Simultaneous quantification of tin and lead species in Antarctic krill and fish by interfacing high-performance liquid chromatography with inductively coupled plasma mass spectrometry based on strong cation-exchange and Amphion columns

Tin and lead are a global concern considering their species-dependent toxicity, bioavailability and transformation. Simultaneous speciation analysis of tin and lead is challenging for a large food capacity containing unstable species. Herein, we developed two sensitive methods for rapid quantification of tin and lead species in Antarctic seafood by high-performance liquid chromatography and inductively coupled plasma mass spectrometry based on strong cation-exchange and Amphion columns. Inorganic tin and lead, four organotin and two organolead compounds can be analysed in 16 min on a 10-cm Amphion II column (mobile phase: 4 mM sodium dodecyl benzene sulfonate at pH 2.0) with 0.02-0.24 μg L-1 detection limits. The method was applied to Antarctic krill and fish, demonstrating the presence of any tin and lead species down to μg kg-1 level. Overall, the proposed methods are sensitive, efficient and environment-friendly for routine speciation analysis of tin and lead in food samples.

Simultaneous preconcentration and quantification of ultra-trace tin and lead species in seawater by online SPE coupled with HPLC-ICP-MS

BACKGROUND

Tin and lead contamination is a global threat to marine ecosystems considering their species-specific toxicity, bioavailability and mobility. Hence simultaneous measurement of multiple tin and lead compounds at μg L-1 to pg L-1 levels in environmental water is always an indispensable but challengeable task. High performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) is one of the most widely used choices for this purpose because of good sensitivity, strong separation power and good compatibility. Previous HPLC-ICP-MS methods based on a single elemental speciation strategy are low-efficiency and sensitivity-insufficient for a large set of unstable samples and interaction of multiple metal(loid)s down to ng L-1 levels.

RESULTS

In this study, we developed a sensitive, efficient and environment-friendly analytical method for accurate quantification of inorganic and organic species of tin and lead simultaneously based on HPLC-ICP-MS with online integration of solid phase extraction (SPE). By using graphene oxide modified silica conditioned with 1 mM benzoic acid to enrich tin and lead species from 10 mL sample, detection limits were improved to 2-8 pg per liter due to satisfactory enrichment factors (522-2848 folds). The SPE-HPLC-ICP-MS method was applicable to quantification of ultra-trace tin and lead species at pg L-1 levels in uncontaminated seawater. Tributyltin was the only tin species detected at subnanograms per liter levels while Pb(II) was the only lead species detected at several nanograms per liter in thirteen coastal seawater samples collected in Hangzhou Bay, indicating light contamination of tin and lead.

SIGNIFICANCE

Overall, the proposed SPE-HPLC-ICP-MS method is highly sensitive, efficient and environment-friendly that are fairly suitable to routine speciation analysis of tin and lead in environmental, food, and biological samples.

Lead speciation in body tissues, gastrointestinal contents, and feces of lead-exposed wild rats (Rattus rattus)

The toxic effects of lead (Pb) are an ongoing concern for which research continues to seek a solution. In Pb-contaminated areas, Pb concentrations in the environment and organisms are quantified to assess the degree of contamination. Understanding organismal uptake of Pb and its behavior in the body requires distinguishing Pb chemical species. We used Pb L3-edge X-ray absorption near-edge structure (XANES) to study the distribution of Pb species in body tissues, digestive tract contents, and feces of wild rats (Rattus rattus) collected from a heavily Pb-contaminated mining area in Zambia. Freeze-drying improved the XANES spectrum quality by approximately 10 μg-Pb/g-dry through concentrating the Pb without changing its chemical state from its wet state. We successfully identified and analyzed the Pb species in seven different tissues (bone, muscle, liver, kidney, spleen, lung, and brain), three different digestive-tract contents (stomach, small intestine, and colon), and feces from three wild rats. We described chemical-form-based details of Pb uptake and distribution that are common among rats, such as the increased Pb binding with thiol groups through the digestive system, distribution of mobile Pb to hematopoietic organs and vascular-related tissues, and Pb binding to thiol groups, especially in the liver and brain.

