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Validation of QuEChERS Based Method for Determination of Fenitrothion Residues in Tomatoes by Gas... Article · March 2017 DOI: 10.1016/j.foodchem.2017.03.017

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Food Chemistry 229 (2017) 814–819

Contents lists available at ScienceDirect

Food Chemistry journal homepage: www.elsevier.com/locate/foodchem

Validation of QuEChERS based method for determination of fenitrothion residues in tomatoes by gas chromatography–flame photometric detector: Decline pattern and risk assessment Farag Malhat a,b,⇑, Julien Boulangé b, Ehab Abdelraheem a, Osama Abd Allah a, Rania Abd El-Hamid a, Shokr Abd El-Salam a a b

Pesticide Residues and Environmental Pollution Department, Central Agricultural Pesticide Laboratory, Agriculture Research Center, Dokki, Giza 12618, Egypt Tokyo University of Agricultural and Technology, 3-5-8 Saiwaicho, Fuchu, Tokyo 183-8581, Japan

a r t i c l e

i n f o

Article history: Received 17 August 2015 Received in revised form 12 August 2016 Accepted 3 March 2017 Available online 6 March 2017 Keywords: Fenitrothion Residues GC-FPD Dissipation Risk assessment

a b s t r a c t A simple and rapid gas chromatography with flame photometric detector (GC-FPD) determination method was developed to detect residue levels and investigate the dissipation pattern and safe use of fenitrothion in tomatoes. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) using an ethyl acetate-based extraction, followed by a dispersive solid-phase extraction (d-SPE) with primary–secondary amine (PSA) and graphite carbon black (GCB) for clean up, was applied prior to GC-FPD analysis. The method showed satisfactory linearity, recovery and precision. The limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.01 mg/kg, respectively. The residue levels of fenitrothion were best described by first order kinetics with a half-life of 2.2 days in tomatoes. The potential health risks posed by fenitrothion were not significant, based on supervised residue trial data. The current findings could provide guidance for safe and reasonable use of fenitrothion in tomatoes and prevent health problems to consumers. Ó 2017 Elsevier Ltd. All rights reserved.

1. Introduction In Egypt, tomatoes are cultivated in approximately 221 thousand hectares, which represent approximately 34% of the average area of vegetables (Malhat, 2013). Tomatoes are among the basic component of diet and consumed almost daily. Tomatoes are subject to a number of diseases/ infestations at all stages of development. Consequently, pesticides are applied to offer protection against damage, and reduced productivity and quality (Romeh & Mekky, 2009; Malhat, 2017). Fenitrothion (O,O-dimethyl-O-(3-m ethyl-4-nitrophenyl phosphorothioate)), a broad-spectrum organophosphate, is employed in agriculture to control penetrating, chewing, and sucking pests on various crops, including tomato. The determination of pesticides is usually accomplished by chromatographic techniques and involves many preliminary steps, such as extraction and clean-up for the removal/ reduction of interference (Malhat, Watanabe, & Youssef, 2015). The most frequently used technique for determination of fenitrothion residues is gas ⇑ Corresponding author at: Pesticide Residues and Environmental Pollution Department, Central Agricultural Pesticide Laboratory, Agriculture Research Center, Dokki, Giza 12618, Egypt. E-mail address: [email protected] (F. Malhat). http://dx.doi.org/10.1016/j.foodchem.2017.03.017 0308-8146/Ó 2017 Elsevier Ltd. All rights reserved.

liquid chromatography (GC) coupled with electron capture detector (ECD) (Diagne, Foster, & Khan, 2002), nitrogen phosphorus detector (NPD) (Ambrus, Lantos, Visi, Csatlos, & Sarvari, 1981; Ferreira & Fernandes, 1980), flame photometric detector (FPD) (Gilles & Victorin, 1980; Tonogai et al., 1992) and mass spectrometry (MS) (Khani, Imani, & Larijani, 2011). Among them, FPD is the technique of choice for detecting small quantities of fenitrothion (Malhat, 2012). FPD is very sensitive for organophosphate pesticides, which is essential if the data are to be used for dietary exposure assessment. Diagne et al. (2002) reported a high performance liquid chromatography (HPLC) method for analyzing fenitrothion residues in white and black beans. Even though the instrumentation provides a great deal of sensitivity, the extraction procedure is also of great importance to identify and quantify a wide variety of pesticide residues (Bakırcı & Hısıl, 2012). So far, several extraction methods were used for fenitrothion-residue analysis; however, the classical approaches including liquid-liquid extraction (LLE) (Fenoll, Hellín, Martínez, Miguel, & Flores, 2007), or solid-phase extraction (SPE) (Albero, Sànchez-Brunete, & Tadeo, 2005; López-Blanco, Gómez-Alvarez, Rey-Garrote, Cancho- Grande, & Simal-Gàndara, 2006) are long and tedious. Procedures based on matrix solid-phase dispersion have been proposed to simplify the extraction step (Torres, Picó,

