In-vessel headspace liquid-phase microextraction

• Published in: Analytica chimica acta Vol. 1172; p. 338670
• Main Authors: Tamen, Aimad-Eddine, Vishnikin, Andriy
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 08-08-2021
• Subjects: Distribution constant; In-vessel headspace liquid-phase microextraction; Iodide determination; Spectrophotometric detection; In-vessel headspace liquid-phase microextraction; Iodide determination; Distribution constant; Spectrophotometric detection
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2021.338670

A new mode of headspace liquid-phase microextraction termed in-vessel headspace liquid-phase microextraction (IV-HS-LPME) has been developed. A plastic vessel was used as a holder for an extraction phase. Problems with drop stability, limitations in the stirring speed, and too little volume of the acceptor phase have been completely eliminated. The proposed approach is fully compatible with ordinary instruments and microcuvettes used in spectrophotometry. The potential of the method was evaluated by determining the iodide concentration in various samples. Iodide in the donor phase was converted to volatile I2 by oxidation with 1 mmol L−1 K2Cr2O7. The reaction mixture was agitated on a magnetic stirrer for 30 min at a stirring speed of 1200 rpm. A 1% (w/v) aqueous solution of KI was used as the acceptor phase. The absorbance of the I3− ion formed in the acceptor phase was measured in a 50 μL microcuvette at 350 nm. For the case of extraction from 10 mL donor solution into 50 μL of acceptor phase, the calibration graph is linear in the range of 20–400 μg L−1 (as I−) with a detection limit of 6 μg L−1. The developed method has a high precision comparable to conventional spectrophotometric methods (0.6–1.5%). The extraction efficiency obtained in the optimal conditions was 10.5%. The distribution constants for equilibria between the donor solution and the headspace and between the headspace and the acceptor solution are 0.8 ± 0.1 and 16 ± 2, respectively. The developed method was successfully applied to determine the iodine content in natural waters, medicines and algae.
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•A new in-vessel head-space liquid-phase microextraction approach is developed.•A plastic vessel is used as a holder for an extracting solvent.•Approach is compatible with common spectrophotometric cuvettes and instruments.•Iodide is determined as triiodide in acceptor phase after conversion to iodine.