Intercomparison among SFE, ASE, Soxhlet and sonication for the trialkylamine determination in sediment and sludge

Accelerated solvent extraction (ASE) and supercritical fluid extraction (SFE) have been compared to Soxhlet and sonication extraction procedures for the determination of long-chain trialkylamines (CH3NR1R2 where R-1 and R-2 = C14H29, C16H33 or C18H37) in Sediment and sludge. An hybrid experimental design was applied for the first time to the optimization of temperature and modifier composition for the SFE of incurred trialkylamines from marine sediment and primary sewage sludge. SFE at 50 degrees C and 30 MPa with CO2 modified dynamically with MeOH and statically with triethylamine yielded concentrations of incurred TAMs 10-77% higher than Soxhlet or sonication (3 extractions) with dichloromethane-methanol mixture (2:1). However, the ASE technique with the same extraction mixture at 150 degrees C and 17 MPa showed the highest extraction efficiency among the extraction methods evaluated. The precision improvement in SFE was attributed to the direct analysis of extracts by GC-NPD without any cleanup step whereas Soxhlet, sonication and ASE extracts required an alumina cleanup prior to their determination. Furthermore, analysis time in SFE and ASE techniques is reduced by a factor of 3 and 20 compared to sonication and Soxhlet extraction, respectively. Solvent usage in both ASE and SFE is reduced.