Rapid Analytical Methods to Measure Pentachlorophenol in Wood

Pentachlorophenol (PCP) was measured in wood following extraction with methanol:0.1% acetic acid. The extract was derivatized with acetic anhydride in a biphasic solvent containing toluene and 0.1 M Na₂CO₃ (pH 11.4), and pentachlorophenyl acetate was quantitated by gas chromatography - mass spectrometry (GC - MS) using [¹³C₆]PCP as an internal standard. A second detection method employed thin layer chromatography (TLC) after nitric acid-mediated oxidation of PCP to tetrachloro-1,4-benzoquinone. The third method was by colorimetry and required a liquid - liquid partitioning of PCP under acidic and alkaline pH against toluene. Then, PCP was coupled to 4-aminoantipyrine in the presence of sodium persulfate to form a dye which was measured at 580 nm. The limit of detection approached 50 ppb by GC - MS and 1 ppm by TLC when 100 mg of wood was used for analysis and 1 ppm for the colorimetric method when 1 g of wood was used for detection. The estimates of PCP were comparable for all three methods.