Adaptation of DGT and reliability of POCIS for pesticides and pharmaceuticals monitoring in surface waters

Les techniques d’échantillonnage passif comme le POCIS (« Polar Organic Chemical Integrative Sampler ») ou le o-DGT (« Diffusive Gradient in Thin films » pour composés organiques) permettent d’obtenir une bonne représentativité de la contamination des eaux de surface par les micropolluants organiques. Cependant, ces dispositifs sont soumis à des conditions environnementales qui engendrent des biais sur la quantification des analytes cibles. Une meilleure connaissance des données issues de l’échantillonnage passif a donc été essentielle afin de les utiliser sur deux têtes de bassin versant. Pour cela un dispositif innovant, utilisant la technique DGT, a été développé et testé sur 4 pesticides ioniques. La robustesse du o-DGT étudiée sur une plage de pH allant de 3 à 8 et de force ionique allant de 0,01 à 1 mol.L-1, lui permette d’être utilisé dans la plupart des eaux naturelles. Des déploiements en milieu naturel et dans une rivière artificielle, en même temps que le déploiement de POCIS, a permis de comparer les performances de ces 2 échantillonneurs. Le POCIS, avec des limites de quantification plus basses, était l’échantillonneur le plus adapté au suivi de contamination des têtes de bassin versant, cependant il a été nécessaire de l’améliorer pour fiabiliser les concentrations de micropolluants mesurées.. Une libération de polyéthylène glycol issu des membranes utilisées pour la fabrication de POCIS provoquant des effets de matrice a été supprimé grâce à deux bains successifs d’1h d’un mélange 50:50 méthanol:eau suivi d’un bain de rinçage à l’eau. De même, une quantification des molécules cibles est obtenue grâce à des taux d’échantillonnage (Rs) déterminés dans conditions proches de celle de l’environnement. Les Rs de 44 molécules pharmaceutiques ont été déterminés grâce à une rivière artificielle. Après cette étape de fiabilisation, le POCIS a été appliqué à deux têtes de bassin versant avec des suivis de 1 et 3 ans sur, respectivement, l’Aixette et l’Auvézère. Des prélèvements ponctuels ont également été réalisés et ont pu mettre en évidence des pics de pollution de pesticides (> 2,3 g.L-1). Ces suivis « semi-continus » ont permis de mettre en évidence et de caractériser l’existence d’une pollution des têtes de bassin versant par les pesticides et les résidus pharmaceutiques.Passive samplers, such as POCIS (Polar Organic Chemical Integrative Sampler) or o-DGT (Diffusive Gradient in Thin films for organic compounds), allow to estimate surface water contamination by organic micropollutants. However, these devices are influenced by environmental conditions and quantification error can occur. A better knowledge of passive sampling data was therefore essential before the samplers’ application on headwater streams. An innovative sampler, using DGT technique, has been developed and tested on 4 ionic pesticides. The sampler is robust in a pH range from 3 to 8 and an ionic strength range from 0,01 to 1 mol.L-1, which allows to use it in the most of natural waters. Field deployments of POCIS alongside o-DGT in natural waters and in an artificial river made it possible to compare their performances. POCIS with lower limits of quantification was the most suitable sampler for monitoring organic compounds in headwater stream. A release of polyethylene glycol from membranes used in POCIS causing matrix effects was removed by two successive baths of 1h of a 50:50 mix of methanol:water followed by a rinsing bath of water. Quantification is achieved through sampling rates (Rs) estimated under revelant conditions. Rs of 44 pharmaceuticals were estimated in an artificial river. After these steps, POCIS was applied in two headwater streams for 1 and 3 years on Aixette and Auvézère, respectively. Grab samples were also collected and pollution peaks of pesticides were detected (> 2,3 g.L-1). These “semi-continuous” monitorings highlighted a pollution of headwater streams by pesticides and pharmaceuticals

Adaptation du DGT et fiabilisation du POCIS pour le suivi des pesticides et résidus de médicaments dans les eaux de surfaces

