Determination of Water- and Methanol-Extractable Pentachlorophenol in Soils Using Vortex-assisted Liquid-Liquid Extraction and Gas Chromatography
Abstract An analytical procedure for determination of water- and methanol-extractable pentachlorophenol (PCP) in soils was developed using vortex-assisted liquid-liquid extraction (VALLE) and gas chromatography (GC). Significant extraction parameters such as vortex speed and liquid-liquid volume ratio were optimized for extracting PCP from solution. The recovery of PCP was the highest (97.4%) with good reproducibility and a small relative standard deviation (RSD, 0.5%) when the vortex speed was at 2000 rpm. Meanwhile, when the volume ratio of derivatization solution to n-hexane was at 10:4, the recovery of PCP was 103% with a RSD of 0.7%. The linearity of the calibration curve for PCP determination ranged from 1.25 μg L−1 to 4000 μg L−1, with a correlation coefficient (R2) of 0.9999. The detection limit of PCP in water samples was below 0.2 μg L−1 and the measuring range was relatively wide, and suitable for trace- and micro-analysis of PCP. Compared with traditional extraction methods (liquid-liquid and solid-phase), VALLE consumes less extractant, requires fewer steps, and achieves higher recovery (96.8%) and smaller RSD (3.7%). The reliability of VALLE was verified in four distinct types (paddy, red, black and alluvial) of soil samples spiked with 1 and 10 mg kg−1 PCP. The total recoveries of PCP in the soil samples were in the range of 89.5%–98.9% by water extraction and 88.7%–98.4% by 3 consecutive extractions with methanol in a sequential procedure. The results indicated that VALLE-GC satisfied the requirements for extracting and determining water- and methanol-extractable PCP in soils polluted by PCP at varying levels.