Organophosphorus Pesticides In Water Research Articles

Optimization of a single-drop microextraction procedure for the determination of organophosphorus pesticides in water and fruit juice with gas chromatography-flame photometric detection

A single-drop microextraction (SDME) procedure was developed for the analysis of organophosphorus pesticides (OPPs) in water and fruit juice by gas chromatography (GC) with flame photometric detection (GC-FPD). The significant parameters affecting the SDME performance such as selection of microextraction solvent, solvent volume, extraction time, stirring rate, sample pH and temperature, and ionic strength were studied and optimized. Two types of SDME mode, static and cycle-flow SDME, were evaluated. The static SDME procedure provided more sensitive analysis of the target analytes. Therefore, static SDME with tributyl phosphate (TBP) as internal standard was selected for the real sample analysis. The limits of detection (LODs) in water for the six studied compounds were between 0.21 and 0.56 ng/mL with the relative standard deviations ranging from 1.7 to 10.0%. Linear response data was obtained in the concentration range of 0.5–50 ng/mL (except for dichlorvos 1.0–50 ng/mL) with correlation coefficients from 0.9995 to 0.9999. Environmental water sample collected from East Lake and fruit juice samples were successfully analyzed using the proposed method, but none of the analytes in both lake water and fruit juice were detected. The recoveries for the spiked water and juice samples were from 77.7 to 113.6%. Compared with the conventional methods, the proposed method enabled a rapid and simple determination of organophosphorus pesticides in water and fruit juice with minimal solvent consumption and a higher concentration capability.

Determination of organophosphorus pesticides in water samples by single drop microextraction and gas chromatography-flame photometric detector

In this paper we have developed single drop microextraction (SDME) with modified 1.00 μl microsyringe, followed by gas chromatography with flame photometric detector (GC-FPD) for determination of 13 organophosphorus pesticides (OPPs) in water samples. By using a 1.00 μl microsyringe the repeatability of drop volume and injection were improved, because of using maximum volume of microsyringe and no dead volume. On the other hand, the modification of needle tip caused increasing cross section of needle tip and increasing adhesion force between needle tip and drop, thereby increasing drop stability and achieving a higher stirrer speed (up to 1700 rpm). The method used 0.9 μl of carbon tetrachloride as extractant solvent, 40 min extraction time, stirring at 1300 rpm and no salt addition. The enrichment factor of this method ranged from 540 to 830. The linear ranges were 0.01–100 μg/l (four orders of magnitude) and limits of detection were 0.001–0.005 μg/l for most of analyte. The relative standard deviation (RSD%) for 2 μg/l of OPPs in water by using internal standard was in the range 1.1–8.6% ( n = 5). The recoveries of OPPs from farm water at spiking level of 1.0 μg/l were 91–104%.

Use of cholinesterase activity as an indicator for the effects of combinations of organophosphorus pesticides in water from environmental sources

Organophosphorus pesticides (OPs) are commonly detected in agricultural products, animal-derived foodstuffs, and environmental samples. Until now, the focus of research has been to evaluate the adverse effect of a single OP. While each OP may be present at concentrations under recognized as “no observed adverse effect level (NOAEL)”, the combined effects of multiple OPs present at these low concentrations have not been sufficiently studied. Therefore, we developed an in vitro testing method to evaluate the toxicity of multiple OPs based on the degree of inhibition of cholinesterase (ChE) activity. This method requires only 10 min to complete and no specialized technology. We examined 15 OPs by this method and categorized them into three groups according to the degree of ChE inhibition. A relationship between the OPs’ chemical structures and the degree of ChE inhibition emerged with the moiety –P–O–C N– showing the strongest action. The degree of ChE inhibition increased with multiple OPs, and the degree of inhibition seemed to be additive. These results demonstrate that the combined toxicity of multiple OPs present in food or environmental samples is an easily determined and toxicologically relevant measure of overall toxicity of complex OPs mixtures. It is possible to apply this testing method as a monitoring technique in water quality management in order to control OPs. As a result, this method can play the role for the potential risk reduction to the ecosystem and may contribute to the preservation of the environment.