F. Malhat et al. / Food Chemistry 229 (2017) 814–819

Redondo, & Mañes, 1996). A solid-phase microextraction (SPME) has been used for the determination of fenitrothion in vegetables (Abdulra’uf & Tan, 2014; Khani et al., 2011; Sapahin & et al., 2015). However, for field trial and dissipation study, microextraction data is sometimes unable to reflect the real field sample due to the sample amount. In turn, an effective rapid method is needed for fenitrothion to handle sufficient reprehensive sample to generate data for regulation. The QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method, developed originally by Anastassiades, Maštovska, and Lehotay (2003), has been used for extraction of pesticide residue in a wide range of foods and agricultural products (Cherta, Beltran, López, & Hernández, 2013; Furlani, Marcilio, Lemea, & Tfouni, 2011). It has received worldwide acceptance because of its simplicity and high throughput, enabling a laboratory to process a high number of samples in a short period of time (Lehotay, 2011; Miao, Kong, Yang, & Yang, 2013; Surma & Sadowska-Rociek, 2014). Few studies have been conducted on residue determination of fenitrothion in different foods matrices, including tomatoes (Aysal, Ambrus, Lehotay, & Cannavan, 2007; Frank et al., 2009). The residue dynamics of fenitrothion have been studied in different matrices, such Lettuce, cauliflowers and apricots (Cabras et al., 1997; Fenoll et al., 2009; Fernandez-Cruz et al., 2006). The use of pesticides for combating pests in agricultural production has no doubt enhanced food production and quality of the product, but their indiscriminate use has led to undesirable side effects on environmental quality and human health (Malhat & Hassan, 2011). Consequently, the analysis of residual quantities of pesticides in raw agricultural crops is at the forefront of measures to protect public health and safety. Therefore, to ensure food safety and the environmental protection, field dissipation studies on pesticide persistence in foodstuffs and pesticide residue behavior are needed. In this study, we set up and validate a modified QuEChERS method followed by gas chromatography using a flame photometric detector to quantify fenitrothion residues in tomatoes. Supervised field trials were conducted to determine the dissipation kinetics in tomatoes. From the generated data, the biological half-life was established based upon the dissipation pattern. Furthermore, it is rather imperative to ascertain the food safety hazard by evaluating residues of fenitrothion in terms of their dietary exposure related to the acceptable daily intake (ADI). We also investigated the effects of application frequency and dosage and of the interval to harvest on terminal residues. These results will aid the government in providing guidance concerning the proper and safe use of fenitrothion. 2. Material and methods 2.1. Chemical and reagents A certified fenitrothion reference standard was obtained from the Central Agricultural Pesticide Laboratory (Dokki, Egypt) (purity >99%). All organic solvents were of HPLC grade and purchased from Merck (Darmstadt, Germany). Primary secondary amine (PSA, 40 mm Bondesil) and graphite carbon black (GCB) sorbents were purchased from Supelco (Bellefonte, USA). Analytical grade anhydrous sodium sulfate, purchased from El Naser Pharmaceutical Chemical Co., (Cairo, Egypt), was activated by heating at 250 °C for 4 h in the muffle furnace, before being cooled and kept in desiccators prior to use. 2.2. Preparation of standard calibration solution The stock standard solution (100 mg L1) of fenitrothion was prepared in ethyl acetate and subsequently stored at 18 °C. An

