Persistence of thiacloprid residues on brinjal(Solanum melongena L.)

Sanjay Kumar Sahoo & Kousik Mandal &Ramandeep Kaur & R. S. Battu & Balwinder Singh

Received: 4 November 2012 /Accepted: 19 February 2013 /Published online: 3 March 2013# Springer Science+Business Media Dordrecht 2013

Abstract Thiacloprid, a neonicotinoid insecticidewith novel mode of action, is found to be effectiveagainst several lepidopteran as well as hemipteranpests. The present studies were carried out to observethe persistence pattern of thiacloprid on brinjal and tosuggest suitable waiting period for the safety of con-sumers. Persistence of thiacloprid in brinjal was stud-ied following three applications of thiacloprid (Alanto240 SC) at 180 and 360 g a.i. ha−1 at 7 days interval.Residues of thiacloprid in brinjal were estimated byhigh-performance liquid chromatography and wereconfirmed by liquid chromatography–mass spectrom-etry. The average initial deposits of thiacloprid wereobserved to be 0.48 and 1.05 mgkg−1 on the brinjalfruit following third application of thiacloprid atrecommended and double the recommended dosages,respectively. Half-life periods for thiacloprid werefound to be 0.47 and 0.50 days at single and doublethe application rates, respectively. Residues ofthiacloprid declined below its limit of quantificationof 0.05 mgkg−1 after 3 and 5 days, respectively, atrecommended and double the recommended applica-tion rates. Therefore, the use of thiacloprid does notseem to pose any risk hazard and a waiting period of

1 day is suggested for safe consumption of brinjalfruits.

Keywords Thiacloprid . HPLC . LC-MS/MS .

Residues . Half-life . Brinjal

Introduction

Brinjal (Solanum melongena L.) is the popular sola-naceous and economically important vegetable fruitcrop and is native to India (Anil and Sharma 2010).It is one of the most important vegetable crops oftropical and subtropical regions of the world. Beingmost affordable, it is known as “common man's veg-etable” grown in almost all over India (Walia et al.2010). In Punjab, brinjal occupied an area of 3.22thousand ha with the production of 48.50 thousandtons during 2009–2010 (Anonymous 2010). The lowproduction of brinjal in the country could be attributedto several factors, the most important being the dam-age caused by various insect pests. The brinjal crop isattacked by these pests during its growth, which sub-stantiates the use of pesticides for sustaining its pro-duction. Amongst these, shoot and fruit borer(Leucinodes orbonalis) is the most devastating and akey pest throughout the cropping season (Patial andMehta 2008). During the recent past, several insecti-cides have been recommended for its management.Heavy applications of insecticides for insect pest man-agement lead to development of resistance in many

Environ Monit Assess (2013) 185:7935–7943DOI 10.1007/s10661-013-3145-z

S. K. Sahoo :K. Mandal (*) :R. Kaur :R. S. Battu :B. SinghPesticide Residue Analysis Laboratory,Department of Entomology, Punjab Agricultural University,Ludhiana 141004, Punjab, Indiae-mail: kousik11@gmail.com

economically important pests of brinjal (Singh 2006).Its resistance to many of the commonly used insecti-cides make it one of the most difficult pests to manage.Recently, thiacloprid has been found to be very effec-tive for the control of brinjal shoot and fruit borer(Atule et al. 2011).

