Farag Malhat

Residues of organochlorine and synthetic pyrethroid pesticides in honey, an indicator of ambient environment, a pilot study

Samples of honey were screened to monitor residues of organochlorine and pyrethroid pesticides. The study meant to examine the quality of honey, and to use honey as a bioindicator of environmental contamination. Residue levels were determined by gas chromatography (GC-μECD). Samples had a wide spectrum of organochlorine and synthetic pyrethroids pesticides, with hexachlorobenzene (HCB) as the most frequently detected organochlorine, followed by permethrin, heptachlor epoxide. Only one sample had a concentration of γ-HCH higher than maximum residue limit of honey (0.01 mg kg(-1)). Residues of organochlorines detected, indicate the presence of some fresh supplies, despite the ban imposed on their use. The study confirmed that honey bee and beehive matrices could be used as gauge for monitoring environment contamination. From public health point of view, the observed levels of pesticide residues in honey do not pose a serious health risk to the consumers, but raises questions of the source of organochlorines.

Residues and dissipation of kresoxim methyl in apple under field condition

The dissipation and residual levels of kresoxim methyl in apple under field condition were determined by using HPLC-DAD with QuEChERS method. At fortification levels of 0.05, 0.1, 0.5 and 1.0 mg kg(-1) in apple, it was shown that recoveries were ranged from 91.1% to 96.9% with coefficient variation of the method (CV%) for repeatability ranged from 1.27% to 4.77%. The limit of quantification (LOQ) of the method was 0.05 mg kg(-1). The dissipation rates of kresoxim methyl were described by using first-order kinetics and its half-life, as they are ranged from 4.58 to 4.77 days in apple. The terminal residues of kresoxim methyl were below the FAO/WHO maximum residue limit (MRL, 0.2 mg kg(-1)) in apple when measured 14 days after the final application, which suggested that the use of this fungicide was safe for humans. This study would help in providing the basic information for developing regulation to guard a safe use of kresoxim methyl in apple orchard and to prevent health problem from consumers.

Residues, dissipation and safety evaluation of chromafenozide in strawberry under open field conditions.

The dissipation and residual levels of new generation insecticide chromafenozide in strawberries under field conditions were studied using HPLC-DAD after QuEChERS extraction. The method was validated using blank samples spiked at three levels and the results showed that recoveries ranged from 99% to 110%. The intra- and inter-day relative standard deviations were less than 7.5% and 9.2%, respectively. Estimated limit of detection and limit of quantification for chromafenozide were 0.003 and 0.01 mg/kg, respectively. The residues of chromafenozide were found to dissipate following first order kinetics and its half-life ranged from 3.53 to 4.07 days. The results showed that the use of chromafenozide at recommended dose does not pose any hazards to consumers. These results can be utilised in formulating spray schedules and safety evaluation for chromafenozide insecticide in strawberry.

Dissipation dynamic, residue distribution and processing factor of hexythiazox in strawberry fruits under open field condition.

Two independent field trials were performed to investigate the dissipation and residue levels of hexythiazox in strawberry. The study presents a method validation for extraction and quantitative analysis of hexythiazox residues in strawberry using HPLC-DAD. The results shown that the mean recoveries ranged from 85% to 93%, furthermore the intra- and inter-day relative standard deviations were less than 10%. The results suggest that the hexythiazox dissipation curves followed the first-order kinetic and its half-life ranged from 3.43 to 3.81 days. The final residues in strawberry were below the Codex maximum residue limit (MRL) (6 mg/kg) after three days of the application. The effects of household processing and storage on the levels of hexythiazox residues were quantified, and its useful for reducing the dietary exposure. The processing factor after each stage were generally less than 1, indicating that the whole process can reduce the residues of hexythiazox in strawberry. The results could provide guidance to safe and reasonable use of hexythiazox in agriculture.

Preparation and Utilization of Polystyrene Nanocomposites Based on TiO2Nanowires

Successful preparation of titanium dioxide nanowires (TiO2-NWs), by a hydrothermal method, then embraced in polystyrene (PS) to form nanocomposites using emulsion polymerization of styrene monomer in presence of different ratios of TiO2 nanowires. The morphology and crystalline structure of the prepared TiO2 were proved by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The thermal stability of the nanocomposites, measured by thermogravimetric analysis (TGA), was found to be upgraded especially at higher loading %s of the nanowires irrespective to pure polystyrene. Furthermore, polystyrene nanocomposites (modified with 4%, 8% and 12% of TiO2 nanowires) were used to remove organochlorine pesticide (OCPs) residues from contaminated water. GLC results showed that the pristine TiO2 nanowires has a poor affinity for removing OCPs residues (from 8.82 to 70%), whereas polystyrene/TiO2-NWs nanocomposites are powerful material for removing OCPs residues (61.76 to 98.64%) due to changing of TiO2 nanowires surfaces from completely hydrophilic to hydrophobic structure as proven by contact angle results. These nanocomposites materials can be used for packaging application and the mainly application of these materials in a water filter, which may be a promising and economically feasible technology for wastewater purification.

