Comparison of simplified methods for pesticide residue analysis. Use of large-volume injection in capillary gas chromatography.
The combination of manual and automated extraction procedures using low sample volumes (5-50 ml) with large-volume oncolumn injection (LVI) (200 microliters) in capillary gas chromatography with flame photometric detection (GC-FPD) has allowed the determination of 16 organophosphorus pesticides in clean water samples at the low ng l-1 level with an important simplification in the sample preparation step. A simple and fast offline liquid-liquid microextraction procedure (2-5 ml water/l ml methyl tert.-butyl ether) has been applied to spiked groundwater samples (containing 0.5 ng of each pesticide) with good recoveries (over 80%) and precision (better than 10%), giving detection limits between 5 and 100 ng l-1 using 200 microliters injections in the GC-FPD system. The application of an inline automated liquid-liquid microextraction-LVI-GC procedure (2 ml water/2 ml methyl tert.-butyl ether: injection of 200 microliters in GC-FPD) using the autosampler ASPEC XL led to lower recoveries (> 50%) as a result of the low efficiency for mixing organic and aqueous phases, although with very satisfactory coefficients of variation (lower than 7%) and detection limits between 20 and 200 ng l-1. Manual and automated solid-phase extraction procedures using the well known C18 cartridges and the new Oasis HLB have been applied to groundwater samples (5-50 ml) spiked with 1 ng of each pesticide. Results obtained for both the manual and the automated procedures were satisfactory (recoveries over 80%) and the limits of detection for 50 ml sample volume ranged from 1 to 6 ng l-1.
López
F J
FJ
Experimental Science Department, University Jaume I, Castelló, Spain.
Beltran
J
J
Forcada
M
M
Hernández
F
F
D001322:Autoanalysis; D002849:Chromatography, Gas / Q000379:methods*; D004784:Environmental Monitoring; D007306:Insecticides / Q000032:analysis*; D008738:Methyl Ethers; D009943:Organophosphorus Compounds; D010573:Pesticide Residues / Q000032:analysis*; D012680:Sensitivity and Specificity; D012997:Solvents; D014867:Water / Q000032:analysis*
D007306:Insecticides; D008738:Methyl Ethers; D009943:Organophosphorus Compounds; D010573:Pesticide Residues; D012997:Solvents; D014867:Water; C043243:methyl tert-butyl ether