A sensitive chemiluminescence enzyme immunoassay based on molecularly imprinted polymers solid-phase extraction of parathion.

The chemiluminescence enzyme immunoassay (CLEIA) method responds differently to various sample matrices because of the matrix effect. In this work, the CLEIA method was coupled with molecularly imprinted polymers (MIPs) synthesized by precipitation polymerization to study the matrix effect. The sample recoveries ranged from 72.62% to 121.89%, with a relative standard deviation (RSD) of 3.74-18.14%.The ratio of the sample matrix-matched standard curve slope rate to the solvent standard curve slope was 1.21, 1.12, 1.17, and 0.85 for apple, rice, orange and cabbage in samples pretreated with the mixture of PSA and C18. However, the ratio of sample (apple, rice, orange, and cabbage) matrix-matched standard-MIPs curve slope rate to the solvent standard curve was 1.05, 0.92, 1.09, and 1.05 in samples pretreated with MIPs, respectively. The results demonstrated that the matrices of the samples greatly interfered with the detection of parathion residues by CLEIA. The MIPs bound specifically to the parathion in the samples and eliminated the matrix interference effect. Therefore, the CLEIA method have successfully applied MIPs in sample pretreatment to eliminate matrix interference effects and provided a new sensitive assay for agro-products.

Effective antibodies immobilization and functionalized nanoparticles in a quartz-crystal microbalance-based immunosensor for the detection of parathion.

BACKGROUND: Biosensor-based detection provides a rapid and low-cost alternative to conventional analytical methods for revealing the presence of the contaminants in water as well as solid matrices. Although important to be detected, small analytes (few hundreds of Daltons) are an issue in biosensing since the signal they induce in the transducer, and specifically in a Quartz-Crystal Microbalance, is undetectable. A pesticide like parathion (M = 292 Da) is a typical example of contaminant for which a signal amplification procedure is desirable. METHODS/FINDINGS: The ballasting of the analyte by gold nanoparticles has been already applied to heavy target as proteins or bacteria to improve the limit of detection. In this paper, we extend the application of such a method to small analytes by showing that once the working surface of a Quartz-Crystal Microbalance (QCM) has been properly functionalized, a limit of detection lower than 1 ppb is reached for parathion. The effective surface functionalization is achieved by immobilizing antibodies upright oriented on the QCM gold surface by a simple photochemical technique (Photonic Immobilization Technique, PIT) based on the UV irradiation of the antibodies, whereas a simple protocol provided by the manufacturer is applied to functionalize the gold nanoparticles. Thus, in a non-competitive approach, the small analyte is made detectable by weighing it down through a "sandwich protocol" with a second antibody tethered to heavy gold nanoparticles. The immunosensor has been proved to be effective against the parathion while showing no cross reaction when a mixture of compounds very similar to parathion is analyzed. CONCLUSION/SIGNIFICANCE: The immunosensor described in this paper can be easily applied to any small molecule for which polyclonal antibodies are available since both the functionalization procedure of the QCM probe surface and gold nanoparticle can be applied to any IgG, thereby making our device of general application in terms of target analyte.

Sonolytic degradation of parathion and the formation of byproducts.

Ultrasonic degradation of parathion has been investigated in this study. At a neutral condition, 99.7% of 2.9 microM parathion could be decomposed within 30 min under 600 kHz ultrasonic irradiation at ultrasonic intensity of 0.69 W/cm(2). The degradation rate increased proportionally with the increasing ultrasonic intensity from 0.10 to 0.69 W/cm(2). The parathion degradation was enhanced in the presence of dissolved oxygen due to formation of more ()OH, but was inhibited in the presence of nitrogen gas owning to the free radical scavenging effect in vapor phase within the cavitational bubbles. CO(3)(2-), HCO(3)(-), and Cl(-) exhibited the inhibiting effects on parathion degradation, and their inhibition degrees followed the order of CO(3)(2-)>HCO(3)(-)>Cl(-). But Br(-) had a promoting effect on parathion degradation, and the effect increased with the increasing Br(-) level. Moreover, both the hydrophobic and hydrophilic natural organic matters (NOM) could slow the parathion degradation, but the inhibiting effect caused by hydrophobic component was greater, especially the strongly hydrophobic NOM. The three reaction pathways of parathion sonolysis were proposed, including formation of paraoxon, formation of 4-nitrophenol, and unknown species products. The kinetics tests showed that anyone of these pathways could not be overlooked, and the fractions of the parathion decomposed in the three pathways were 28.19%, 32.92% and 38.89%, respectively. In addition, 66.61% of paraoxon produced was degraded into 4-nitrophenol. Finally, kinetics models were established to adequately predict the concentrations of parathion, paraoxon and 4-nitrophenol as a function of time.

