Detection Limits Of Pesticides Research Articles

Rapid analysis of pesticide residues in drinking water samples by dispersive solid-phase extraction based on multiwalled carbon nanotubes and pulse glow discharge ion source ion mobility spectrometry.

An analytical method based on dispersive solid-phase extraction with a multiwalled carbon nanotubes sorbent coupled with positive pulse glow discharge ion mobility spectrometry was developed for analysis of 30 pesticide residues in drinking water samples. Reduced ion mobilities and the mass-mobility correlation of 30 pesticides were measured. The pesticides were divided into five groups to verify the separation capability of pulse glow discharge in mobility spectrometry. The extraction conditions such as desorption solvent, ionic strength, conditions of adsorption and desorption, the amounts of multiwalled carbon nanotubes, and solution pH were optimized. The enrichment factors of pesticides were 5.4- to 48.7-fold (theoretical enrichment factor was 50-fold). The detection limits of pesticides were 0.01∼0.77μg/kg. The linear range was 0.005-0.2mg/L for pesticide standard solutions, with determination coefficients from 0.9616 to 0.9999. The method was applied for the analysis of practical and spiked drinking water samples. All results were confirmed by high-performance liquid chromatography with tandem mass spectrometry. The proposed method was proven to be a commendably rapid screening qualitative and semiquantitative technique for the analysis of pesticide residues in drinking water samples on site.

Study of the ESI and APCI interfaces for the UPLC–MS/MS analysis of pesticides in traditional Chinese herbal medicine

In this work, 53 selected pesticides of different chemical groups were extracted from Chinese herbal medicines and determined by ultra-high-performance liquid chromatography (UHPLC)-tandem mass spectrometry (MS/MS) using both electrospray ionization (ESI) and atmospheric-pressure chemical ionization (APCI). Extracts were obtained using the acetonitrile-based quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation technique. Cleanup was performed by dispersive solid-phase extraction using primary secondary amine, graphitized carbon black, and octadecylsilane. Two atmospheric-pressure interfaces, ESI and APCI, were checked and compared. The validation study, including detection limits, linearity, and matrix effects, was conducted on fritillaria, radix ginseng, folium isatidis, semen persicae, and flos lonicerae in multiple reaction monitoring mode. These matrices represent a variety of plants used in traditional Chinese medicine. Fritillaria and radix ginseng were chosen as representatives for roots, folium isatidis was chosen as a representative for leaves, semen persicae was chosen as a representative for seeds, and flos lonicerae was chosen as a representative for flowers. The limits of detection for pesticides were lower in the UHPLC-ESI-MS/MS method than in the UHPLC-APCI-MS/MS method. Matrix effects on the two ionizations were evaluated for the five matrices. Soft signal enhancement in UHPLC-APCI-MS/MS and signal suppression in UHPLC-ESI-MS/MS were observed.

限外ろ過法を用いたＬＣ／ＭＳ／ＭＳによる農産物中の残留農薬一斉分析

A method for simultaneous determination of multiple pesticide residues in agricultural products was developed by using a pretreatment with ultrafiltration, followed by liquid chromatography-tandem mass spectrometry (LC/MS/MS). The pretreatment process (extraction of pesticides from agricultural products with methanol, dilution of the extract with water, and ultrafiltration) gave recoveries in the range of 50-150% for 63 of 83 pesticides spiked at 0.25 microg/ g into 6 agricultural products. The detection limits of pesticides by LC/MS/MS were below 0.0005-0.05 micro/g. This method is useful for screening purposes and for multiresidue analysis of pesticides in agricultural products. Pesticide residues in 50 domestic crops were investigated by this method, and residues of 14 pesticides were detected in 30 crops.

