Osvaldo E. Troccoli

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.

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.

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%.

Automatic on-line ultratrace determination of Cd species of environmental significance in natural waters by FI-ETAAS

The ultratrace determination of Cd species in natural waters by using an automatic on-line extraction preconcentration system coupled to a graphite furnace atomic absorption spectrometer is presented. Two operational fractions with environmental meaning (able and not able to be accumulated by aquatic organisms) were determined through kinetic discrimination; a Chelex-100 labile fraction consisting of Cd ions and weak Cd complexes and a silica C18 hydrophobic inert fraction consisting of stable cadmium–organic complexes. The figures of merit for the determination of both fractions are given and the obtained values are fully discussed. The aptitude of different resins for the extraction of each fraction is evaluated taking into account retention capacity, pre-concentration efficiency, ease of elution, type of eluant (i.e., compatible with the graphite furnace operation) and the sample–resin time of contact. Special attention is given to the characterization of humic acids and their Cd complexes and to their sorption and elution capabilities from different extracting materials.

Integrated conductimetric detection: mass distribution in a dynamic sample zone inside a flow injection manifold

The insights provided by integrated detection (conductimetric) as a novel approach to follow physical dispersion in continuous-flow manifolds are presented. This approach replaces the conventional instantaneous detection and permits to follow the dispersion phenomena, including details of the radial component as the sample plug travels the manifold. Integrated detection permits to look at the radial dispersion in a detailed manner inaccessible to instantaneous detection. The effect of different experimental parameters affecting mass distribution was studied (e.g., flow rate, tube length and diameter, injected sample volume, and reactor type) and their effects on integrated response curves are discussed. A single channel manifold employing aqueous nitric acid as the conducting carrier, and water injected as sample plug, and playing the role of an insulator, provided the physicochemical model for the reported studies.

Atomic absorption spectrometric determination of inorganic and organic arsenic in some marine benthic algae of the southern atlantic coasts

Arsenic in the inorganic and organic forms was analyzed in species of marine macro-algae growing in the South Atlantic Ocean. Species of the genera Lessonia, Gigartina, Adenocystis, Leathesia and Colpomenia were investigated. Arsenic accumulation was found in all species studied. Total As content ranged from 5.3 to 56.9 microg As g(-1) and the levels of the inorganic forms ranged from 0.2 to 2.0 microg As g(-1). The complete analytical procedure was validated against a standard reference material (NBS, SRM 1572, citrus leaves) and the value obtained was in good agreement with the certified value. Some commercial seaweed products were also analyzed.