Multiresidue Determination of Pesticides in Drinking and Related Waters by Solid-Phase Extraction and Liquid Chromatography with Ultraviolet Detection: Interlaboratory Study

As part of a project funded by the European Commission (EC) for the development and evaluation of multiresidue methods for analysis of drinking and related waters, 17 European laboratories evaluated a method using styrene–divinylbenzene copolymer solid-phase extraction followed by liquid chromatography with diode array detection. The main aim of the study was to evaluate whether the method meets the requirements of EC Drinking Water Directive 98/83 in terms of accuracy, precision, and detection limit for 21 pesticides according to the following requirements: limit of detection, ≤0.025 μg/L; accuracy expressed as recovery, between 75 and 125%; and precision expressed as repeatability relative standard deviation of the method, <12.5%, and as reproducibility relative standard deviation of the method, <25%. Analyses for unknown concentrations were performed with commercial bottled and tap waters. All laboratories were able to achieve detection limits of 0.01 μg/L for all pesticides except pirimicarb (0.02 μg/L). The criteria for repeatability were met for all compounds. Terbutryn in bottled water and carbendazim in tap water did not meet the criteria for reproducibility. In terms of accuracy, the method met the requirements for all pesticides in both matrixes, except for metamitron. However, several compounds (linuron, terbutryn, propazine, metobromuron, and isoproturon) showed recoveries slightly below 75%.

Optimization of stir bar sorptive extraction applied to the determination of odorous compounds in drinking water

The off-flavour compounds 2-methylisoborneol (MIB), geosmin, 2,4,6-trichloroanisole, 2,3,6-trichloroanisole, 2,3,4-trichloroanisole and 2,4,6-tribromoanisole were analyzed in water samples by Stir Bar Sorptive Extraction (SBSE) followed by on-line thermal desorption (TD)-capillary GC/MS. Quantification was performed using MS in the single ion monitoring mode (SIM) with 2,4,6-trichloroanisol-D5 as internal standard. Quantification limits are 0.1 ng/l to 0.2 ng/l for the haloanisoles, 0.5 ng/l for geosmin and 1 ng/l for MIB. The relative standard deviations at the quantification limit are ranging from 7 to 14.6%. SBSE-recovery was evaluated by spiking real water samples and varied from 87 to 117%. More than twenty samples per day can be analyzed by SBSE-TD-capillary GC-MS. The same technique in combination with olfactometry was used to elucidate unknown odorous compounds in water samples.

Analysis of off-flavors in the aquatic environment by stir bar sorptive extraction-thermal desorption-capillary GC/MS/olfactometry

The off-flavor compounds 2-methylisoborneol (MIB), geosmin, 2,4,6-trichloroanisole, 2,3,6-trichloroanisole, 2,3,4-trichloroanisole, and 2,4,6-tribromoanisole were analyzed in water samples by stir bar sorptive extraction (SBSE) followed by on-line thermal desorption (TD) capillary GC/MS. Quantification was performed using the MS in the single-ion-monitoring mode (SIM) with 2,4,6-trichloroanisole-D(5 )as internal standard. Quantification limits are 0.1-0.2 ng L(-1) for the haloanisoles, 0.5 ng L(-1) for geosmin, and 1 ng L(-1) for MIB. The relative standard deviations at the quantification limit ranged from 7 to 14.6%. SBSE recovery was evaluated by spiking real water samples and varied from 87 to 117%. More than twenty samples per day can be analyzed by SBSE-TD-capillary GC-MS. The same technique in combination with olfactometry was used to elucidate unknown odorous compounds in water samples.