HPLC-ICP-MS speciation of selenium in Se-cultivated Flammulina velutipes

Selenium is an essential micronutrient required at trace levels for human health, and dietary intake is the only source of selenium, which appears mainly in the form of selenocompounds. In this study, Flammulina velutipes was grown for 80 days in standard medium containing selenite, and the level of total selenium in the organism was then determined by inductively-coupled plasma mass spectrometry (ICP-MS). In Se-cultivated F. velutipes, selenium was mainly distributed in the water-soluble form and the content of soluble selenium-containing species in Se-cultivated F. velutipes was 47.10 mg kg⁻¹, accounted for 72.5% of the total selenium content. The water-soluble proteins in F. velutipes were extracted and precipitated by different ammonium sulfate saturation concentrations. Size-exclusion high performance liquid chromatography (SEC-HPLC) analysis of these proteins revealed the presence of at least six selenium-containing protein species, with molecular weights ranging from 9000 to 74,000 Da, Selenium-containing proteins represented about 7.0% of the total soluble selenium. The result of this study suggested that Se-cultivated F. velutipes could potentially be considered as a selenium supplement for human.     

Separation and quantification of quantum dots and dissolved metal cations by size exclusion chromatography–ICP-MS

The prevalence of engineered metallic nanoparticles within electronic products has evoked a need to assess their occurrence and fate within environmental systems upon potential release of these nanoparticles. Quantum dots (QDs) are mixed-metal nanocrystals with the smallest of particle sizes (2–10 nm) that readily leach heavy metal cations in water, potentially creating a co-occurrence of nanoparticulate and dissolved metal pollutants. In this report, we develop a size exclusion chromatography–inductively coupled plasma–mass spectrometry method (SEC-ICP-MS) for the rapid separation and quantification of ~5-nm-sized CdSe/ZnS QDs and dissolved Cd²⁺ and Zn²⁺ cations in water. The SEC-ICP-MS method provided a wide chromatographic separation of CdSe/ZnS QDs and dissolved Cd²⁺ and Zn²⁺ cations only when using the smallest SEC column pore size available and an eluent composition that prevented loss of metals to column polymer surfaces by using a surfactant to ensure elution of QDs (ammonium lauryl sulfate) and a complexing ligand to ensure elution of metal cations (ethylenediaminetetraacetate). Detection limits were between 0.2 and 2 µg L^–1 for Cd²⁺ and Zn²⁺ among dissolved cation and QD phases, and ranges of linearity covered two to three orders of magnitude. Gold nanoparticles of sizes 5, 10, 20 and 50 nm were also effectively separated from dissolved Au³⁺ cations, illustrating the method applicability to a wide range of nanoparticle sizes and compositions. QD and dissolved metal concentrations measured by SEC-ICP-MS were comparable to those measured using the more conventional method of centrifuge ultrafiltration on split samples for dissolved and total metals. The applicability of the SEC-ICP-MS method to environmental systems was verified by measuring QDs and dissolved metals added to samples of natural waters. The method was also applied to monitoring CdSe/ZnS dissolution kinetics in an urban river water. The SEC-ICP-MS developed here may offer improved automation for characterising heterogeneous suspensions containing >1 µg L^–1 heavy metals.     

Investigation of distribution of soil antimony using sequential extraction and antimony complexed to soil-derived humic acids molar mass fractions extracted from various depths in a shooting range soil

