Optimization and validation of a new method for analysis of linear alkylbenzene sulfonates in sewage sludge by liquid chromatography after microwave-assisted extraction

摘要

A new approach has been developed for the monitoring of linear alkylbenzene sulfonates (LAS) (C_(10)-C_(13)) in sewage sludge.It is based on microwave-assisted extraction (MAE) prior to high performance liquid chromatography coupled with diode array (HPLC-DAD) and fluorescence (HPLC-FL) detectors.Column Zorbax XDB-C8,150 mm x 4.6 mm i.d.,5 pjn particle size was used as well as acetonitrile-water containing 0.1 M NaC1O4 (65:35) and isocratic elution.Compounds were isocratically eluted over 6min runtime at a flow rate of 1 mLmin~(-1).Since polar interferences are eluted between 0 and 2 min,they do not interfere in the analysis.The column was thermostated at a temperature of 25 °C.For the determination of LAS,DAD-UV (lambda_(ex)=225 nm) and fluorescence (lambda_(ex)=225 nm,lambda_(em)=295 run) detectors were employed.The main factors affecting the extraction efficiency (extractant volume,microwave power and irradiation time) were optimized using a compost sludge.The detection limit for total LAS in the sludge was <5 mg kg~(-1).The extraction of C_(10)-C_(13) homologues is carried out by using an extraction time of 10 min and 5 mL of methanol;whereas Soxhlet needs a 12 h extraction.The method did not require clean-up or preconcentration steps.Concentration levels of LAS were between 13037 mg kg~(-1) for digested sludge and 2492 mg kg~(-1) for compost sludge.