Abstract
In this study, simple and efficient ultrasound-assisted emulsification microextraction (USAEME) based on applying low density organic solvents combined with gas chromatography-flame ionization detector (GC-FID) was developed for the preconcentration and determination of mononitrotoluenes (MNTs) in water samples. In this method, the fine droplets of toluene were formed and dispersed in the sample with the help of ultrasonic waves which accelerated the formation of the fine cloudy solution without using disperser solvents. Several factors influencing the extraction efficiency such as the nature and volume of organic solvent, extraction temperature, ionic strength and centrifugation time were investigated and optimized. Using optimum extraction conditions, dynamic linear ranges of 0.5-500 μg L-1, and limit of detections (LOD) of 0.3 μg L-1 were obtained for o-nitrotoluene, m-nitrotoluene and p-nitrotoluene. Finally, the method was successfully applied to the extraction and determination of MNTs in the water samples in the range of micrograms per liter with relative standard deviations (RSD) < 12%.
Highlights
Isomers of mononitrotoluenes (MNTs) are widely presented in the aquatic environmental due to their vast spread of uses in several industrial and chemical manufacturing applications
An ultrasound-assisted emulsification microextraction (USAEME) based on applying low density organic solvents as a new sample preparation technique was used for the extraction of MNTs from water samples
The selection of a suitable extraction solvent is critical for the USAEME process
Summary
Isomers of mononitrotoluenes (MNTs) are widely presented in the aquatic environmental due to their vast spread of uses in several industrial and chemical manufacturing applications. The cloudy state results from the formation of fine droplets of extraction solvent dispersed in the sample solution. In the USAEME technique, the application of ultrasonic radiation facilitates the emulsification phenomenon and accelerates the mass‐transfer process between two immiscible phases This leads to an increment in the extraction efficiency in a minimum amount of time.[16] this preconcentration technique has been developed by Regueiro et al.,[17] who successfully applied it to determine synthetic musk fragrances, phthalate esters and lindane in aqueous samples. After centrifuging at 3500 rpm for 5 min, the organic solvent droplet was floated on the surface of the aqueous solution due to low density below water. Extraction efficiency / % 1-Octanol 1-Undecanol Toluene 1-Dodecanol o-MNT m-MNT p-MNT aExtraction conditions: extraction solvent volumes: 20.0 μL (1-octanol), 10.0 μL (1-undecanol), 14.0 μL (toluene), 12.0 μL (1-dodecanol); concentration of analytes: 100 μg L-1
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