Dispersive liquid–liquid microextraction method based on solidification of floating organic droplet for the determination of thiamphenicol and florfenicol in environmental water samples

• DLLME-SFO combined with HPLC-UV was used for determination of thiamphenicol (TAP) and florfenicol (FF) in water samples.
• The method provided good repeatability and extraction recoveries and high enrichment factors.
• The new method reduced the use of toxic extraction solvents.

Dispersive liquid–liquid microextraction with solidification of a floating organic droplet (DLLME-SFO) followed by high performance liquid chromatography-ultraviolet (HPLC-UV) detection was applied for the determination of thiamphenicol (TAP), florfenicol (FF) in water samples. 1-Undecanol was used as the extraction solvent which has lower density than water, low toxicity, and low melting point (19 °C). A mixture of 800 mL acetone (disperser solvent) and 80 µL of 1-undecanol (extraction solvent) was injected into 20 mL of aqueous solution. After 5 min, 0.6 g of NaCl was added and the sample vial was shaken. After 5 min, the sample was centrifuged at 3500 rpm for 3 min, and then placed in an ice bath. When the extraction solvent floating on the aqueous solution had solidified, it was transferred into another conical vial where it was melted quickly at room temperature, and was diluted with methanol to 1 mL, and analyzed by HPLC-UV detection. Parameters influencing the extraction efficiency were thoroughly examined and optimized. The extraction recoveries (ER) and the enrichment factors (EF) ranged from 67% to 72% and 223 to 241, respectively. The limits of detection (LODs) (S/N=3) were 0.33 and 0.56 µg L−1 for TAP and FF, respectively. Linear dynamic range (LDR) was in the range of 1.0–550 µg L−1 for TAP and 1.5–700 µg L−1 for FF, the relative standard deviations (RSDs) were in the range of 2.6–3.5% and the recoveries of spiked samples ranged from 94% to 106%.