Speciation of inorganic selenium in environmental water samples by inductively coupled plasma optical emission spectrometry after preconcentration by using a mesoporous zirconia coating on coal cinder

Determination of selenite and selenomethionine in kefir grains by reversed-phase high-performance liquid chromatography-inductively coupled plasma-optical emission spectrometry

A new and efficient reversed-phase high-performance liquid chromatography-inductively coupled plasma-optical emission spectrometry method was developed for the simultaneous separation and determination of SeO₃ ^2- and seleno-dl-methionine in kefir grains. For the system, limits of detection and quantitation values for SeO₃ ^2- and seleno-dl-methionine were calculated as 0.52/1.73 mg/kg (as Se) and 0.26/0.87 mg/kg (as Se), respectively. After performing the system analytical performance, recovery experiment was done for kefir grains and percent recovery results for SeO₃ ^2- and seleno-dl-methionine were calculated as 98.4 ± 0.8% and 93.6 ± 1.0%, respectively. It followed by the feeding studies that the kefir grains were exposed to three different concentrations of SeO₃ ^2- (20, 30, and 50 mg/kg) for approximately 4 days at room temperature to investigate the conversion/non-conversion of SeO₃ ^2- to seleno-dl-methionine. Next, the fed grains were extracted with tetramethylammonium hydroxide pentahydrate solution (20%, w/w) and then sent to the developed system. There was no detectable seleno-dl-methionine found in fed kefir grains at different concentrations of SeO₃ ^2- while inorganic or elemental selenium in the fed kefir grains was determined between 1579.5 - 3116.0 mg/kg (as Se). Selenium species in the kefir grains samples was found in the form of SeO₃ ^2- proved by using an anion exchange column.

Selenium analysis in waters. Part 2: Speciation methods

In aquatic ecosystems, there is often no correlation between the total concentration of selenium present in the water column and the toxic effects observed in that environment. This is due, in part, to the variation in the bioavailability of different selenium species to organisms at the base of the aquatic food chain. The first part of this review (Kumkrong et al., 2018) discusses regulatory framework and standard methodologies for selenium analysis in waters. In this second article, we are reviewing the state of speciation analysis and importance of speciation data for decision makers in industry and regulators. We look in detail at fractionation methods for speciation, including the popular selective sequential hydride generation. We examine advantages and limitations of these methods, in terms of achievable detection limits and interferences from other matrix species, as well as the potential to over- or under-estimate operationally-defined fractions based on the various conversion steps involved in fractionation processes. Additionally, we discuss methods of discrete speciation (through separation methods), their importance in analyzing individual selenium species, difficulties associated with their implementation, as well as ways to overcome these difficulties. We also provide a brief overview of biological treatment methods for the remediation of selenium-contaminated waters. We discuss the importance of selenium speciation in the application of these methods and their potential to actually increase the bioavailability of selenium despite decreasing its total waterborne concentration.

Selenium speciation in tea by dispersive liquid-liquid microextraction coupled to high-performance liquid chromatography after derivatization with 2,3-diaminonaphthalene

Selenium is an important element for human health, and it is present in many natural drinks and foods. Present study described a new method using dispersive liquid-liquid microextraction prior to high-performance liquid chromatography with a UV variable wavelength detector for the determination of the total selenium, Se(IV), Se(VI), and total organoselenium in tea samples. In the procedure, 2,3-diaminonaphthalene was used as the chelating reagent, 400 μL acetonitrile was used as the disperser solvent and 60 μL chlorobenzene was used as the extraction solvent. The complex of Se(IV) and 2,3-diaminonaphthalene in the final extracted phase was analyzed by high-performance liquid chromatography. The factors influencing the derivatization and microextraction were investigated. Under the optimal conditions, the limit of detection was 0.11 μg/L for Se(IV) and the linearity range was in the range of 0.5-40 μg/L. This method was successfully applied to the determination of selenium in four tea samples with spiked recoveries ranging from 91.3 to 100%.