Determination of Biphenyl in Citrus Fruits by Quantitative Thin-Layer Chromatography

Abstract

Residues of the fungicide biphenyl in citrus fruits have been determined by direct scanning of spots on phosphor-impregnated high performance silica gel TLC plates under UV light. Biphenyl was separated from fruit tissue by steam liquid-liquid extraction. Recoveries from spiked samples ranged from 92–99% at 100, 50, and 10 ppm levels. The precision of the TLC determination and overall procedure are shown to be adequate for residue analysis.     

Rapid and Sensitive Screening Method for the Determination of Carbaryl and Propoxur Using p-Nitroaniline

Abstract

A rapid screening method for the determination of carbaryl and propoxur using p-nitroaniline is described. Carbaryl and propoxur are determined spectrophotometrically: carbaryl forms a stable blue coloured species with diazotized p-nitroaniline in a fairly alkaline medium while propoxur forms a purple coloured species with the same reagent under similar conditions. The blue and purple coloured species are extracted into 3-methyl-1-butanol showing absorbance maxima at 605 and 540 nm, respectively. The relationship between absorbance and concentration is linear in the range of 0.12 - 0.96 ppm and 0.19–1.5 ppm, respectively for carbaryl and propoxur. The method can successfully be applied for the determination of carbaryl and propoxur to levels as low as 0.04 and 0.06 and 0.12 and 0.19 ppm in water and grain samples, respectively.     

Polycyclic Aromatic Hydrocarbon Burden in Fruit and Vegetable Species Cultivated in Allotments in an Industrial Area

The polycyclic aromatic hydrocarbon (PAH) burden of various fruit and vegetable species (strawberries, apples, tomatoes, lettuce, kohlrabi, potatoes, parsley and kale) cultivated in allotments in the industrial area of Bitterfeld-Wolfen (Germany) were determined. In addition, the garden soils of the sampling sites were analysed. The total PAH concentrations of fruit and vegetables investigated varied in the range of 1-120 µg/kg fresh weight, with the highest being found in parsley and kale. As the highest concentration of benzo(a)pyrene (BaP) was 0.55 µg/kg in a parsley sample, none of the samples exceeded the recommended BaP limit in vegetable foods of 1 µg/kg. A positive relationship between the total PAH burden and the cultivating site was only found for the more highly contaminated species parsley and kale. The total PAH concentrations in the garden soils ranged from 28 to about 7000 µg/kg dry weight.     

De-contamination of pesticide residues in food by ionizing radiation

The role of gamma irradiation on removal of pesticides in aqueous solutions or in vegetables and fruits was investigated. Radiation - induced decontamination of pesticides is generally greater in aqueous solutions than in selected vegetables and fruits. Residues of malathion (0.5 ppm in potatoes, 8 ppm in onions and dates), pirimiphos-methyl (1 ppm in onions and grapes) and cypermethrin (0.05 ppm in potatoes and 0.1 ppm in onions) were not reduced to below maximum residue limits (MRLs) for irradiation doses up to 1 kGy. The same trend was observed when irradiation was performed for grapes fortified with malathion (8 ppm) and cypermethrin (2 ppm) for absorbed doses up to 2 kGy. Ionizing radiation reduced the residues of pirimiphos-methyl (0.05 ppm in potatoes at1 kGy, 1 ppm in grapes at 2 kGy and 0.1 ppm in dates at1 kGy), malathion (8 ppm in grapes at 7 kGy) and cypermethrin (2 ppm in grapes at 7 kGy) to below maximum residue limits (MRLs).     

Pesticide residues on fruits and vegetables from Ontario, Canada, 1991-1995

For the 5-year period 1991 to 1995, 1536 vegetable and 802 fruit samples were analyzed. The purpose of this study was to determine if pesticides were present on Ontario-produced fruits and vegetables, and if so, to determine if residues violated maximum residue limits (MRLs). Overall, 31.5% of the samples had no detectable pesticide residues, whereas 68.5% contained one or more residues. Most of the residues were present at very low concentrations; 48% of the detections were < 0.1 parts per million (ppm), and 86% were < 1 ppm. However, violations of MRL were observed in only 3.2% of the vegetables samples and 3.1% of the fruit samples. In addition, 4.8% of the samples contained a "technical" violation, that is, there was no specified MRL for the pesticide-commodity combination and the residues exceeded 0.1 ppm. Of the detectable residues, 63% were < 10% of the MRL, whereas 89% were < 50% of the MRL. More fruit samples (91.4%) had a detectable residue, compared with vegetable samples (56.6%). Fruit is often treated close to harvest or post harvest to ensure that wholesome produce reaches the consumer. Forty-six percent of the samples contained 2 or more residues, and 2% of all samples had more than 5 different pesticides detected; fruit samples tended to have more multiple residues. The most frequently found pesticides were captan, the dithiocarbamate fungicides, endosulfan, azinphos-methyl, phosmet, parathion, and iprodione. These pesticides were also used in the greatest quantity for crop production. Overall, the data agree fairly closely with those reported for the U.S. Department of Agriculture Pesticide Data Program because the 2 programs have similar analytical goals and objectives.     