Thiacloprid [(Z)-3-(6-chloro-3-pyridylmethyl)-1,3-thiazolidin-2-ylidenecyanamide] is a neonicotinoid in-secticide with systemic properties. It was recentlyintroduced into India for foliar application andbroad-spectrum efficacy against sucking and bitinginsects (Fig. 1; Dhivahar and Dhandapani 2003). Ithas activity not only against sucking insects such asaphids, whiteflies, and some jassids, but is also activeagainst weevils, leaf miners, and Cydia pomonella inapples and various species of beetles (e.g.,Leptinotarsa decemlineata, Anthonomus pomorum,Lissorhoptrus oryzophilus, and Lema oryzae) andshows good plant compatibility in all relevant crops(Ciglar and Barić 2002; Elbert et al. 2000). On thebasis of its high insecticidal activity with a favorableecological profile and safety to bees, it is particularlyuseful in horticulture as well as in modern crop pro-tection systems. Like other chloronicotinyl insecti-cides, thiacloprid acts selectively on the insectnervous system as an agonist of the nicotinic acetyl-choline receptor. This compound has been found to besafe towards the egg parasitoid Trichogrammacacoeciae Marchal (Schuld and Schmuck 2002), bees,and important beneficial organisms and showed nophytotoxicity to any of the crops tested even at highconcentrations (Elbert et al. 2000; Jeschke et al. 2001).

Pesticides applied to food crops leave residueswhich may be hazardous to the consumers. The per-sistence of an insecticide varies with the nature ofinsecticides, dosage applied, number of applications,crop variety, and agroclimatic conditions (Jyot et al.2005). Since no published information seems to beavailable on the residues of thiacloprid under

subtropical contribution in Punjab, the present studieswere undertaken to determine the residues ofthiacloprid on brinjal fruit at different time intervalsand suggest suitable waiting periods for the safety ofconsumers.

Materials and methods

Chemicals and reagents

The technical grade analytical standard of thiacloprid(purity 99.0 %) was supplied by M/s BayerCropScience India Ltd., Mumbai, India. Thiacloprid(Alanto 240 SC) formulation was used for field appli-cation. This formulation was also obtained from M/sBayer CropScience, Mumbai, India. Analysis of ace-tonitrile extract of the formulation showed onlythiacloprid, and none of its metabolic products and nointerfering peaks were observed under the retention timeof the compounds being estimated. Moreover, the con-centration of thiacloprid was found to be accurate withrespect to its purity as claimed by the manufacturers.

Solvents like acetonitrile (high-performance liquidchromatography (HPLC) grade) and chloroform wereprocured from Merck, Darmstadt, Germany. Sodiumchloride (ASC reagent grade ≥99.9 %) was alsoobtained from Merck, Darmstadt, Germany. Sodiumsulfate anhydrous (AR grade) and activated charcoaldecolorizing powder was procured from S.D. FineChemicals, Mumbai, India. All common solvents wereredistilled in all-glass apparatus before use. The suitabil-ity of the solvents and other chemicals was ensured byrunning reagent blanks along with test samples.

Preparation of standard solution

A standard stock solution of the thiacloprid (1 mgmL−1)was prepared in HPLC grade acetonitrile. The standardsolutions required for constructing a calibration curve(2.00, 1.50, 1.00, 0.50, 0.25, and 0.10 μgmL−1) wereprepared from stock solution by serial dilution withacetonitrile. All standard solutions were stored at 4 °Cbefore use.

Field trials

Brinjal (var. Jamuni Gola) was raised during summer of2010 at the Entomological Research Farm, PunjabFig. 1 Chemical structure of thiacloprid

7936 Environ Monit Assess (2013) 185:7935–7943

Agricultural University, Ludhiana followingrecommended agronomic practices (Anonymous2010). There were three replications for each treatment(i.e., control, recommended, and double therecommended dosages) arranged in a randomized blockdesign, and the size of the each plot was 100 m2. Thesoil under crop was of light texture with low content oforganic matter. Other relevant properties of the soilwere: organic carbon=0.30 %, pH=8.0; sand=78.0 %; silt=10.2; clay=11.8 %; and EC=0.30 dSm−1.

The first application of thiacloprid (Alanto 240 SC)was made at 50 % fruit initiation stage at 180 and360 g a.i. ha−1 followed by another two applications at7 days interval. In control plots, only water wassprayed. The insecticide was sprayed as foliar appli-cation with the help of an ASPEE Knapsack sprayerfitted with a hollow cone nozzle.

