Determination of sub-picomolar levels of platinum in the pristine Krka River estuary (Croatia) using improved voltammetric methodology

2020 ◽  
Vol 17 (2) ◽  
pp. 77 ◽  
Author(s):  
Jasmin Pađan ◽  
Saša Marcinek ◽  
Ana-Marija Cindrić ◽  
Nicolas Layglon ◽  
Cedric Garnier ◽  
...  
Keyword(s):  
Natural Waters ◽  
Limit Of Detection ◽  
Small Deviation ◽  
Salinity Gradient ◽  
River Estuary ◽  
Stripping Voltammetry ◽  
Fine Tuning ◽  
Surface Active ◽  
Dissolved Form ◽  
Active Substances

Environmental contextPlatinum concentrations in natural waters such as oceans, rivers and lakes are extremely low, hindering studies of Pt distributions and biogeochemical cycles. An improved electrochemical method was used to reliably determine Pt in estuarine conditions at trace concentrations. Platinum displayed a near-conservative behaviour along the salinity gradient of the estuary, with about 90% remaining in the dissolved form. AbstractExtremely low concentrations of platinum in natural waters require very sensitive analytical techniques, with adsorptive cathodic stripping voltammetry (AdCSV) being one of the most frequently used techniques. A ‘fine tuning’ of the voltammetric parameters, along with advanced data treatment based on derivative transformations, allowed us to determine reliably Pt levels down to 50 fM (0.05 pM). By using short modulation and interval times of the differential pulse stripping waveform, and applying a 4th derivative transformation to the voltammograms, the limit of detection (LOD) was lowered down to 10 fM. Although very small concentrations of surface-active substances (e.g. 0.025mgL−1 fulvic acid) strongly influenced the method sensitivity, recoveries of spiked samples were not impacted (~100%). The application of a desorption step (Eds=−1.35V; tds=2s) at the end of the accumulation significantly improved the sensitivity, presumably through the removal of adsorbed surface-active substances. Using this optimised methodology, we determined the Pt distribution in the pristine Krka River estuary in the winter and summer periods by performing both horizontal transects and vertical profiles (salinity ~1 to 39). In surface waters, dissolved Pt concentrations gradually increased towards the seawater end-member (from ~0.15 to ~0.3 pM). A small deviation from the conservative mixing line was observed at salinities below 10, which may reflect changes in Pt redox speciation. In bottom waters, the trend was opposite with dissolved Pt concentrations increasing towards the freshwater end-member, probably owing to progressive accumulation related to seawater residence time. On average, 90% of Pt was present in the dissolved form.

scholarly journals Redox Speciation of Vanadium in Estuarine Waters Using Improved Methodology Based on Anion Exchange Chromatography Coupled to HR ICP-MS System

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2436
Author(s):  
Lucija Knežević ◽  
Dario Omanović ◽  
Niko Bačić ◽  
Jelena Mandić ◽  
Elvira Bura-Nakić
Keyword(s):  
Anion Exchange ◽  
Ethylenediaminetetraacetic Acid ◽  
Matrix Effects ◽  
Limit Of Detection ◽  
Salinity Gradient ◽  
River Estuary ◽  
Direct Determination ◽  
Estuarine Waters ◽  
Icp Ms ◽  
Redox Speciation

An improved methodology was developed for V redox speciation in estuarine waters using a hyphenated technique consisting of ion chromatograph (IC) with an anion exchange column and a high-resolution inductively coupled plasma mass spectrometer (HR ICP-MS). This approach enables the direct determination of V(V), whereas reduced species (mainly V(IV)) are calculated by subtracting V(V) concentrations from the measured total V concentration. Based on the “on-column” V(V) chelation mechanism by EDTA, with the eluent composed of 40 mmol L−1 ammonium bicarbonate, 40 mmol L−1 ammonium sulphate, 8 mmol L−1 ethylenediaminetetraacetic acid and 3% acetonitrile, the method was successfully used for analyses of V redox speciation in samples taken in the vertical salinity gradient of the highly stratified Krka River estuary. Due to the matrix effects causing different sensitivities, a standard addition method was used for V(V) quantification purposes. The limit of detection (LOD) was also found to be matrix related: 101.68 ng L−1 in the seawater and 30.56 µg L−1 in the freshwater. Performed stability tests showed that V redox speciation is preserved at least 7 days in un-treated samples, possibly due to the stabilization of V-reduced species with natural organic matter (NOM). The dominant V form in the analysed samples was V(V) with the reduced V(IV) accounting for up to 26% of the total dissolved pool. The concentration of V(IV) was found to correlate negatively with the oxygen concentration. Significant removal of dissolved V was detected in oxygen depleted zones possibly related to the particle scavenging.

