The Swedish EPA (Naturv&#229;rdsverket) (agreement 2208-13-001) and Centre for Chemical Pesticides (CKB) are gratefully acknowledged for funding this project. We thank M&#228;rit Peterson, Henrik Jernstedt, Emma Gurnell and Elin Paulsson at the OMK-lab, SLU, for skillful assistance with analytical support and supply of pesticide standards.

1. Passive Sampler Design and Preparation
<ol>
	<li>Silicone rubber sheets
	<ol>
		<li>Cut the silicone rubber sheets (600 mm x 600 mm, 0.5 mm thick) into stripes of 2.5 mm x 600 mm and 2.5 mm x 314 mm using a stainless steel cutter and connect them using a stainless steel blind rivet (3.2 mm x 10 mm) with a rivet gun to obtain a total sampler stripe size of 2.5 mm x 914 mm (surface area = 457 cm2, sorbent mass = 15.6 g, volume = 22.9 cm3).</li>
	</ol>
	</li>
	<li>Place the silicone rubbers in an extraction chamber of a Soxhlet apparatus. Add 50 ml EA in the extraction chamber and add 250 ml EA and three boiling stones in a 500 ml round bottle flask.
	<ol>
		<li>Connect the extraction chamber with the bottle flask and a condenser. Clean the silicone rubbers by Soxhlet extraction for 96 hr at approximately 80 &#176;C, and dry them thereafter under gentle nitrogen gas.</li>
	</ol>
	</li>
	<li>Attach the silicone rubber stripe to a stainless steel spider sample holder by wrapping the silicone rubber stripe around the rods on the holder (Figure 1). Attach each end of the silicone rubber stripe to a rod on the holder using cable ties.</li>
</ol>
<img alt="Figure 1" src="/files/ftp_upload/54053/54053fig1.jpg" /> 
Figure 1. Schematic of silicone rubber. Passive sampler schematic for silicone rubber showing the attachment of the silicone rubber stripe to a stainless steel spider sample holder A) from the top and B) the side view. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54053/54053fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>POCIS-A and POCIS-B
	<ol>
		<li>For POCIS-A, place 220 mg of HLB bulk sorbent (surface area = 1.78 x 106 cm2) between two 9.0 cm by 9.0 cm square polyethersulfone (PES) membranes (Figure 2).</li>
		<li>For POCIS-B, place 220 mg of a sorbent mixture (i.e., hydroxylated polystyrene-divinylbenzene resin (80%) and a carbonaceous adsorbent dispersed on a styrene divinylbenzene copolymer (20%)) (surface area = 2.82 x 106 cm2) between two PES membranes (Figure 2).</li>
		<li>Compress the sorbent and two PES between two stainless steel rings manually (inner &#216; = 5.4 cm) and secure it on a stainless steel sample holder (Figure 2).</li>
	</ol>
	</li>
</ol>
<img alt="Figure 2" src="/files/ftp_upload/54053/54053fig2.jpg" /> 
Figure 2. Schematic of passive sampler disks. Passive sampler schematic for POCIS A, POCIS B, SDB-RPS disk and C18 disk showing A) the assembling of the passive sampler using stainless steel rings, polyethersulfone (PES) membranes, and the receiving phase, and B) the assembling on a stainless steel sample holder. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54053/54053fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="3">
	<li>SDB-RPS disk and C18 disk
	<ol>
		<li>Place the SDB-RPS (surface area = 35 cm2, sorbent mass = 0.34 g, volume = 1.7 cm3) and C18 disks (surface area = 35 cm2, sorbent mass = 0.58 g, volume = 1.7 cm3) between two PES membranes (Figure 2). Compress the disks and two PES between two stainless steel rings manually (inner &#216; = 5.4 cm) and secure it on a stainless steel sample holder (Figure 2).</li>
	</ol>
	</li>
</ol>
2. Laboratory Uptake Experiments
NOTE: The Laboratory uptake experiments were performed to quantitatively characterize the uptake kinetics for 124 individual pesticides for five different passive sampler devices under controlled conditions.
<ol>
	<li>Conduct the uptake study in rectangular glass containers (each ~95 L): Tank 1) silicone rubber (n = 16), tank 2) POCIS-A (n = 16), POCIS-B (n = 16), and tank 3) SDB-RPS disk (n = 16), C18 disk (n = 16). Fill natural water into the three tanks.</li>
	<li>Perform all experiments at a constant water temperature (~20 &#176;C) and under turbulent water conditions (~10 cm sec-1) using two electric pumps attached to the wall on each side. Perform the experiments in the dark to minimize the effect of photodegradation.</li>