Determination of organophosphorus pesticides in cucumber and potato by stir bar sorptive extraction

Organophosphorus pesticides (OPPs) in vegetables were determined by stir bar sorptive extraction (SBSE) and capillary gas chromatography with thermionic specific detection (TSD). Hydroxy-terminated polydimethylsioxane (PDMS) prepared by sol–gel method was used as extraction phase. The effects of extraction temperature, salting out, extraction time on extraction efficiency were studied. The detection limits of OPPs in water were ≤1.2 ng/l. This method was also applied to the analysis of OPPs in vegetable samples and matrix effect was studied. Linear ranges of OPPs in vegetable samples were 0.05–50 ng/g with detection limits ≤0.15 ng/g and the repeatability of the method was less than 20% relative standard deviation.

Selective solid-phase extraction using molecularly imprinted polymer for the analysis of polar organophosphorus pesticides in water and soil samples

An analytical methodology for the analysis of four polar organophophorus pesticides (monocrotophos, mevinphos, phosphamidon, omethoate) in water and soil samples incorporating a molecularly imprinted solid-phase extraction (MISPE) process using a monocrotophos-imprinted polymer was developed. Binding study demonstrated that the polymer showed excellent affinity and high selectivity to monocrotophos. The MISPE procedure including the clean-up step to remove any interferences was optimized. The accuracy and selectivity of the MISPE process developed were verified using a non-imprinted (blank) polymer and a classical ENVI-18 cartridge as the SPE matrix during control experiments. The use of MISPE improved the accuracy and precision of the GC method and lowered the limit of detection. The recoveries of four polar organophosphorus pesticides (OPPs) extracted from 1 L of river water at a 100 ng/L spike level were in the range of 77.5–99.1%. The recoveries of organophosphorus pesticides extracted from a 5-g soil sample at the 100 μg/kg level were in the range of 79.3–93.5%. The limit of detection varied from 10 to 32 ng/L in water and from 12 to 34 μg/kg in soil samples. The molecularly imprinted polymer (MIP) enabled the selective extraction of four organophosphorus pesticides successfully from water and soil samples, demonstrating the potential of molecularly imprinted solid-phase extraction for rapid, selective, and cost-effective sample pretreatment.

The adsorption behavior of three organophosphorus pesticides in peat and soil samples and their degradation in aqueous solutions at different temperatures and pH values

The sorption behavior of three organophosphorus pesticides, methyl parathion, parathion and phoxim, was studied with batch equilibrium experiments in three different soil and peat samples. The results showed that their sorption behavior could be best described by the Freundlich adsorption isotherm. The soil organic matter content plays a controlling role in the adsorption of these pesticides on the soils. The normalized carbon adsorption constants (K oc) for the three pesticides, ranging from 657 to 1976, were relatively high and thus the mobilities of these pesticides are expected to be moderate for methyl parathion and very low for parathion and phoxim. The hydrolysis of these pesticides was investigated in double distilled water incubated under different temperature and pH conditions. Temperature showed a significant effect on the rates of hydrolysis. Methyl parathion hydrolyzed in the dark with a half-life of 2.25 days at 45°C compared to 68 days at 8°C. The three pesticides are unstable in alkaline conditions, especially phoxim. Hydrolysis rather than photodegradation was found to be the main degradation path for these three pesticides in aqueous conditions. The results showed that degradation of the three organophosphorus pesticides in water follows first-order kinetics. The half-lives of these pesticides were low, hence they are not expected to persist in the environment.

Fluorescence screening of organophosphorus pesticides in water by an enzyme inhibition procedure on TLC plates

An enzymatic inhibition method sufficiently sensitive for rapid screening of seven organophosphorus pesticides in water is described. Azinophos methyl, chlorpyriphos, diazinon, fenthion, methamidophos, methidathion, and omethoate were enriched from water samples by solid-phase extraction (SPE) on SDB-1 and C 18 cartridges. Recovery rates were between 94 and 102% for both extraction materials except for chlorpyriphos on C 18 ; relative standard deviations were ±0.7–3.7% and 1.1–4.9% for SDB-1 and C 18 cartridges, respectively. The pesticides were separated on silica gel TLC plates with n -hexane-acetone, 75 + 30 ( v / v ) as mobile phase. Calibration plots were linear between 100 and 2000 ng for all pesticides; correlation coefficients, r , were between 0.9994 and 0.9997. An enzymatic analysis technique on TLC plates was developed using 7-diethylamino-3-(4′-maleimidylphenyl)-4-methylcoumarin (maleimide CPM) as fluorogenic reagent. It reacts with thiocholine released after hydrolysis of acetylthiocholine wi...