Sampling procedure

About five to six marketable size brinjal fruit sampleswere collected randomly from control and treated plotsfrom each treatment before the start of final thirdapplication of the insecticide. Thereafter, on the com-pletion of third application, the samples were collectedat 0 (2 h), 1, 3, and 5 days after application of theinsecticide. The samples from each treatment plotwere collected separately, packed in polyethylenebags, and brought to the laboratory for processing.Samples were extracted and cleaned up immediatelyafter sampling.

Extraction and cleanup

The samples were processed and analyzed at PesticideResidue Analysis Laboratory, Department ofEntomology, Punjab Agricultural University,Ludhiana. The whole of the sample collected fromeach treatment plot was macerated in a high-speedblender (Blixer 6 V.V. Robot Coupe) and a represen-tative 50-g sample of macerated brinjal fruits wasdipped separately overnight into 100 mL acetonitrilein an Erlenmeyer flask for 24 h. The extract wasfiltered into a 1-L separatory funnel throughWhatman filter paper no. 1 along with rinsings ofacetonitrile. The filtrate in the separatory funnel wasdiluted with 600 mL brine solution (almost saturatedsodium chloride solution) and partitioned the contentsthree times into 100, 50, and 50 mL chloroform. The

combined organic layers were dried over anhydroussodium sulfate and treated with 500 mg activatedcharcoal powder for about 2–3 h at room temperature.The clear extract so obtained was filtered throughWhatman filter paper no. 1, concentrated to near dry-ness. About 20 mL of acetonitrile was added and againconcentrated using a rotary vacuum evaporator at<40 °C. The final volume was reconstituted to about5 mL using HPLC grade acetonitrile.

Instrumental analysis

Quantification by HPLC The quantification ofthiacloprid residues was done by using HPLC. Thehigh-performance liquid chromatograph (model DGU-2045) was equipped with a reversed-phase C18 columnand photodiode array detector; dual pump was sup-plied by M/S Shimadzu Corporation, Kyoto, Japan.The HPLC column, a Luna 5-μm C18 column (250×4.6 mm size; 5.20±0.30 μm particle size; 2.20±0.30(90 %/10 %) particle distribution; 95±15 Å pore di-ameter; 430±40 m2g−1 surface area; <55.0 ppm metalcontent; 19.00±0.70 % total carbon; and 3.25±0.50 μmolm−2 surface coverage), was obtained fromM/S Spincotech Pvt. Ltd. Chennai, India. The sampleinjector was equipped with a 20-μL loop. For instru-ment control, data acquisition, and processing, LCSolution software was used. The HPLC analysis wascarried out under controlled room temperature at 25 °Cconditions. Acetonitrile was used as mobile phase at0.5 mLmin−1. The instrument was operated at a wave-length of 254 nm. Residues of thiacloprid were quanti-fied by comparison of peak height/peak area ofstandards with that of unknown or spiked samples rununder identical conditions of operation.

Confirmation by LC-MS/MS The residues ofthiacloprid were confirmed using a MDS SciexApplied Biosystem API 2000 Q-Trap mass spectrom-eter. Electrospray (ESI) was tested for the determina-tion of thiacloprid in both the positive and negativemodes, respectively. ESI in the negative mode did notgive any signal for thiacloprid, whereas in positivemode, compound was detected with infusion at therate of 0.6 mL/h of standard solutions of thiaclopridat 5,000 μg/L. The full-scan spectrum for thiaclopriddepicted the isotopic pattern typical for a structurecontaining two chlorines and one bromine. The liquidchromatography–mass spectrometry (LC-MS) was

Environ Monit Assess (2013) 185:7935–7943 7937

operated in the positive ion mode using multiple reac-tion monitoring (MRM) of the transitions m/z253→125.90, m/z 253→99.00, and m/z 253→89.90(Figs. 2 and 3). The experimental conditions were asfollows: ion spray voltage 5,500 V; curtain gas 15 psi;temperature 400 °C; and ion source gas (1) 50 psi andion source gas (2) 55 psi. Declustering potential andcollision energy were optimized for each transitionmonitored.

