Calibration of a passive sampling device for time-integrated sampling of hydrophilic herbicides in aquatic environments

Two types of solid-phase materials, a styrenedivinylbenzene copolymer sorbent (embedded in a SDB-XC Empore™ disk) and a styrenedivinylbenzene copolymer sorbent modified with sulfonic acid functional groups (embedded in a SDB-RPS Empore disk), were compared as a receiving phase in a passive sampling device for monitoring polar pesticides. The SDB-XC Empore disk was selected for further evaluation, overlayed with either a polysulfone or a polyethersulfone diffusion membrane. The target herbicides included five nonionized herbicides (simazine, atrazine, diuron, clomazone, and metolachlor) and four phenoxy acid herbicides (dicamba, (2,4-dichlorophenoxy)acetic acid [2,4-D], (4-chloro-2-methylphenoxy)acetic acid [MCPA], and triclopyr) with log octanol/water partition coefficient (log KOW) values of less than three in water. Uptake of these herbicides generally was higher into a device constructed of a SDB-XC Empore disk as a receiving phase covered with a polyethersulfone membrane compared to a similar device covered with a polysulfone membrane. Using the device with a SDB-XC Empore disk covered with a polyethersulfone membrane, linear uptake of simazine, atrazine, diuron, clomazone, and metolachlor was observed for up to 21 d, and daily sampling rates of the herbicides from water in a laboratory flow-through system were determined. The uptake rate of each nonionized herbicide by the Empore disk-based passive sampler was linearly proportional to its concentration in the water, and the sampling rate was independent of the water concentrations over the 21-d period. Uptake of the phenoxy acid herbicides (2,4-D, MCPA, and triclopyr) obeyed first-order kinetics and rapidly reached equilibrium in the passive sampler after approximately 12 d of exposure. The Empore disk-based passive sampler displayed isotropic kinetics, with a release half-life for triclopyr of approximately 6 d. © 2007 SETAC

Determination of commonly used polar herbicides in agricultural drainage waters in Australia by HPLC

The present study describes the application of different extraction techniques for the preconcentration of ten commonly found acidic and non-acidic polar herbicides (2,4-D, atrazine, bensulfuron-methyl, clomazone, dicamba, diuron, MCPA, metolachlor, simazine and triclopyr) in the aqueous environment. Liquid-liquid extraction (LLE) with dichloromethane, solid-phase extraction (SPE) using Oasis® HLB cartridges or SBD-XC EmporeTM disks were compared for extraction efficiency of these herbicides in different matrices, especially water samples from contaminated agricultural drainage water containing high concentrations of particulate matter. Herbicides were separated and quantified by high performance liquid chromatography (HPLC) with an ultraviolet detector. SPE using SDB-XC EmporeTM disks was applied to determine target herbicides in the Murrumbidgee Irrigation Area (NSW, Australia) during a two-week survey from October 2005 to November 2005. The daily aqueous concentrations of herbicides from 24-h composite samples detected at two sites increased after run-off from a storm event and were in the range of: 0.1-17.8 μg l-1, <0.1-0.9 μg l-1 and 0.2-17.8 μgl-1 at site 1; <0.1-3.5 μg l-1, <0.1-0.2 μgl-1 and <0.2-3.2 μg l-1 at site 2 for simazine, atrazine and diuron, respectively. Crown Copyright © 2006

Optimisation of the separation of herbicides by linear gradient high performance liquid chromatography utilising artificial neural networks

An artificial neural network (ANN) was employed to model the chromatographic response surface for the linear gradient separation of 10 herbicides that are commonly detected in storm run-off water in agricultural catchments. The herbicides (dicamba, simazine, 2,4-D, MCPA, triclopyr, atrazine, diuron, clomazone, bensulfuron-methyl and metolachlor) were separated using reverse phase high performance liquid chromatography and detected with a photodiode array detector. The ANN was trained using the pH of the mobile phase and the slope of the acetonitrile/water gradient as input variables. A total of nine experiments were required to generate sufficient data to train the ANN to accurately describe the retention times of each of the herbicides within a defined experimental space of mobile phase pH range 3.0-4.8 and linear gradient slope 1-4% acetonitrile/min. The modelled chromatographic response surface was then used to determine the optimum separation within the experimental space. This approach allowed the rapid determination of experimental conditions for baseline resolution of all 10 herbicides. Illustrative examples of determination of these components in Milli-Q water, Sydney mains water and natural water samples spiked at 0.5-1 μg/L are shown. Recoveries were over 70% for solid-phase extraction using Waters Oasis® HLB 6 cm3 cartridges. © 2006 Elsevier B.V. All rights reserved

Development and application of an off-line SPE-LC-UV methodology for the determination of penoxsulam in aquatic systems adjacent to rice fields

An accurate, simple, reproducible and sensitive off-line SPE–LC–UV method was developed and validated for the determination of penoxsulam, a new triazolopyrimidine sulphonamide herbicide widely used in rice culture. The method was validated in terms of precision, linearity, detection limit, quantification limit and accuracy. The repeatability and intermediate precision of LC–UV conditions chosen were evaluated, with an RSD always bellow 10%. A limit of detection of 0.07 lgL -1 was achieved after SPE concentration. Recovery studies, performed in two different matrixes (run-off water from rice fields and brackish water), ranged from 93 to 105%. The methodology was successfully used to detect penoxsulam in aquatic systems, during an application period in rice fields.publishe

Uptake and release kinetics of 22 polar organic chemicals in the Chemcatcher passive sampler

The Chemcatcher passive sampler, which uses Empore (TM) disks as sampling phase, is frequently used to monitor polar organic chemicals in river water and effluents. Uptake kinetics need to be quantified to calculate time-weighted average concentrations from Chemcatcher field deployments. Information on release kinetics is needed if performance reference compounds (PRCs) are used to quantify the influence of environmental conditions on the uptake. In a series of uptake and elimination experiments, we used Empore (TM) SDB disks (poly(styrenedivinylbenzene) copolymer modified with sulfonic acid groups) as a sampling phase and 22 compounds with a logK (ow) (octanol-water partitioning coefficient) range from -2.6 to 3.8. Uptake experiments were conducted in river water or tap water and lasted up to 25 days. Only 1 of 22 compounds (sulfamethoxazole) approached equilibrium in the uptake trials. Other compounds showed continuing non-linear uptake, even after 25 days. All compounds could be released from SDB disks, and desorption was proportionally higher in disks loaded for shorter periods. Desorption showed two-phase characteristics, and desorption was proportionally higher for passively sorbed compounds compared to actively loaded compounds (active loading was performed by pulling spiked river water over SDB disks using vacuum). We hypothesise that the two-phase kinetics and better retention of actively loaded compounds-and compounds loaded for a longer period-may be caused by slow diffusion of chemicals within the polymer. As sorption and desorption did not show isotropic kinetics, it is not possible to develop robust PRCs for adsorbent material like SDB disks