A new model of fast and convenient liquid–liquid–liquid microextraction (LLLME), combining low-density solvent-based solvent-demulsification dispersive liquid–liquid microextraction (LDS-SD-DLLME) and single drop microextraction (SDME), was introduced to separate sulfonamides from environmental water samples for the first time. The extraction procedure includes a 2 min LDS-SD-DLLME fore extraction and a 15 min SDME back-extraction. A mixture of an extraction solvent (1-octanol) and disperser solvent (methanol) was rapidly injected into the aqueous sample to form an emulsion for pre-extraction. Then a demulsifier solvent (acetonitrile) was injected into the extraction system. The emulsion turned clear in a few seconds and a layer of the organic phase formed at the top of the aqueous phase. Finally, a drop of acceptor solution was introduced into the upper layer and SDME was carried out for the back-extraction. The whole procedure does not need any electric equipment (centrifuge, stirrer or ultrasonic cleaner) because the centrifugation in DLLME and the stirring step typically involved in SDME and LLLME are avoided by the successful coupling of LDS-SD-DLLME and SDME. Four sulfonamides were first transferred from the donor phase to the organic phase by the LDS-SD-DLLME pre-extraction and then back-extracted into the acceptor droplet directly suspended in the upper layer of the organic phase. Factors affecting extraction efficiency were studied, including the organic solvent, the disperser solvent, the demulsifier solvent, the composition of the donor phase and acceptor phase, and the extraction time. Under optimal conditions, the method showed a low detection limit (0.22–1.92 μg L−1) for the four sulfonamides, and good linearity (from 1.0–500 to 10–500 μg L−1, depending on the analytes) and repeatability (RSD below 4.6%, n = 3). The simple, fast, and efficient feature of the proposed method was demonstrated by the analysis of sulfonamides in lake water, fishery water and wastewater samples.

A simple and fast method of low-density extraction solvent-based solvent terminated dispersive liquid–liquid microextraction (ST-DLLME) was developed for the highly sensitive determination of carbamate pesticides in the water samples by gas chromatography-tandem mass spectrometry (GC-MSMS). After dispersing, the obtained emulsion cleared into two phases quickly when an aliquot of acetonitrile was introduced as a chemical demulsifier into the aqueous bulk. Therefore, the developed procedure does not need centrifugation to achieve phase separation. It was convenient for the usage of low-density extraction solvents in DLLME. Under the optimized conditions, the limits of detection for all target carbamate pesticides were in range of 0.001–0.50 ng mL−1 and the precisions were in the range of 2.3–6.8% (RSDs, 2 ng mL−1, n = 5). The proposed method has been successfully applied to the analysis of real water samples and good spiked recoveries over the range of 94.5–104% were obtained.

A novel method of ultrasonic probe-assisted ionic liquid dispersive liquid–liquid microextraction combined with electrothermal atomic absorption spectrometry (ETAAS) was developed for the determination of chromium(VI) species in water samples. In this procedure, the hydrophobic chelate of chromium(VI) with ammonium pyrrolidinedithiocarbamate (APDC) was extracted into the fine droplets of 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF6]), which was dispersed into the aqueous sample solution by ultrasonication using an ultrasonic probe. Several variables such as the volume of [Hmim][PF6], sample pH, concentration of APDC, and extraction time were investigated in detail. Under the optimum conditions, the limit of detection of the proposed method was 0.07 ng mL−1 for Cr(VI) and the relative standard deviation for five-replicated determination of 2.0 ng mL−1 Cr(VI) was 9.2%. The proposed method has been also successfully applied to the determination of chromium(VI) species in lake and tap water samples.

A new method was developed for the determination of cadmium in water samples using ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction (IL-based USA-DLLME) followed by electrothermal atomic absorption spectrometry (ETAAS). The IL-based USA-DLLME procedure is free of volatile organic solvents, and there is no need for a dispersive solvent, in contrast to conventional DLLME. The ionic liquid, 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF6), was quickly disrupted by an ultrasonic probe for 1 min and dispersed in water samples like a cloud. At this stage, a hydrophobic cadmium–DDTC complex was formed and extracted into the fine droplets of HMIMPF6. After centrifugation, the concentration of the enriched cadmium in the sedimented phase was determined by ETAAS. Some effective parameters of the complex formation and microextraction, such as the concentration of the chelating agent, the pH, the volume of the extraction solvent, the extraction time, and the salt effect, have been optimized. Under optimal conditions, a high extraction efficiency and selectivity were reached for the extraction of 1.0 ng of cadmium in 10.0 mL of water solution employing 73 µL of HMIMPF6 as the extraction solvent. The enrichment factor of the method is 67. The detection limit was 7.4 ng L− 1, and the characteristic mass (m0, 0.0044 absorbance) of the proposed method was 0.02 pg for cadmium (Cd). The relative standard deviation (RSD) for 11 replicates of 50 ng L− 1 Cd was 3.3%. The method was applied to the analysis of tap, well, river, and lake water samples and the Environmental Water Reference Material GSBZ 50009-88 (200921). The recoveries of spiked samples were in the range of 87.2–106%.