Amperometric screen-printed biosensor arrays with co-immobilised oxidoreductases and cholinesterases

Amperometric screen-printed biosensor arrays for detection of pesticides (organophosphates and carbamates) and phenols have been developed. Cholinesterases (AChE and BChE), tyrosinase (TYR), peroxidases (SBP, soybean and HRP, horseradish) and cellobiose dehydrogenase (CDH) were combined on the same array consisting of one Ag/AgCl reference electrode surrounded by eight radially distributed working electrodes of either carbon or platinum. Mainly cross-linking with glutaraldehyde was employed for enzyme immobilisation. The substrates for the enzymes were acetylthiocholine for cholinesterases (ChEs), cellobiose for CDH and hydrogen peroxide for peroxidases. Hydrogen peroxide was generated in the presence of glucose by co-immobilised glucose oxidase (GOx). All measurements were performed in an electrochemical steady state system specially constructed for eight channel screen-printed electrode arrays. The achieved relative standard deviation values calculated for different enzyme substrates (10 measurements) were typically below 7% and one assay was completed within less than 10 min. The detection limits for pesticides and phenols were in the nanomolar and micromolar ranges, respectively. The developed biosensor array was evaluated on wastewater samples. To simplify interpretation of results, the measured data were treated with multivariate analysis–principal component analysis (PCA).

Multienzyme electrochemical array sensor for determination of phenols and pesticides

The screen-printed four-electrode system was used as the amperometric transducer for determination of phenols and pesticides using immobilised tyrosinase, peroxidase, acetylcholinesterase and butyrylcholinesterase. Acetylthiocholine chloride was chosen as substrate for cholinesterases to measure inhibition by pesticides, hydrogen peroxide served as co-substrate for peroxidase to measure phenols. The compatibility of hydrolases and oxidoreductases working in the same array was studied. The detection of p-cresol, catechol and phenol as well as of pesticides including carbaryl, heptenophos and fenitrothion was carried out in flow-through and steady state arrangements. In addition, the effects of heavy metals (Cu 2+, Cd 2+, Fe 3+), fluoride (NaF), benzene and dimethylsulphoxide on cholinesterase activities were evaluated. It was demonstrated that electrodes modified with hydrolases and oxidoreductases can function in the same array. The achieved R.S.D. values obtained for the flow system were below 4% for the same sensor and less than 10% within a group of five sensors. For the steady state system, R.S.D.s were approximately twice higher. One assay was completed in less than 6 min. The limit of detection for catechol using tyrosinase was equal to 0.35 and 1.7 μM in the flow and steady state systems, respectively. On the contrary, lower limits of detection for pesticides were achieved in the steady state system—carbaryl 26 nM, heptenophos 14 nM and fenitrothion 0.58 μM.

Simultaneous determination of various pesticides in fruit juices by HPLC-DAD

A suitable method for the simultaneous determination of four fungicides (folpet, chlorothalonil, quinomethionat, tetradifon) and one herbicide (trifluralin) in fruit juices has been developed. The method involves the preconcentration of 25 g fruit juice samples through C18 solid-phase extraction cartridges. The pesticides were separated and quantified by reversed-phase high-performance liquid chromatography with UV-diode array detection at 220 and 260 nm. Analytical separation was performed using a concave gradient elution with acetonitrile and water on a C18 column. Recoveries from spiked apple, cherry juices and peach nectar, ranged from 93.8% to 99.5% and relative standard deviations were less than 3.4% in the concentration range of 1–16 μg/kg. The limits of detection for pesticides investigated are in the range of 0.5–1 μg/kg and the calibration curves showed good linearity >0.9988. The developed method has been tested on canned pure apple, cherry juices and peach nectar manufactured in Turkey. Results of this study showed that these samples analyzed contained no detectable residues.

Resistively heated gas chromatography coupled to quadrupole mass spectrometry

The potential of fast temperature-programmed gas chromatography (GC) was studied by combining a resistively heated gas chromatograph and a quadrupole mass spectrometer (MS). An EZ Flash GC was used, which generates temperature ramps up to 1200 °/min and cools down from 300 to 50°C in some 30 s; samples were injected via a conventional split/splitless injector in both injection modes. The combination of a short narrow-bore column (5 m×0.1 mm ID), a high gas flow rate, and fast temperature programs typically decreased conventional analysis times of 30 min to about 3 min. The scan speed of the quadrupole mass spectrometer (16 spectra/s in the range m/z 50–310) was found to be sufficient for a proper reconstruction of the chromatographic peaks, and good-quality mass spectra could be obtained. Six scans across a peak were sufficient for peak integration. The system was linear in the range of 0.01–3 ng injected mass and detection limits for pesticides were in the range of 1–25 pg in the full-scan and 0.1–5 pg in the selected ion monitoring mode. Series of apple and mole liver extracts were analyzed to demonstrate the high sample throughput and suitability of EZ Flash GC for fast screening.

