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 SeO 3 2– and seleno‐ dl ‐methionine in kefir grains. For the system, limits of detection and quantitation values for SeO 3 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 SeO 3 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 SeO 3 2– (20, 30, and 50 mg/kg) for approximately 4 days at room temperature to investigate the conversion/non‐conversion of SeO 3 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 SeO 3 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 SeO 3 2– proved by using an anion exchange column.