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intermediate solution (10 mg L1) was prepared by further dilution with ethyl acetate. The calibration standards (five calibration points) ranging from 0.005 to 5.0 mg L1 were prepared by successive dilution of the intermediate working standard with pure solvent or blank matrix extract. All standard solutions were stored at 18 °C in dark amber bottles until further analysis. Bracketing calibration was attained in which the matrix-matched calibration solutions were injected at the beginning and at the end of each sequence to insure that the determination system was free from any significant drift. 2.3. Open field experimental design The open field experimental trails including the dissipation and final residue study were conducted in a randomized block design in open field, which was previously found to be free of the pesticide. The supervised trials were carried out in Meit-Gamer and Menof, Egypt. Field trials were conducted in separate plots measuring 40 m2 each in three replicates. None of the plots had been treated with fenitrothion in the past. To ensure the reliability of the experimental results, field management was carried out in accordance with the local methods. The average maximum and minimum temperature during the experiment were 39 °C and 27 °C. There was no rainfall at any time during the experimental period. 2.3.1. Residue dynamic experiment To investigate the dissipation of fenitrothion, tomato was sprayed with fenitrothion formulation (50% EC) in the experiment plots each with three replicates. The dosage was 2.5 kg a.i. ha1 (two times the recommended dosage) with one time spray. A plot of the same size but with no fenitrothion application was compared simultaneously. Samples (tomato fruit) were collected at random from sampling plots at 0 (2 h after spraying), and 1, 3, 7, 10, 14, 18 and 21 days after treatment. Immediately after picking, samples were put into polyethylene bags and transported to the lab, where they were chopped and thoroughly mixed. The sample was kept deep-frozen (20 °C) until analysis. Control samples were obtained from the control plots. 2.3.2. Final residue experiments To investigate the final residues of fenitrothion in tomato, the plants were sprayed, in three replicates, with fenitrothion at two dosages of 1.25 kg a.i. ha1 (recommended dosage) and 2.5 kg a.i. ha1 (two times the recommended dosage). Each dosage level was designed to be sprayed two and three times at an interval 14 days. Representative tomato samples were collected at days 7 and 14 before harvest. Collected tomato samples were put into polyethylene bags and transported to the lab, where they were chopped and thoroughly mixed and stored at 20 °C until analysis. 2.4. Analytical methods 2.4.1. Sample Preparation The tomato samples were homogenized in a food processor (Thermomix; Vorwerk) and 10 g of the homogenate of each sample were placed into 50-mL centrifuge tube. 2.4.2. Extraction and clean up A 10 g sample of homogenized tomato was extracted with 10 ml ethyl acetate followed by 20 g anhydrous sodium sulfate (Lehotay et al., 2010). The mixture was vortex-mixed followed by centrifugation at 3000 rpm for 10 min. An aliquot of 2 ml of the supernatant was aspirated into a 15 ml polypropylene tube containing 50 mg of PSA and 10 mg GCB. The mixture was shaken vigorously and centrifuged at 3000 rpm for 5 min. An aliquot of the

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supernatant was decanted, filtered through a 0.2 mm PTFE syringe filter and then directly analyzed by GC-FPD. 2.4.3. Gas chromatographic analysis GC analysis was performed with an Agilent 7890, gas chromatograph equipped with flame photometric detector. Analysis was conducted on a PAS-1701 (Agilent, Folsom, CA) fused silica capillary column of 30 m length, 0.32 mm id., and 0.25 mm film thicknesses. The oven temperature was programmed from an initial temperature 180 (2 min hold) to 240 °C at a rate of 8 °C min1 and was maintained for 10 min. Injector and detector temperatures were maintained at 240 and 260 °C, respectively. Nitrogen was used as a carrier gas at a flow rate of 3 mL/min. Hydrogen and air flow rate were 75 and 100 mL/min, respectively. Peak was identified by comparing the sample retention time with that of the corresponding pure standard compound. 2.5. Method Validation The method was validated following a conventional validation parameters; including linearity, matrix effect, LOD, LOQ, accuracy (recovery) and precision (repeatability and intermediate precision) as recommended by SANCO (2013). 2.5.1. Linearity Fenitrothion standard calibration curve was constructed by plotting analyte concentrations against peak areas. The fit of the calibration was plotted and inspected by calculation of the residuals, avoiding over-reliance on correlation coefficient, to insure that the fit is satisfactory within the concentration range of the pesticide detected. The residuals were calculated as follows

