Solid‐phase extraction of pesticides from surface water using discs, bulk sorbents and supercritical fluid extraction (SFE)

Abstract

Extraction of pesticides from river water samples using the classical liquid‐liquid extraction (LLE) approach is a labour‐intensive procedure that requires relatively large volumes of solvent. With the solid‐phase extraction (SPE) technique using membranes, the volumes of solvent are reduced. However, it is necessary to pre‐filter and often also to acidify the river water to pH < 2 to prevent plugging of the capillary pores. This low pH may decompose some pesticides and therefore a fast and inexpensive technique with bulk sorbent and without prefiltration and acidification was developed. To reduce the solvent volumes further, extractions of discs and bulk sorbent were performed with supercritical fluids (SF). Seven pesticides with different polarities were studied. Mean recoveries from the bulk sorbent and the discs were of the same order (61%). However, recoveries from the latter improved to 82% with SFE of the discs, providing results comparable to LLE (94%) recovery.

Supercritical Fluid Chromatography and Extraction

“…Ho and Budde also used the combined SPE disk-SFE approach to monitor rotenone levels in natural river waters (504). The low pH necessary for the SPE of some pesticide/sorbent combinations may degrade some sensitive pesticides (505). The use of bulk sorbents and SFE alleviated the acidification problem.…”

Supercritical fluid extraction strategies of liquid-based matrices

“…Bengtsson et al [54] have described a procedure involving the use of loose CIS sorbent held on a glass-fibre filter disc placed within the filtration apparatus for the rapid extraction of pesticides from river water prior to SFE. The method does not require sample prefiltration or acidification to prevent plugging.…”

“…A heated stainless-steel restrictor was used by Bengtsson et at. [54] which prevented freezing, although a two-phase system formed in the collection vial containing cyclohexane as pesticide-trapping solvent. To prevent phase separation, a methanol/acetone mixture was used for analyte trapping.…”

Method for the Analysis of Triadimefon and Ethofumesate from Dislodgeable Foliar Residues on Turfgrass by Solid-Phase Extraction and In-Vial Elution

“…Others have evaluated the use of Empore disks for the extraction of pesticide residues and other pollutants from water (Hagen et al, 1990;Davı `et al, 1992;Viana et al, 1996;Bengtsson et al, 1994;McDonnell and Rosenfeld, 1993). One reported advantage of using Empore disks for SPE is that they have a greater crosssectional area than SPE cartridges, resulting in reduced plugging.…”

“…Because Empore disks have a small pore size, researchers have often found it necessary to use a prefilter when loading samples containing organic matter or suspended particulates to avoid clogging of the disks. This has been successfully achieved by acidifying the water (Davı `et al, 1992), placing prefilters directly on top of Empore disks (Markell et al, 1991;McDonnell and Rosenfeld, 1993;Bengtsson et al, 1994), or by prefiltering water samples and loading the filtrate onto Empore disks (McDonnell and Rosenfeld, 1993;Field et al, 1997).…”