Passive samplers, such as POCIS (Polar Organic Chemical Integrative Sampler) or o-DGT (Diffusive Gradient in Thin films for organic compounds), allow to estimate surface water contamination by organic micropollutants. However, these devices are influenced by environmental conditions and quantification error can occur. A better knowledge of passive sampling data was therefore essential before the samplers’ application on headwater streams. An innovative sampler, using DGT technique, has been developed and tested on 4 ionic pesticides. The sampler is robust in a pH range from 3 to 8 and an ionic strength range from 0,01 to 1 mol.L-1, which allows to use it in the most of natural waters. Field deployments of POCIS alongside o-DGT in natural waters and in an artificial river made it possible to compare their performances. POCIS with lower limits of quantification was the most suitable sampler for monitoring organic compounds in headwater stream. A release of polyethylene glycol from membranes used in POCIS causing matrix effects was removed by two successive baths of 1h of a 50:50 mix of methanol:water followed by a rinsing bath of water. Quantification is achieved through sampling rates (Rs) estimated under revelant conditions. Rs of 44 pharmaceuticals were estimated in an artificial river. After these steps, POCIS was applied in two headwater streams for 1 and 3 years on Aixette and Auvézère, respectively. Grab samples were also collected and pollution peaks of pesticides were detected (> 2,3 g.L-1). These “semi-continuous” monitorings highlighted a pollution of headwater streams by pesticides and pharmaceuticals.Les techniques d’échantillonnage passif comme le POCIS (« Polar Organic Chemical Integrative Sampler ») ou le o-DGT (« Diffusive Gradient in Thin films » pour composés organiques) permettent d’obtenir une bonne représentativité de la contamination des eaux de surface par les micropolluants organiques. Cependant, ces dispositifs sont soumis à des conditions environnementales qui engendrent des biais sur la quantification des analytes cibles. Une meilleure connaissance des données issues de l’échantillonnage passif a donc été essentielle afin de les utiliser sur deux têtes de bassin versant. Pour cela un dispositif innovant, utilisant la technique DGT, a été développé et testé sur 4 pesticides ioniques. La robustesse du o-DGT étudiée sur une plage de pH allant de 3 à 8 et de force ionique allant de 0,01 à 1 mol.L-1, lui permette d’être utilisé dans la plupart des eaux naturelles. Des déploiements en milieu naturel et dans une rivière artificielle, en même temps que le déploiement de POCIS, a permis de comparer les performances de ces 2 échantillonneurs. Le POCIS, avec des limites de quantification plus basses, était l’échantillonneur le plus adapté au suivi de contamination des têtes de bassin versant, cependant il a été nécessaire de l’améliorer pour fiabiliser les concentrations de micropolluants mesurées.. Une libération de polyéthylène glycol issu des membranes utilisées pour la fabrication de POCIS provoquant des effets de matrice a été supprimé grâce à deux bains successifs d’1h d’un mélange 50:50 méthanol:eau suivi d’un bain de rinçage à l’eau. De même, une quantification des molécules cibles est obtenue grâce à des taux d’échantillonnage (Rs) déterminés dans conditions proches de celle de l’environnement. Les Rs de 44 molécules pharmaceutiques ont été déterminés grâce à une rivière artificielle. Après cette étape de fiabilisation, le POCIS a été appliqué à deux têtes de bassin versant avec des suivis de 1 et 3 ans sur, respectivement, l’Aixette et l’Auvézère. Des prélèvements ponctuels ont également été réalisés et ont pu mettre en évidence des pics de pollution de pesticides (> 2,3 g.L-1). Ces suivis « semi-continus » ont permis de mettre en évidence et de caractériser l’existence d’une pollution des têtes de bassin versant par les pesticides et les résidus pharmaceutiques

Limitation of flow effect on passive sampling accuracy using POCIS with the PRC approach or o-DGT: A pilot-scale evaluation for pharmaceutical compounds

