Speciation of inorganic and organic species of mercury and arsenic in lotus root using high performance liquid chromatography with inductively coupled plasma mass spectrometric detection in one run

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.

Toxicity, arsenic speciation and characteristics of hyphenated techniques used for arsenic determination in vegetables. A review

Arsenic (As) speciation is an interesting topic because it is well recognized that the toxicity of this metalloid ultimately depends on its chemical form. More than 300 arsenicals exist naturally. However, As can be present in four oxidation states: As-III, As0, AsIII and AsV. Long-term exposure to As from different sources, such as anthropogenic processes, or water, fauna and flora contaminated with As, has put human health at risk for decades. There are many side-effects correlated with exposure to InAs species, such as skin problems, respiratory diseases, kidney problems, cardiovascular diseases and even cancer. There are different levels and types of As in foods, particularly in vegetables. Furthermore, different chemical methods and techniques have been developed. Therefore, this review focuses on the general properties of various approaches used to identify As species in vegetation samples published worldwide. This includes various approaches (different solvents and techniques) used to extract As species from the matrix. Then, versatile chromatographic and non-chromatographic systems to separate different forms of As are reviewed. Finally, the general properties of the most common instruments used to detect As species from samples of interest are listed.

Determination of xanthates as Cu(II) complexes by high-performance liquid chromatography - Inductively coupled plasma tandem mass spectrometry

The present study provides a novel, selective analysis method for the determination of low xanthate concentrations. The rising concern over the environmental effects of xanthates demands the development of analysis methods which this study answers. Complex formation in aqueous solution between xanthates and an excess of Co(II), Ni(II), Pb(II), Cd(II), Cu(II), and Zn(II) ions was utilized to selectively determine xanthates by high-performance liquid chromatography-inductively coupled plasma tandem mass spectrometry for the first time. The complexes that were formed were extracted to ethyl acetate using liquid-liquid extraction and separated by high-performance liquid chromatography technique before the quantitative determination of metal ions and sulfur in the xanthate complexes. Good separation and high measurement sensitivity were achieved using Cu(II) as the complex metal ion. The analysis method was optimized for the determination of sodium isopropyl xanthate and sodium isobutyl xanthate with detection limits of 24.7 and 13.3 μg/L, respectively. With a linear calibration range of 0.1-15 mg/L and a total analysis time of 4-5 min, the present method is a fast and sensitive option for selective xanthate determination.

Novel covalent organic frameworks based electrospun composite nanofiber membranes as pipette-tip strong anion exchange sorbent for determination of inorganic arsenic in rice

Novel covalent organic frameworks (COFs) based PAN@TpBD(NH₂)₂ electrospun composite nanofiber membranes (ECNMs) were fabricated as strong anion exchange sorbent by implementing electrospinning technology. The finished sorbent was characterized, and key parameters of pipette-tip solid phase extraction (PTSPE) procedures were investigated. Inorganic arsenic (iAs) was successfully separated from rice under the optimal precondition conditions, and quantified by hydride generation-atomic fluorescence spectrometry (HG-AFS). This PTSPE-HG-AFS methodology achieved 0.015 μg L^-1 detection limit, 4.67 % relative standard deviation, and 86.48～99.11 % recoveries. In this work, preparation and characterization of this novel COFs-based anion exchange sorbent, PAN@TpBD(NH₂)₂ ECNMs, is described and its suitability for PTSPE applications is demonstrated.

Detection of organic arsenic based on acid-base stable coordination polymer

Organic arsenic, usually found in animal feed and livestock farm wastewater, is a carcinogenic and life-threatening substance. Hence, for the rapid and sensitive detection of organic arsenic, the development of new fluorescent sensors is quite essential. Here, an acid-base stable coordination polymer (HNU-62) was constructed by the introduction of hydrophobic fluorescence ligand, which can be used as a highly selective sensor for the detection of roxarsone (ROX) in water. The limit of detection (LOD) of HNU-62 for ROX was 4.5 × 10^-6 M. Furthermore, HNU-62 also exhibits good anti-interference and recyclability, which can be used in detecting ROX in real samples of pig feed. This work provides an alternative approach for the construction of water-stable coordination polymer-based fluorescence sensors.

