Determination of booster biocides in sediments by focused ultrasoundassisted extraction and stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

Abstract

Booster biocides present in natural waters may be captured by the sediments. Highly sensitive, robust, selective and reliable analytical methods are required to evaluate their presence in the sediments. A focused ultrasound assisted extraction method for the simultaneous determination of five organic booster biocides (Chlorothalonil, Dichlofluanid, Sea-Nine 211, Irgarol 1051 and TCMTB) in marine sediments is proposed. The isolation of the target compounds from 0.5 g of sediment was efficient using 2.5 mL of methanol as solvent, an output amplitude of 50 W, 100% duty cycle and an extraction time of 300 s. The extraction procedure was followed by solid-phase clean-up on non-polar sorbents (Oasis HLB). The compounds were sampled using stir bars (20 mm length, 0.5 mm film thickness) coated with polydimethylsiloxane (PDMS). The stir bars were stirred at 900 rpm for 3 hours at room temperature. Desorption was carried out by thermal desorption (TD), and the analytes were separated in the gas chromatography (GC). They were detected by triple quadrupole mass spectrometry (MS/MS) using the multiple reaction monitor (MRM) mode. The detection limits (DLs) of booster biocides were in the range of 0.02 to 2.2 ng g-1 dry weight. The regression coefficients were higher than 0.999. The average recovery was higher than 86% (R.S.D.: 7–15%). The analytical procedure was applied to determination of the booster biocides in port sediment samples from the southwestern Spain. Sea-Nine 211 was found in one sediment at a level of 2.1 ng g-1. Irgarol was present in all the sediments at concentrations between 2 and 9 ng g-1.