	<li>Spike each glass container with a pesticide standard mixture containing 124 pesticides using a glass syringe (c &#8776; 400 ng L-1 for individual pesticides in the water tank). Take out the passive samplers manually from the tanks, at time intervals of 5, 11, 20, and 26 days, to determine the sampling rates of the pesticides.</li>
	<li>Monitor the concentrations of the pesticides in each tank by collecting 100 ml water samples at day 0, 5, 11, 20, and 26. The analysis of the water samples is performed as described elsewhere21.
	<ol>
		<li>For quality control, expose blank samples to room air for 1 hr at day 0 and then store and treat them as real samples. Store all extracts as well as the 100 ml water samples collected from the tanks at -18 &#176;C until further analysis.</li>
	</ol>
	</li>
</ol>
3. Sample Extraction
<ol>
	<li>Silicone rubber
	<ol>
		<li>Prior to extraction, dry the silicone rubber stripe under a stream of high purity nitrogen gas.</li>
		<li>For gas chromatography-mass spectrometry (GC-MS) analysis, carry out the solid-liquid extraction using Soxhlet extraction22.
		<ol>
			<li>Place the silicone rubber into the Soxhlet extractor. Add 250 ml PE/ACE (50/50, v/v) and 3 boiling stones into the round bottle flask.</li>
			<li>Spike the silicone rubber with 100 &#181;l of an IS mixture (c = 5 ng ml-1) using a glass syringe. Add 50 ml PE/ACE (50/50, v/v) into the Soxhlet extractor. Switch on the heater and run the Soxhlet extraction for 19 hr and then switch off the heater.</li>
			<li>Concentrate the extracts by rotary evaporation followed by gentle nitrogen blow-down to 1 ml. Exchange the solvent to CH/ACE (90/10, v/v) by adding three times 1 ml CH/ACE (90/10, v/v) during the nitrogen blow-down to 1 ml.</li>
		</ol>
		</li>
		<li>For liquid chromatography&#8722;tandem mass spectrometry (LC-MS/MS) analysis, carry out the extraction using Soxhlet extraction22.
		<ol>
			<li>Place the silicone rubber into the Soxhlet extractor. Add 250 ml MeOH and 3 boiling stones into the round bottle flask and 50 ml MeOH into the Soxhlet extractor. Spike the silicone rubber with 100 &#181;l of an IS mixture (c = 5 ng ml-1) using a glass syringe.</li>
			<li>Switch on the heater and run the Soxhlet extraction for 19 hr and then switch off the heater. Concentrate the extracts by rotary evaporation followed by gentle nitrogen blow-down to 1 ml. Exchange the solvent to ACN by adding 1 ml ACN during the nitrogen blow-down to 1 ml.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>POCIS-A and POCIS-B
	<ol>
		<li>Open the POCIS sampler carefully and transfer the sorbent with ultrapure water using a funnel into a pre-cleaned empty polypropylene solid phase extraction (SPE) cartridge (6 ml) containing two polyethylene (PE) frits. Dry the sorbent by vacuum to remove water. Record the weight of the empty and packed SPE cartridge to control the weight of the sorbent material. Please note that different cartridges are used for GC-MS and LC-MS/MS analysis.</li>
		<li>Prior to elution, spike the sorbent with 100 &#181;l of an IS mixture (c = 5 ng ml-1) using a glass syringe. Elute POCIS-A and POCIS-B sorbents using 5 ml EA for GC-MS22.
		<ol>
			<li>Concentrate the extracts to 1 ml by gentle nitrogen blow-down. Exchange the solvent to CH/ACE (90/10, v/v) by adding three times 1 ml CH/ACE (90/10, v/v) during the nitrogen blow-down to 1 ml.</li>
		</ol>
		</li>
		<li>Elute POCIS-A and POCIS-B cartridges using 1.5 ml MeOH followed by 8 ml DCM/MeOH (80/20, v/v) for LC-MS/MS analysis22. Concentrate the extracts to 1 ml by gentle nitrogen blow-down. Exchange the solvent to ACN by adding 1 ml ACN during the nitrogen blow-down to 1 ml.</li>
	</ol>
	</li>
	<li>SDB-RPS and C18 disk
	<ol>
		<li>Transfer individual disks of SDB-RPS and C18 disk into a glass beaker and dry them under nitrogen gas. Spike the disks with 100 &#181;l of an IS mixture (c = 5 ng ml-1) using a glass syringe and sonicate them two times in a glass beaker at room temperature, first with 5 ml of EA for 10 min and then with 3 ml of EA for 10 min.</li>
		<li>Transfer both extracts into one glass tube, concentrate them to 2 ml by gentle nitrogen blow down, and split them into two 1 ml fractions (for GC-MS and LC-MS/MS analysis, respectively).</li>
		<li>Concentrate the extracts to 0.5 ml by gentle nitrogen blow-down and exchange the solvent to CH/ACE (90/10, v/v) for GC-MS analysis22. Concentrate the extracts to 0.5 ml by gentle nitrogen blow-down and exchange the solvent to ACN for LC-MS/MS analysis22.</li>
	</ol>
	</li>
</ol>
4. Water Samples
<ol>