Representative commodity for five brassica vegetables based on the determination and dissipation of six pesticide residues

A Quick, Easy, Cheap, Effective, Rugged and Safe method for determination of thiophanate-methyl, carbendazim, metalaxyl, fluazifop-P-butyl, chlorpyrifos and lambda-cyhalothrin in five brassica vegetables by high performance liquid chromatography-mass spectrometry/mass spectrometry and gas chromatography-electron capture detector has been developed. The average recoveries of six pesticides in five brassica vegetables were in the range of 77.4%–117.4% with relative standard deviation of 3.7–10.8%. Residues of thiophanate-methyl, carbendazim, metalaxyl, fluazifop-P-butyl, chlorpyrifos and lambda-cyhalothrin in five brassica vegetables were studied with the developed method for the classification of crop group and selection of representative commodity of five brassica vegetables. Totally 48 open field trials on five brassica vegetables were conducted at two locations in two different seasons. The residue dynamics and final residues of the six pesticides at three preharvest intervals in different vegetables were compared. All six pesticides had the longest half-lives in cabbage (2.1–3.5 days). Residues of carbendazim (sum of thiophanate-methyl and carbendazim), metalaxyl, chlorpyrifos and lambda-cyhalothrin had similar trend in different brassica vegetables. The maximal concentrations of these pesticide residues were found in kale (0.28–10.9 mg kg^?1). Fluazifop-P-butyl residues were at low levels in all five brassica vegetables (<0.01–0.03 mg kg^?1). Cabbage, red cabbage, Brussels sprouts and kohlrabi had no significant difference in all six pesticide residues and could be classified in a subgroup of Head Brassicas. Cabbage should be selected as the representative commodity. Considering the highest residues in kale and its different morphology, kale should not be classified into the subgroup of Head Brassicas.     

Oxygen Plask-TLC Microdetermination of Binary and Ternary Mixtures of Hg(II), Cu(II) and Cd in their Organic Compounds and Some Pharmaceutical Preparations

Abstract

Binary and ternary mixtures of the organic compounds of the title elements are decomposed either by wet digestion in the Kjeldahl flasks or through combustion in the oxygen flask using 1:1 HNO₃ soln. as absorbent and Pt gauze as sample holder. An aliquot of 15 μl of each decomposed mixture is separated on thin layer plate, using silica gel (G 60) as stationary phase and a mixture of 100 ml benzene: 80 ml acetone : 20 ml DMF as a mobile phase in normal saturation system at 25°C. The spots areas are determined, from which the individual concentrations of the cations are calculated. Parallely the spots are scratched from the plates and are eluted with water. Their concentrations are measured in the UV-region, for Hg(II) at 205 nm, for Cu(II) at 203 and for Cd at 201 nm. Concentrations are obtained from previously constructed calibration curves which are linear for Hg(II) in the range 0.0 – 0.375 ppm, for Cu(II) in the range 0.0 – 3.811 ppm and for Cd from 0.7 – 13.48 ppm.     

A piezoelectric immunosensor for the determination of pesticide residues and metabolites in fruit juices

A quartz crystal microbalance (QCM) immunosensor was developed for the determination of the insecticide carbaryl and 3,5,6-trichloro-2-pyridinol (TCP), the main metabolite of the insecticide chlorpyrifos and of the herbicide triclopyr. The detection was based on a competitive conjugate-immobilized immunoassay format using monoclonal antibodies (MAbs). Hapten conjugates were covalently immobilized, via thioctic acid self-assembled monolayer (SAM), onto the gold electrode sensitive surface of the quartz crystal. This covalent immobilization allowed the reusability of the modified electrode surface for at least one hundred and fifty assays without significant loss of sensitivity. The piezoimmunosensor showed detection limits (analyte concentrations producing 10% inhibition of the maximum signal) of 11 and 7 μg l⁻¹ for carbaryl and TCP, respectively. The sensitivity attained (I₅₀ value) was around 30 μg l⁻¹ for both compounds. Linear working ranges were 15-53 μg l⁻¹ for carbaryl and 13-83 μg l⁻¹ for TCP. Each complete assay cycle took 20 min. The good sensitivity, specificity, and reusability achieved, together with the short response time, allowed the application of this immunosensor to the determination of carbaryl and TCP in fruits and vegetables at European regulatory levels, with high precision and accuracy.     