Trace level determination of organophosphorus pesticides in water with the new direct-electron ionization LC/MS interface.

A new LC/MS method for the determination of organophosphorus pesticides in water, based on the use of direct-electron ionization (EI) interface, is presented. Direct-EI is a new device that, in a very simple fashion, couples a nano-HPLC system with a mass spectrometer equipped with electron ionization capability. The nanoscale liquid flow allows for a direct introduction of eluate into the ion source and, after nebulization, for its ionization under typical EI conditions. Library-matchable EI spectra are generated for a choice of full scan or SIM detection of the analytes. In our case, a selection of organophosphorus pesticides, commonly distributed in local sugar beet cultivation, were considered. The new interface permits a very sensitive detection of the analytes in a wide range of linear response (0.09-9 ng). When applied to a real sample, the method allowed detecting four different pesticides at a concentration level of approximately 3 ng x L(-1).

Determination of polar organophosphorus pesticides in aqueous samples by direct injection using liquid chromatography–tandem mass spectrometry

It was demonstrated that four out of six of the very polar organophosphorus pesticides (OPs), i.e. acephate, methamidophos, monocrotophos, omethoate, oxydemeton-methyl and vamidothion, could not be extracted from water using commonly available SPE cartridges. In addition, GC analysis on all six compounds was found to be troublesome due to their polar and thermolabile character. This initiated the development of an alternative highly sensitive and selective method for the determination of the above mentioned very polar OPs in water, based on LC–MS. Large volume (1 ml) water samples were directly injected onto an RP18 HPLC column with a polar endcapping. The latter was essential for obtaining retention and maintaining column performance under 100% aqueous conditions during the sampling. The compounds were ionized using atmospheric pressure chemical ionization and detected on a tandem mass spectrometer operated in multiple reaction-monitoring mode. The detection limits were in the range of 0.01–0.03 μg/l. Compared to conventional GC methods, the developed LC–MS procedure is very straightforward, fast and more reliable. This application demonstrates the applicability of LC–MS for analysis of polar OPs in surface, ground and drinking water, as a more favourable alternative to GC.

Ellipsometry measurements and impedance spectroscopy on Langmuir–Blodgett membranes on Si/SiO 2 for ion sensitive sensor

LB films containing butyrylcholinestrase (BuChE) are fabricated to realize an ion-sensitive field-effect transistor (ISFET) for the detection of organophosphorus pesticides in water. A common pesticide known as trichlorfon is examined in our work. Adsorbing the enzyme molecules onto stearylamine monolayer using the electrostatic force forms the BuChE-immobilised Langmuir–Blodgett (LB) films. Enzyme/stearylamine mixed LB films are immobilized onto ISFET and treated by glutaraldehyde vapor to improve the LB film’s stability. Two techniques, the ellipsomerty and spectroscopy methods, have been used to investigate the homogeneity and stability of these films. In ellipsometry the refractive index and thickness of Si/SiO 2/LB films are measured. By utilizing the spectroscopy technique the impedance spectrum of Si/SiO 2 and Si/SiO 2/LB films are obtained and compared to ellipsometry results.

Analysis of organophosphorus pesticides in water samples using a continuous membrane permeation extractor

A membrane permeation method used for the determination of organophosphorus pesticides (OPPs) at trace levels in water is described. OPPs were collected on Tenax-TA polymeric resin after permeating through a silicone polycarbonate membrane. OPPs were then stripped by thermal desorption and directed into a gas chromatograph using a helium stream for quantitative analysis. A linear relationship was found between the mass collected on Tenax-TA and the product of external concentration and exposure time. The method detection limits (MDL) for OPPs were 0.26–2.37 μg/l with the relative standard deviations (R.S.D.) less than 20%. This method provides an easy, low-cost way of preconcentrating samples. It eliminates the involvement of any organic solvent, and has the potential for automated on-site analysis of OPPs in water.

