Sequential photocatalyst-assisted digestion and vapor generation device coupled with anion exchange chromatography and inductively coupled plasma mass spectrometry for speciation analysis of selenium species in biological samples

Fabrication of a Microfluidic-Based Device Coated with Polyelectrolyte-Capped Titanium Dioxide to Couple High-Performance Liquid Chromatography with Inductively Coupled Plasma Mass Spectrometry for Mercury Speciation

Mercury (Hg) is a toxic element which impacts on biological systems and ecosystems. Because the toxicity of Hg species is highly dependent on their concentration levels and chemical forms, the sensitive identification of the chemical forms of Hg-i.e., Hg speciation-is of major significance in providing meaningful information about the sources of Hg exposure. In this study, a microfluidic-based device made of high-clarity poly(methyl methacrylate) (PMMA) was fabricated. Then, titanium dioxide nanoparticles (nano-TiO2s) were attached to the treated channel's interior with the aid of poly(diallyldimethylammonium chloride) (PDADMAC). After coupling the nano-TiO2-coated microfluidic-based photocatalyst-assisted reduction device (the nano-TiO2-coated microfluidic-based PCARD) with high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS), a selective and sensitive, hyphenated system for Hg speciation was established. Validation procedures demonstrated that the method could be satisfactorily applied to the determination of mercury ions (Hg2+) and methylmercury ions (CH3Hg+) in both human urine and water samples. Remarkably, the zeta potential measured clearly indicated that the PDADMAC-capped nano-TiO2s with a predominance of positive charges indeed provided a steady force for firm attachment to the negatively charged device channel. The cause of the durability of the nano-TiO2-coated microfluidic-based PCARD was clarified thus.

Automated infrared ashing with palladium nitrate as an ashing aid for the determination of selenium in plant foods by inductively coupled plasma mass spectrometry

Based on the automatic light wave ashing instrument, palladium nitrate was used as an ashing aid for the first time to collect selenium in the process of food ashing pre-treatment, and a method for the determination of selenium in food by ashing method was established with inductively coupled plasma mass spectrometry. At the same time, the effects of magnesium nitrate, rhodium nitrate, and nickel nitrate as ashing aids on selenium collection were investigated using certified plant standard materials. The capture of selenium by magnesium nitrate, rhodium nitrate, and nickel nitrate as ashing aids did not exceed 50%. Using palladium nitrate as an ashing aid, six food standard materials were measured, with selenium recovery rates ranging from 97 to 106%. A complete analysis cycle can be completed within an hour. The method detection limit of selenium was 0.021 μg g-1, and the relative standard deviation of five measurements was less than 7%. The experimental results show that palladium nitrate is an excellent ashing aid for capturing selenium, and it is far superior to the other three aids. In addition, the mechanism of palladium nitrate as an ashing aid for capturing selenium was discussed.

Speciation Analysis of Trace Arsenic, Mercury, Selenium and Antimony in Environmental and Biological Samples Based on Hyphenated Techniques

In order to obtain a well understanding of the toxicity and ecological effects of trace elements in the environment, it is necessary to determine not only the total amount, but also their existing species. Speciation analysis has become increasingly important in making risk assessments of toxic elements since the toxicity and bioavailability strongly depend on their chemical forms. Effective separation of different species in combination with highly sensitive detectors to quantify these particular species is indispensable to meet this requirement. In this paper, we present the recent progresses on the speciation analysis of trace arsenic, mercury, selenium and antimony in environmental and biological samples with an emphasis on the separation and detection techniques, especially the recent applications of high performance liquid chromatography (HPLC) hyphenated to atomic spectrometry or mass spectrometry.