Interactive effects of biochar amendment and lead toxicity on soil microbial community

This study determined the interactive effects of biochar and lead toxicity on the soil microbial community in a phytoextraction experiment. Arranged with a completely randomized design in a greenhouse, banana liners were planted singly in a sandy soil spiked with Pb(NO3)2 at 0, 400 and 1200 mg kg-1 and amended with bamboo biochar (pyrolyzing at 600 °C) at 0, 1, 3%. Soil samples were taken from triplicated pots five months after planting and measured for (i) content of lead and organic carbon; (ii) lead speciation; and (iii) microbial community composition through 16S rRNA gene sequencing. DNA sequencing results showed that lead and biochar treatments had significant individual and interactive effects on soil microbial dissimilarities from taxonomic levels of phyla to genera. While some specific taxa were lead resistant, biochar addition apparently alleviated lead toxicity and increased their richness (e.g., Alkanibacter, Muciaginibacter, Burkholderiaceae, and Beggiatoaceae). Soil analysis data indicated that biochar not only helped retain more lead in the soil matrix but created a soil environment inducive for transformation of lead into highly insoluble pyromorphite. This study highlights the effectiveness of biochar for lead remediation and the sensitivity of soil microorganisms in sensing changes in soil environment and lead bioavailability.

Simultaneous enrichment of inorganic and organic species of lead and mercury in pg L-1 levels by solid phase extraction online combined with high performance liquid chromatography and inductively coupled plasma mass spectrometry

Quantification of ultra-trace inorganic and organic species of lead and mercury in unpolluted environmental water is crucial to estimate the mobility, toxicity and bioavailability and interactions. Simultaneous pre-concentration of Pb and Hg species in pg L^-1 levels followed by multi-elemental speciation analysis makes great sense to a large set of unstable samples because of time advantages. Herein simultaneous enrichment and speciation analysis of ultra-trace lead and mercury in water was developed by online solid-phase extraction coupled with high performance liquid chromatography and inductively coupled plasma mass spectrometry (SPE-HPLC-ICP-MS) for this aim. Pb(II), trimethyl lead (TML), triethyl lead (TEL), Hg(II), methylmercury (MeHg) and ethylmercury (EtHg) were baseline separated in 11 min under gradient elution using 5 mM l-cysteine (Cys) at pH 2.5 in the 0-1 and 4-15 min and 5 mM Cys + 0.5 mM tetrabutyl ammonium hydroxide solution at pH 2.5 in the 1-4 min. Lead and mercury species in 10 mL intact water samples were adsorbed on a 1 cm C₁₈ enrichment column pre-conditioned with 10 mL of 1 mM 2-mercaptoethanol at 10 mL min^-1, and then directly desorbed by the mobile phases. High enrichment factors (459 for Pb(II), 1248 for TML, 1627 for TEL, 2485 for Hg(II), 1984 for MeHg and 1866 for EtHg) were obtained with good relative standard deviations (<5%), leading to low LODs (0.001-0.011 ng L^-1) and LOQs (0.004-0.036 ng L^-1). Good accuracy of this method was validated by two certified reference materials of total lead in water (GBW08601) and total mercury in water (GBW08603) along with spiked recoveries (89-93%). The method was applied to analyze trace lead and mercury species in river, lake, tap and rain water, and purified and mineral water. Inorganic lead of 13-68 ng L^-1 and inorganic mercury of 21-49 ng L^-1 were measured in the nine water samples whereas TML, TEL and MeHg were not detected with 2-5 ng L^-1 EtHg presented only in one river water and tap water.

Chronic effects of lead exposure on topsmelt fish (Atherinops affinis): Influence of salinity, organism age, and relative sensitivity to other marine species

The aim of the present study was to determine the influence of salinity and organism age on the chronic toxicity of waterborne lead (Pb) to Atherinops affinis and to compare the relative Pb sensitivity of A. affinis with other marine species. Chronic Pb exposure experiments were conducted in a water flow-through testing system. Survival, standard length, dry weight, and tissue Pb concentration were measured and lethal concentrations (LCs), effect concentrations (ECs), and bioconcentration factors (BCFs) were calculated. In general, increasing salinity and organism age decreased Pb toxicity. The LC50s for larval fish at 14 and 28 ppt salinity were 15.1 and 79.8 μg/L dissolved Pb, respectively; whereas, the LC50 for juvenile fish was 167.6 μg/L dissolved Pb at 28 ppt salinity. Using standard length data, the EC10 values for larval fish were 16.4 and 82.4 μg/L dissolved Pb at 14 and 28 ppt salinity, respectively. The dry weight EC25s for low and high salinity were 15.6 and 61.84 μg/L dissolved Pb, respectively. The BCFs were higher with the lower salinity study (1703) in comparison to the higher salinity study (654). Results of Pb speciation calculation showed higher fraction of Pb²⁺ in water with lower salinity, explaining the higher observed toxicity of Pb in lower salinity water than higher salinity water. Atherinops affinis is more sensitive to Pb than several other marine species. Evidence of abnormal swimming and skeletal deformities were observed in Pb exposure treatments. Results of the present study are useful for marine biotic ligand modeling and support ecological risk assessment and deriving Pb environmental quality criteria for marine environments. Environ Toxicol Chem 2018;37:2705-2713. © 2018 SETAC.

