title: Determination of selenomethionine and seleno-methyl-selenocysteine in biota by ultrasonic-assisted enzymatic digestion and multi-shot stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry.
abstract: A method based on stir bar sorptive extraction (SBSE) and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS) has been optimized for the determination of seleno-methyl-selenocysteine (SeMetSeCys) and selenomethionine (SeMet) in biota samples. Aliquots of freeze-dried tissue, a mixture of protease XIV-lipase and water were sonicated for 2min. After extraction, the extract was separated by centrifugation and subjected to derivatization and SBSE-TD-GC-MS. The parameters affecting derivatization, absorption and desorption steps were investigated. The optimized conditions consist of a derivatization with 40μL of ethyl chloroformate (ECF) in 400μL of a water:ethanol:pyridine (60:32:8) mixture, followed by dilution to 1.5mL of 70g NaClL(-1) in water at neutral pH and an extraction step using 10mm×1mm PDMS stir bar, stirring at 800rpm for 20min at room temperature (23±1°C). Three stir bars were used for the extraction of three different aliquots of the same sample and then placed in a single glass desorption liner and simultaneously desorbed for GC-MS analysis. The desorption step required the following conditions: 300°C (desorption temperature), 6min (desorption time), 50mLmin(-1) (vent flow) and -5°C (cryotrapping temperature). The method provided precise (8.1%) and accurate results in the mgSekg(-1) range (using the selected-ion monitoring-SIM mode) against certified reference material SELM-1 yeast, with recoveries higher than 80% for spiked algae and clams samples.
authors.affiliation: Universidad Nacional de Santiago del Estero, Avda. Belgrano (s) 1912, 4200 Santiago del Estero, Argentina.
authors.forename: F
authors.initials: F
authors.lastname: Mellano
authors.forename: M
authors.initials: M
authors.lastname: Bujalance
authors.forename: I
authors.initials: I
authors.lastname: Giráldez
authors.forename: P
authors.initials: P
authors.lastname: Ruiz-Azcona
authors.forename: D
authors.initials: D
authors.lastname: Sánchez-Rodas
authors.forename: E
authors.initials: E
authors.lastname: Morales
mesh_terms: D000042:Absorption; D000818:Animals; D058448:Biota; D049872:Bivalvia / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D058087:Haptophyta / Q000737:chemistry; D016014:Linear Models; D008049:Lipase / Q000737:chemistry; D011402:Pronase / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D017279:Selenocysteine / Q000031:analogs & derivatives* / Q000032:analysis / Q000302:isolation & purification; D012645:Selenomethionine / Q000032:analysis* / Q000302:isolation & purification; D013010:Sonication / Q000379:methods*
chemical_list: D011725:Pyridines; D017279:Selenocysteine; D000431:Ethanol; D012645:Selenomethionine; D008049:Lipase; D011402:Pronase; C023666:pyridine; C002979:selenomethylselenocysteine
keywords: Derivatization; Gas chromatography–mass spectrometry; Multi-shot mode; Selenoamino acid; Sonication probe; Stir bar sorptive extraction