Development of a safer and improved analytical method for polycyclic aromatic hydrocarbons in creosote products

Polycyclic aromatic hydrocarbons (PAHs) in creosote products used for wood preservation are regulated in Japan. Although the analytical method for this regulation has been stipulated by law, two main problems have been highlighted, namely the use of dichloromethane, a potential carcinogen, as a solvent and inadequate purification. Therefore, an analytical method to solve these problems was developed in this study. Actual creosote-treated wood samples were examined, and it was found that acetone could be used as an alternative solvent. Purification methods using centrifugation, silica gel cartridges, and strong anion exchange (SAX) cartridges were also developed. It was found that the SAX cartridges strongly retained PAHs, and an effective purification method was developed using this phenomenon, in which contaminants were removed by washing with diethyl ether/hexane (1/9 v/v), which could not be achieved with a silica gel cartridge. This strong retention was attributed to cation-π interactions. The analytical method developed in this study yielded good recoveries (81.4-113.0%) with low relative standard deviations (<6.8%), and the limit of quantification (0.02-0.29 µg/g) was significantly lower than the current creosote product regulation. Therefore, this method can safely and effectively extract and purify PAHs from creosote products.