Flow velocity is known to alter passive sampling accuracy. We investigated the POCIS (Polar Organic Chemical Integrative Sampler) with PRC (Performance Reference Compounds) approach and Diffusive Gradients in Thin Films samplers (o-DGT) to limit the effect of flow on the quantification accuracy of ten model pharmaceuticals compounds (0.16 <= log K-ow <= 4.51). POCIS and o-DGT samplers were exposed for seven days in controlled pilot-scale (hundreds of liters) experiments under quiescent or flowing (2 < V < 18 cm s(-1)) conditions. Under flowing conditions, both POCIS-PRC and o-DGT efficiently limited the flow effect and led, in most cases, to biases within analytical uncertainty (20%). Under quiescent conditions, o-DGT performed accurately (bias <30% for most compounds) whereas the PRC approach was unsuitable to improve upon the accuracy of POCIS (PRC was unable to desorb). Therefore, both approaches are helpful in limiting the effects of flow on accuracy, but only o-DGT is efficient in quiescent conditions. However, o-DGT currently suffers from poorer sensitivity compared to POCIS, but the future development of o-DGT devices with wider windows could overcome this limitation

Improvement of POCIS ability to quantify pesticides in natural water by reducing polyethylene glycol matrix effects from polyethersulfone membranes

International audienceThe presence of polyethylene glycol compounds (PEG) in extracts from polar organic chemical integrative samplers (POCIS) was shown by high resolution time-of-flight mass spectrometry. PEG compounds, which are released by polyethersulfone (PES) membranes used to build POCIS, can induce matrix effects during quantification of performance reference compounds (PRC, DIA-d5) and target pesticides by mass detection, even after chromatographic separation. Dilution of POCIS extracts can reduce this matrix effect, but dilution may induce a decrease in POCIS performance, primarily for quantification limits. To reduce PEG interference during chromatographic analysis, a simple non-damaging washing protocol for PES membranes is proposed. The method consists of 2 successive baths of washing solution (140mL per membrane) of ultrapure water (UPW) and methanol (50/50), stirred at 300 rotations per minute (rpm), followed by a final membrane rinse with UPW (140 mL). The signal from PEG compounds was significantly decreased for washed membranes (between 4 and 6 fold lower). After field deployment, total ion current chromatograms of extracts from POCIS built with washed PES membranes did not display a significant PEG fingerprint. This led to improved quantification accuracy for compounds co-eluting with PEG, i.e. PRC (performance and reference compound, DIA-d5) and some pesticides and metabolites. With washed membranes, an accurate quantification of PRC and pesticides sampled by POCIS was indeed possible without a large extract dilution; 10 times instead of the 25 times needed in unwashed conditions. Assuming that the PRC approach corrects for environmental conditions and sampling rates (R s), a proper PRC (DIA-d5) quantification significantly improved pesticide time weighted average concentration (TWAC) determination in natural water after field deployment

Adaptation of diffusive gradients in thin films technique to sample organic pollutants in the environment: An overview of o-DGT passive samplers

The adaptation of the diffusive gradients in thin films technique (DGT) to sample organic pollutants in the environment, called o-DGT has been performed since 2011 for various types of organic compounds (e.g. pesticides, pharmaceuticals, hormones, endocrine disrupting chemicals, household and personal care products). To sample these different compounds, configuration of the samplers (mainly receiving phase and diffusive gel) has to be adapted. Up-to-date, sampling of 142 organic compounds by this passive sampler have been tested. This review provides the state-of-art of o-DGT passive sampler development, describing theory and modelling, calibration, configuration of the devices, and field applications. The most used configurations were agarose-XAD-18 and agarose-HLB configuration. o-DGT can be used to sample soils and most of natural waters (range of pH 4-9 and ionic strength 0.001-0.1 M).This review discusses current limitation of o-DGT in light of the feedback of DGT use to sample inorganic contaminants. It mainly concern the low sampling rates currently obtained by o-DGT compared to other passive samplers. This weakness could be compensated in the future with new sampler's design allowing an increase in exposure area

Passive sampling of anionic pesticides using the Diffusive Gradients in Thin films technique (DGT)