Study on the determination of pesticide residues in crops by ion-trap GC/MS/MS

Ion-trap GC/MS/MS was evaluated for the multi-residue determination of pesticides in agricultural products. Matrices were extracted from samples (spinach, carrot, onion and brown rice) with acetone and submitted to gel permeation chromatography, followed by a clean-up step through a graphite carbon cartridge. Thirty-five pesticides were added to either matrix, and analyzed by GC/MS/MS. Detection limits of pesticides by GC/MS/MS was almost the same as those by GC/MS (SIM). Coefficients of variation of peak area in 5 measurements of each pesticide at 0.1 microgram/mL or 0.05 microgram/mL with or without matrices were mostly acceptable, though those of 20 pesticides out of 35 were higher than 10% at a concentration of 0.02 microgram/mL. It was indicated that matrix artifacts, which interfere with GC/MS-Scan analysis, could be eliminated in some cases by using GC/MS/MS.

Multiresidue analysis of nitrogen-containing and sulfur-containing pesticides in agricultural products using dual-column GC-NPD/FPD

We investigated simultaneous analytical methods for pesticide residues in large numbers of agricultural products samples. Extraction of each sample with acetonitrile was followed by a salting-out step using a graduated cylinder. The test solution was cleaned up with gel permeation chromatography (GPC), which separated the pesticide eluate into 2 fractions, and then with a tandem mini-column. Analysis was done with a dual-column GC equipped with a dual NPD and FPD (S mode) detector. Use of the Siltek-deactivated liner, guard column, and Y connector, and Silcosteel-treated NPD jet was effective for preventing the breakdown of sulfur-containing pesticides. Recoveries of 87 nitrogen-containing and sulfur-containing pesticides from fortified spinach, tomato, apple, strawberry and brown rice, ranged from 71 to 127% with RSD values of 1-24%, except for recoveries of aldicarb, amitraz, ethiofencarb, imazalil, propamocarb and triflumizole. Detection limits of pesticides were very good (0.3-5 ppb (NPD) and 2-20 ppb (FPD)) for routine analysis of pesticide residues in foods. Surveillance of pesticides in agricultural products was carried out by using the present method. From 22 out of 33 samples, 21 pesticides (43 in total) were detected. The results indicated that the present method can be applied as an efficient and reliable means for monitoring pesticide residues in agricultural products.

Multiresidue analysis of organophosphorus pesticides in vegetables and fruits using dual-column GC-FPD, -NPD

We investigated simultaneous and consecutive analytical methods for pesticide residues in large numbers of vegetable and fruit samples. Extraction of the sample with acetonitrile was followed by a salting-out step using a graduated cylinder. Co-extractives were removed by gel permeation chromatography (GPC) and the pesticide eluate was separated to 2 fractions. Firstly, the second fraction (85-125 mL) was passed through a silica-gel mini-column. After putting a Florisil mini-column before the silica-gel mini-column, the first fraction (55-85 mL) was passed through the tandem mini-columns, which were then eluted with 15 mL of 50% acetone/petroleum ether. The eluate was subjected to dual-column GC with dual FPD (P mode, column Rtx-OPPesticides) and NPD (column Rtx-200) detectors. Recoveries of 63 organophosphorus pesticides from fortified spinach, tomato, apple and strawberry, ranged from 71 to 126% with RSD values of 1-18%, except for the RSDs of omethoate, isoxathion, and pyraclofos (20% <). Detection limits of pesticides were 0.5-2 ng/g. Surveillance of pesticides in vegetables and fruits was carried out by using the present method. From 20 out of 30 samples, 15 pesticides (39 in total) were detected. The results indicated that the present method can be applied as an efficient and reliable tool for monitoring organophosphorus pesticide residues in vegetables and fruits.