Ionic liquid-based dispersive liquid-liquid microextraction followed high-performance liquid chromatography for the determination of organophosphorus pesticides in water sample.

Using 1-octyl-3-methylimidazolium hexafluorophosphate ([C(8)MIM][PF(6)]) ionic liquid as extraction solvent, organophosphorus pesticides (OPPs) (parathion, phoxim, phorate and chlorpyifos) in water were determined by dispersive liquid-liquid microextraction (DLLME) combined with high-performance liquid chromatography (HPLC). The extraction procedure was induced by the formation of cloudy solution, which was composed of fine drops of [C(8)MIM][PF(6)] dispersed entirely into sample solution with the help of disperser solvent (methanol). Parameters including extraction solvent and its volume, disperser solvent and its volume, extraction time, centrifugal time, salt addition, extraction temperature and sample pH were investigated and optimized. Under the optimized conditions, up to 200-fold enrichment factor of analytes and acceptable extraction recovery (>70%) were obtained. The calibration curves were linear in the concentration range of 10.5-1045.0 microg L(-1) for parathion, 10.2-1020.0 microg L(-1) for phoxim, 54.5-1089.0 microg L(-1) for phorate and 27.2-1089.0 microg L(-1) for chlorpyifos, respectively. The limits of detection calculated at a signal-to-noise ratio of 3 were in the range of 0.1-5.0 microg L(-1). The relative standard deviations for seven replicate experiments at 200 microg L(-1) concentration level were less than 4.7%. The proposed method was applied to the analysis of four different sources water samples (tap, well, rain and Yellow River water) and the relative recoveries of spiked water samples are 99.9-115.4%, 101.8-113.7% and 87.3-117.6% at three different concentration levels of 75, 200 and 1000 microg L(-1), respectively.

Determination of parathion residues in rice samples using a flow injection chemiluminescence method.

A sensitive flow injection chemiluminescence method is described for the determination of parathion pesticide, based upon its direct chemiluminescence reaction with luminol and hydrogen peroxide in the presence of non-ionic surfactant polyethylene glycol 400. Under the selected experimental conditions, the concentration of parathion is proportional to the CL intensity in the range 0.02-1.0 mg/L. The detection limit was 0.008 mg/L and the relative standard deviation was 2.8% for 0.2 mg/L parathion solution (n = 11). This method was successfully applied to the determination of parathion residue in rice samples.

Optimizing microwave-assisted solvent extraction (MASE) of pesticides from soil.

Microwave-assisted solvent extraction (MASE) was investigated as an alternative for extraction of parathion (O,O-diethyl O-4-nitrophenyl phosphorothioate), methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate), p,p'-DDE [1,1'-dichloro-2,2-bis(4-chlorophenyl)ethane], hexachlorobenzene (HCB), simazine (6-chloro-N2,N4-diethyl- 1 ,3,5-triazine-2,4-diamine) and paraquat dichoride (1,1'-dimethyl-4,4'-bipyridinium) from two different soils and from an earthworm-growing substrate. The matrices were fortified with 14C-radiolabeled pesticides and extracted with various solvent systems under different microwave conditions. Recoveries of more than 80% could be obtained depending on the used microwave conditions and solvent, except for paraquat whose recovery was generally less efficient. Thus, MASE can be successfully used to extract pesticides from environmental and biological samples and could be a viable alternative to conventional extraction methods. The technique uses smaller amounts of organic solvents, thereby minimizing the costs of the analysis and the disposal of waste solvent.

Solid-phase microextraction of organophosphorus pesticides from water.

Frequent occurrences of pollution in natural drainage by industrial chemicals, especially pesticides, have triggered interest in the development of fast and unambiguous analytical techniques to verify these pollutants in order to facilitate rapid remedial actions. In this work, we report the development of a solid-phase microextraction (SPME) method to analyse two common industrial pesticides in water, i.e. malathion and parathion. SPME analysis facilitates direct analysis of chemical species in aqueous systems and avoids lengthy sample preparation procedures. In this study, we compare five commercially available fibres: 7 microns polydimethylsiloxane, 30 microns polydimethylsiloxane. 85 microns polyacrylate, 65 microns Carbowax-divinylbenzene and 65 microns polydimethylsiloxane-divinylbenzene fibres. Profiles of uptake by the fibres against adsorption times were established. The results obtained indicated that the polarity of the fibres is not the main factor affecting the uptake. The structures of the fibres also affected the permeation of the analytes onto the fibres. The limits of detection were determined to be in the low ppb level with a flame ionization detector. These methods have great potential for use in rapid on-site analytical work which is highly demanded in environmental studies.