Solid-phase extraction of polar pesticides from environmental water samples on graphitized carbon and Empore-activated carbon disks and on-line coupling to octadecyl-bonded silica analytical columns.
The suitability of Empore-activated carbon disks (EACD), Envi-Carb graphitized carbon black (GCB) and CPP-50 graphitized carbon for the trace enrichment of polar pesticides from water samples was studied by means of off-line and on-line solid-phase extraction (SPE). In the off-line procedure, 0.5-2 l samples spiked with a test mixture of oxamyl, methomyl and aldicarb sulfoxide were enriched on EnviCarb SPE cartridges or 47 mm diameter EACD and eluted with dichloromethane-methanol. After evaporation, a sample was injected onto a C18-bonded silica column and analysed by liquid chromatography with ultraviolet (LC-UV) detection. EACD performed better than EnviCarb cartridges in terms of breakthrough volumes (> 2 l for all test analytes), reproducibility (R.S.D. of recoveries, 4-8%, n = 3) and sampling speed (100 ml/min); detection limits in drinking water were 0.05-0.16 microgram/l. In the on-line experiments, 4.6 mm diameter pieces cut from original EACD and stacked onto each other in a 9 mm long precolumn, and EnviCarb and CPP-50 packed in 10 x 2.0 mm I.D. precolumn, were tested, and 50-200 ml spiked water samples were preconcentrated. Because of the peak broadening caused by the strong sorption of the analytes on carbon, the carbon-packed precolumns were eluted by a separate stream of 0.1 ml/min acetonitrile which was mixed with the gradient LC eluent in front of the C18 analytical column. The final on-line procedure was also applied for the less polar propoxur, carbaryl and methiocarb. EnviCarb could not be used due to its poor pressure resistance. CPP-50 provided less peak broadening than EACD: peak widths were 0.1-0.3 min and R.S.D. of peak heights 4-14% (n = 3). In terms of analyte trapping efficiency on-line SPE-LC-UV with a CPP-50 precolumn also showed better performance than when Bondesil C18/OH or polymeric PLRP-S was used, but chromatographic resolution was similar. With the CPP-50-based system, detection limits of the test compounds were 0.05-1 microgram/l in surface water.
Slobodník
J
J
Free University, Department of Analytical Chemistry, Amsterdam, Netherlands.
Oztezkizan
O
O
Lingeman
H
H
Brinkman
U A
UA
D000327:Adsorption; D000448:Aldicarb / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry; D002219:Carbamates / Q000032:analysis / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000295:instrumentation / Q000379:methods; D007306:Insecticides / Q000032:analysis / Q000737:chemistry*; D008714:Methiocarb / Q000032:analysis / Q000737:chemistry; D008724:Methomyl / Q000032:analysis / Q000737:chemistry; D009862:Online Systems; D001074:Propoxur / Q000032:analysis / Q000737:chemistry; D015203:Reproducibility of Results; D012822:Silicon Dioxide / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry*; D014877:Water Pollution, Chemical / Q000032:analysis*
D002219:Carbamates; D007306:Insecticides; D014867:Water; D008724:Methomyl; D002244:Carbon; D012822:Silicon Dioxide; C030579:aldicarb sulfoxide; D000448:Aldicarb; D001074:Propoxur; D008714:Methiocarb; C011960:oxamyl