Limitations of Integrative Passive Samplers as a Tool for the Quantification of Pharmaceuticals in the Environment - A Critical Review with the Latest Innovations

Evaluation of the DGT passive samplers for integrating fluctuating concentrations of pharmaceuticals in surface water

Diffusive gradients in thin films (DGTs) have been well-documented for the measurement of a broad range of organic pollutants in surface water. However, the performance has been challenged by the inherent periodic concentration fluctuations for most organic pollutants. Therefore, there is an urgent need to assess the true time-weighted average (TWA) concentration based on fluctuating concentration profiles. The study aimed to evaluate the responsiveness of DGT and accuracy of TWA concentrations, considering various concentration fluctuating scenarios of 20 pharmaceuticals in surface water. The reliability and accuracy of the TWA concentrations measured by the DGT were assessed by comparison with the sum of cumulative mass of DGT exposed at different stages over the deployment period. The results showed that peak concentration duration (1-5 days), peak concentration fluctuation intensity (6-20 times), and occurrence time of peak concentration fluctuation (early, middle, and late stages) have minimal effect on DGT's response to most target pharmaceutical concentration fluctuations (0.8 < CDGT/CTWA < 1.2). While the downward-bent accumulations of a few pharmaceuticals on DGT occur as the sampling time increases, which could be accounted for by capacity effects during a long-time sampling period. Additionally, the DGT device had good sampling performance in recording short fluctuating concentrations from a pulse event returning to background concentrations with variable intensity and duration. This study revealed a satisfactory capacity for the evaluation of the TWA concentration of pharmaceuticals integrated over the period of different pulse deployment for DGT, suggesting that this passive sampler is ideally suited as a monitoring tool for field application. This study represents the first trial for evaluating DGT sampling performance for pharmaceuticals with multiple concentration fluctuating scenarios over time, which would be valuable for assessing the pollution status in future monitoring campaign.

Ecotoxicological risk of antibiotics and their mixtures to aquatic biota with the DGT technique in sediments

Antibiotics are emerging contaminants and widely used in human healthcare, livestock, and aquaculture. The toxicity posed by antibiotics and their mixtures in sediments depends on their bioavailability. Now, the bioavailability of organic materials can be determined accurately by the diffusive gradients in thin films (DGT) technique. This technique was used for the first time ever in this study to evaluate in detail the integral toxicity of antibiotics in sediments to aquatic biota. Zhelin Bay was selected as a case study, because it is the largest mariculture area in eastern Guangdong, South China. Two antibiotics, chlortetracycline (CTC) (A) and sulfachlorpyridazine (SCP), were detected at average concentrations of 2.83 and 1.14 ng/ml, respectively. The other fifteen antibiotics were undetectable. The single risk assessment based on the risk quotient (RQ) of CTC and SCP shows that a relatively low risk has occurred. After this careful assessment of probabilistic ecotoxicological risks, the combined toxicity of antibiotic mixtures (CTC and SCP) clearly indicates that the toxicity probability of surface sediments to aquatic organisms was relatively low (0.23%).

Passive Sampling: A Greener Technique for the 'Dual Carbon' Goal While Implementing the Action Plan for Controlling Emerging Pollutants

In response to global climate change, China recently committed to achieving peak carbon emissions by 2030 and carbon neutrality by 2060. Carbon emission reduction should be considered in every sector of society including environmental monitoring. As an energy-saving technique in environmental monitoring, passive sampling has many advantages, such as in-situ sampling and a reduction in time/labour requirements. This perspective illustrates the "greenness" of passive sampling techniques, by comparison with traditional sampling methods, and its potential contribution to the 'dual carbon' goal. At the same time passive sampling can provide key support for the action plan for controlling emerging pollutants in China.

A Review on Polyethersulfone Membranes in Polar Organic Chemical Integrative Samplers: Preparation, Characterization and Innovation

The membranes in polar organic chemical integrative samplers (POCIS) enclose the receiving sorbent and protect it from coming into direct contact with the environmental matrix. They have a crucial role in extending the kinetic regime of contaminant uptake, by slowing down their diffusion between the water phase and the receiving phase. The drive to improve passive sampling requires membranes with better design and enhanced performances. In this review, the preparation of standard polyethersulfone (PES) membranes for POCIS is presented, as well as methods to evaluate their composition, morphology, structure, and performance. Generally, only supplier-related morphological and structural data are provided, such as membrane type, thickness, surface area, and pore diameter. The issues related to the use of PES membranes in POCIS applications are exposed. Finally, alternative membranes to PES in POCIS are also discussed, although no better membrane has yet been developed. This review highlights the urge for more membrane characterization details and a better comprehension of the mechanisms which underlay their behavior and performance, to improve membrane selection and optimize passive sampler development.

An optimized processing method for polar organic chemical integrative samplers deployed in seawater: Toward a maximization of the analysis accuracy for trace emerging contaminants

Passive sampling of emerging contaminants (ECs) in seawater represents a challenge in environmental monitoring. A specific protocol for Polar Organic Chemical Integrative Sampler (POCIS) processing may be necessary when dealing with marine applications, due to the peculiarity of the considered matrix. Herein, both the instrumental LC-MS/MS analysis and the sampler processing for the determination of 22 ECs in seawater were carefully optimized. The study entailed a test simulating POCIS sorbent exposure to seawater as well as the processing of replicated field POCIS with different elution solvents. The final method involved washing the sorbent with water, to eliminate most salts, and a two-step elution, by using methanol and a small volume of a dichloromethane-isopropanol mixture. With this protocol, recoveries between 58 and 137% (average 106%) were obtained for most analytes, including non-steroidal anti-inflammatory drugs, UV-filters, perfluorinated substances and caffeine. Still, the protocol was not suitable for very hydrophilic compounds (recovery under 20% for artificial sweeteners and the pharmaceutical salbutamol), which also showed remarkable ion suppression (matrix effects in the range 4-46%). For all other chemicals, the matrix effects were in the range 67-103% (average 86%), indicating satisfactory accuracy. Also, the overall method showed high sensitivity (detection limits in the range 0.04-9 ng g^-1 of POCIS sorbent) and excellent specificity, thanks to the monitoring of two "precursor ion-product ion" MS transitions for identity confirmation. The method was applied to samplers deployed in the Ligurian coast (Italy), detecting caffeine, bisphenol A, ketoprofen and two UV-filters as the most concentrated in the POCIS sorbent.