Abstract: The membrane extraction-pre-concentration (MEP) cell consisted of two channels separated by a Celgard 2500 membrane (0.025 mm thick, 45% porosity, 0.04 µm effective pore size). Oil samples diluted with hexane (1:4) were propelled through one channel and the acceptor solution was propelled through the other channel. The acceptor solution was held stationary during the extraction-pre-concentration period while the diluted oil sample was circulated continuously. The MEP cell was coupled online to FIA or HPLC systems for the determination of triazines in vegetable oils. The FIA system used 0.1 M HClO4 as the acceptor solution. At the end of the 5-15 min MEP period, the acceptor solution was propelled to the diode-array spectrophotometer where the total triazines were determined at 220 nm. The calibration graphs were linear (range not given) with detection limits of 0.91 ppm. RSD (n = 10) were 6%. The HPLC system used 5 mM HClO4 in methanol/H2O (9:1) as the acceptor solution. After MEP, the acceptor solution was analyzed on a 5 µm Spheri-5-RP 18 column (25 cm x 4.6 mm i.d.) with 50% aqueous acetonitrile as mobile phase (1.25 ml/min) and detection at 220 nm. Calibration graphs for the determination of atrazine, ametryne, prometryne and terbutryne in corn, sunflower and olive oil were linear for 0.05-20 ppm and the detection limits were ~e;0.1 ppm. RSD (n = 10) were 10%.

Abstract: A two-step procedure was used to optimize instrumental parameters in the cited techniques (details given). Surface or drinking water (3-5 mL) was injected into a carrier solution (1.5 ml/min) of 0.1 M ammonium acetate/acetonitrile (9:1) and analyzed by MS with a thermospray interface at vaporizer and source block temperature 105 and 200°C, respectively. The parent ion intensities were obtained in the single-scan Q3-MS scan mode and daughter ions after collision with Ar at 3-4 mTorr and collision offset voltage l8 and 22 eV, respectively, for phenoxyacid herbicides and bentazone (I). Multiple-reaction monitoring was used with monitoring of two parent ion-daughter ion pairs for the phenoxyacids and one parent and three daughter ions for I (m/e values given). Calibration graphs were linear for 50 µg/l of each analyte with detection limits of 0.2 µg/l for 2,4,5-(trichlorophenoxy)propionic acid to 0.8 µg/l for 2,4,5-(trichlorophenoxy)acetic acid. The method was fully automated with a sample analysis time of 10 min. Results obtained agreed well with those of LC with UV detection.