Identification of mercury species in coal combustion by-products from power plants using thermal desorption-atomic fluorescence spectrometry on-line coupling system

Along with the environmental protection policies becoming strict in China, the air pollution control devices (especially selective catalytic reduction (SCR)) are widely equipped in coal-fired power plants. The installation and run of these devices will inevitably affect mercury (Hg) species distribution in coal fired by-products such like fly ash (FA) and gypsum. In this work, a new on-line coupling system based on atomic fluorescence spectrometry (AFS) with a home-made chromatographic workstation was successfully developed to identify Hg species through thermal programmed desorption (TPD). The influences of matrix, furnace temperature, and carrier gas flow on analytical performance were investigated and the parameters were optimized. The FA and gypsum samples from coal-fired power plants equipped with SCR were collected and the mercury species were analyzed by the developed coupling system. HgCl₂ and HgO were the main species in FA, while Hg₂Cl₂ and HgO were the main species in gypsum. All of Hg species in the studied FA and gypsum samples were released below 400 °C. A sequential extraction procedure was applied to further verify the operational Hg species including mobile and non-mobile fractions in FA and gypsum samples. This study demonstrated that AFS coupled with TPD procedure was an effective method to analyze Hg species in coal combustion by-products from power plants.

A method for the analysis of methylmercury and total Hg in fungal matrices

The aim of the study was to develop an efficient method for the determination of monomethyl-mercury (MeHg) and total mercury (THg) content in materials such as fungal sporocarps and sclerotia. Certified Reference Materials (CRMs) with the assigned values of MeHg and THg as well as the control materials (dried mushrooms) with known content of THg were evaluated for method validation. Recovery of MeHg from reference materials was at the following levels: from tuna fish at 87.0 ± 2.3% (THg at 101.9 ± 1.2%), from fish protein at 99.4 ± 1.3% (THg at 92.70 ± 0.41%), and from dogfish liver at 96.45 ± 0.73%. Recovery of THg from the fungal control material CS-M-5 was at 104.01 ± 0.60% (contribution of MeHg in THg content was at 6.2%), from CS-M-4 at 101.1 ± 2.0% (contribution at 3.2%), from CS-M-3 at 100.55 ± 0.67% (contribution at 0.6%), and from CS-M-2 at 101.5 ± 2.7% (contribution at 3.7%). The content of MeHg in randomly selected wild fungi and their morphological parts was in the range from 0.006 to 0.173 mg kg^-1 dry weight (dw). In the case of THg, the concentration values were in the range from 0.0108 to 10.27 mg kg^-1 dw. The MeHg content in the control materials with the assigned THg values was determined. Since the control materials play an important role in all elements of the quality assurance system of measurement results, they can be used to analyse MeHg as the first control material for fungi. KEY POINTS: • An extraction procedure for MeHg analysis in fungi was developed and optimized. • Recovery of MeHg from the certified reference non-fungal materials was > 87%. • Fungal control materials with assigned THg concentration can serve also for MeHg analysis.

Sensitive Mercury Speciation Analysis in Water by High-Performance Liquid Chromatography-Atomic Fluorescence Spectrometry Coupling with Solid-Phase Extraction

An efficient method based on high-performance liquid chromatography coupled with atomic fluorescence spectrometry (HPLC-AFS) was successfully developed for the simultaneous determination of four mercury species including Hg²⁺, methylmercury (MeHg), ethylmercury (EtHg), and phenylmercury (PhHg) in water. Samples were enriched and cleaned up with a solid-phase extraction (SPE) pretreatment using a thiol cartridge. Some key parameters including the selection of a SPE cartridge, eluent type, eluent volume, and interference factors were systematically investigated. Chromatographic separation was achieved on a C₁₈ column using a mobile phase consisting of methanol and 60 mmol L^-1 ammonium acetate with 10 mmol L^-1 L-cysteine by gradient elution. Under the optimized conditions, good linearity (r ≥ 0.9991) was observed between 0.20 to 10.0 μg L^-1. The limits of detection were in the range of 0.001 - 0.002 μg L^-1. High recoveries (87.2 to 111%) and good reproducibility (1.1 - 6.5%) were obtained. Such a method is sensitive, selective and accurate, which can be applied to the quantification of mercury species in water samples.

