Examination of Analytical Method for Polycyclic Aromatic Hydrocarbons in Creosote Products to Revise the Official Methods Based on “Act on the Control of Household Products Containing Harmful Substances”

Creosote, a derivative of coal tar, is used as a wood preservative. In Japan, regulations govern three specific polycyclic aromatic hydrocarbons (PAHs) present in creosote and creosote-treated wood: benzo[a]pyrene, benz[a]anthracene, and dibenz[a,h]anthracene. However, the existing standardized analytical methods in Japan have raised concerns regarding the safety of reagents employed and insufficient purification processes. To overcome these challenges, we developed an analytical method incorporating effective purification techniques, such as centrifugation, silica gel cartridges, and anion exchange cartridges, while eliminating the use of potentially carcinogenic dichloromethane. The validity of this method was evaluated through interlaboratory collaborative tests involving seven institutions. The analysis focused on 10 PAHs, including the three compounds regulated in Japan, across three concentration levels that encompassed current regulatory values. Validation results demonstrated that the method met the trueness and repeatability criteria, established at 70-120% and <10%, respectively. Most reproducibility data satisfied the <15% requirement. Exceptions were observed for two non-regulated compounds in Japan, as well as for samples with high matrix components spiked with the low concentrations of target analytes. The inherent difficulty of analyzing trace compounds in complex matrix components likely contributed to these unsatisfactory results. Despite these limitations, the developed method was validated as suitable for the analysis of at least three regulated PAHs in Japan.