Separation/preconcentration of ultra-trace levels of inorganic Sb and Se from different sample matrices by charge transfer sensitized ion-pairing using ultrasonic-assisted cloud point extraction prior to their speciation and determination by hydride gener

• The method is based on ion-association of Sb(III) and Se(IV) with NRH+ in presence of pyrogallol and CTAB at pH 6.0.
• NRH+ was adopted as charge transfer sensitized ion-pairing reagent in the preconcentration step.
• Analytical figures of merit of the method were established.
• A sensitivity enhancement factor of 155 and 120 for each analyte was obtained.
• It allows to speciative determination of inorganic Sb and Se with a highly low detection limit.

In the existing study, a new, simple and low cost process for separation/preconcentration of ultra-trace level of inorganic Sb and Se from natural waters, beverages and foods using ultrasonic-assisted cloud point extraction (UA-CPE) prior to their speciation and determination by hydride generation AAS, is proposed. The process is based on charge transfer sensitized complex formations of Sb(III) and Se(IV) with 3-amino-7-dimethylamino-2-methylphenazine hydrochloride (Neutral red, NRH+) in presence of pyrogallol and cetyltrimethylammonium bromide (CTAB) as both sensitivity enhancement and counter ion at pH 6.0. Under the optimized reagent conditions, the calibration curves were highly linear in the ranges of 8–300 ng L−1 and 12–250 ng L−1 (r2≥0.993) for Se(IV) and Sb(III), respectively. The limits of detection were 2.45 and 3.60 ng L−1 with sensitivity enhancement factors of 155 and 120, respectively. The recovery rate was higher than 96% with a relative standard deviation lower than 5.3% for five replicate measurements of 25, 75 and 150 ng L−1 Se(IV) and Sb(III), respectively. The method was validated by analysis of two certified reference materials (CRMs), and was successfully applied to the accurate and reliable speciation and determination of the contents of total Sb/Sb(III), and total Se/Se(IV) after UA-CPE of the pretreated sample matrices with and without pre-reduction with a mixture of l-cysteine and tartaric acid. Their Sb(V) and Se(VI) contents were calculated from the differences between total Sb and Sb(III) and/or total Se and Se(IV) levels.

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