Complex formation is among the mechanisms affecting metal bioaccessibility. Hence, the quantification of organic metal complexation in food items is of interest. Organic ligands in solutions of ...environmental and/or food origin function as buffering agents against small changes in dissolved metal concentrations, being able to maintain free metal ion concentrations below the toxicity threshold. Organic matter in vinegars consists of bioactive compounds, such as polyphenols, Maillard reaction endproducts, etc., capable of complexing metal ions. Furthermore, transition metal ions are considered as micronutrients essential for living organisms exerting a crucial role in metabolic processes. In this study, differential pulse anodic stripping voltammetry (DPASV), a sensitive electrochemical technique considered to be a powerful tool for the study of metal speciation, was applied for the first time in vinegar samples. The concentrations of Cu complexing ligands (
) in 43 vinegars retailed in Greece varied between 0.05 and 52 μM, with the highest median concentration determined in balsamic vinegars (14 μM), compared to that of common vinegars (0.86 μM). In 21% of the vinegar samples examined,
values were exceeded by the corresponding total Cu concentrations, indicating the presence of free Cu ion and/or bound within labile inorganic/organic complexes. Red grape balsamic vinegars exhibited the highest density of Cu ligands per mass unit of organic matter compared to other foodstuffs such as herbal infusions, coffee brews, and beers. Among the 16 metals determined in vinegars, Pb is of particular importance from a toxicological point of view, whereas further investigation is required regarding potential Rb biomagnification.
In a time-series study, surface microlayer (SML) and underlying (ULW) water samples were collected in 3 sampling seasons from 5 coastal microenvironments of the Eastern Mediterranean. Examination of ...the isotopic composition (δ18O, δ2H and δ13C) of the water samples demonstrated that most of them lie around the mixing zone between the Greek/local precipitation water line (PWL) and seawater. Samples from the areas of Loutropyrgos, Pahi and Vourkari, within the Saronikos Gulf, correspond mainly to seawater, the Asopos samples are influenced by the local meteoric waters, whereas Chalkida samples seem to be affected by local fresh water inputs attributed to the discharge site of a sewage treatment plant.
In almost half of the samples examined no enrichment of the SML in Cu complexing capacity (LT) was recorded. A wider range of LT was determined at SML (51.5 to 679.6nM with an average value of 229.6nM) than in the ULW (55.2 to 346.4nM with an average value of 208.5nM).
While the enrichment factor (EF) of a compound is defined as the ratio of the concentration in the SML to that in the corresponding underlying water, the mean EF values of dissolved surface active substances (SASd: 5.8±5.8) and transparent exopolymer particles (TEPcolor: 2.2±1.8, TEPmicro: 3.8±5.6) were significantly greater than unity (p=0.0121, 0.0220 and 0.0404 respectively) indicating a general enrichment of these organic materials in SML. SASs, normalized to DOC concentrations, have shown that the organic matter pool studied was mostly hydrophilic. During winter (February 2013) an enrichment of LT in SML was detected at all of the sampling sites examined, paralleled by TEP aggregation suggesting a role for TEP in copper complexation.
•A multiparameter approach was used for organics characterization in the sea surface.•Surface active substances (SASs) were particularly enriched in the surface microlayer.•The predominance of hydrophilic SAS in surface microlayer was demonstrated.•No enrichment of surface microlayer in Cu complexing ligands was found.•Isotopic composition analysis (δ18O, δ2H and δ13C) of water samples was carried out.
Barely any data exist on metal speciation in the marine surface microlayer (SML), a rather complex environment, the study of which contributes to enhancement of knowledge on metal speciation and its ...effect to the ocean. Metal speciation is significant since life requires a wide variety of trace metals that are essential for the growth of the organisms. Ligand concentrations (
L
) of copper (Cu), zinc (Zn), and cadmium (Cd) were studied by anodic stripping voltammetry (ASV) in the SML of coastal areas within the Aegean Sea in the Eastern Mediterranean. Complexing capacities in the SML in decreasing order ranged for Cu from 29 to 201 nM (median 101 nM), for Zn 24–149 nM (45 nM), and for Cd 1.0–1.5 nM (1.4 nM). Average enrichment factors (EFs) of SML samples compared to subsurface ones (SSW) were calculated equal to 0.9 ± 0.8, 1.2 ± 0.5, and 1.7 ± 1.6 for
L
Zn
,
L
Cu
, and
L
Cd
, respectively. In five out of the six total paired samples of SML and SSW, lower concentrations of
L
Zn
were measured in the SML, which is not the case for
L
Cu
and
L
Cd
. Due to elevated dissolved Zn concentrations in the SML, its complexation is incomplete, contrary to those of Cu and Cd, which are fully complexed. These trace metals are essential nutrients for biological functions, hence any differences on their concentration and chemical speciation may directly influence the distribution of phytoplankton species in the upper water column and neuston. EFs of SML relatively to subsurface water ranged in average between 1.2 and 2.4 for total organic carbon (TOC), chlorophyll
a
(Chl
a
), and plankton, being generally >2 for most of the amino acids detected, demonstrating a relative enrichment of the SML in organic matter. A significant correlation was found between Cu ligands and dinoflagellates <20 μm, confirming older findings supporting that marine dinoflagellates of
Gymnodinium
genera produce Cu ligands. New insights are provided in the study and the importance of investigating bio-essential metal ions (Cu, Zn, Cd) and their organic complexes in the SML is pointed. Data on Zn and Cd complexing capacities in the SML are the first published so far.
