PARENT SESSION
PS12 - Applications of LC-MS in Environmental Analysis
Sunday, 17 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P128) Determination of Phenoxy Acid Herbicides in Water and Sediments by LLE and SBSE using Electrospray Ionization Mass Spectrometry (ESI-LC/MS) .

Arroyo, Luis^*,1, Gardinali, Piero¹, ¹ Florida International University, Department of Chemistry / SERC, Miami, Florida, USA

ABSTRACT- A sensitive and specific analytical procedure for determining twelve different herbicides in aqueous and sediment samples from Everglades and Biscayne Bay National Parks, using pneumatic assisted electrospray (ESI) liquid chromatography-mass spectrometry (LC/MS) is presented. The analytes of interest were bentazon, picloram, acifluorfen and the phenoxy-acid herbicides: 2,4-D; MCPA, Dicamba, MCPP, Dichlorprop, 2,4-DB, 2,4,5-T, Silvex, and Dinoseb. Target compounds were analized using a Finnigan Navigator aQa mass spectrometer in the SIR mode. The ESI source was operated in negative mode (ESI-), at 300 °C with an optimized cone voltage of 15 V. The HPLC sepatration was achieved with a Zorbax XDB C18 Column (250 x 4.6 mm x 5 m) using MeOH and HOAc 1% as phase modifier. A gradient elution from 75:25 (MeOH:HOAC 1%) to 82:18 was used for a total run time of 25 minutes. A linear response for the quantitation (r2=0.99 or better) was obtained at the concentrations of interest using 2,4-diclorophenoxy-acetic-acid as internal standard. The limit of detection (LODs) for the aforementioned herbicides in spiked water and sediments were structure dependent and ranged from 10 ng/L to 150 ng/L. Two different extractions procedures were used to evaluate and compare the recovery of the pesticides studied: LLE and a Stir Bar Sorptive Extraction (SBSE). For LLE in water samples the recoveries for the phenoxy acids ranged from 60 % to 98 % and for bentazon, picloram and aciflourfen were 60 %, 30% and 100 % respectively. In sediments the recoveries ranged from 25% to 95 %. The use of a PDMS coated stir bar showed similar recoveries ranges while providing the advantages reducing the use of extraction solvents and processing time.

Key words: Herbicides, ESI-, LC/MS, Sedmients and Water