Direct determination of surface active substances in natural waters

1987 ◽  
Vol 22 (2-4) ◽  
pp. 363-373 ◽  
Author(s):  
Bo<zena Ćosović ◽  
Vjero<cka Vojvodic
Keyword(s):  
Natural Waters ◽  
Direct Determination ◽  
Surface Active ◽  
Active Substances

scholarly journals Organic Copper Speciation by Anodic Stripping Voltammetry in Estuarine Waters With High Dissolved Organic Matter

2021 ◽  
Vol 8 ◽  
Author(s):  
Jasmin Pađan ◽  
Saša Marcinek ◽  
Ana-Marija Cindrić ◽  
Chiara Santinelli ◽  
Simona Retelletti Brogi ◽  
...  
Keyword(s):  
Organic Matter ◽  
Humic Substances ◽  
Natural Waters ◽  
Anodic Stripping Voltammetry ◽  
River Estuary ◽  
Stripping Voltammetry ◽  
High Background ◽  
Organic Matter Concentration ◽  
Anodic Stripping

The determination of copper (Cu) speciation and its bioavailability in natural waters is an important issue due to its specific role as an essential micronutrient but also a toxic element at elevated concentrations. Here, we report an improved anodic stripping voltammetry (ASV) method for organic Cu speciation, intended to eliminate the important problem of surface-active substances (SAS) interference on the voltammetric signal, hindering measurements in samples with high organic matter concentration. The method relies on the addition of nonionic surfactant Triton-X-100 (T-X-100) at a concentration of 1 mg L−1. T-X-100 competitively inhibits the adsorption of SAS on the Hg electrode, consequently 1) diminishing SAS influence during the deposition step and 2) strongly improving the shape of the stripping Cu peak by eliminating the high background current due to the adsorbed SAS, making the extraction of Cu peak intensities much more convenient. Performed tests revealed that the addition of T-X-100, in the concentration used here, does not have any influence on the determination of Cu complexation parameters and thus is considered "interference-free." The method was tested using fulvic acid as a model of natural organic matter and applied for the determination of Cu speciation in samples collected in the Arno River estuary (Italy) (in spring and summer), characterized by a high dissolved organic carbon (DOC) concentration (up to 5.2 mgC L−1) and anthropogenic Cu input during the tourist season (up to 48 nM of total dissolved Cu). In all the samples, two classes of ligands (denoted as L1 and L2) were determined in concentrations ranging from 3.5 ± 2.9 to 63 ± 4 nM eq Cu for L1 and 17 ± 4 to 104 ± 7 nM eq Cu for L2, with stability constants logKCu,1 = 9.6 ± 0.2–10.8 ± 0.6 and logKCu,2 = 8.2 ± 0.3–9.0 ± 0.3. Different linear relationships between DOC and total ligand concentrations between the two seasons suggest a higher abundance of organic ligands in the DOM pool in spring, which is linked to a higher input of terrestrial humic substances into the estuary. This implies that terrestrial humic substances represent a significant pool of Cu-binding ligands in the Arno River estuary.

scholarly journals Simple Electrochemical Determination of Surface-Active Substances in Natural Waters

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Željka Cvrković-Karloci ◽  
Damir Krznarić ◽  
Marijan Šeruga ◽  
Božena Ćosović
Keyword(s):  
Humic Acid ◽  
Natural Waters ◽  
Electrochemical Determination ◽  
Danube River ◽  
Calibration Plot ◽  
Linear Calibration ◽  
Capacitive Current ◽  
Surface Active ◽  
Active Substances

A simple electrochemical determination of surface-active substances by using time-dependent variation of the capacitive current in a.c. voltammetry at the HMDE is described. Surface-active substances were accumulated by stirring solution at the deposition potential of −0.6 V versus Ag/AgCl (sat. NaCl). The capacitive current was recorded for different deposition times in the range 0–120 s, wherefrom the linear calibration plot is constructed. The proposed method was verified for model surfactant TritonX-100 in the concentration range 0.02–0.25 mg/L and for humic acid in the concentration range 1.65–20 mg/L. The application of the method was demonstrated for freshwater samples of the Drava river, Danube river, and the wetland Kopački Rit, Croatia. The shape of theiac-Ecurves as well as the obtained concentrations of surface-active substances by using humic acid as the calibration substance are quite well describing the type and the nature of organic matter in the freshwater samples.

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