High polar organic-inorganic hybrid coating stir bar sorptive extraction combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry for the speciation of seleno-amino acids and seleno-oligopeptides in biological samples

In this work, partially sulfonated polystyrene-titania (PSP-TiO2) organic-inorganic hybrid stir bar coating was prepared by sol-gel and blending methods, and a new method of PSP-TiO2 coating stir bar sorptive extraction (SBSE)-high performance liquid chromatography (HPLC)-inductively coupled plasma mass spectrometry (ICP-MS) was established for the analysis of seleno-amino acids (selenocystine (SeCys(2)). methylseleno-cysteine (MeSeCys). selenomethionine (SeMet) and selenoethionine (SeEt)) and seleno-oligopeptides (gamma-glutamyl-Se-methyl-selenocysteine (gamma-GluMeSeCys) and selenodiglutathione (GS-Se-SG)) in biological samples. The prepared high polar PSP-TiO2 hybrid coating avoided the swelling of PSP and cracking of TiO2 coating by combining the good film-forming property of PSP with the high mechanical strength of TiO2. The scanning electron microscope (SEM) showed that no obvious swelling and damage occurred for the PSP-TiO2 hybrid stir bar coating after 30 extraction/desorption cycles. The preparation reproducibility of PSP-TiO2 coated stir bar, evaluated with the relative standard deviations (RSDs), was in the range of 6.7-12.6% (n = 5) in one batch, and 9.9-17.6% (n = 7) among different batches. The limits of detection (LODs) of the developed method for six target selenium species were in the range of 50.2-185.5 ng L-1 (as Se-77) and 45.9-158.8 ng L-1 (as Se-82) with the RSDs within 4.9-11.7%. The dynamic linear range was found to cover three orders of magnitude with correlation coefficient of 0.9995-0.9999. The developed method was applied for the analysis of Certified Reference Material SELM-1 selenium enriched yeast and the determined values were in good agreement with the certified values. The method has also been applied for the analysis of seleno-amino acids and seleno-oligopeptides in human urine and garlic samples. Different from the conventional organic polymer SBSE coatings (such as polydimethylsiloxane, PDMS), the extraction mechanism of PSP-TiO2 organic-inorganic hybrid SBSE coating was based on the cation exchange interaction, which made it feasible to directly extract high polar seleno-amino acids and seleno-oligopeptides in biological samples without derivatization. This coating could also be suitable for stir bar sorptive extraction of other cationic compounds from the environmental and biological samples. (C) 2012 Elsevier B.V. All rights reserved.