%Residuals ¼

100ðSE SCÞ SE

ð1Þ

where: % Residuals: residual at particular point, SE: signal of the calibration point obtained experimentally. SC: signal of the calibration provided by calibration function. 2.5.2. Accuracy Recoveries were carried out in 5 replicates at 3 fortification levels (0.01, 0.10, and 1.0 mg kg1) by spiking standard solution to 10 g of homogenized blank sample (Table 1). According to the document SANCO/12571/2013 (SANCO, 2013), acceptable mean recoveries are those within the range of 70–120%. 2.5.3. Matrix effect The matrix effect of the present method was investigated by comparing standard in solvent with matrix-matched standard for 5 replicates at 0.1, 0.25 and 1.0 mg kg1 (Fig. 1). Matrix effect (% ME) was calculated using the following equation:

%ME ¼ 100

M matrix M solv ent Mmatrix

ð2Þ

where %ME is the matrix effect, and M matrix and M solvent are the slops of calibration curves in the matrix and in pure solvent, respectively

Table 1 Recovery percentage and relative standard deviation of fenitrothion in tomato (n = 5). Samples

Spiking level (mg/kg)

Recovery%

RSD%

Tomato

0.01 0.10 1.00

92.4 95.8 92.2

5.9 9.8 9.6

Fig. 1. GC-FPB chromatogram of (A) control samples; (B) standard fenitrothion at 1.0 mg kg1; and spiked samples at 0.25 mg kg1.

2.5.4. Repeatability and reproducibility The sample was injected 10 times, and the relative standard deviation (RSD) values were evaluated. The precision of the method was determined by repeatability and reproducibility, expressed as RSD values. The repeatability relative standard deviation (RSDr) was measured by comparing the SD values of the recoveries from spiked samples analyzed on the same day. The reproducibility relative standard deviation (RSDR) values, determined by the analyses of spiked samples on 3 different days.

%RSD ¼ 100

SD M

ð3Þ

where SD is the standard deviation of the replicate, and M is the mean value of the recovery 2.5.5. Limits of detection and quantification The limit of quantitation was defined as the lowest concentration of fenitrothion that has been validated with acceptable true-

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ness (70–120%) and precision (RSDr 20%) by applying the complete analytical method. According to the document SANCO/12495/2013 (SANCO, 2013) the Limit of quantification should be MRL. The maximum residue limit (MRL) for fenitrothion is 0.01 mg/kg for tomato (European Union, 2014).

Table 2 Recovery RSDr and RSDR values obtained from analysis of samples spiked with fenitrothion at 0.01 mg/kg (n = 5). Sample

Analysis day

Recovery%

RSDr%

RSDR%

Tomato

1 2 3

92.6 94.1 92.9

7.9 11.2 8.5

8.4

2.6. Kinetic curve fitting The dissipation kinetics of fenitrothion in tomatoes were determined by plotting the residue concentration against time and the maximum squares of correlation coefficient found were used to determine the equations of best fit curves. For all the samples studied, exponential relationships were found to apply, corresponding to the first order rate equation. Confirmation of the first order kinetics was further made graphically from the following equation:

3.2.4. Limits of detection and quantification In this study, the LOD and LOQ were estimated to be 0.005 and 0.01 mg/kg, respectively. According to the document SANCO/12571/2013 (SANCO, 2013), the LOQ values are acceptable where LOQ MRL (0.01 mg/kg for tomato, (European Union, 2014).

C t ¼ C 0 ekt

3.3. Dissipation of fenitrothion in tomato

ð4Þ

where Ct represents the concentration of the pesticide residue at the time of t, C0 represents the initial deposits after application and k is the degradation rate constant in days1. The half-life (t1/2) was calculated from the k value for each experiment, being:

3. Results

The dissipation curves of fenitrothion in tomatoes under field conditions are shown in Fig. 2. The initial concentrations of fenitrothion in tomatoes were 11.15 and 10.02 mg kg1 in MietGamer and Menof with half-lives of 2.28 and 2.20 days, respectively. As shown in the figure, there was a sharp decrease in the amount of fenitrothion residues 10 days after application. Concentrations were reduced to less than 1% 14 days after application. The half-life (t1/2), dissipation regressive equation, and correlation coefficient (R2) are summarized in Table 3.

3.1. Extraction and clean-up

3.4. Final residue levels

Extraction and clean-up were carried out under precise and timed steps for all samples and blanks. The time between spiking and extraction was fixed to 20 min whereas shaking time was set at 5 min. Table 1 shows that acceptable recoveries were obtained by using 0.01 g of GCB in the cleanup step.

