidal marsh. Pb in plants was undetectable. Metal content was higher in rhizomes, except Cr, which was mainly stored in stems. Rhizome metal content was higher in the river, probably related to the higher redox potential of its sediments. Inflorescence metal content was higher in the marshes: the highest Zn, Cr and Fe contents were measured in the tidal marsh; the highest Cu content was in the floodplain marsh, together with the highest organic matter content of the sediments. Zn, Cr and Fe increased in standing drying stems and in inflorescences in late fall. Inflorescences showed the highest metal content after seeds had been released.

Flow dissolution of 1,5-diphenylcarbazide for the determination of chromium(VI)

An alternative procedure for the flow injection spectrophotometric determination of CrVI with 1,5-diphenylcarbazide (DPC), involving on-line dissolution of the reagent, is presented. Solid DPC (25% m/m in silica) is packed in a PTFE column, which is then incorporated in a single-line flow system so that reagent dissolution is effected as the sample passes through the column. This procedure reduces the chemical contribution to the dispersion value to a minimum and gives a low detection limit owing to the absence of refractive index peaks. An improvement of the figures of merit compared with those reported previously is shown. The calibration graph is linear up to 0.800 mg l–1 CrVI, with a slope of 0.49 l mg–1; the detection limit is 0.005 mg l–1. The relative standard deviation is better than 1%.