Selenium speciation in environmental and clinical samples
Methods for selenium speciation using chromatographic and atomic spectrometric methods were developed. The objectives of the study were to quantify low concentrations of selenium and identify the different Se species present in some clinical and environmental samples. A 10 to 1000-fold improvement in detection limit was observed. The application of an inductively coupled plasma optical emission spectrometry (ICP-OES) instrument (a PerkinElmer Optima 4300DV) with flow injection hydride generation (FI-HG) sample handling (a PerkinElmer FIAS 400) as a method for the determination of selenium was described. The flow injection signals were processed by version 3.0 of PerkinElmer's Winlab32 ICP software that allows time-based transient signals to be processed, as well as the normal wavelength-based transients obtained with steady-state sample introduction.
The FI-HG-ICP-OES was coupled to online preconcentration. A silica-based Discovery SAX resin was used as a preconcentration material for selenite. The method was used to determine percent recovery of low ppt levels of Se in different water samples such as spring water, river water, lake water, and seawater.
The use of the Multi Mode Sample Introduction System (MSIS™) was also evaluated for the determination of selenium. The efficiency of the HG procedure improved the detection limit by 100 fold when compared to that of conventional nebulization. The procedure also allowed better tolerance to interfering ions.
The Se uptake of Brassica napus was investigated. Different Se species were added to the soil and hydroponic media. Selenomethionine and the "newly identified selenoaminoacid", S-(methylseleno)cysteine were identified in the plant extracts by gas chromatography with atomic emission detection (GC-AED).
Ion exchange chromatography with inductively coupled plasma mass spectrometry detection (IC-ICP-MS) was developed to identify the Se species in total parenteral nutrition (TPN) and the urine of neonates. Since the identity and amount of the selenium used in supplementation is known, identifying the resulting metabolites can give a new aspect on the selenium metabolic pathway in neonates.
Preliminary determination of selenite by GC-AED was investigated. Inorganic Se in the form of selenite (SeO32-) was converted to piazselenol. The use of both 2,3-diaminonaphthalene and 4-chloro- o-phenylendiamine as derivatizing agents was investigated.