International audienceDGT passive samplers using Oasis® HLB or Oasis® MAX sorbent were developed for anionic pesticides sampling. They were tested using four model compounds (i.e. bentazon, chlorsulfuron, ioxynil and mecoprop). Polyacrylamide diffusive gel was found to be more suitable than agarose gel for most anionic pesticides sampling. An elution procedure was optimized and diffusion coefficients were determined for quantitative use of the samplers. Depending on the DGT configuration used (HLB or MAX), accuracies better than 30% were demonstrated in laboratory for pH from 3 to 8 and ionic strengths from 10−2 to 1 M. Combined with the effective binding capacities of samplers (≥9 μg for each pesticide) and limits of quantification of the method (≤13 ng.L−1 using Q-TOF detector) monitoring of numerous aquatic systems can be expected. Except for ioxynil, accurate quantifications were demonstrated in laboratory using a spiked natural water for HLB-DGT whereas MAX-DGT did not give satisfactory results. A further in situ validation was performed in two rivers and showed identical detection frequency between HLB-DGT and POCIS of anionic pesticides (bentazon and mesotrione) whereas calculated concentrations, although within the same order of magnitude, could differ (<70%). HLB-DGT could therefore constitute an interesting alternative to other passive samplers for the monitoring of several anionic pesticides in aquatic systems but more work is required for quantification of molecules from hydroxybenzonitrile chemical group (ioxynil)

Development of a multi-hormone analysis method by LC-MS/MS for environmental water application using diffusive gradient in thin films

International audienceAn analysis method for four families of hormones (estrogens, progestins, androgens and prostaglandins), dedicated to an efficient water monitoring with passive sampling, was developed using a liquid chromatography tandem mass spectrometry with triple quadrupole coupling and universal electrospray ionisation. Thirteen natural and synthetic hormones in ultra-pure water could be analysed in a single run according to the French Standard NF T90-210: calibration range of 0.1 (except for 17 beta-Estradiol, Estriol, Estrone and Diethylstilbestrol, from 0.5 mu g/L; and Ethinylestradiol, from 1 mu g/L) to 20 mu g/L with linear regressions (R2 >= 0.96), maximum accuracy deviations of 30% at intermediate fidelity for three concentration references (1, 10 and 20 mu g/L) and instrumental LOQs from 0.05 to 1 mu g/L. The stability of 11 hormones (10 mu g/L) was studied under several storage conditions and sample evaporation. All selected hormones were stable for 60 days at -18 degrees C, 7 days at 4 degrees C and 7 days at 20 degrees C but continued drying flow after evaporation should be avoided, especially for 17 alpha-Estradiol, Estrone and Diethylstilbestrol. Observed matrix effects using o-DGT extracts (diffusive gradient in thin-film sampler for polar organics) containing an environmental matrix varied from 24 to 92% but all matrix effects were corrected with IS use. Therefore, the developed method, coupled with o-DGT, was tested with the o-DGT deployment in rivers. Using diffusion coefficients from the literature or lab determined, the concentrations in the rivers varied for Estrone from 1.8 ng/L to 2.5 ng/L, and for Androstenedione from 0.4 to 1.1 ng/L

Proposal of a new empirical model with flow velocity to improve time-weighted average concentration estimates from the Polar Organic Chemical Integrative Samplers

It is now widely recognized that the sampling rate of Polar Organic Chemical Integrative Samplers (POCIS) is significantly affected by flow velocity, which can cause a consequent bias when determining time-weighted average concentrations (TWAC). In previous works, we observed the desorption of a compound such as deisopropylatrazine (DIA) over time when added to the receiving phase of a POCIS. In particular, it was found in situ that its desorption rate was also influenced by flow velocity, in an agitated water environment. In the method presented here, we calibrated 30 pesticides under controlled laboratory conditions, varying the flow velocity over four levels. At the same time, we studied the desorption rate of DIA-d5 (a deuterated form of DIA) over time. An empirical model based on a power law involving flow velocity was used to process the information provided by the accumulation kinetics of the compounds of interest and the elimination of DIA-d5. With this type of model, it was possible to take into account the effect of this crucial factor on exchange kinetics, and then to obtain more accurate TWACs, with reduced bias and more acceptable dispersion of the results