Search

HPLC-ICP-MS based on ion-paired reversed phase chromatography for the selenium speciation using the mixture of 1-butanesulfonic acid (BA) and trifluoroacetic acid (TFA) as the mixed ion-pairing reagents was developed and applied to selenium-enriched pakchoi (Brassica chinensis Jusl var parachinensis (Bailey) Tsen & Lee). Several conditions of ion-paired reversed phase HPLC-ICP-MS, such as pH of the mobile phase, concentration of ion pairing reagents, types and length of analytical column, and flow rate of the mobile phase, were optimised for five selenium species; selenate (Se(VI)), Selenite (se(IV)), selenocysteine (SeC), Se-methylselenocysteine (SeMC) and selenomethionine (SeM). The results showed that the optimum conditions for pH, BA and TFA condition, type of separating column and flow rate, were 4.5, 8mM, 4mM, C18 (250 mm length × 4.6mm I.D) and 1.2 mL min(-1), respectively. These conditions archived separation of the organic selenium species. The limits of detection (LOD) and quantitation (LOQ) of each selenium species were lower than 5 and 16 ng Se mL(-1), respectively. Furthermore, the recoveries of most selenium species were good, except for SeC. In this research, selenium-enriched pakchoi was cultivated by supplementing inorganic selenium from selenate into sand. The result showed that inorganic selenium, SeMC, SeM and several unknown species were found in selenium-enriched pakchoi sprouts by using the proposed method. Thereby, the biotransformation of selenate in pakchoi was similar to other Brassicaceae plants such as kale and broccoli., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A flow injection system with anion exchange resin minicolumns was coupled with dynamic reaction cell (DRCtrade mark) ICP-MS for the determination and speciation of selenite and selenate at sub mugL(-1) levels. The charged selenate and uncharged selenite were separated on the first resin column in which only selenate was retained. The unretained selenite was then deprotonated with alkaline solution, and the resulting anionic selenite species was collected on the second column serially connected downstream. By setting a sample loop, total selenium can be determined together with selenite and selenate. The selenium species was eluted by nitric acid and carried to DRCtrade mark ICP-MS for their detection. Using ammonia as reaction gas, the detection of (78)Se was improved. The enrichment factor was 20 for 10mL of sample. The standard deviations (n=5) of peak heights were 4.9%, 4.1%, and 7.0% for a 5.0x10(-2)mugL(-1) selenite and selenate, and total Se, respectively. The calibration graphs were linear from 2.0x10(-2) to 1.0mugL(-1) selenite and selenate. And, the linearity for total selenium was good in the range of 10.0x10(-2) to 1.0mugL(-1). The proposed method has been demonstrated for the application to natural and bottled drinking water samples.