Enzyme–octadecylamine Langmuir–Blodgett membranes for ENFET biosensors

Langmuir–Blodgett (LB) films containing butyrylcholinesterase (BuChE) are fabricated to realise an enzymatic field effect transistor (ENFET) for the detection of organophosphorus pesticides in water. Trichlorfon as a common pesticide is examined in our work. The BuChE-immobilised LB films are formed by adsorbing the enzyme molecules onto a stearylamine monolayer using the electrostatic force. Enzyme/stearylamine mixed LB films are immobilized onto a pH-ISFET surface and treated by glutaraldehyde vapour to improve the LB film’s stability. The ENFET thus obtained worked as a potentiometric biosensor for trichlorfon detection on the basis of enzyme inhibition. The detection limit for trichlorfon can reach 10 −7 M (26 ppb). The surface characteristics of BuChE/stearylamine LB films obtained under various conditions of the dipping surface pressures are analysed qualitatively by atomic force microscopy (AFM) and analysed quantitatively by FTIR spectroscopy.

Multiresidue procedures for determination of triazine and organophosphorus pesticides in water by use of large-volume PTV injection in gas chromatography

Two procedures, based on large-volume injection with a programmed-temperature vaporizer (PTV), have been developed for the determination of several triazine and organophosphorus pesticides. The use of PTV for injection in gas chromatography (GC) has enabled the introduction of up to 200 μL sample extract into the GC, thus increasing the sensitivity of the method. PTV injection has been combined off-line with two different microextraction procedures—liquid-liquid partition and solid-phase extraction. A simple and rapid off-line liquid-liquid microextraction procedure (5 mL water/1 mL methyltert-butyl ether) was applied to surface water samples spiked at levels between 0.01 and 5μg L−1. Recoveries of the overall procedure were >80% and the precision was better than 15%. Detection limits were 80% and coefficients of variation <12%) and the limits of detection ranged from 1 to 9 ng L−1. Finally, several surface water samples were anlysed, and triazine herbicides were detected at concentrations of approx. 0.1–0.2 μg L−1. The results were similar to those obtained by conventional solvent extraction then GC-MSD after splitless injection of 2 μL.

Determination of organophosphorus pesticides in water by solid-phase microextraction

A solid-phase microextraction method coupled with a flame photometric detector was developed for the analysis of organophosphorus pesticides in water. Two kinds of fiber (100 μm polydimethyl siloxane (PDMS) and 85 μm polyacrylate (PA) fibers) were used and compared. Parameters that may affect the extraction, such as the duration of absorption and desorption, temperature of absorption, ionic strength, elutropic strength, and concentration of humic acid were investigated. Higher sensitivity and lower detection limits were achieved using a PA fiber than using a PDMS fiber. The detection limit is less than 0.3 μg l −1 for most of the analytes, except for mevinphos (420 μg l −1). The precision is better than 9%.

Determinação de pesticidas organofosforados em água usando microextração em fase sólida e CGAR-EM

Solid-phase microextraction (SPME) has been applied to direct extraction of 11 organophosphorus pesticides in water using a 100 mm fiber polydimethylsiloxane. The method was evaluated with respect time of exposure, detection limits (LODs), linearity and precision. The detection limits (S/N = 3) depend of each pesticide and varie about ng/L levels. The linearity was satisfactory with coefficients of correlation usually greater than 0.993. The precision of the method was determined by extraction from 4.0 mg/L aqueous standard with coefficients of variation between 5.7 to 17.2%.