Determination of Carbaryl in River Water and Food Samples Based on the Quenching Effect on Resonance Light Scattering

Abstract

A new method has been developed for the quantification of carbaryl with DNA based on a resonance light scattering technique. In the presence of carbaryl and under acidic conditions, the intensity of resonance light scattering of DNA is significantly quenched. The decrease in IRLS at this wavelength is proportional to the concentration of carbaryl. The calibration curve is linear over the range of 0.02–1.4 µg mL^?1. Using this method, the recovery rates of carbaryl in river water and food samples were determined with satisfactory results. The interaction mechanism was also discussed.     

Bay 93820 Residues: Their Determination and Persistence in Coastal Bermudagrass,Forage Corn,and Corn Silage

Residues of Bay 93820 (isopropyl salicylate O-ester with O-methyl phosphoramidothioate) and its oxygen analog were determined in Coastal bermudagrass (Cynodyn dactylon (L.) Pers.), corn, and corn silage. The insecticide was applied in the field as aqueous sprays of an emulsifiable concentrate at rates of 6, 12, and 24 oz (active ingredient) per acre. Glass jar silage was made from 1-day post-field treatment corn. Residues were analyzed by gas chromatography by using a flame photometric detector sensitive to phosphorus; details of the analytical procedure are presented.

Residue levels of Bay 93820 in both corn and grass diminished to less than 1 ppm after 14 days of weathering in the field. Residues of the O-analog were lower than those of Bay 93820; however, they represented a much larger portion of the total residue than with any other O-analog-forming organophosphorus insecticide previously tested at our laboratory. Residues of Bay 93820 were essentially stable and persistent in corn silage, whereas the small amounts of O-analog tended to increase slightly.     

Conducting Polymer/Ionic Liquid Composite Modified Carbon Paste Electrode for the Determination of Carbaryl in Real Samples

A new method has been described for carbaryl determination using a simple electrochemical sensor. The unique properties of poly‐pPhenylenediamine and ionic liquid were exploited to fabricate carbon paste electrode modified with composite based on conducting polymer/ionic liquid. Electrode surface characterization was performed by electrochemical methods (cyclic voltammetry and electrochemical impedance spectroscopy) and by scanning electron microscopy. Differential pulse voltammetry was employed for the detection of carbaryl in acetate buffer solution. Different parameters affecting the carbaryl response were optimized such as ionic liquid amounts, cycle number of polymerization and monomer concentration, pH, and accumulation time. Under the optimum experimental conditions, a linear response was obtained between 0.5 and 200 μmol/L, with detection limit of 0.09 μmol/L. The developed sensor offered satisfactory results for carbaryl detection in spring water and fruit samples.     

Determination of Chlorpyrifos and its Metabolite 3,5,6-Trichloro-2-Pyridinol in Tap Water and Bananas by Quantitative TLC on Preadsorbent Silica Gel

Abstract

Chlorpyrifos insecticide and its metabolite TCP were determined in tap water and banana samples by TLC of extracts on preadsorbent silica gel layers, detection with silver nitrate reagent, and densitometric scanning. Cleanup steps were required for the fruit sample extracts. Recovery of chlorpyrifos from tap water at 5 ppb averaged 87.5% and from banana at 0.05 ppm was 84.6%. Recovery of TCP from water at 5 ppb averaged 84.0% and from banana at 0.05 ppm was 86.8%. The sensitivity and precision of the method were shown to be adequate for routine residue analysis.     

Development of a Highly Sensitive and Selective Bismuth Optical Sensor Based on (2E,4E)-5-(2,4-Dinitrophenyl Amino)penta-2,4-dienal

Abstract

An optical sensor based on (2E,4E)-5-(2,4-dinitrophenyl amino)penta-2,4-dienal as ionophore has been developed for the determination of bismuth(III) ions in aqueous solutions. This proposed membrane works on the basis of a cation-exchange mechanism and shows a significant absorbance signal change on exposure to 1 M HCl solution of pH 0.0 containing bismuth ions. The optode membrane shows a reproducible and reversible response toward bismuth in the concentration range 0.2 to 60.5 ppm with a detection limit of 0.095 ppm. This sensor has been used for determination of bismuth in real samples.     