The residue of fenitrothion in tomatoes under different dosages, different frequencies and different intervals to harvest were shown in Table 4. The tomatoes were sampled two times during the harvest period to analyse fenitrothion residues. When the pesticide fenitrothion was sprayed at high dosage (2.5 kg a.i. ha1) over 2 and 3 times application, the final residue in tomatoes was 0.183– 2.302 mg kg1; when it was sprayed at low dosage (1.25 kg a.i. ha1) over 2 and 3 times application, the final residue was 0.147–2.01 mg kg1.

t 1=2 ¼

ln 2 k

ð5Þ

3.2. Validation data 3.2.1. Linearity Good linear determination coefficient between the peak area and the concentration assayed (0.005–5.0 mg mL1) with R2 > 0.998 for fenitrothion in all cases were obtained for solvent and matrix stuff (tomato). The fit of the calibration is satisfactory with residuals ±8% for GC-FPD analysis. According to the document SANCO/12571/2013 (SANCO, 2013), the acceptable limit of residuals deviation is 20%, where the fit of calibration inspected by calculation of the residuals avoids over-reliance on correlation coefficient. 3.2.2. Accuracy and matrix effect The obtained mean recoveries ranged from 92.2% to 95.8% with RSD ranged between 5.8% to 9.8% in tomato. The matrix-matched calibration solutions were used to circumvent errors associated with matrix-induced enhancement and suppressions effects in GC response. The matrix effect for GC-FPD analysis for tomato was 21%. Therefore all quantifications of fenitrothion in tomato samples were performed using standards prepared in tomato matrix extract in order to obtain a more accurate quantification. 3.2.3. Repeatability and reproducibility The RSDr values ranged from 7.9% to11.2% for tomato. According to the document SANCO/12571/2013 (SANCO, 2013), the obtained RSDr values were within the acceptable range 20% (Table 2), ranged from, 8.4 to 10.5% for the spiking level shown in Table 2.

Fig. 2. Dissipation pattern of fenitrothion in tomato under open field condition.

Table 3 Regression equation, correlation coefficient, and half-life of fenitrothion in tomato. Experiment site

Regression equation

Correlation coefficient (R2)

Half-life (days)

Meit-Gamer Menof

Ct = 10.879e0.303t Ct = 9.9362e0.314t

0.991 0.972

2.28 2.20

818


Table 4 Terminal residue of fenitrothion in tomatoes. Dosage (kg a.i/ha)

Number of times sprayed

Days after spraying

Residues in tomato (mg/kg) Meit Gamer

Menof

1.25

2

7 14 7 14

1.87 0.162 2.01 0.18

1.591 0.147 1.94 0.201

7 14 7 14

2.25 0.213 2.27 0.201

2.221 0.199 2.302 0.183

3 2.5

2 3

Table 5 The final residues of fenitrothion at PHI of 14 days on tomatoes under GAP application. Final residues (mg/kg) Tomatoes

0.147

0.162

0.180

0.183

3.5. Risk assessment The supervised trial median residue (STMR) in tomatoes was 0.2 mg/kg according to Table 5. Residues implication of foliar application of fenitrothion on tomato crop has been evaluated by comparing the estimated daily intake (IEDI) of the insecticide with its acceptable daily intake (ADI). The ADI of fenitrothion was established as 0.006 mg/kg bw based on its No Observed Adverse Effect Level (NOAEL) of 0.6 mg/kg bw per day and a 100-fold coefficient of safety factor. The IEDI was defined according to the following formula:

IEDI ¼ ðSTMR 0:077Þ=60

ð6Þ

Where 60 kg is the average body weight of an Egyptian adult (Malhat, El Sharkawi, Loutfy, & Ahmed, 2014); 0.077 kg/Egyptian adult was the daily dietary intake of tomatoes according to GEMS/Food regional diet, (WHO., 2003). IEDI of fenitrothion in tomato was 0.0256 mg/kg bw. The ADI% was defined according to the formula:

ADI% ¼ ðIEDI 100Þ=ADI;