	<li>Spike 20 ml water sample with 100 &#181;l of an IS mixture (c = 5 ng ml-1) using a glass syringe, add 3 ml of DCM, vortex for 3 min, and decant into a phase separator for GC-MS analysis 22.
	<ol>
		<li>After the two phases are separated, percolate the DCM phase into a glass tube. Repeat the extraction using 3 ml DCM, and rinse the tube with 2 ml DCM. Finally, concentrate the extracts to 0.5 ml by gentle nitrogen blow-down and exchange the solvent to CH/ACE (90/10, v/v).</li>
	</ol>
	</li>
	<li>Analyze the water samples using large volume injection, similar to the method described elsewhere by LC-MS/MS 21.</li>
</ol>
5. Instrumental Analysis
<ol>
	<li>GC-MS analysis
	<ol>
		<li>Perform the instrumental analysis of the CH/ACE extracts using GC-MS systems in electron ionization (EI) and negative chemical ionization (NCI) mode, respectively22.</li>
		<li>For the GC-MS method using EI, inject aliquots of 1 &#181;l with splitless injection method on a HP-5MS UI column (30 m, 0.25 mm inner diameter, 0.25 &#181;m film).</li>
		<li>For the GC-MS method using CI, inject aliquots of 3 &#181;l on a HP-5MS UI column (30 m, 0.25 mm inner diameter, 0.25 &#181;m film).</li>
	</ol>
	</li>
	<li>HPLC-MS/MS analysis
	<ol>
		<li>Perform the instrumental analysis of the ACN extracts using HPLC-MS/MS interfaced with an electrospray ionization source in negative ((-)ESI) and positive-ion mode ((+)ESI)22.</li>
		<li>For (+)ESI, dilute 100 &#181;l of the ACN extracts with 900 &#181;l ultrapure water adjusted to pH 5 using FA .</li>
		<li>For (-)ESI, dilute 100 &#181;l of the ACN extracts with 900 &#181;l solution of 1% FA in ultrapure water.</li>
		<li>For (+)ESI, use a binary gradient consisting of 2-propanol/methanol/10 mM ammonium formate (6/2/92, v/v/v) and MeOH at a flow rate of 0.3 ml min-1.</li>
		<li>For (-)ESI, use a binary gradient consisting of ACN/ultrapure water 0.1% HAc and ACN + 0.1% HAc at a flow rate of 0.3 ml min-1.</li>
		<li>Inject all samples using a large volume injection of 500 &#181;l using two online SPE columns (both 20 x 2 mm id and 20-25 &#181;m particle size), and an analytical column (C18, 100 x 3 mm, 3.5 &#181;m)21.</li>
	</ol>
	</li>
</ol>
6. Theory on Passive Sampling
NOTE: The uptake profile of the chemical to the passive sampler medium (PSM) is divided into three sections: Linear, curvilinear and equilibrium (Figure 3).
<img alt="Figure 3" src="/files/ftp_upload/54053/54053fig3.jpg" /> 
Figure 3. Passive sampler uptake curve. A) and C) uptake curve for the accumulated amount of acetamiprid and dimethoate, respectively, in the passive samplers (Nt) in ng absolute, and B) and D) water tank concentration of acetamiprid and dimethoate, respectively, in ng L-1. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54053/54053fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol>
	<li>Calculate the equivalent water volume (Veq L) for a passive sampler by dividing the accumulated amount of target compounds in the passive sampler after t days of exposure (N&#39;t, ng) by the concentration in the water phase using grab and time integrated active sampling (cw, ng L-1). 
	<img alt="Equation 1" src="/files/ftp_upload/54053/54053eq1.jpg" /> (1)</li>
	<li>Derive the sampling rate (RS, L day-1) from the linear uptake phase of the uptake profile, by taking the slope of Veq versus deployment time.</li>
	<li>Calculate the KPW (L kg-1) for individual pesticides using Eq. 2. 
	<img alt="Equation 2" src="/files/ftp_upload/54053/54053eq2.jpg" /> (2) 
	where mp is the sorbent mass per sampler (ng).</li>
	<li>In the linear uptake phase, calculate the TWA concentration of the analyte in water derived by the passive sampler (cTWA, ng L-1) using Eq. 3. 
	<img alt="Equation 3" src="/files/ftp_upload/54053/54053eq3.jpg" />&#160;(3) 
	where RS is the sampling rate (L day-1), and t is the deployment time (days).</li>
	<li>In the curvilinear phase, calculate cTWA using Eq. 4. 
	<img alt="Equation 4" src="/files/ftp_upload/54053/54053eq4.jpg" /> (4)</li>
	<li>In the equilibrium phase, calculate cTWA using Eq. 5. 
	<img alt="Equation 5" src="/files/ftp_upload/54053/54053eq5.jpg" /> (5)</li>
</ol>
&#160;&#160;&#160;
7. Statistical Data Analysis
<ol>
	<li>Test non-normal distribution of the data using a Shapiro-Wilk test23. Use non-parametric Spearman&#39;s rank correlation for KPW and RS vs physicochemical properties of the tested pesticides (Spearman&#39;s rho ranging from -1 to 1)24.</li>
</ol>

