Ts. Thompson et Rg. Treble, SOLID-PHASE EXTRACTION AND GC-MS TECHNIQUES FOR THE CONFIRMATION OF CHLORPYRIFOS CONTAMINATION OF SURFACE-WATER SUPPLIES, Bulletin of environmental contamination and toxicology, 57(4), 1996, pp. 525-531
Chlorpyrifos, hyl-O-[3,5,6-trichloro-2-pyridyl]-phosporothioate, is an
organophosphorus insecticide which is used in Saskatchewan to protect
crops from aphids, armyworms, cutworms, diamondback moths, grasshoppe
rs, and wheat midges. It is the active ingredient in the insectide for
mulations known as Dursban and Lorsban. Like other organophosphorus in
secticides, chlorpyrifos primarily affects the human nervous system by
inhibiting the function of the cholinesterase enzyme. In addition to
the central nervous system, the cardiovascular and respiratory systems
are also impacted by exposure to chlorpyrifos. Application of chlorpy
rifos to crops may be performed using either ground or aerial spraying
equipment. In a recent incident in rural Saskatchewan, a landowner cl
aimed that his surface water supply (a dugout) had been contaminated d
uring aerial spraying of his neighbor's crops. Upon inquiry, the claim
ant discovered that the material sprayed contained the formulation Lor
sban. Since this water supply was utilized for drinking purposes (both
human and animal), the landowner requested that his water be tested f
or contamination. Solid phase extraction disks consisting of an inert
membrance impregnated with adsorbents such as octadecylsilane (C18), o
ctylsilane (CX), and styrene-divinylbenzene (SDB) have recently replac
ed liquid-liquid partitioning procedures in numerous analytical method
s. Applications to the determination of pesticides in water samples in
clude chlorinated acid herbicides (Hodgeson 1994), triazine herbicides
(Brouwer 1990), organochlorine insecticides (Tang 1993; Hendriks 1993
), and organophophorus pesticides (Lacorte 1993). SPE disks have been
used for the trace enrichment of various pesticides from river and sea
water samples (Barcelo 1993; Durand 1992; Durand 1993). Beltran(1993)
compared SPE disks and cartridges for use in extracting organochlorine
and organophosphorus pesticides from ground water samples. Chiron and
Barcelo (1993) used SPE disks coupled with on-line HPLC analysis for
the determination of pesticides in drinking water. In a recent study,
SPE disks were used to extract organochlorine and organophosphorus pes
ticides from water samples with subsequent elution using supercritical
fluid extraction (Barnabus 1994). Our laboratory has routinely used s
olid phase extraction techniques combined with GC-MS detection for the
determination of a variety of pesticides in ground and surface water
samples. The methodology used for the analysis of a series of chlorina
ted phenoxyacid herbicides was adapted for use in determining chlorpyr
ifos (Thompson and Morphy 1995).