ð7Þ

Where the ADI% is the percentage of ADI. When ADI% 100%, then the chronic risk of fenitrothion is acceptable; the smaller the ADI%, the lower the chronic risk (Chun & Kang, 2003). When ADI%˃ 100%, then the chronic risk of fenitrothion is unacceptable; the higher the ADI%, the greater the chronic risk. The ADI% of fenitrothion in tomato was found to be 4.16%. 4. Discussion The dissipation data showed that a gradual and continuous decrease of the fenitrothion residues in tomatoes was observed. Same order of magnitude half-lives were reported in studies focusing on the dissipation rate of fenitrothion in lettuce (Fenoll et al., 2009) and in cauliflowers (Fernandez-Cruz et al., 2006), however studies made in apricots showed a higher half-life than the current finding (Cabras et al., 1997). Different species, weather condition and different doses may be responsible for the different dissipation rates of this insecticide. A growth dilution factor might play an important role in pesticide dissipation in the plant, in addition to the effect of physical and chemical factors such as light, heat, pH and moisture (Romeh & Mekky, 2009; Malhat, Almaz, Arief, ElDin, & Fathy, 2012; Khay, Choi, & Abd El-Aty, 2008; Malhat, 2013; Malhat, Abdallah, & Nasr, 2012). The growth dilution factor is important in reducing fenitrothion residues levels in tomatoes

0.199

0.201

0.203

0.213

because the residue is expressed as a proportion of weight (mg/ kg). The tomatoes fruits were picked in different stages of growth in this study, and as the weight of tomatoes fruits materials increase, the proportion of residue decreases. The use of pesticides on food crops lead to unwanted residues, which may constitute barriers to exporters and domestic consumptions when the levels exceed the MRLs. According to the terminal residue results, the residue behavior of fenitrothion in tomatoes under different treatments followed a trend in which shorter harvest intervals led to more residual fenitrothion. The ADI% was less than 100%, indicating that the chronic risk of fenitrothion is within acceptable limits. The results indicate that the potential health risk induced by fenitrothion was not significant and that the recommended application doses were safe. Accumulation of toxic residues in fruits and vegetables can be minimized to some extent by fixing the safe waiting period between the time of application and packing up (harvesting) of fruits and vegetables (Kumari, Madan, Singh, Singh, & Kathpal, 2004; Malhat, Loutfy, & Ahmed, 2016). The results of this study are expected to assist in establishment of the safe and proper use of fenitrothion in tomato crops grown under field conditions in Egypt. 5. Conclusion There is no record of any studies that reported the dissipation of fenitrothion in tomatoes in Egypt. In this study, the dissipation and safety evaluation of fenitrothion residues in tomatoes were investigated using GC-FPD. A relative simple and fast method was developed to analyze the residues in tomato fruit. The residue of fenitrothion dissipated following first order kinetics. Dissipation study showed that the half-life of fenitrothion was approximately 2.2 day in tomato, in an open field trial. The results of this study are expected to help establish the safe and proper use of fenitrothion in tomato crops grown under field conditions in Egypt. Open field studies should be carried out for all pesticide applied, as different compounds can have dissimilar behavior and affect safety and quality of fruit in a different way. Acknowledgments The authors are grateful to all the stuff in Central Agricultural Pesticide Laboratory (Egypt) for their technical support. The author grateful of Professor Abd El-Aty Mostafa Abd El-Aty for their contribution to improve this article.