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Forensics. 2 (4), 359-362 (2001).</li><li>Morin, N., Mi&#232;ge, C., Coquery, M., Randon, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+calibration,+performance,+validation+and+applications+of+the+polar+organic+chemical+integrative+sampler+(POCIS)+in+aquatic+environments.">Chemical calibration, performance, validation and applications of the polar organic chemical integrative sampler (POCIS) in aquatic environments.</a> TrAC - Trend. Anal. Chem. 36, 144-175 (2012).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Water+Quality+-+Sampling+-+Part+23:+Guidance+on+Passive+Sampling+in+Surface+Waters.">Water Quality - Sampling - Part 23: Guidance on Passive Sampling in Surface Waters.</a> ISO 5667-23:2011. , (2011).</li><li>Morin, N., Camilleri, J., Cren-Oliv&#233;, C., Coquery, M., Mi&#232;ge, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+uptake+kinetics+and+sampling+rates+for+56+organic+micropollutants+using+"pharmaceutical"+POCIS.">Determination of uptake kinetics and sampling rates for 56 organic micropollutants using "pharmaceutical" POCIS.</a> Talanta. 109, 61-73 (2013).</li></ol>

The authors have nothing to disclose.

For quality control, as standard procedure, laboratory blanks, limits of detection (LOD), recoveries, and repeatability were examined23. A few pesticides were detected in the blank samples at low concentration levels. LODs were set as the value of the lowest point on the calibration curve which meets the criteria of a signal to noise ratio of 3. The average LODs were 8.0 pg absolute injected on column for silicone rubber, 1.7 pg absolute for POCIS-A, 1.6 pg absolute for POCIS-B, 3.0 pg absolute for SDB-RPS disk, and 1.6 pg absolute for C18 disk. All concentrations were corrected by the spiked IS mixture. Average method recoveries based on spiked passive samples of the native pesticides (n = 3) were 68%, 110%, 92%, 89% and 70% for silicone rubber, POCIS-A, POCIS-B, SDB-RPS disk and C18 disk, respectively. The average repeatability for individual pesticides (n = 10) were 19%, 20%, 16%, 33% and 36% for silicone rubber, POCIS-A, POCIS-B, SDB-RPS disk and C18 disk, respectively.
Most pesticides had a short linear uptake curve (5 to 10 days) and equilibrated after 26 days, i.e., 89 of the 124 for silicone rubber, 97 of 124 for POCIS-A, 99 of 124 for POCIS-B, 32 of 124 for SDB-RPS disk and 36 of 124 for C18 disk. Therefore, for most pesticides a log K&#39;PW could be calculated (Table 1). If a pesticide did not equilibrate, a log K&#39;PW was assumed to be higher than the calculated log K&#39;PW for the equilibration phase. The median R&#39;S (L day-1) were 0.86 for silicone rubber, 0.22 for POCIS-B, 0.18 for POCIS-A, 0.05 for SDB-RPS disk and 0.02 for C18 disk. The high R&#39;S for silicone rubber can be explained by the higher sorbent mass (mp) of silicone rubber (mp = 15.6 g) compared to the other passive samplers (mp = 0.22-0.58 g). The median log KPW (L kg-1) were 4.78 for POCIS-B, 4.56 for POCIS-A, 3.17 for SDB-RPS disk, 3.14 for silicone rubber and 2.71 for C18 disk. Differences can be explained by different surface areas (ap) which were higher for POCIS-A and POCIS-B (ap = 1.78 &#215; 106 cm2 and 2.82 &#215; 106 cm2, respectively) compared to silicone rubber (ap = 457 cm2), SDB-RPS disk and C18 disk (ap = 35 cm2 for both). It is important to note that the R&#39;S can vary between different calibration methods and the type of passive sampler, thus there is a need to define standardized protocols for calibration procedures25.
This study was performed using static depletion which has the advantage to have a simple set-up with many replicates but concentration depletion over time needs to be considered. Future uptake studies should be performed using flow-through exposure tanks with constant exposure concentrations or in-situ under realistic field deployment conditions19. Natural water was used in the laboratory calibration experiments, however, the DOC can have an influence on the determination of sampling rates.19 Furthermore, the usage of performance and reference compounds (PRCs), which are spiked to the passive samplers before deployment, can be used to calculate in-situ uptake rates and allow for more accurate estimates of TWA concentrations.26
The log KPW of silicone rubber and C18 disk showed a significant positive correlation with log KOW (Spearman&#39;s rho = 0.53 and 0.48, respectively; p &#60; 0.0001). For the log RS values, a significant positive correlation was only found between log RS and log KOW of silicone rubber (Spearman&#39;s rho = 0.56, p &#60; 0.0001). In general, the KOW has been shown to be a good parameter to predict the suitability of the passive sampler for specific target compounds14,27. A variety of different pesticides were investigated in this study with a log KOW ranging from -2.6 to 7.0. In general, the five tested passive samplers were capable to accumulate pesticides with a wide range of different KOW for silicone rubber (KOW = 0.70 - 7.0), POCIS A (-1.9 - 5.3), POCIS B (-1.9 - 5.2), SDB-RPS disk (-1.2 - 4.7) and C18 disk (1.3 - 5.3) (Figure 4). Our results showed that silicone rubber is more suitable for hydrophobic compounds (log KOW &#62; 5.3), whereas more polar compounds (log KOW &#60; 0.70) were better taken up by POCIS A, POCIS B and SDB-RPS disk (Figure 4).