Determination of Carbamate Pesticides in Vegetables by Octadecyl Modified Graphene Reinforced Hollow Fiber Liquid Phase Microextraction Combined with High-Performance Liquid Chromatography

A novel adsorbent, octadecyl modified graphene, was prepared for hollow fiber liquid phase microextraction to increase the efficiency of the preconcentration process. The modified material was employed for the isolation of metolcarb, carbaryl, isoprocarb, and diethofencarb from vegetables prior to determination by high-performance liquid chromatography with diode array detection. Octadecyl modified graphene dispersed in 1-octanol served as the acceptor phase of the sorbent, resulting in enhanced efficiency. The optimization of several parameters was carried out to achieve the maximum efficiency. Under the optimized conditions, the calibration curve was linear from 0.5 to 100.0 nanograms per gram for carbaryl and 1.0 to 100.0 nanograms per gram for the other analytes with correlation coefficients (r) between 0.9952 and 0.9990. The limits of detection for the carbamates were from 0.2 to 0.6 nanogram per gram. The recoveries of the analytes ranged from 90.3 to 107.4 percent, indicating the excellent performance of the method for the determination of carbamates in vegetables.     

Application of dispersive liquid-liquid microextraction for the analysis of triazophos and carbaryl pesticides in water and fruit juice samples

In this work, a simple, rapid and sensitive sample pretreatment technique, dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography-fluorescence detection (HPLC-FLD), has been developed to determine carbamate (carbaryl) and organophosphorus (triazophos) pesticide residues in water and fruit juice samples. Parameters, affecting the DLLME performance such as the kind and volume of extraction and dispersive solvents, extraction time and salt concentration, were studied and optimized. Under the optimum extraction conditions (extraction solvent: tetrachloroethane, 15.0 μL; dispersive solvent: acetonitrile, 1.0 mL; no addition of salt and extraction time below 5 s), the performance of the proposed method was evaluated. The enrichment factors for the carbaryl and triazophos were 87.3 and 275.6, respectively. The linearity was obtained in the concentration range of 0.1-1000 ng mL⁻¹ with correlation coefficients from 0.9991 to 0.9999. The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, ranged from 12.3 to 16.0 pg mL⁻¹. The relative standard deviations (RSDs, for 10 ng mL⁻¹ of carbaryl and 20 ng mL⁻¹ of triazophos) varied from 1.38% to 2.74% (n = 6). The environmental water (at the fortified level of 1.0 ng mL⁻¹) and fruit juice samples (at the fortified level of 1.0 and 5.0 ng mL⁻¹) were successfully analyzed by the proposed method, and the relative recoveries of them were in the range of 80.4-114.2%, 89.8-117.9% and 86.3-105.3%, respectively.     

Multiresidue determination of pesticides in fruit and vegetables by gas chromatography/tandem mass spectrometry

Pesticide residues in fruit and vegetables were determined by gas chromatography/tandem mass spectrometry (GC/MS/MS). Electron impact (EI)/MS/MS and chemical ionization (CI)/MS/MS were developed for 80 compounds, including organochlorine, organophosphorus, organonitrogen, and pyrethroids, providing unambiguous spectral confirmation for these complex matrixes. Residues were extracted from samples with acetone followed by a mixture of dichloromethane-petroleum ether. Two injections per sample were required for analysis of the entire pesticide list by EI/MS/MS and CI/MS/MS. Initial steps involving cleanup and concentration of extracts were eliminated. The excellent selectivity and good linearity allowed quantification and identification of low levels of pesticides in the most difficult matrixes. The method has been used for routine analysis of many vegetables.     

Residues of some organophosphorus pesticides on and in fruits and vegetables available in Poland,an assessment based on the European union regulations and health assessment for human populations