The top of the ocean, sea surface microlayer (ML), covers more than 70% of the world's surface. It is a sink for natural and anthropogenic material that depends on its chemical composition. This ...article is aimed at providing novel data on the characterization of organic matter in ML and underlying waters (ULW) in the rarely investigated subarctic, north Norwegian fjords region, in July 2001, August 2002 and June 2003. A multiparameter approach was used, including DOC measurements, characterization of surface active organic substances (SAS), determination of Cu complexing capacity (
L
T) and specific analysis of fatty acids (FA). The characteristics of organic matter in fjords' sea surface microlayers showed that organic substances in the films were mainly produced in the subsurface water. There was negligible fractionation of hydrophobic substances to the microlayer and even depletion of fatty acids was found in some ML samples. Fjords' surface waters were found to be very rich in fatty acids in July, up to 201 μg/l, with high contributions of polyunsaturated compounds. The enrichment of DOC and SAS concentrations in ML as compared to the ULW was in the range of 1.2–2.8, while higher enrichment factors (1.3–5.1) were determined for copper complexing ligands, indicating increased contribution of hydrophilic, lower molecular weight molecules. The detected characteristics and concentrations of organic substances in the surface microlayer and adjacent subsurface water were dependent on the month of sampling.
The study on dissolved organic ligands capable to complex copper ions (L
T), surface-active substances (SAS) and dissolved organic carbon (DOC) in the Northern Adriatic Sea station (ST 101) under the ...influence of Po River was conducted in period from 2006–2008. The acidity of surface-active organic material (Ac
r) was followed as well. The results are compared to temperature and salinity distributions. On that way, the contribution of the different pools of ligands capable to complex Cu ions could be determined as well as the influence of aging and transformation of the organic matter. The L
T values in the investigated period were in the range of 40–300
nmol
l
−1. The range of DOC values for surface and bottom samples were 0.84–1.87
mg
l
−1 and 0.80–1.30
mg
l
−1, respectively. Total SAS concentrations in the bottom layer were 0.045–0.098
mg
l
−1 in equiv. of Triton-X-100 while those in the surface layer were 0.050–0.143
mg
l
−1 in equiv. of Triton-X-100. The majority of organic ligands responsible for Cu binding in surface water originate from new phytoplankton production promoted by river borne nutrients. Older, transformed organic matter, possessing higher relative acidity, is the main contributor to the pool of organic ligands that bind copper in the bottom samples. It was estimated that ∼9% of DOC in surface samples and ∼12% of DOC in the bottom samples are present as ligands capable to complex copper ions.
•Chondroitin sulfate and Na–alginate form inert complexes with copper ions.•Carrageenans, dextran and dextran sulfate do not form complexes with copper ions.•All investigated PS exhibit the ...properties of surface activity (SAS). The highest SAS value was obtained for dextran.•Catalytic hydrogen evolution wave is characteristic for the PS with sulfate and/or carboxylic groups.•PS are the main component of the exopolymer substances in seawater which due to their physico-chemical properties retain different nutrients important for biological activity.
The goal of this study was to investigate to which extent polysaccharides (PS) contribute to the complexing capacity for copper ion (LT), to determine their property of surface activity and evaluate their capability to cause the catalytic hydrogen evolution wave (peak “H”) due to their adsorption and the catalytic groups in their structure. Complexing capacities and apparent stability constants (Kapp) were measured electrochemically for model polysaccharides (PS): carrageenans (κ-, ι- and λ-), chondroitin sulfate, dextran, dextran sulfate, Na-alginate and humic material. Cu-complexing capacities were determined for Na-alginate (logKapp=8.32) and chondroitin sulphate (logKapp=8.14). PS adsorb on different surfaces due to their amphyphylic properties and on that way they could increase the interaction of copper ions with these surfaces by forming the surface complexes with Cu ions.