Investigating the relationship between lead speciation and bioaccessibility of mining impacted soils and dusts

Lead (Pb) bioaccessibility measurements have been the subject of much research in recent years, given the desire to develop a cost-effective and reliable alternative method to estimate its bioavailability from soils and dusts. This study investigates the relationship between Pb bioaccessibility estimated using the Relative Bioavailability Leaching Procedure (RBALP) and solid phase speciation of Pb using mining impacted soils and associated dusts. Solid phase speciation was conducted prior to and after RBALP extractions. The average Pb concentrations were 59, 67, and 385 mg/kg for top soil, sub-soil, and house dust samples, respectively. Lead bioaccessibility in selected top soils and dusts ranged from 16.7 to 57.3% and 8.9 to 98.1%, respectively. Solid phase speciation of Pb in <250 μm residues prior to and after RBALP extraction revealed 83% decrease in Pb bound to carbonate fraction after RBALP extraction. This accounts for 69% of RBALP-extractable Pb. Besides contribution from carbonate bound Pb, 76.6 and 53.2% of Pb bound to Mn oxyhydroxides and amorphous Fe and Al oxyhydroxides contributed to bioaccessible Pb, respectively. However, Pb bound to Mn oxyhydroxides and amorphous Fe and Al oxyhydroxides account for only 13.8 and 20.0% of total RBALP-extractable Pb, respectively. Both non-specifically bound and easily exchangeable fractions and strongly bound inner-sphere complexes were also part of bioaccessible Pb. The present study demonstrates that bioaccessible Pb is released from both soil solution phase Pb as well as that from all soil solid phase with the most contribution being from Pb bound to carbonate mineral phase.

Influence of UV-B radiation on lead speciation in the presence of natural particles of estuarine waters

The influence of UV-B irradiation on filtered and non-filtered water samples collected in a non-polluted area of Tagus estuary was evaluated in this study. In the laboratory, both samples were titrated with lead (Pb(+2)) followed by differential pulse anodic stripping voltammetry (DPASV), before and after 1 and 10 days under UV-B irradiation. Metal-ligand complexing parameters were obtained based on a macromolecular heterogeneous ligand described by two distinct sites with a labile behavior, and a third small homogeneous weaker group, which concentration was determined from a potentiometric titration. Under UV-B radiation, the complexing strength decreased with time in both (filtered and non-filtered) irradiated samples, but this effect was more pronounced in the non-filtered water, which might be due to some adsorption of dissolved macromolecular ligands on the particles and/or to further degradation of dissolved organic matter (DOM). Furthermore, the presence of particles favored the break-down of the macromolecular ligand under long UV-B exposure time. These results present ecological implications for the estuarine ecosystems such as bioavailability and toxicity.

Complexation of lead by organic matter in Luanda Bay, Angola

Speciation is defined as the distribution of an element among different chemical species. Although the relation between speciation and bioavailability is complex, the metal present as free hydrated ion, or as weak complexes able to dissociate, is usually more bioavailable than the metal incorporated in strong complexes or adsorbed on colloidal or particulate matter. Among the analytical techniques currently available, anodic stripping voltammetry (ASV) has been one of the most used in the identification and quantification of several heavy metal species in aquatic systems. This work concerns the speciation study of lead, in original (natural, non-filtered) and filtered water samples and in suspensions of particulate matter and sediments from Luanda Bay (Angola). Complexes of lead with organics were identified and quantified by differential pulse anodic stripping voltammetry technique. Each sample was progressively titrated with a Pb(II) standard solution until complete saturation of the organic ligands. After each addition of Pb(II), the intensity, potential and peak width of the voltammetric signal were measured. The results obtained in this work show that more than 95 % of the lead in the aquatic environment is bound in inert organic complexes, considering all samples from different sampling sites. In sediment samples, the lead is totally (100 %) complexed with ligands adsorbed on the particles surface. Two kinds of dominant lead complexes, very strong (logK >11) and strong to moderately strong (8< logK <11), were found, revealing the lead affinity for the stronger ligands.