Pesticides are continuously introduced to the aquatic environment and may pose a risk to aquatic organisms1. Monitoring of pesticides in the aqueous environment is typically performed using grab sampling, however, this sampling technique does not fully account for temporal variations in concentrations due to fluctuations in flow or episodic inputs (e.g., precipitation, combined sewer overflows, sewage lagoon release)2,3. Thus, monitoring methods need to be improved for a better estimation of environmental risks associated with pesticides. Passive sampling allows continuous monitoring over an extended period of time with minimal infrastructure and low contaminant concentrations4,5.
Passive samplers have been shown to be a valuable tool for the monitoring in groundwater6, fresh water7-10, wastewater11 and marine waters12. Besides monitoring purposes13,14, passive samplers have also been used for non-target analysis15, toxicology testing16,17, and as an alternative to sediment- and biomonitoring18. Passive samplers accumulate chemicals continuously from water and provide time weighted average (TWA) concentrations14. The uptake of the contaminant depends on the sampling rate (RS) and passive sampler-water partition coefficient (KPW), which depends on the passive sampler design, sampler material, physicochemical properties of the contaminant, and environmental conditions (e.g., water turbulence, temperature)13,14,19,20.
The detailed video aims to show how to calibrate and apply passive samplers for pesticides in water. The specific objectives included i) to perform preparation, extraction and instrumental analysis for 124 individual pesticides using five different types of passive samplers, including silicone rubber, polar organic chemical integrative sampler (POCIS)-A, POCIS-B, SDB-RPS and C18 disk, ii) to assess RS and KPW for the pesticides in a laboratory uptake study, and iii) to demonstrate how to select the appropriate passive sampler of the target compound of interest and how to calculate TWA concentrations for the respective passive sampler.
Reference standards and passive sampler devices
Target compounds included 124 legacy and currently used pesticides including herbicides, insecticides and fungicides (Table 1). Internal standard mixture (IS mixture) included fenoprop (2,4,5-TP), clothianidin-D3, ethion and terbuthylazine-D5. Other used chemicals included methanol (MeOH), acetonitrile (ACN), acetone (ACE), dichloromethane (DCM), cyclohexane (CH), ethyl acetate (EA), petroleum ether (PE), 2-propanol, 25% ammonia solution, acetic acid (HAc) and formic acid (FA). Five different passive sampling devices were characterized, including silicone rubber, POCIS-A and POCIS-B, SDB-RPS, and C18 disk1,21.
Table 1. Passive sampler sampling rate (R&#39;S, L day-1), sampler-water partition coefficients (K&#39;PW, L kg-1) and equations (Eq.) used for the calculation of concentrations in field samples for individual pesticidesa. (Reprinted from Journal of Chromatography A, 1405, Lutz Ahrens, Atlasi Daneshvar, Anna E. Lau, Jenny Kreuger, Characterization of five passive sampling devices for monitoring of pesticides in water, 1-11, Copyright (2015), with permission from Elsevier.)22 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54053/Table_1.xlsx" target="_blank">Please click here to download this file.</a>

<table border="0" cellpadding="0" cellspacing="0" width="1047">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Methanol</td>
			<td style="width:164px;">Merck Millipore</td>
			<td style="width:163px;">1.06035.2500</td>
			<td style="width:228px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acetonitrile</td>
			<td>Merck Millipore</td>
			<td>1.00029.2500&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:22px;width:492px;">Acetone</td>
			<td>Merck Millipore</td>
			<td style="width:163px;">1.00012.2500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-propanol</td>
			<td>Merck Millipore</td>
			<td>1.00272.2500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dichloromethane</td>
			<td>Merck Millipore</td>
			<td>1.06054.2500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammoniak</td>
			<td>Merck Millipore</td>
			<td>1.05428.1000</td>
			<td>Purity 25%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Formic acid</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td>94318-50ML-F</td>
			<td>Purity ~98%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:22px;">Ethyl acetate&#160;</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td>31063-2.5L</td>
			<td>for pesticide residue analysis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:22px;">Petroleum ether&#160;</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td>34491-4X2.5L</td>
			<td>for pesticide residue analysis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acetic acid&#160;</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td>320099-500ML</td>
			<td>Purity &#8805;99.7%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cyclohexane&#160;</td>
			<td style="width:164px;">Fisher Chemicals</td>
			<td>C/8933/17</td>
			<td>for residue analysis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Empty polypropylene SPE Tube with PE frits, 20 &#956;m porosity, volume 6&#160;mL</td>
			<td style="width:164px;">Supelco</td>
			<td>57026</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Empore SPE Disks, C18, diam. 47&#160;mm</td>
			<td>Supelco</td>
			<td style="width:163px;">66883-U</td>
			<td>Passive sampler</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Empore SPE Disks, SDB-RPS (Reversed-Phase Sulfonate), diam. 47&#160;mm</td>
			<td>Supelco</td>
			<td style="width:163px;">66886-U&#160;</td>
			<td>Passive sampler</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">POCIS-A&#160;</td>
			<td>EST</td>
			<td style="width:163px;">POCIS-HLB</td>
			<td>Passive sampler</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">POCIS-B</td>
			<td>EST</td>
			<td style="width:163px;">POCIS-Pesticide&#160;</td>
			<td>Passive sampler</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Polyethersulfone (PES) membranes</td>
			<td>EST</td>
			<td style="width:163px;">PES</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Silicone rubber sheet</td>
			<td style="width:164px;">Altec</td>
			<td style="width:163px;">03-65-4516</td>
			<td>Passive sampler</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Agilent 5975C</td>
			<td style="width:164px;">Agilent Technologies</td>
			<td style="width:163px;">5975C</td>
			<td>GC-MS</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:492px;">HP-5MS UI</td>
			<td style="width:164px;">J&#38;W Scientific</td>
			<td style="width:163px;">HP-5MS</td>
			<td>Analytical column for GC-MS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Agilent 6460</td>
			<td style="width:164px;">Agilent Technologies</td>
			<td style="width:163px;">6460</td>
			<td>HPLC-MS/MS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Strata C18&#8211;E, 20 x 2 mm id and 20&#8211;25 &#956;m particle size</td>
			<td style="width:164px;">Phenomenex</td>
			<td style="width:163px;">Strata C18&#8211;E</td>
			<td style="width:228px;">Online SPE column for LC-MS/MS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Strata X, 20 x 2 mm id and 20&#8211;25 &#956;m particle size</td>
			<td style="width:164px;">Phenomenex</td>
			<td style="width:163px;">Strata X</td>
			<td style="width:228px;">Online SPE column for LC-MS/MS</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:492px;">Zorbax Eclipse Plus C18</td>
			<td style="width:164px;">Agilent Technologies</td>
			<td style="width:163px;">Zorbax Eclipse Plus C18</td>
			<td>Analytical column for LC-MS/MS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Isolute phase separator, 25 mL</td>
			<td style="width:164px;">Biotage</td>
			<td style="width:163px;">120-1907-E</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:492px;">Stainless steel blind rivet, 3.2x10 mm</td>
			<td style="width:164px;">Ejot &#38; Avdel</td>
			<td style="width:163px;">951222</td>
			<td></td>
		</tr>
	</tbody>
</table>

