Determination of Se in urine by flow injection hydride generation electrothermal atomic absorption spectrometry with in-atomizer trapping

Abstract

Following digestion of the sample in a mixture of bromate and hydrobromic acid, the inorganic selenium produced was quantified by trapping hydrogen selenide, formed when a 500 ml sample volume injected into a hydrochloric acid carrier stream merged with a stream of sodium borohydride solution, on the iridium-pretreated interior of a graphite furnace atomizer. A number of parameters relating to the digestion, flow injection manifold and trapping in the atomizer were investigated, including a study of factors affecting the detection limit. It was found necessary to heat the digest under reflux at a temperature of 150ЊC for 2 h. Quantitative recoveries, from a human urine matrix, of selenite, selenate, trimethylselenium, selenocystine, selenopurine and selenomethionine spikes were obtained. The efficiency of hydride generation, transport and trapping was 75%. The major factors affecting the detection limit were the reagent purity and the volume injected. For high-purity hydrobromic acid and borohydride free of caking agent, the detection limit, based on three times the standard deviation of the blank, was 0.06 mgl − 1 for a 1000 ml injection volume corresponding to a detection limit of 3 mgl − 1 for a urine sample. The method was validated by the accurate analyses of Standard Reference Material 2670 from the National Institute of Standards and Technology, and urine samples from an interlaboratory comparison program. The procedure avoids the need for perchloric acid and produces selenium in the + 4 oxidation state and thus no reduction is needed prior to generation of the hydrogen selenide. The use of a graphite furnace atomizer avoids the need for frequent reconditioning of the atomizer surface and the need for the standard additions method, both of which are drawbacks of procedures which make use of the quartz tube atomizer. All sample handling procedures following the digestion were automated by the use of flow injection technology.

Flow injection hydride generation electrothermal atomic absorption spectrometry with in-atomizer trapping for the determination of lead in calcium supplements

“…Peaks were quantified by area. The interior of the furnace was pre-treated with 120 mg of iridium by the sequential transfer and thermal processing of three 40-ml portions of a 1000 mg l − 1 iridium solution as described previously [24]. The FI program is shown in Table 1.…”

A geração química de vapor em espectrometria atômica

“…Existem, na literatura, inúmeras aplicações da técnica de geração de hidretos com detecção por espectrometria atômica, em uma ampla variedade de amostras: alimentos (As) [163][164][165][166] ; água (As) 6,[167][168][169][170][171][172] , (Pb) 173 , (Sn) 174 , (Sb) [175][176][177] , (Se) [178][179][180] , (Tl) 181 , (As e Se) 182 , (As, Se e Sb) 183 , (As, Se, Sb e Ge) 184 ; água e solo (Pb) 185 , amostras ambientais (As) 186 , (Cd) 187 , (Sb) 188,189 , (Sn) 190 ; amostras biológicas (Se) 7 , (As e Bi) 191 ; amostras biológicas e ambientais (As) 192 , (Cd) 193 , (As e Se) 194 ; amostras clíni-cas: cabelo (Se) 195 , (Sb) 196 , urina (As) [197][198][199][200][201] , (Bi) 202 , (Se) 203,205 ; bebidas: vinho (Sb) 206 , vinho e cerveja (As) 207<...>…”

Hydride generation atomic absorption spectrometry with insitu graphite tube trapping for the determination of Se (IV) and Se (VI) in baltic sea water samples

“…In order to enhance the e®ectiveness of the pre-concentration, the walls of the graphite tube are covered with a modi¯er, which is either introduced at the appropriate stage of the thermal cycle or electrothermally deposited [3]. The modi¯ers can be the compounds of palladium [4][5][6][7][8], magnesium [6,9,10], zirconium [11], iridium [8,[11][12][13][14], or permanent modi¯ers like Zr, Ir, W, Nb [5,15,16]. Palladium and other metals are able to bind selenium as intermetallic compounds, which evaporate at temperatures higher than selenium itself [17,18], although this mechanism has been criticised by other authors [19].…”