Field dissipation and health hazard assessment of Fenhexamid on Egyptian grapes

Dissipation behavior and hazard assessment of the fungicide fenhexamid applied to grapes were investigated under climatic conditions in Egypt. Fenhexamid residues were extracted from grape samples with ethyl acetate. The extract was cleaned up by QuEChERS (quick, easy, cheap, effective, rugged, and safe) method, and determined by gas chromatographic method (GC-μECD). The average recoveries ranged between 94.2% and 99.4% with associated relative standard deviation not exceeding 12%. The estimated limit of quantification for fenhexamid was 0.1 mg/kg. The field results showed that fenhexamid dissipated rapidly from grapes and had a half-life of approximately 4.21 days. Hazard assessment was evaluated by using the hazard quotient (HQ). Data showed that the HQ value was significantly less than HQ = 1. Results indicate that hazard of fenhexamid use in grape even at 1.5-fold higher than recommended dosage was negligible to humans. This study could provide guidance for safe and reasonable use of fenhexamid in grapes and prevent health problems to consumers. However, further hazard assessment studies are needed to ascertain the hazard of fenhexamid residues on grape to vulnerable groups, including children, pregnant women, and elderly consumers.

Dissipation kinetics of novaluron in tomato, an arid ecosystem pilot study

Novaluron, a newly introduced insecticide, is used for control of a number of field pests. However, information regarding novaluron residues and dissipation profile is limited. In this study, dissipation and residual levels of novaluron in tomato under open field conditions were investigated using high performance liquid chromatography equipped with diode array detector (HPLC-DAD) with quick, easy, cheape, effective, rugged (QuEChERS) method. The method was validated using blank samples spiked at three levels and results showed that recoveries ranged from 93% to 99%. Novaluron residues tend to dissipate following first-order rate kinetics with half-life of 2.08 days. Data demonstrated that the use of novaluron at recommended doses would not pose any hazards to consumers. The present results aid to establish the safe use of this pesticide on tomatoes, and possibly on other crops in Egypt.

Determination of etoxazole residues in fruits and vegetables by SPE clean-up and HPLC-DAD.

A method for determination of etoxazole residues in apples, strawberries and green beans was developed and validated. The analyte was extracted with acetonitrile from foodstuff and a charcoal-celite cartridge was used for clean-up of raw extracts. Reversed phase high performance liquid chromatography with photodiode array detector (HPLC-DAD) was used for the determination and quantification of etoxazole residues in the studied samples. The calibration graphs of etoxazole in a solvent or three blank matrixes were linear within the tested intervals 0.01–2 mg L−1, with correlation coefficient of determination >0.999. The combined solid phase extraction (SPE) clean-up and the chromatographic method steps were sensitive and reliable for simultaneous determination of etoxazole residues in the studied samples. The average recoveries of etoxazole in the tested foodstuffs were between 93.4 to 102% at spiking levels of 0.01, 0.10, and 0.50 mg kg−1, with relative standard deviations ranging from 2.8 to 4.7%, in agreement with directives for method validation in residue analyses. The limit of detection (LOD) of the HPLC-DAD system was 100 pg. The limit of quantification of the entire method was 0.01 mg kg−1.

Residue Levels, Profiles, Emission Source and Daily Intake of Polycyclic Aromatic Hydrocarbons Based on Smoked Fish Consumption, An Egyptian Pilot Study

Residue levels and spectrum of polycyclic aromatic hydrocarbons (PAHs) were determined in smoked fish, and canned smoked fish, collected from grocery shops from Cairo, Giza, Menoufya, and Ismailia governorates, Egypt. Residues of PAHs were monitored using gas liquid chromatography, equipped with a flame ionization detector. The concentrations of ∑13 PAHs in the smoked fish and the canned smoked fish ranged from 36.06–547.1 μg/kg, respectively. Benzo(a)pyrene was not detected in smoked canned fish, while its mean residues in smoked fish amounted to 1.1 μg/kg, corresponding to one fifth of the maximum tolerable limit of 5 μg/kg established by EU. The congeners profile showed that the sources of PAHs in the two brands of smoked fish are mainly petrogenic. Based on smoked fish the daily intake of 13 PAHs and benzo(a)pyrene were 45.59 μg/day and 0.092 μg/day, respectively, while for canned smoked fish the intake was fifteen times lower (3 μg/day), and the intake of benzo(a) pyrene is zero μg/day. Results showed that the consumption of smoked fish would pause some risk to consumers; meanwhile canned smoked fish showed no risk to Egyptian consumers.

Degradation profile and safety evaluation of methomyl residues in tomato and soil

Summary A high performance liquid chromatography with the photodiode array detector (HPLCDAD) analytical method was developed to determine the residue levels and investigate the dissipation pattern and safety use of methomyl in tomato and soil. Methomyl residues were extracted from tomato and soil samples with ethyl acetate. The extract was cleaned up with the QuEChERS method. The results showed that the average recoveries were in the range of 87.1-94.5%, with RSD of 6.9-11.2%. Limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.007 mg/kg, respectively. The residue levels of methomyl were best described to first order rate kinetics and half-lives ranged from 1.34 to 1.8 days in tomato and soil, respectively. The theoretical maximum residue contributions for methomyl on tomato were found to be less than the maximum permissible intake values even on zero days, therefore consumer health risks are minimal at the recommended dose on tomato.