characterization and application of passive samplers for monitoring of pesticides in water

Five different water passive samplers were calibrated under laboratory conditions for measurement of 124 legacy and current used pesticides. This study provides a protocol for the passive sampler preparation, calibration, extraction method and instrumental analysis. Sampling rates (RS) and passive sampler-water partition coefficients (KPW) were calculated for silicone rubber, polar organic chemical integrative sampler POCIS-A, POCIS-B, SDB-RPS and C18 disk. The uptake of the selected compounds depended on their physicochemical properties, i.e., silicone rubber showed a better uptake for more hydrophobic compounds (log octanol-water partition coefficient (KOW) &#62; 5.3), whereas POCIS-A, POCIS-B and SDB-RPS disk were more suitable for hydrophilic compounds (log KOW &#60; 0.70).

Five different passive sampler techniques were compared for the uptake of 124 legacy and current used pesticides including silicone rubber (Figure 1), and POCIS A, POCIS B, SDB-RPS and C18 disk (Figure 2). The performance of the extraction method and instrumental analysis was optimized. The outcome of the laboratory uptake experiments can be used to calculate the R&#39;S and log K&#39;PW values (Table 1) based on the uptake profile for individual pesticides (Figure 3). The results showed that silicone rubber is more suitable for hydrophobic compounds (log octanol-water partition coefficient (K&#39;OW) &#62; 5.3), whereas more polar compounds (log K&#39;OW &#60; 0.70) were better taken up by POCIS A, POCIS B and SDB-RPS disk (Figure 4). R&#39;S (L day-1), K&#39;PW (L kg-1) and equations (Eq.) can be used for the calculation of concentrations in field samples for individual pesticides (Table 1)22.
<img alt="Figure 4" src="/files/ftp_upload/54053/54053fig4.jpg" /> 
Figure 4. KOW vs passive sampler type. Box-Whisker-Plots for individual pesticides taken up by silicone rubber (n = 86), polar organic chemical integrative sampler (POCIS)-A (n = 106), POCIS-B (n = 110), SDB-RPS disk (n = 65), and C18 disk (n = 54) in relation to their octanol-water partition coefficient (KOW). Note: Pesticides were only included if the mean pesticide concentration in the passive sampler was greater than 0.1% compared to the mean pesticide concentration in the water. (Modified from Journal of Chromatography A, 1405, Lutz Ahrens, Atlasi Daneshvar, Anna E. Lau, Jenny Kreuger, Characterization of five passive sampling devices for monitoring of pesticides in water, 1-11, Copyright (2015), with permission from Elsevier.)22 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54053/54053fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Characterization and Application of Passive Samplers for Monitoring of Pesticides in Water at JoVE.com

Characterization and Application of Passive Samplers for Monitoring of Pesticides in Water

A protocol about the characterization and application of five different passive sampling devices is presented.

Five different water passive samplers were calibrated under laboratory conditions for measurement of 124 legacy and current used pesticides. This study ...

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9.4K Views.  Swedish University of Agricultural Sciences. A protocol about the characterization and application of five different passive sampling devices is presented.

Video: Characterization and Application of Passive Samplers for Monitoring of Pesticides in Water

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Chronoamperometric growth of anodic electroactive microbial biofilms in a fed-batch reactor using a three-electrode setup, controlled by a potentiostat, is demonstrated. The extracellular electron transfer is characterized using cyclic voltammetry in the presence of the electron donor and in the absence of the electron donor. Fundamental data analysis is demonstrated.

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EPA Method 1615 was developed with a goal of providing a standard method for measuring enteroviruses and noroviruses in environmental and drinking waters. The standardized sampling component of the method concentrates viruses that may be present in water by passage of a minimum specified volume of water through an electropositive cartridge filter. The minimum specified volumes for surface and finished/ground water are 300 L and 1,500 L, respectively. A major method limitation is the tendency for the filters to clog before meeting the sample volume requirement. Studies using two different, but equivalent, cartridge filter options showed that filter clogging was a problem with 10% of the samples with one of the filter types compared to 6% with the other filter type. Clogging tends to increase with turbidity, but cannot be predicted based on turbidity measurements only. From a cost standpoint one of the filter options is preferable over the other, but the water quality and experience with the water system to be sampled should be taken into consideration in making filter selections.

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Agricultural ammonia (NH3) emissions (90% of total EU emissions) are responsible for about 45% airborne eutrophication, 31% soil acidification and 12% ...