On‐line determination of organophosphorus pesticides in water by solid‐phase microextraction and gas chromatography with thermionic‐selective detection

AbstractThis paper describes the extraction of 49 organophosphorus pesti‐cides (OPPs) from water samples using solid‐phase microextraction (SPME). Three fibers, including a 15‐μm XAD‐coated fiber, a 85‐μm polyacrylate‐coated fiber, and a 30‐μm polydimethylsilox‐ane‐coated fiber (PDMS), were evaluated here. The effects of stirring and the addition of NaCl to the sample were examined for the polyacrylate‐coated fiber. The precision of the technique was examined for all three fibers and the extraction kinetics were investigated using the XAD‐ and polyacrylate‐coated fibers. With some exceptions, the XAD‐ and polyacrylate‐coated fibers performed better than the PDMS‐coated fiber. The superiority of the XAD‐nd polyacrylate‐coated fiber. The superiority of the XAD‐ and polyacrylate‐coated fibers over the PDMS‐coated fibers can be attribuibuted to the aromatic functionalities of the XAD and the polar functionalities in the polyacrylate. The relatively high percent RSDs indicate that the SPME technique needs to be further refined before it can be used for anything other than screening. A more effective form of agitation than mechanical stirring may be neccessary to reduce variability and achieve a faster equilibrium between the sample and the SPME fiber.

Trace analysis of triazines and organophosphorus pesticides in water.

A method for the determination of trace levels of triazines and organophosphorus pesticides in water is presented. The extraction method is based on a solid-phase extraction on C-18 bound silica SPE cartridges. A precolumn filled with Merck C-18 bound silica and home-made C-18 bound silica have been tested at a flow-rate of 3 ml/min with comparable preconcentration yields. A SIM-MS method using a (15)N labelled internal standard has been developed for the organophosphorus pesticides. Detection limits lower than 1 microg/L have been obtained. Separations have been carried out on a conventional GC column OV 17 (1 m) and a capillary column OV 17 (25 m) with a temperature program from 150 degrees C (2 min) to 300 degrees C (rate of 6 degrees C/min).

Pentachlorophenol (PCP), PCDD, PCDF and pesticide concentrations in a freshwater lake catchment

The concentrations of pentachlorophenol (PCP), polychlorinated dibenzo-p-dioxins (PCDDs) polychlorinated dibensofurans (PCDFs) and organochlorine and organophosphorus pesticides in water, sediments and biota from the Lake Rotorua catchment were determined to evaluate the relative significance of various contaminants and their potential sources. PCP was found in water, sediments and biota (fish and freshwater mussels) and the highest concentrations in water (3.62 μ g.L −1) and in sediments (400 ng.g −1 dry weight (DW) were found in and near a stream that had been affected by PCP contamination from a sawmill. PCDD and PCDF concentrations in all cases, except for the waters and sediments of the stream near to the sawmill, were relatively low compared to values reported in the literature for similar sites. Negligible pesticide contamination was found in the Lake Rotorua catchment. Pesticides found included low concentrations of p.p′-DDE, p.p-TDE and dieldrin in rainbow trout from the lake.

Determination of Organophosphorus Pesticides in Water by Solid-Phase Extraction Followed by Liquid Chromatography/High-Flow Pneumatically Assisted Electrospray Mass Spectrometry

Priority organophophorus pesticides in water samples were subjected to analysis by solid-phase extraction followed by liquid chromatography/high-flow pneumatically assisted electrospray mass spectrometry (LC/ESP-MS). The operational parameters of ESP optimized by use of an eluent flow rate of 0.3 mL/min and at a source temperature of 150 o C were as follows: driyng gas flow rate, 250-300 L/h; ESP nebulizing gas flow, 5-20 L/h; ESP voltage, 2-3.5 kV; HV lens voltage, 0.2-1.0 L/h; ESP voltage, 2-3.5 kV; HV lens voltage, 0.2-1.0 kV; extraction voltage, 20-130 V; focus voltage, and the ion energy

Determination of Organophosphorus Pesticides in Water Using C18 or Florisil Sep‐Pak Cartridge and Gas Chromatography with Flame‐Photometric Detection

AbstractSimple methods for the concentration and clean‐up of fifteen organophosphorus pesticides in water using a C18 Sep‐Pak cartridge or a Florisil Sep‐Pak cartridge and subsequently determining the pesticides by gas chromatography with flame photometric detection have been developed. The conditions for stepwise or simultaneous desorption of these pesticides from the Sep‐Pak cartridges are given.