Initial Studies of Selenium Speciation inBrassica junceaby LC with ICPMS and ES-MS Detection:  an Approach for Phytoremediation Studies

Abstract

Various Brassica species accumulate Se into the thousands of ppm. This suggests some of them as candidates for Se phytoremediation. Brassica juncea (Indian mustard) was used to accumulate selenium by growing with sodium selenite as the selenium source under hydroponic conditions resulting in Se accumulation of up to hundreds of ppm in various parts of the plant. To date, few selenium speciation studies have been done in plants, with most studies reporting total selenium concentration in various parts of the plant. Se species extraction was evaluated by several digestion/extraction procedures, including the use of HCl, Tris-HCl buffer, and enzymatic hydrolysis (using proteinase K and protease XIV). The best extraction was obtained with proteinase K (extracting approximately 75% of the total Se present in the plant). Some of the species produced by the plant, such as selenomethionine, can be identified at ppb levels by RP-HPLC-ICPMS, since standards are readily available. Others needed to be further characterized by ES-MS. Enzymatic hydrolysis releases mostly Se-methionine from juncea leaves, although other Se-containing species can also be observed by HPLC-ICPMS. In this initial study, the possible identification (by ES-MS) of a small chromatographic peak containing a Se-S bridged seleno amino acid with a structure similar to cystine is suggested.

Toxicometallomics for Research on the Toxicology of Exotic Metalloids Based on Speciation Studies

“…[17][18][19] ESI is a softer technique than ICP, and can provide molecular information. In addition, MS-MS enables structure elucidation.…”

Chromatographic speciation of anionic and neutral selenium compounds in Se-accumulating Brassica juncea (Indian mustard) and in selenized yeast

“…The common procedures used for the speciation of selenium in yeast, plants and vegetables have been hot water extraction, enzymatic hydrolysis, buffers, water-methanol and HCl extraction [6,7,[28][29][30]. In this study, protease XIV enzymatic extraction was used to cleave peptide bonds in proteins in order to characterize low molecular weight selenium compounds in the plants.…”

“…Plants may transform some toxic contaminants to environmentally harmless volatile species, which may be dispersed away from polluted areas [2]. Such detoxification processes have been used for the elimination of pesticides or polycyclic aromatic hydrocarbons (PAHs) from soils, and recently, successful results have been obtained for removing selenium from soils [3,4] and hydroponic media [5][6][7][8].…”

Review: Biological methylation of less‐studied elements

“…and selenomethionine 71 were formed by Indian mustard (Brassica juncea) seedlings exposed to selenite and selenate salts. Bacteria in the plant rhizosphere are necessary for this biomethylation, 69 and the dimethylselenide generated appears to require 3-dimethylselenopropionate, CH 3 2 Se CH 2 CH 2 CO À 2 ,as a precursor.…”