Determination of selenium by X-ray fluorescence spectrometry using dispersive solid-phase microextraction with multiwalled carbon nanotubes as solid sorbent

Abstract

A dispersive solid-phase microextraction (DSPME) with multiwalled carbon nanotubes (MWCNTs) as solid sorbent and ammonium pyrrolidinedithiocarbamate (APDC) as chelating agent was developed for determination of selenium. In the proposed procedure, the Se(IV)-APDC complex is adsorbed on MWCNTs dispersed in aqueous samples. After the adsorption process, the aqueous samples are filtered and MWCNTs with selenium chelate are collected onto a filter. The loaded filters are directly measured using X-ray fluorescence (XRF) spectrometry. In order to obtain high recovery of the Se ions on MWCNTs, the proposed procedure was optimized for various analytical parameters such as pH, amounts of MWCNTs and APDC, sample volume and time of the sorption process. Under optimized conditions Se ions can be determined with very good recovery (97 AE 3%), precision (RSD ¼ 3.2%) and detection limits (from 0.06 to 0.2 ng mL À1 , depending on counting time and XRF equipment). The effect of common coexisting ions was also investigated. Se(IV) can be determined in the presence of heavy metal ions and alkali metals. The chemical interferences observed for high concentrations of Cu(II), Fe(III), and Zn(II) can be completely eliminated using precipitation with NaOH. The proposed method was applied for the determination of Se in mineral water and biological samples (Lobster Hepatopancreas). The proposed method can also be applied for selenium speciation. The concentration of selenate can be obtained as the difference between the concentration of selenite after and before prereduction of selenate to selenite.

Speciation of inorganic selenium in environmental samples after suspended dispersive solid phase microextraction combined with inductively coupled plasma spectrometric determination

“…The comparative results are summarised in Table 5. The analytical figures of merit obtained revealed that the SDSPME/ICP-OES method has relatively lower LOD and better precision when compared with those reported in the literature [12,[22][23][24]. However, the preconcentration factor for the developed was lower than those reported by Duan et al [12].…”

Dispersive micro solid-phase extraction using multiwalled carbon nanotubes combined with portable total-reflection X-ray fluorescence spectrometry for the determination of trace amounts of Pb and Cd in water samples

“…The procedure used in this paper for the oxidation of the MWCNTs is described in detail in ref. 13. In this work quartz glass discs with a diameter of 30 mm and a thickness of 3 mm AE 0.1 mm were used as sample holders for introducing the sample into the TXRF instrument.…”

Recent Microextraction Techniques for Determination and Chemical Speciation of Selenium

“…A reliable accuracy, which also agreed with published standards [19] and was calculated by recovery, was 97%. The detection limit calculated based on the sensitivity, background count rate, and continuing time was 0.06-0.20 ng/ml [50]. This method is fast, has high selectivity, and is reliable, and it possesses the possibility of sample multi-measurement Kocot and others [51] have developed a new method for the determination and speciation of selenium (Table 10) using dispersive micro solid phase extraction (DMSPE) with graphene as adsorbent coupled with energy dispersive X-ray fluorescence spectrometry (ED-XFS).…”

“…One such report involves a novel method for determination of selenite (Table 10) after chemical modification by ammonium pyrrolidine dithiocarbamate (APDC) and using dispersive solid phase microextraction (DSPME) prior to X-ray fluorescence spectrometry analysis [50]. Oxidized multi-walled carbon nanotubes (MWCNTs) were used as an adsorbent.…”