Comparative efficiency of soxhlet and accelerated solvent extraction (ASE) methods for dioxin/furan analysis in ash samples: A green chemistry perspective

Soxhlet extraction method was developed several hundred years ago, remains the standard method for dioxin/furan extraction today. Accelerated solvent extraction (ASE), a modern technique, was designed to address some of the limitations of Soxhlet extraction, including longer extraction times, excessive solvent use, and limited automation. Fly ash and bottom ash samples collected from an aluminum scrap smelter were analyzed for dioxins and furans using both ASE and Soxhlet methods, followed by analysis on HRGC/HRMS equipment. The TEQ values of PCDD/Fs in the fly ash and bottom ash samples were found to be 3,689 ng TEQ/kg and 13.7 ng TEQ/kg, respectively. The congeners OCDF, OCDD, and 1,2,3,4,6,7,8-HpCDD were the most dominant in the fly ash samples. The recovery efficiency of the spiked 13C isotope standards and native standards, used to assess the extraction efficiency, was high and met the requirements set forth in US EPA 1613b method. Deviations in the results for the 17 dioxin/furan congeners in the fly ash and bottom ash samples extracted by the two methods ranged from -15.5 % to 25.6 % and -15.0 % to 32.9 %, respectively, both of which fall within the acceptable range according to AOAC guidelines for method performance. ASE extraction, performed under high temperature and pressure conditions, yields faster extraction times, reduced solvent usage, enhanced operator safety, lower energy consumption, and higher automation compared to Soxhlet extraction. The green score assessment results using AGREE Prep software indicate that the ASE extraction method is more environmentally friendly and safer than Soxhlet extraction.