Extraction of Organochlorine Pesticides from Plastic Pellets and Plastic Type Analysis

Plastic resin pellets, categorized as microplastics (&#8804;5 mm in diameter), are small granules that can be unintentionally released to the environment during manufacturing and transport. Because of their environmental persistence, they are widely distributed in the oceans and on beaches all over the world. They can act as a vector of potentially toxic organic compounds (e.g., polychlorinated biphenyls) and might consequently negatively affect marine organisms. Their possible impacts along the food chain are not yet well understood. In order to assess the hazards associated with the occurrence of plastic pellets in the marine environment, it is necessary to develop methodologies that allow for rapid determination of associated organic contaminant levels. The present protocol describes the different steps required for sampling resin pellets, analyzing adsorbed organochlorine pesticides (OCPs) and identifying the plastic type. The focus is on the extraction of OCPs from plastic pellets by means of a pressurized fluid extractor (PFE) and on the polymer chemical analysis applying Fourier Transform-InfraRed (FT-IR) spectroscopy. The developed methodology focuses on 11 OCPs and related compounds, including dichlorodiphenyltrichloroethane (DDT) and its two main metabolites, lindane and two production isomers, as well as the two biologically active isomers of technical endosulfan. This protocol constitutes a simple and rapid alternative to existing methodology for evaluating the concentration of organic contaminants adsorbed on plastic pieces.

Microplastics act as vector of potentially toxic organic contaminants with unpredictable effects. This protocol describes an alternative methodology for assessing the levels of organochlorine pesticides adsorbed on plastic pellets and identifying the polymer chemical structure. The focus is on pressurized fluid extraction and attenuated total reflectance Fourier transform infrared spectroscopy.

Plastic resin pellets, categorized as microplastics (&#8804;5 mm in diameter), are small granules that can be unintentionally released to the environment ...

Continuous Instream Monitoring of Nutrients and Sediment in Agricultural Watersheds

Pollutant concentrations and loads in watersheds vary considerably with time and space. Accurate and timely information on the magnitude of pollutants in water resources is a prerequisite for understanding the drivers of the pollutant loads and for making informed water resource management decisions. The commonly used &#34;grab sampling&#34; method provides the concentrations of pollutants at the time of sampling (i.e., a snapshot concentration) and may under- or overpredict the pollutant concentrations and loads. Continuous monitoring of nutrients and sediment has recently received more attention due to advances in computing, sensing technology, and storage devices. This protocol demonstrates the use of sensors, sondes, and instrumentation to continuously monitor in situ nitrate, ammonium, turbidity, pH, conductivity, temperature, and dissolved oxygen (DO) and to calculate the loads from two streams (ditches) in two agricultural watersheds. With the proper calibration, maintenance, and operation of sensors and sondes, good water quality data can be obtained by overcoming challenging conditions such as fouling and debris buildup. The method can also be used in watersheds of various sizes and characterized by agricultural, forested, and/or urban land.

With the advancement of technology and the rise in end-user expectations, the need and use of higher temporal resolution data for pollutant load estimation has increased. This protocol describes a method for continuous in situ water quality monitoring to obtain higher temporal resolution data for informed water resource management decisions.

Pollutant concentrations and loads in watersheds vary considerably with time and space. Accurate and timely information on the magnitude of pollutants in ...

Continuous Hydrologic and Water Quality Monitoring of Vernal Ponds

Vernal ponds, also referred to as vernal pools, provide critical ecosystem services and habitat for a variety of threatened and endangered species. However, they are vulnerable parts of the landscapes that are often poorly understood and understudied. Land use and management practices, as well as climate change are thought to be a contribution to the global amphibian decline. However, more research is needed to understand the extent of these impacts. Here, we present methodology for characterizing a vernal pond's morphology and detail a monitoring station that can be used to collect water quantity and quality data over the duration of a vernal pond's hydroperiod. We provide methodology for how to conduct field surveys to characterize the morphology and develop stage-storage curves for a vernal pond. Additionally, we provide methodology for monitoring the water level, temperature, pH, oxidation-reduction potential, dissolved oxygen, and electrical conductivity of water in a vernal pond, as well as monitoring rainfall data. This information can be used to better quantify the ecosystem services that vernal ponds provide and the impacts of anthropogenic activities on their ability to provide these services.

Understanding the ecosystem services and processes provided by vernal ponds and the impacts of anthropogenic activities on their ability to provide these services requires intensive hydrologic monitoring. This sampling protocol using in-situ monitoring equipment was developed to understand the impact of anthropogenic activities on water levels and quality.

Vernal ponds, also referred to as vernal pools, provide critical ecosystem services and habitat for a variety of threatened and endangered species. ...