Trace metal contamination from bullet fragments in shooting ranges is a major environmental concern. In particular, trace metals such as lead, antimony, and copper are toxic and have the potential to enter groundwater supplies and to be absorbed by plants. Soil humic acids can play a critical role in mobilizing some of these released metals through complexation. The purpose of this study is to investigate the antimony complexed to soil-derived humic molar mass fractions extracted from various depths in a shooting range soil and to examine the distribution of antimony in various fractions of shooting range soils using sequential chemical extraction approach. The surface soil and soil core samples from a local shooting range were collected. Soil-derived humic acids were extracted from different depths of the top soil layer and characterized by various spectroscopic methods. Results of sequential chemical extraction demonstrated that Sb was found in shooting range in the upper 30 cm depth of the soil core. Highly elevated Sb is present in the exchangeable and ammonium acetate extracted fractions. Antimony is also present in the residual fraction in both surface and core soil samples, but is most likely present in a lithic phase which may not be readily bio-available. Leached antimony complexed to soil humic acid molar mass fractions was determined by size exclusion chromatography coupled to inductively coupled plasma-mass spectrometry (SEC-ICP-MS). The results demonstrate that Sb is ‘tightly’ bound to humic acid mass molar mass fractions and confined in the top 10 cm of soil-derived humic acids.     

体积排阻色谱与电感耦合等离子体质谱联用技术在富硒金针菇硒多糖形态分析中的应用研究

提取含硒7.97μg/g的富硒金针菇硒多糖,采用体积排阻色谱与电感耦合等离子体质谱(SE-HPLC-ICP-MS)联用技术进行在线分离分析,确定富硒金针菇中至少含有三种硒多糖,其分子量分别为4.27 kDa1、.868 kDa和1.54 kDa,含硒量分别占可溶性硒多糖中硒含量的14.95%、40.39%和44.66%。进一步研究证明:在金针菇的富硒培养过程中,硒不仅参与了生物大分子的合成,而且在富硒金针菇体内存在大量的具有生物活性的硒多糖。从分子生物学角度对新的补硒资源和生物活性因子进行有益的探索,为研究人类硒源的生物安全性和高效可利用性提供科学的理论依据。     

Biospeciation of tungsten in the serum of diabetic and healthy rats treated with the antidiabetic agent sodium tungstate

It is known that oral administration of sodium tungstate preserves the pancreatic beta cell function in diabetic rats. Healthy and streptozotocin-induced diabetic rats were treated with sodium tungstate for one, three or six weeks, after which the species of W in serum, were analysed. An increase in serum W with treatment time was observed. After six weeks, the serum W concentration in diabetic rats (70 mg L⁻¹) was about 4.6 times higher than in healthy specimens. This different behaviour was also observed for Cu accumulation, while the Zn pattern follows the contrary. The patterns observed in the retention of Cu and Zn may be attributable to a normalization of glycaemia. The speciation analysis of W was performed using 2D separations, including an immunoaffinity packing and a SEC (Size Exclusion Chromatography) column coupled to an ICP-MS (Inductively Coupled Plasma Mass Spectrometry) for elemental detection. Ultrafiltration data together with SEC-ICP-MS results proved that around 80% of serum W was bound to proteins, the diabetic rats registering a higher W content than their healthy counterparts. Most of the protein-bound W was due to a complex with albumin. An unknown protein with a molecular weight higher than 100 kDa was also found to bind a small amount of W (about 2%). MALDI-TOF (Matrix-Assisted Laser Desorption Ionization Time-of-Flight) analysis of the desalted and concentrated chromatographic fractions confirmed albumin as the main protein bound to tungstate in rat serum, while no binding to transferrin (Tf) was detected. The interaction between glutathione and W was also evaluated using standard solutions; however, the formation of complexes was not observed. The stability of the complexes between W and proteins when subjected to more stringent procedures, like those used in proteomic methodologies (denaturing with urea or SDS, boiling, sonication, acid media, reduction with β-mercaptoethanol (BME) or DTT (dithiotreitol) and alkylation with iodoacetamide (IAA), was also evaluated. Our results indicate that the stability of the complexes between W and proteins is not too high enough to remain unaltered during protein separation by SDS-PAGE in denaturing and reducing conditions. However, the procedures for in-solution tryptic digestion and for ESI-MS analysis in MeOH/H₂O/with 0.1% formic acid could be used for protein identification without large loss of binding between W and proteins.