References Abdulra’uf, L. B., & Tan, G. H. (2014). Chemometric study and optimization of headspace solid-phase microextraction parameters for the determination of multiclass pesticide residues in processed cocoa from Nigeria using gas chromatography/mass spectrometry. Journal of AOAC International, 97(4), 1007–1011. Albero, B., Sànchez-Brunete, C., & Tadeo, J. L. (2005). Multiresidue determination of pesticides in juice by solid-phase extraction and gas chromatography–mass spectrometry. Talanta, 66, 917–924. Ambrus, M., Lantos, J., Visi, E., Csatlos, I., & Sarvari, L. (1981). General method for determination of pesticide residues in samples of plant origin, soil and water. I. Extraction and clean-up. Journal Association of Official Analytical Chemists, 1981 (64), 733–742. Anastassiades, M., Maštovska, K., & Lehotay, S. J. (2003). Evaluation of analyte protectants to improve gas chromatographic analysis of pesticides. Journal of Chromatography A, 1015, 163. Aysal, P., Ambrus, R., Lehotay, S., & Cannavan, A. (2007). Validation of an efficient method for the determination of pesticide residues in fruits and vegetables using ethyl acetate for extraction. Journal of Environmental Science and Health, Part B: Pesticides, Food Contaminants, and Agricultural Wastes, 42(5), 481–490. Bakırcı, G. T., & Hısıl, Y. (2012). Fast and simple extraction of pesticide residues in selected fruits and vegetables using tetrafluorethane and toluene followed by ultrahigh-performance liquid chromatography/tandem mass spectrometry. Food Chemistry, 135, 1901–1913. Cabras, P., Angioni, A., Garau, V., Minelli, E., Cabitza, F., & Cubeddu, M. (1997). Residues of some pesticides in fresh and dried apricots. Journal of Agriculture and Food Chemistry, 45, 3221–3222. Cherta, L., Beltran, J., López, F., & Hernández, F. (2013). Comparison of simple and rapid extraction procedures for the determination of pesticide residues in fruit juices by fast gas chromatography-mass spectrometry. Food Analytical Methods, 2013(6), 1170. Chun, O. K., & Kang, H. G. (2003). Estimation of risks of pesticide exposure by food intake, to Koreans. Food and Chemical Toxicology, 41, 1063–1076. Diagne, R., Foster, G., & Khan, S. (2002). Comparison of soxhlet and microwaveassisted extractions for the determination of fenitrothion residues in beans. Journal of Agriculture and Food Chemistry, 50, 3204–3207. Document SANCO/12571/2013. (2013) Guidance document on analytical quality control and validation procedures for pesticide residues analysis in food and feed. . European Union. (2014). Maximum residue limits for pesticides. . Fenoll, J., Hellin, P., Lopez, J., Gonzalez, A., Lacasa, A., & Flores, P. (2009). Dissipation rates of fenitrothion in greenhouse grown lettuce and under cold storage conditions. International Journal of Food Science and Technology, 44, 1034–1040. Fenoll, J., Hellín, P., Martínez, C. M., Miguel, M., & Flores, P. (2007). Multi residue method for analysis of pesticides in pepper and tomato by gas chromatography with nitrogen-phosphorus detection. Food Chemistry, 105, 711–719. Fernandez-Cruz, M., Barreda, M., Villarroya, M., Peruga, A., Llanos, S., & GarciaBaudin, J. (2006). Captan and fenitrothion dissipation in field-treated cauliflowers and effect of household processing. Pest Management Science, 62, 637–645. Ferreira, J. R., & Fernandes, A. M. S. S. (1980). Gas-liquid chromatographic determination of organophosphorus insecticide residues in fruits and vegetables. Journal Association of Official Analytical Chemists, 1980(63), 517–522. Frank, S., Jon, W., Chenseng, L., Jing, L., Jim, R., & LaTonya, M. (2009). Multiresidue analysis of 102 organophosphorus pesticides in produce at parts-per-billion levels using a modified QuEChERS method and gas chromatography with pulsed flame photometric detection. Journal of AOAC International, 92(2), 561–573. Furlani, R. P. Z., Marcilio, K. M., Lemea, F. M., & Tfouni, S. A. V. (2011). Analysis of pesticide residues in sugarcane juice using QuEChERS sample preparation and gas chromatography with electron capture detection. Food Chemistry, 126, 1283. Gilles, G., & Victorin, N. (1980). Development of an analytical method for fenitrothion and five derivatives in water using XAD Resins and Gas Liquid Chromatography (GLC). International Journal of Environmental Analytical Chemistry, 8(4), 291–301. Khani, M., Imani, S., & Larijani, K. (2011). Determination of malathion and fenitrothion residues in wheat by solid phase microextraction/gas chromatography-mass spectrometery (SPME/GC-MS) method. African Journal of Food Science, 5(8), 499–502.

