Vortex-assisted liquid-liquid microextraction procedure for iodine speciation in water samples

Microbial involvement in iodine cycle: mechanisms and potential applications

Stable iodine isotopes are essential for humans as they are necessary for producing thyroid gland hormones. However, there are hazardous radioactive iodine isotopes that are emitted into the environment through radioactive waste generated by nuclear power plants, nuclear weapon tests, and medical practice. Due to the biophilic character of iodine radionuclides and their enormous biomagnification potential, their elimination from contaminated environments is essential to prevent the spread of radioactive pollution in ecosystems. Since microorganisms play a vital role in controlling iodine cycling and fate in the environment, they also can be efficiently utilized in solving the issue of contamination spread. Thus, this paper summarizes all known on microbial processes that are involved in iodine transformation to highlight their prospects in remediation of the sites contaminated with radioactive iodine isotopes.

Dispersive liquid-liquid microextraction and diffuse reflectance-Fourier transform infrared spectroscopy for iodate determination in food grade salt and food samples

A novel method based on diffused reflectance Fourier-transform infrared spectroscopy (DRS-FTIR) was employed for iodate determination in food grade salt and food products. The method attained sensitivity that was comparable to or better than that in most of the contemporary spectrophotometric methods. This was realized through a combination of azo dye formation and dispersive liquid-liquid microextraction of dye when a 37-fold enrichment was obtained. FT-IR enabled integrating alternative target peak, and freedom in sample solvent composition relative to UV-visible spectrophotometry where the solvent polarity, pH, and presence of ions may affect the spectral properties of the measurable coloured species. Food samples containing iodide or covalently bonded iodine were oxidized with alkaline permanganate for mineralization and iodate formation. Optimization of both reaction conditions was carried out by means of response surface methodology. The method had a linear range 0.04-10 mg kg^-1 iodate and limit of detection of 4.4 µg kg^-1.

In-vessel headspace liquid-phase microextraction

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.

Development of extraction separation technology based on deep eutectic solvent and magnetic nanoparticles for determination of three sex hormones in milk

A rapid, reliable and eco-friendly method for the determination of three sex hormones in five kinds of milk was developed and validated by combining vortex-assisted liquid-liquid microextraction (VALLME) and magnetic solid-phase extraction (MSPE). Deep eutectic solvents (DESs) such as choline chloride/urea were considered as the extraction solvent in VALLME and multi-walled carbon nanotubes (MMWCNTs) were used as the adsorbent which could adsorb DESs on the surface. The optimum experimental conditions were as follows: amount of MMWCNTs for 10 mg, volume of acetone for 4 mL, no sodium chloride and extraction pH at 7. After the optimization of several main variables, satisfactory sensitivity levels were achieved as low as 1.0-1.3 ng mL^-1 and 2.5-4.5 ng mL^-1 for the limit of method detections and the limit of method quantitation, respectively. The recoveries of the three hormones in different milk samples were in the range of 80.1%-116.4%. Consequently, this method is suitable for monitoring the trace amount of sex hormones in milk matrices.

Direct immersion single-drop microextraction of semi-volatile organic compounds in environmental samples: A review

Single-drop microextraction (SDME) techniques are efficient approaches to pretreatment of aqueous samples. The main advantage of SDME lies in the miniaturization of the solvent extraction process, minimizing the hazards associated with the use of toxic organic solvents. Thus, SDME techniques are cost-effective, and represent less harm to the environment, subscribing to green analytical chemistry principles. In practice, two main approaches can be used to perform SDME - direct immersion (DI)-SDME and headspace (HS)-SDME. Even though the DI-SDME has been shown to be quite effective for extraction and enrichment of various organic compounds, applications of DI-SDME are normally more suitable for moderately polar and non-polar semi-volatile organic compounds (SVOCs) using organic solvents which are immiscible with water. In this review, we present a historical overview and current advances in DI-SDME, including the common analytical tools which are usually coupled with DI-SDME. The review also focuses on applications concerning SVOCs in environmental samples. Currents trends in DI-SDME and possible future direction of the procedure are discussed.

Vortex-assisted liquid–liquid microextraction and indirect spectrophotometric determination of chromium(vi)

A novel, simple, sensitive and selective method for the indirect spectrophotometric determination of Cr(vi) was developed on the basis of vortex-assisted liquid–liquid microextraction of an ion association pair between the I₃^– and cationic dye ABR.

A simple solvent based microextraction for high performance liquid chromatographic analysis of aflatoxins in rice samples

This paper describes the development of a simple solvent based microextraction, namely vortex assisted low density solvent-microextraction (VALDS-ME), followed by high performance liquid chromatography-fluorescence detection (HPLC-FD) for the simultaneous determination of four aflatoxins (AFs) including AFB1, AFB2, AFG1 and AFG2 in rice samples. In VALDS-ME, a mixture of low density solvents (1-octanol and toluene) was used as the extraction solvent. The extraction was rapidly achieved with the assistance of vortex agitation and phase separation was easily obtained after the addition of Na₂SO₄. The effects of various parameters on the extraction efficiency were optimized. Under the optimum conditions, high enrichment factors (42-132), low limits of detection (LODs) in the range of 0.0011-0.17μgkg^-1 and good precisions (RSDs lower than 6.2%) were obtained. AFB1 and AFG1 were detected in berry rice sample at 0.26 and 2.1μgkg^-1, respectively. The recoveries in AFs-spiked rice samples ranged from 70% to 104%. Moreover, the present method was comparable to the conventional immunoaffinity chromatography method.