An air-assisted liquid–liquid extraction using a dual-valve sequential injection manifold (DV-SIA): Determination of copper

Abstract

This work introduces an approach to liquid-liquid extraction for the sequential injection technique by improving on a previously reported dual-valve sequential injection manifold (DV-SIA). The system is made up of three units: a Mixing unit (for aqueous phase only), an Extraction unit, and a Detection unit (for organic phase only). The extraction was carried out by controlled aeration in the Extraction unit. The efficiency of the suggested extraction procedure was demonstrated by the spectrophotometric determination of copper extracted as an ion associate of Cu(I) with the polymethine dye 1,3,3-trimethyl-2-[5-(1,3,3-trimethyl-1,3-dihydroindol-2-ylidene)-penta-1,3-dienyl]-3H-indolium (DIDC). Appropriate experimental conditions were found to be: 40 mL of 2 mol L À1 NaCl; 50 mL of sample, 20 mL of 1 mmol L À1 DIDC (pH 3), flow rate 50 mL s À1 . A linear response was obtained in the range 0.13-2.0 mg mL À1 of Cu, and the limit of detection, calculated based on three times the standard deviation of the blank test (n ¼ 10), was 0.02 mg mL À1 . The method was applied to an assay of copper in pharmaceutical materials.

Application of DV-SIA manifold for determination of thiocyanate ions in human saliva samples

“…To ensure the best mixing of aqueous and organic phases in the extraction part, three methods of mixing were studied: (1) unidirectional -sample and reagents passed directly through the holding coil to the extraction cell, (2) flow reversals in the holding coil and (3) mixing with air bubbles in the extraction cell. In the last case, zone of the air was aspirated followed by all reagents and bubbling in the extraction cell ensured effective mixing of all solutions [23]. The value of the slope and the linearity of the analytical curve were established as main criteria to choose among the methods.…”

“…A simple, user-friendly and universal dual-valve sequential injection (DV-SIA) system with the online incorporation of LLE cell into the SIA manifold has been designed [22,23]. The design of the SIA manifold was based on the separation of extraction and detection units, avoiding some common problems in such kind of flow systems due to the different affinity of the organic and aqueous phase to the walls of the PTFE tubing, and bubble formation.…”

A single-valve sequential injection manifold (SV-SIA) for automation of air-assisted liquid-phase microextraction: stopped flow spectrophotometric determination of chromium(vi)

“…21 When using organic solvents in ow systems, parasitic signals can occur due to the change of phases having different affinities to the walls of the Teon tubing or because of air bubbles or the bubbles of one solvent appearing in the other solvent. 25 One solution was achieved by the recent development of a dual-valve SI manifold [25][26][27][28] which consists of two separately working units, each equipped with a selection valve, a syringe pump and a holding coil. One part is used for handling the aqueous phase, while the second works for aspiration of the extraction phase, with subsequent continuous ow detection.…”

Solid phase extraction of trace copper in water samples via modified corn silk as a novel biosorbent with detection by flame atomic absorption spectrometry

“…Flame atomic absorption spectrometry (FAAS) 1 and inductively coupled plasma atomic emission spectrometry (ICP-AES) 2 are the most used techniques for the quantication of copper content in environmental samples, although these quantitative methodologies are usually limited by restricted sensitivity and matrix interferences; therefore, an appropriate sample pretreatment procedure is usually necessary and helpful in order to eliminate the heavy matrix interferences, and at the same time facilitate the preconcentration of copper. Various separation and preconcentration methods including solid phase extraction (SPE), 3,4 coprecipitation, 5 liquid-liquid extraction 6 and cloud point extraction 7 have been developed. Among these methods, the solid phase extraction technique is the most widely employed due to its simple operation, high preconcentration efficiency and the large choice of sorbent materials, including modied silica gel, 8 ion imprinted polymer, 9 resin, 10 activated carbon, 11 carbon nanotubes, 12 PTFE, 13 zeolites, 14 metal oxides, 15 biosorbent, 16,17 so on.…”