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Khay, S., Choi, J., & Abd El-Aty, M. (2008). Dissipation behavior of lufenuron, benzoyphenylurea insecticide, in/on Chines cabbage applied by foliar spraying under greenhouse condition. Bulletin of Environment Contamination and Toxicology, 81, 369–372. Kumari, B., Madan, K., Singh, J., Singh, S., & Kathpal, T. (2004). Monitoring of pesticidal contamination of farm gate vegetables from Hissar. Environmental Monitoring and Assessment, 90, 1–3. Lehotay, S. J. (2011). QuEChERS sample preparation approach for mass spectrometric analysis of pesticide residues in foods. Methods in Molecular Biology, 747, 65. Lehotay, S. J., Son, K. A., Kwon, H., Koesukwiwat, U., Fu, W., & Mastovska, K. ... (2010) Comparison of QuEChERS sample preparation methods for the analysis of pesticide residues in fruits and vegetables, (2010). Journal of Chromatography A, 1217(16), 2548–2560. López-Blanco, C., Gómez-Alvarez, S., Rey-Garrote, M., Cancho- Grande, B., & SimalGàndara, J. (2006). Determination of pesticides by solid phase extraction followed by gas chromatography with nitrogen phosphorus detection in natural water and comparison with solvent drop microextraction. Analytical and Bioanalytical Chemistry, 384, 1002–1006. Malhat, F. (2012). Residues and dissipation of fenitrothion in green bean (Phaseolus vulgaris) and soil. ISRN Soil Science. http://dx.doi.org/10.5402/2012/365317. Malhat, F. (2013). Simultaneous determination of spinetoram residues in tomato by high performance liquid chromatography combined with QuEChERS method. Bulletin of Environmental Contamination & Toxicology, 90(2), 222–226. Malhat, F. M. (2017). Persistence of metalaxyl residues on tomato fruit using high performance liquid chromatography and QuEChERS methodology. Arabian Journal of Chemistry, 10(Suppl. 1), S765–S768. Malhat, F., Abdallah, H., & Nasr, I. (2012). Estimation of etofenprox residues in tomato fruits by QuEChERS methodology and HPLC–DAD. Bulletin of Environmental Contamination and Toxicology, 88, 891. http://dx.doi.org/ 10.1007/s00128-012-0627-6. Malhat, F., Almaz, M., Arief, M., El-Din, K., & Fathy, M. (2012). Residue and dissipation dynamics of lufenuron in tomato fruit using QuEChERS methodology. Bulletin of Environmental Contamination and Toxicology, 89, 1037. http://dx.doi.org/10.1007/s00128-012-0823-4. Malhat, F., El Sharkawi, H., Loutfy, N., & Ahmed, M. T. (2014). Field dissipation and health hazard assessment of Fenhexamid on Egyptian grapes. Toxicological & Environmental Chemistry, 96(5), 722–729. Malhat, F., & Hassan, A. (2011). Level and fate of etoxazole in green bean (Phaseolus vulgaris). Bulletin of Environmental Contamination and Toxicology, 87, 190. http:// dx.doi.org/10.1007/s00128-011-0336-6. Malhat, F., Loutfy, N., & Ahmed, M. T. (2016). Dissipation pattern and risk assessment of the synthetic pyrethroid Lambda-cyhalothrin applied on tomatoes under dryland conditions, a case study. International Journal of Food contamination. http://dx.doi.org/10.1186/s40550-016-0029-3. Malhat, F., Watanabe, H, & Youssef, A (2015). Degradation profile and safety evaluation of methomyl residues in tomato and soil. Hellenic Plant Protection Journal, 8(2), 55–62. Miao, Q., Kong, W., Yang, S., & Yang, M. (2013). Rapid analysis of multi-pesticide residues in lotus seeds by a modified QuEChERS-based extraction and GC-ECD. Chemosphere, 91, 955. Romeh, A., & Mekky, M. (2009). Dissipation of profenofos, imidaclopride and penconazole in tomato fruits and products. Bulletin of Environment Contamination and Toxicology, 83, 812–817. Sapahin, H. A. et al. (2015). Determination of organophosphorus pesticide residues in vegetables using solid phase micro-extraction coupled with gas chromatography–flame photometric detector. Arabian Journal of Chemistry. http://dx.doi.org/10.1016/j.arabjc.2014.12.001. Surma, M. K., & Sadowska-Rociek, A. B. (2014). Evaluation of the QuEChERS method with GC-MS Detection for the Determination of Organochlorine Pesticides in Food of Animal Origin. Food Analytical Methods, 7, 366. Tonogai, Y., Tsumura, Y., Nakamura, Y., Ito, Y., Watanabe, Y., & Shiomi, Y. (1992). Determination of organophosphorus pesticides in imported foods by FPD-GC and GC-MS. Eisei Shikenjo Hokoku, 110, 140–143. Torres, C. M., Picó, Y., Redondo, M. J., & Mañes, J. (1996). Matrix solidphase dispersion extraction procedure for multiresidue pesticide analysis in oranges. Journal of Chromatography A, 719, 95–103. WHO. (2003). GEMS/Food regional diets (regional per capita consumpation of raw and semi-processed agricultural commodities). http://www.who.int/foodsafty/ publications/chem/regional_diets/en.