Development of a dispersive liquid–liquid microextraction method with a new sequence of steps and its comparison with a conventional method

Abstract

In this paper, a dispersive liquid-liquid microextraction method with a new sequence of steps from the view of salt addition has been developed for the extraction and preconcentration of some organophosphorous pesticides from aqueous samples before analysis by gas chromatography with flame ionization detection. In this method, an appropriate mixture of extraction and disperser solvents is rapidly injected by a syringe into the aqueous sample. Then, sodium chloride is added into the solution to increase its ionic strength. The obtained results by the proposed method are compared with those of the conventional dispersive liquid-liquid microextraction in which the salt is added into the aqueous phase before dispersion of the extraction solvent. Some effective parameters on the method efficiency including type and volume of extraction and disperser solvents, type and percent of salt, etc. are investigated. Under the optimal conditions, limits of detection and quantification of the proposed method compared to conventional one were improved by a factor between 1.4-2.2 and 1.3-2.3, respectively. Extraction recoveries and enrichment factors of the proposed method with respect to conventional one enhanced from 43-60 to 72-99% and 1433-2000 to 2404-3285, respectively.

Salt‐assisted dispersive liquid–liquid microextraction for enhancing the concentration of matrine alkaloids in traditional Chinese medicine and its preparations

“…The effects of experimental variables on the EFs of target analytes, such as the type and the volume of extraction solvent, the pH and the volume of sample phase, salt concentration, and extraction time, were investigated and optimized in the test. EF is defined as the ratio between the analyte concentration in the extraction phase ( C o ) and the initial sample solution ( C 0 ): …”

Deep eutectic solvent based gas-assisted dispersive liquid-phase microextraction combined with gas chromatography and flame ionization detection for the determination of some pesticide residues in fruit and vegetable samples

“…However, these methods have some disadvantages such as (a) the use of relatively expensive and fragile fibers, and also occurrence of sample carryover in SPME; (b) organic drop instability and possibility of air bubble formation in single‐drop microextraction; (c) requirement of long extraction time in hollow‐fiber LPME; and (d) the use of relatively high volume of a disperser solvent in conventional DLLME methods, which leads to reduced extraction efficiency, and the use of hazardous solvents such as halogenated hydrocarbons in the vast majority of them . Compared to the other microextraction methods mentioned above, DLLME results in significantly reduced extraction times is simpler and in most cases offers higher extraction efficiencies . To overcome the drawbacks of DLLME, significant efforts have been made to perform the extraction in the absence of disperser solvent and replace the halogenated solvents with more environmentally friendly ones.…”

Development of a novel hollow-fiber liquid-phase microextraction based on oil-in-salt and its comparison with conventional one

“…Farajzadeh et al. developed a dispersive liquid–liquid microextraction with a new sequence of steps from the view of salt addition to extract and preconcentrate some organophosphorous pesticides from aqueous samples before analysis by GC, in which the authors thought that salt effect is more effective when salt is added into the sample solution after dispersion of extraction solvent than before. Recently, Gao et al.…”

“…Fiorini et al [16] improved the efficiency of the headspace solid-phase microextraction of short and medium chain free fatty acids through a salting-out system; Wen et al [17] used the salting-out assisted liquid-liquid extraction with HPLC to determine the benzimidazole fungicides in high-salinity samples; Liu et al [18] developed a saltingout homogeneous extraction combined with ionic liquid/ionic liquid dispersive liquid-liquid microextraction and used it to analyze sulfonamides in blood. Farajzadeh et al [19] developed a dispersive liquid-liquid microextraction with a new sequence of steps from the view of salt addition to extract and preconcentrate some organophosphorous pesticides from aqueous samples before analysis by GC, in which the authors thought that salt effect is more effective when salt is added into the sample solution after dispersion of extraction solvent than before. Recently, Gao et al [20] proposed an oil-insalt liquid-phase microextraction (LPME) on permutite and introduced it, with HPLC, for the enrichment and determination of alkaloids in Coptis chinensis.…”