Fast and clean determination of total selenium in biological materials by an improved oxygen flask combustion method combined with hydride generation atomic fluorescence spectrometry

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.

Zirconium nanoparticles based dispersive solid phase extraction prior to slotted quartz tube-flame atomic absorption spectrophotometry for the determination of selenium in green tea samples

In this study, a novel, easy, rapid and green zirconium nanoparticles (Zr-NPs) based dispersive solid phase extraction (DSPE) method is presented for the precise and sensitive determination of selenium by slotted quartz tube-flame atomic absorption spectrophotometry (SQT-FAAS). Influential parameters of the extraction procedure were optimized by altering one parameter while keeping the other parameters constant. The optimum conditions were selected as 10 mg of Zr-NPs, 75 s vortex period, and 200 µL of concentrated HCl for 30 mL of sample/standard solution. The linear range of the developed method was found to be between 25 and 100 µg/L, and the respective limits of detection and quantification were 5.3 and 18 µg/L. About 415 folds enhancement in detection power was achieved by the optimized method relative to the conventional FAAS. Green tea samples were spiked and used for recovery experiments and the results obtained were between 92 and 102%.