Dispersive liquid-liquid microextraction (DLLME) coupled with high-performance liquid
chromatography-variable wavelength detector (HPLC-VWD) was developed for extraction
and determination of chloramphenicol (CAP) and thiamphenicol (THA) in honey. In this
extraction method, 1.0 mL of acetonitrile (as dispersive solvent) containing 30 microL
1,1,2,2-tetrachloroethane (as extraction solution) was rapidly injected by syringe
into a 5.00-mL water sample containing the analytes, thereby forming a cloudy solution.
After extraction, phase separation was performed by centrifugation and the enriched
analytes in the sedimented phase were determined by HPLC-VWD. Some important parameters,
such as the nature and volume of extraction solvent and dispersive solvent, extraction
time, sample solution pH, sample volume and salt effect were investigated and optimized.
Under the optimum extraction condition, the method yields a linear calibration curve
in the concentration range from 3 to 2000 microg kg(-1) for target analytes. The enrichment
factors for CAP and THA were 68.2 and 87.9, and the limits of detection (S/N=3) were
0.6 and 0.1 microg kg(-1), respectively. The relative standard deviations (RSDs) for
the extraction of 10 microg kg(-1) of CAP and THA were 4.3% and 6.2% (n=6). The main
advantages of DLLME-HPLC method are simplicity of operation, rapidity, low cost, high
enrichment factor, high recovery, good repeatability and extraction solvent volume
at microliter level. Honey samples were successfully analyzed using the proposed method.