Improving Infrared Spectroscopy Characterization of Soil Organic Matter with Spectral Subtractions

Soil organic matter (SOM) underlies numerous soil processes and functions. Fourier transform infrared (FTIR) spectroscopy detects infrared-active organic bonds that constitute the organic component of soils. However, the relatively low organic matter content of soils (commonly &#60; 5% by mass) and absorbance overlap of mineral and organic functional groups in the mid-infrared (MIR) region (4,000-400 cm-1) engenders substantial interference by dominant mineral absorbances, challenging or even preventing interpretation of spectra for SOM characterization. Spectral subtractions, a post-hoc mathematical treatment of spectra, can reduce mineral interference and enhance resolution of spectral regions corresponding to organic functional groups by mathematically removing mineral absorbances. This requires a mineral-enriched reference spectrum, which can be empirically obtained for a given soil sample by removing SOM. The mineral-enriched reference spectrum is subtracted from the original (untreated) spectrum of the soil sample to produce a spectrum representing SOM absorbances. Common SOM removal methods include high-temperature combustion (&#39;ashing&#39;) and chemical oxidation. Selection of the SOM removal method carries two considerations: (1) the amount of SOM removed, and (2) absorbance artifacts in the mineral reference spectrum and thus the resulting subtraction spectrum. These potential issues can, and should, be identified and quantified in order to avoid fallacious or biased interpretations of spectra for organic functional group composition of SOM. Following SOM removal, the resulting mineral-enriched sample is used to collect a mineral reference spectrum. Several strategies exist to perform subtractions depending on the experimental goals and sample characteristics, most notably the determination of the subtraction factor. The resulting subtraction spectrum requires careful interpretation based on the aforementioned methodology. For many soil and other environmental samples containing substantial mineral components, subtractions have strong potential to improve FTIR spectroscopic characterization of organic matter composition.

SOM underlies many soil functions and processes, but its characterization by FTIR spectroscopy is often challenged by mineral interferences. The described method can increase the utility of SOM analysis by FTIR spectroscopy by subtracting mineral interferences in soil spectra using empirically obtained mineral reference spectra.

Soil organic matter (SOM) underlies numerous soil processes and functions. Fourier transform infrared (FTIR) spectroscopy detects infrared-active organic ...

The Plant Infection Test: Spray and Wound-Mediated Inoculation with the Plant Pathogen Magnaporthe Grisea

Plants possess a powerful system to defend themselves against potential threats by pathogenic fungi. For agriculturally important plants, however, current measures to combat such pathogens have proved too conservative and, thus, not sufficiently effective, and they can potentially pose environmental risks. Therefore, it is extremely necessary to identify host-resistance factors to assist in controlling plant diseases naturally through the identification of resistant germplasm, the isolation and characterization of resistance genes, and the molecular breeding of resistant cultivars. In this regard, there is need to establish an accurate, rapid, and large-scale inoculation method to breed and develop plant resistance genes. The rice blast fungal pathogen Magnaporthe grisea causes severe disease symptoms and yield losses. Recently, M. grisea has emerged as a model organism for studying the mechanisms of plant-fungal pathogen interactions. Hence, we report the development of a plant virulence test method that is specific for M. grisea. This method provides for both spray inoculation with a conidial suspension and wounding inoculation with mycelium cubes or droplets of conidial suspension. The key step of the wounding inoculation method for detached rice leaves is to make wounds on plant leaves, which avoids any interference caused by host penetration resistance. This spray/wounding protocol contributes to the rapid, accurate, and large-scale screening of the pathotypes of M. grisea isolates. This integrated and systematic plant infection method will serve as an excellent starting point for gaining a broad perspective of issues in plant pathology.

The Plant Infection Test: Spray and Wound-Mediated Inoculation with the Plant Pathogen Magnaporthe Grisea

Here, we present a protocol to test plant virulence with the plant pathogen Magnaporthe grisea. This report will contribute to the large-scale screening of the pathotypes of fungi isolates and serve as an excellent starting point for understanding the resistant mechanisms of plants during molecular breeding.

Plants possess a powerful system to defend themselves against potential threats by pathogenic fungi. For agriculturally important plants, however, current ...

Visualizing Efficacy of Pesticides Against Disease Vector Mosquitoes in the Field

Efficacy of public health pesticides targeting nuisance and disease-vector insects such as mosquitoes, sand flies, and filth-breeding flies is not uniform across ecological zones. To best protect public and veterinary health from these insects, the environmental limitations of pesticides need to be investigated to inform effective use of the most appropriate pesticide formulations and techniques. We have developed a research program to evaluate combinations of pesticides, pesticide application equipment, and application techniques in hot-arid desert, hot-humid tropical, warm and cool temperate, and urban locations to derive pesticide use guidelines specific to target insect and environment. To these ends we designed a system of protocols to support efficient, cost-effective, portable, and standardized evaluation of a diverse range of pesticides and equipment across multiple environments. At the core of these protocols is the use of an array of small cages with colony-reared sentinel mosquitoes (adults and immatures) and sand flies (adults), strategically arranged in natural habitats and exposed to pesticide spray. Spatial and temporal patterns of pesticide efficacy are derived from percent mortality in sentinel cages, then mapped and visualized in a geographic information system. Maps of sentinel mortality data may be statistically compared to evaluate relative efficacy of a pesticide across multiple environments, or to study multiple pesticides in a single environment. Protocols may be modified to accommodate a variety of scenarios, including, for example, the vertical orientation of sentinels in canopy habitats or simultaneous testing of ground and aerial application methods.

The efficacy of public health pesticides targeting nuisance and disease-vector insects is not uniform across different ecological zones. Here we present a system of techniques using captive vector insects as sentinels for pesticide efficacy to derive electronic maps supporting the standard evaluation of pesticides across multiple environments.

Efficacy of public health pesticides targeting nuisance and disease-vector insects such as mosquitoes, sand flies, and filth-breeding flies is not uniform ...