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

Summary

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

Abstract

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 (R_S) and passive sampler-water partition coefficients (K_PW) 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 (K_OW) > 5.3), whereas POCIS-A, POCIS-B and SDB-RPS disk were more suitable for hydrophilic compounds (log K_OW < 0.70).

Introduction

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 infrastru....

Protocol

1. Passive Sampler Design and Preparation

1. Silicone rubber sheets
   1. 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).
2. 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....

Results

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'_S and log K'_PW values (Table 1

Discussion

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 dis.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Methanol	Merck Millipore	1.06035.2500
Acetonitrile	Merck Millipore	1.00029.2500
Acetone	Merck Millipore	1.00012.2500
2-propanol	Merck Millipore	1.00272.2500
Dichloromethane	Merck Millipore	1.06054.2500
Ammoniak	Merck Millipore	1.05428.1000	Purity 25%
Formic acid	Sigma-Aldrich	94318-50ML-F	Purity ~98%
Ethyl acetate	Sigma-Aldrich	31063-2.5L	for pesticide residue analysis
Petroleum ether	Sigma-Aldrich	34491-4X2.5L	for pesticide residue analysis
Acetic acid	Sigma-Aldrich	320099-500ML	Purity ≥99.7%
Cyclohexane	Fisher Chemicals	C/8933/17	for residue analysis
Empty polypropylene SPE Tube with PE frits, 20 μm porosity, volume 6 ml	Supelco	57026
Empore SPE Disks, C18, diam. 47 mm	Supelco	66883-U	Passive sampler
Empore SPE Disks, SDB-RPS (Reversed-Phase Sulfonate), diam. 47 mm	Supelco	66886-U	Passive sampler
POCIS-A	EST	POCIS-HLB	Passive sampler
POCIS-B	EST	POCIS-Pesticide	Passive sampler
Polyethersulfone (PES) membranes	EST	PES
Silicone rubber sheet	Altec	03-65-4516	Passive sampler
Agilent 5975C	Agilent Technologies	5975C	GC-MS
HP-5MS UI	J&W Scientific	HP-5MS	Analytical column for GC-MS
Agilent 6460	Agilent Technologies	6460	HPLC-MS/MS
Strata C18–E, 20 x 2 mm id and 20–25 μm particle size	Phenomenex	Strata C18–E	Online SPE column for LC-MS/MS
Strata X, 20 x 2 mm id and 20–25 μm particle size	Phenomenex	Strata X	Online SPE column for LC-MS/MS
Zorbax Eclipse Plus C18	Agilent Technologies	Zorbax Eclipse Plus C18	Analytical column for LC-MS/MS
Isolute phase separator, 25 ml	Biotage	120-1907-E
Stainless steel blind rivet, 3.2x10 mm	Ejot & Avdel	951222