Detection of pesticides from liquid matrices by ion mobility spectrometry

The detection of different pesticide compounds from liquid matrices was achieved by aspiration ion mobility spectrometry. This technique is based on ion mobility which is proportional to the molecular weight and charge. The ion mobility spectrometer is able to measure mobility changes of product ions as well as mobility changes of reactant ions. In the ion mobility spectrometer used, it is possible to measure positive and negative ion clusters at the same time in six different electrodes. Each measuring electrode detects a different portion of the ion mobility distribution formed within the cell’s radioactive source. The pattern recognition used is based on differences in the gas phase profiles of the different compounds. The results of this study reveal that the ion mobility spectrometer MGD-1 can also be used to measure pesticides even from liquid matrices. On the basis of projection calculation, the responses for 2-propanol (= background) and pesticide compounds were easily separated from each other. The greatest responses for pesticides were seen in the 2nd positive channel. Correspondingly, only minor background signals were measured in the 1st and 2nd positive channels. The detection limits of pesticides were at ng or μg levels. The sensitivity of detection of the ion mobility spectrometer for different pesticides decreased in the order: diazinon, aldicarb, dimethoate and parathion. In comparison with the traditional ion mobility spectrometric technique, the main advantages of this aspiration technique are its fast response, high sensitivity, real time vapor monitoring, straightforward maintenance and low cost. In addition, the cell tolerates high chemical concentrations and still recovers quickly.

A direct optical immunosensor for atrazine detection

Immunoanalytical techniques represent one of the most important applications of biomolecules in analytical procedures. Direct monitoring of immunoreactions by an analytical device is a particularly attractive approach to environmental sensing as it offers speed, a simple test scheme and does not require labelled compounds. Target limits of detection for pesticides are imposed by the EU drinking water act (0.1 μg/l for a single pesticide). A competitive test format with surface immobilised antigen is common for pesticide detection with direct immunosensors. Free pesticide binds to antibody in solution decreasing the amount of antibody binding to the transducer. As the concentration of antibody in a competitive test must be comparable to the concentration of the analyte (0.1 ppb atrazine ≈ 0.5 nM), the transducer must be able to resolve changes in antibody concentration below 1 nM. A prototype atrazine sensor based on reflectometric interference spectroscopy (RIFS) was investigated. The slope of the binding curve was used as a measure for antibody concentration. Binding curves of monoclonal anti-atrazine to an atrazine-modified surface were recorded at different concentrations. A reproducibility of 10% was found for the determination of antibody concentrations (100 to 1000 ng/ml). In competitive binding experiments with free atrazine inhibition of 50% was observed at 0.5 ppb atrazine (500 ng/ml antibody) and at 1 ppb (1 μg/ml antibody). The results are discussed with respect to the theoretical performance of the device and practical requirements. A comparison to other optical transducers and a critical discussion about the feasibility of direct optical immunosensors in pesticide detection is given.

Rapid Determination of Organochlorine Pesticides and Poly chlorinated Biphenyls, Using Selected Ion Monitoring Mass Spectrometry

Methane chemical ionization (CI)-selected ion monitoring (SIM) mass spectrometry was used to identify and conclusively distinguish 19 organochlorine pesticides from polychlorinated biphenyls (PCBs) at parts-per-trillion to parts-per-billion levels in environmental water sample extracts with minimal sample cleanup. Two CI-SIM screens were developed. One set of ions scanned specifically for the presence of 4 classes of pesticides: diphenylmethane derivatives, bridged polycyclic chlorinated hydrocarbons, chlorinated benzenes, and acetanilide pesticides. The second set of ions responded exclusively to PCBs with biphenyl moieties containing from 1 to 8 chlorine atoms. Eight commercial Aroclor mixtures were analyzed and distinguished from the pesticide groups. The detection limit for pesticides and PCBs by CI-SIM screening was 0.005 and 0.1 ppb, respectively. CI-SIM can be used as an alternative method for the analysis of biological or environmental samples containing interferences that complicate the detection of PCBs and chlorinated pesticides.