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.

Ammonium acetate as a novel buffer for highly selective robust urinary HPLC-ICP-MS arsenic speciation methodology

Ammonium acetate is employed in order to develop a novel HPLC-ICP-MS arsenic speciation methodology applicable to six arsenic species, i.e, AC, AB, As^III, As^V, DMA and MMA. The most predominant species in the toxicological field are covered in a 30-min chromatogram with reproducible and repeatability peak area ratio. Moreover, typical problems from traditional methods are sorted out by using a robust, high-selective and ⁷⁵ArCl⁺ interference-free methodology. Chromatographic and detector optimization ensures low LOQs for each species with acceptable precision and accuracy values obtained using four urinary arsenic speciation PTS enabling to be useful for sub ng mL^-1 arsenic exposure assessments.

The ameliorative effects of exogenous inoculation of Piriformospora indica on molecular, biochemical and physiological parameters of Artemisia annua L. under arsenic stress condition

Aim of the current study was to investigate the effect of exogenously inoculated root endophytic fungus, Piriformospora indica, on molecular, biochemical, morphological and physiological parameters of Artemisia annua L. treated with different concentrations (0, 50, 100 and 150 μmol/L) of arsenic (As) stress. As was significantly accumulated in the roots than shoots of P. indica-inoculated plants. As accumulation and immobilization in the roots is directly associated with the successful fungal colonization that restricts most of As as compared to the aerial parts. A total of 4.1, 11.2 and 25.6 mg/kg dry weight of As was accumulated in the roots of inoculated plants supplemented with 50, 100 and 150 μmol/L of As, respectively as shown by atomic absorption spectroscopy. P. indica showed significant tolerance in vitro to As toxicity even at high concentration. Furthermore, flavonoids, artemisinin and overall biomass were significantly increased in inoculated-stressed plants. Superoxide dismutase and peroxidase activities were increased 1.6 and 1.2 fold, respectively under 150 μmol/L stress in P. indica-colonized plants. Similar trend was followed by ascorbate peroxidase, catalase and glutathione reductase. Like that, phenolic acid and phenolic compounds showed a significant increase in colonized plants as compared to their respective control/un-colonize stressed plants. The real-time PCR revealed that transcriptional levels of artemisinin biosynthesis genes, isoprenoids, terpenes, flavonoids biosynthetic pathway genes and signal molecules were prominently enhanced in inoculated stressed plants than un-inoculated stressed plants.

Autocatalytic DNA circuit for Hg2+ detection with high sensitivity and selectivity based on exonuclease III and G-quadruplex DNAzyme

Utilizing G-quadruplex as the signal report probe, an ultrasensitive and label-free autocatalytic DNA circuit for Hg²⁺ detection on the basis of exonuclease III (Exo III)-assisted cascade signal amplification has been proposed. In the absence of Hg²⁺, the hairpin A and the DNA1 cannot hybridize due to the thymine-thymine (T-T) mismatches. Therefore, hairpin probes with the 3'-protruding terminus can be resistant to Exo III digestion, preventing the G-rich sequence to be released. In the presence of Hg²⁺, the combination of the DNA1 with the 3' end-extruding hairpin A via T-Hg²⁺-T coordination chemistry triggers the digestion reaction of Exo III, leading to the release of the DNA1 and the sequence with domains c, d, and e. Both of the DNA1 and the sequence with domains c, d, and e can combine with other hairpin probes and activate another round of the cleavage reaction. The produced G-rich sequence can form G-quadruplex structure by binding with N-Methyl mesoporphyrin IX (NMM). The biosensor exhibits excellent selectivity and high sensitivity for Hg²⁺. The linear range of this biosensor is from 10 fM to 100 nM, and the linear equation can be expressed as: F₆₁₀ = 1.3 × 10⁵ Lg C + 7.40 × 10⁴ (R² = 0.998), in which F₆₁₀ is the fluorescence intensity at 610 nm, C represents the Hg²⁺ concentrations, and Lg is the logarithm of 10. The detection limit is 10 fM. The biosensor is robust and can be applied to the detection of Hg²⁺ in water samples. By substituting the target-recognition elements, this sensing system can also be used for the detection of other metal ions.