Abstract
The passive sampling method of diffusive gradients in thin-films (DGT) was developed to provide a quantitative and time-integrated measurement of microcystin-LR (MC-LR) in waters. The DGT method in this study used HLB (hydrophilic-lipophilic-balanced) material as a binding agent, and methanol as an eluent. The diffusion coefficient of MC-LR was 5.01 × 10−6 cm2 s−1 at 25 °C in 0.45 mm thick diffusion layer. This DGT method had a binding capacity of 4.24 μg per binding gel disk (3.14 cm2), ensuring sufficient capacity to measure MC-LR in most water matrices. The detection limit of HLB DGT was 0.48 ng L−1. DGT coupled to analysis by HPLC appears to be an accurate method for MC-LR monitoring. Comparison of DGT measurements for MC-LR in water and a conventional active sampling method showed little difference. This study demonstrates that HLB-based DGT is a useful tool for in situ monitoring of MC-LR in fresh waters.
Highlights
The passive sampling method of diffusive gradients in thin-films (DGT) was developed to provide a quantitative and time-integrated measurement of microcystin-LR (MC-LR) in waters
The average binding rate calculated from the DGT unitwas0.59 ng cm−2 min−1 when they were deployed in 200 μg L−1 of MC-LR at 25 °C
The adsorption rate discrepancy between DGT device and binding gel suggests that MC-LR binds onto the gels in DGT with sufficient speed to ensure that the concentration of MC-LR at the diffusive gel/binding gel interface is almost zero, validating the use of Eq (1)
Summary
The passive sampling method of diffusive gradients in thin-films (DGT) was developed to provide a quantitative and time-integrated measurement of microcystin-LR (MC-LR) in waters. Dominant passive sampling approaches include the Polar Organic Chemical Integrative Sampler (POCIS)[17], Chemcatcher[18], Solid Phase Adsorption Toxin Tracking (SPATT)[19], and Diffusive Gradients in Thin films (DGT)[20]. Both POCIS and SPATT have been deployed successfully to detect or monitor microcystins[21,22,23], providing a robust way to monitor microcystin concentrations. The DGT technology was developed by Davison and Zhang[26] and initially was used to detect trace metals in natural fresh water systems[20]
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