Unrefined sea salt originates from seawater, typically by natural evaporation. Being minimally processed, it contains the natural minerals and impurities of seawater. Despite the wide applications of ...salt for culinary and food preservation purposes, the available composition data is particularly limited. Since seawater often contains various harmful substances at a trace or ultra-trace level, their determination in unrefined salt is significant in terms of quality control and food safety. Twenty-four (24) samples of unrefined sea and rock salts retailed in Greece were studied in terms of their trace metals and polycyclic aromatic hydrocarbon (PAH) content, which constitute the usual pollutants examined in seawater. In addition, samples’ color and mineralogy were recorded and their attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectra were obtained. No statistically significant differences were found between sea and rock salts regarding their trace metal (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) content (excluding V) and the 15 PAHs examined. ATR FT-IR succeeded to discriminate among sea, rock, flower, and underground salty water salts. Compared with the typical trace metal concentrations in seawater, quite high Pb values were determined in both sea and rock salts, whereas outliers in the rest of the trace elements examined were scarce. Median values of the sum of PAH (ΣPAHs) concentrations were calculated equal to 2.1 and 2.6 ng g
−1
for sea and rock salts, respectively. Environmental interactions of salt production with trace elements and PAHs are also discussed.
Complex formation is among the mechanisms affecting metal bioaccessibility, hence the evaluation of the extent of interactions between trace elements and organic matter in food items is of great ...interest. Sensitive electrochemical techniques, considered powerful tools for the study of such interactions, were applied for the first time in beer samples. The concentration of Cu complexing ligands (LT) determined in 30 Greek beers by Differential Pulse Anodic Stripping Voltammetry (DPASV) varied between 37.1 and 348μM. In all beer samples examined total Cu concentrations were lower than the corresponding LT values, evidence that Cu is fully complexed. The concentrations of organic matter measured as total organic carbon (OC; 30–56gL−1) and total carbohydrates (CHOs; 0.82–9.2gL−1) were relatively high, their presence influencing metals speciation in beers. In an attempt to partially characterize the physico-chemical properties of organic material the surface active substances (SAS) and catalytically active compounds (CAC) were measured for the first time in beers by electrochemical techniques. A characterization of the beer samples examined, according to their elemental content was also carried out by determining 15 minor and trace elements with inductively coupled plasma mass spectrometry (ICP-MS). The median values of As, Cd, Co, Cs and Pb concentrations were determined at 0.04–3.4μgL−1, of Ba, Cr, Cu, Ni, V and Zn at 12–35μgL−1 and those of Fe, Mn, Rb and Sr at 122–225μgL−1.
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•Polysaccharides are one of the main organics in beers.•Organics “buffer” the concentrations of free metal ion species.•Cu ligands ranged between 37.1 and 348μΜ and logKapp ranged from 7.0 to 9.0.•Cu contained in beers was fully complexed.•Pb and Cd in beers range from 0.39 to 11 and <0.01 to 1.0μgL−1, respectively.
On small and medium karstic coastal islands in the Adriatic Sea, brackish lakes are often the only source of freshwater. Therefore, it is important to adequately evaluate the biogeochemical processes ...occurring in these complex water systems, as well as to determine the origin of contaminants present. In this study, the distribution and origin of trace metals (Tl, Hg, Cd, Pb, Cu, Zn, Ni, Co) and organic matter in the water column, sediment, and surrounding soil of the brackish lakes on Mljet Island, South Adriatic Sea, Croatia, were evaluated. Thallium and mercury concentrations in the lake water were up to two orders of magnitude higher compared to ranges found in the adjacent coastal sea water. Elevated thallium concentrations were of anthropogenic origin resulting from previous use of rodenticide, while elevated mercury content was naturally enhanced. Levels for the other metals were characteristic of uncontaminated water systems. Speciation modelling showed that dissolved trace metals such as Cu, Pb, and Zn were mostly associated with organic matter, while Tl, Co, and Ni were present predominantly as free ions and inorganic complexes. The presence of organic matter (OM) clearly influenced the speciation and distribution of some trace metals. OM was characterised by the determination of the complexing capacity for Cu ions (CuCC), surface active substances, and catalytically active compounds. Reduced sulphur species (glutathione and other thiols) representing significant Cu-binding ligands were determined and discussed as well.
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