Abstract

The use of organophosphorus pesticides is undeniably beneficial in agriculture and veterinary medicine, but their excessive use can pollute the environment, as well as contaminate foodstuffs. The objective of this study was to assess contamination of vegetables and fruits available in Poland by organophosphate pesticides (ethoprophos, diazinon, chlorpyrifos, chlorpyrifos-methyl, parathion-methyl, fenchlorphos, merfos,, as well as to assess a potential health risk posed to consumers. The pesticide content was determined by gas chromatography-mass spectrometry (GC-MS). The pesticides were detected in the peel and pulp of vegetables and fruits from Polish crops, as well as imported ones. Pesticide levels in most products were higher in the peel than in the pulp. Neither chlorpyrifos-methyl nor fenchlorphos were found in the material under study. Chlorpyrifos was the pesticide occurring in the highest levels in the peel of both vegetables (31?ng?·?g^?1 w.w.) and fruit (9.3?ng?·?g^?1 w.w.). The Maximum Residue Level (MRL) for parathion-methyl was exceeded in some samples of zucchini pulp of Spanish origin and in the peel of potato from Poland. But levels of other pesticides in the studied vegetables and fruits were significantly lower than the current MRLs. The assessment of consumer health risk showed a significantly lower Lifetime Average Daily Dose (LADD) of pesticides under this study comparing to the Acceptable Daily Intake (ADI). Moreover, the Hazard Quotient (HQ) was low with a maximum of 3.93?×?10^?2 for vegetables and 4.26?×?10^?3 for fruits. These estimated HQs were within the safe acceptable limits, indicating low risk to human populations from exposure to organophosphorus pesticides in the study area.     

Rapid and simultaneous analysis of dichlorvos, malathion, carbaryl, and 2,4-dichlorophenoxy acetic acid in citrus fruit by flow-injection ion spray ionization tandem mass spectrometry

A simple method for the rapid and simultaneous analysis of dichlorvos (DDVP), malathion, carbaryl, and 2,4-dichlorophenoxy acetic acid (2,4-D) in citrus fruit, which uses flow-injection ion spray ionization tandem mass spectrometry, has been developed for the first time. The method involves the combined use of stable isotopically labeled internal standards (DDVP-d₆, malathion-d₁₀, carbaryl-d₇, and 2,4-D-d₅) and a multiple reaction monitoring technique. The average recoveries for the pesticides at the same concentrations as their tolerance levels (DDVP: 0.1-0.2 μg g⁻¹; malathion: 0.5-4.0 μg g⁻¹; carbaryl: 1.0 μg g⁻¹; 2,4-D: 1.0-2.0 μg g⁻¹) ranged from 90 to 119% with the relative standard deviation (R.S.D.) ranging from 1.0 to 13.1% (n = 5). Analysis time, including sample preparation and determination, was only 15 min. The present method is effective for screening DDVP, malathion, carbaryl, and 2,4-D in citrus fruit.     

Preparation,Homogeneity and Stability of Polar Pesticides in Freeze-Dried Water Interlaboratory Exercise

Abstract

An interlaboratory exercise was carried out to improve the state of the art of some polar pesticide determination in water (atrazine, simazine, carbaryl, propanil, linuron, fenamiphos and permethrin). The preparation, the homogeneity and the stability of freeze-dried water samples containing the above pesticides was studied. The final concentration of each pesticide in water was in the 50–80 μg.^?1 range with a salt content of 2.5 g.l^?1 of NaCl. After the lyophilization the residue was reho-mogenised, filled into amber glass bottles and stored at -20 °C and +20 °C. Every three months, one sample was analysed to verify the stability of the residue.

All pesticides were determined by high performance liquid chromatography with diode-array detection (HPLC-DAD) except permethrin which was determined by gas chromatography with electron capture detection (GC-ECD).

The results obtained show that the atrazine, carbaryl, propanil, linuron and fenamiphos samples were homogeneously distributed, whereas simazine and permethrin were not. With respect to the stability over three months, all pesticides were stable at ?20 °C. Atrazine, simazine, carbaryl, propanil and linuron are also stable for the maximum storage time at +20 °C but the concentration of fenamiphos decreased by about 70% after one month.

The results obtained in the interlaboratory study by the participants were in good agreement for many of the pesticides.     

Determination of the Speciation of Chromium from a Bicycle Factory Discharge

Abstract

The discharge from a bicycle factory in Dar-es-Salaam was analysed for dissolved trace metals so as to monitor what was being introduced onto the environment. An X-ray Fluorescence Spectrophotometer with a Si (Li) detector connected to a multichannel analyser Canberra 40 series was used for the analysis. computation of the peaks and results was done by a Professional Deck 350 computer. The elements contained in the discharge were Ca (596 ppm), Ti (369 ppm), Cr (11 ppm), Zn (0.98%) and Sr (73.5 ppm). Further analysis of the speciation of chromium revealed that there was Cr(III) (9 ppm) and Cr(VI) 2 ppm. The level of Cr(VI) was considered too high considering its toxicity.