The most intense ions were the isotope A + 1proton adduct (m/z 253). The first transition m/z253→125.90, second transition m/z 253→99.00, andthird transition m/z 253→89.90 were used for confir-matory purpose. The MRM of the thiacloprid byHPLC-ESI-MS/MS was also done for further confir-mation. The analyte ESI-MS/MS (±) transitions andinstrument conditions are as follows: MW, 252;

precursor mass (m/z) and [A + Z]+. First transitionsare mass (m/z): 253→125.90; DP (V), 28; FP (V),380; EP, 10; CE (V), 31; and CXP, 1. Second transi-tions are mass (m/z): 253→99.00; DP (V), 28; EP, 10;FP (V), 380; CE (V), 61; and CXP, 5. And thirdtransitions are mass (m/z): 253→89.90, DP (V) 28;EP, 10; FP (V), 380; CE (V), 50; and CXP, 1.

Statistical analysis

The degradation kinetics of the thiacloprid in brinjalfruit were determined by plotting residue concentrationagainst time, and the maximum squares of correlationcoefficients found were used to determine the equationsof best fit curves. For all the samples studied, exponen-tial relations were found to be applicable, correspondingto first-order rate equation. Confirmation of the first-

XIC of +MRM (3 pairs): 253.0/125.9 amu from Sample 3 (Thiacloprid= 0.1 ppm) of Thiacloprid std 1.0 ng-27-01-12-01.wiff (Turbo Spra... Max. 3246.7 cps.

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5Time, min

0

500

1000

1500

2000

2500

3000

32470.75

1.12

+MRM (3 pairs): 0.752 min from Sample 3 (Thiacloprid= 0.1 ppm) of Thiacloprid std 1.0 ng-27-01-12-01.wiff (Turbo Spray) Max. 3246.7 cps.

253.0/125.9 253.0/99.0 253.0/89.9

Q1/Q3 Masses, amu

0

500

1000

1500

2000

2500

3000

Fig. 2 MRM mass spectra of standard thiacloprid

7938 Environ Monit Assess (2013) 185:7935–7943

order kinetics was further made graphically from thelinearity of the plots of C against time. The persistenceof these insecticides is generally expressed in terms ofhalf-life (t1/2) or DT50, i.e., time for disappearance ofpesticide to 50 % of its initial concentration.

Results and discussion

Efficiency of the method

The linearity of a method is a measure of range withinwhich the results are directly, or by a well-defined

mathematical transformation, proportional to the con-centration of analyte in samples within a given range(Francotte et al. 1996). The calibration curves withrespect to thiacloprid produce a linear relationshipbetween detector response (y) and analyte concentra-tion (x). The parameters obtained by the selected chro-matographic conditions for thiacloprid calibrationcorrespond to: y=6469x+4346, R2=0.998, where y=peak area, x=thiacloprid concentration (in milligramper liter), and R=correlation coefficient (Fig. 4).

The parameters like limit of detection (LOD), limitof quantification (LOQ), and relative standard devia-tion (RSD) were derived keeping in view the

XIC of +MRM (3 pairs): 253.0/125.9 amu from Sample 1 (Thiaclorid= 0.05 ppm) of Thiacloprid std 0.5 ng- 27-01-12-01.wiff (Turbo Spra... Max. 1813.3 cps.

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Time, min

0

200

400

600

800

1000

1200

1400

1600

18000.76

0.951.17

+MRM (3 pairs): 0.760 min from Sample 1 (Thiaclorid= 0.05 ppm) of Thiacloprid std 0.5 ng- 27-01-12-01.wiff (Turbo Spray) Max. 1813.3 cps.

253.0/125.9 253.0/99.0 253.0/89.9

Q1/Q3 Masses, amu

0

200

400

600

800

1000

1200

1400

1600

1800

Fig. 3 MRM mass spectra of thiacloprid on spiked brinjal samples at 0.05 mg/kg level

Environ Monit Assess (2013) 185:7935–7943 7939

guidelines as mentioned by Thompson et al. (2002). Inthe present investigations, recovery experiments werecarried out at different levels to establish the reliabilityand validity of the analytical method and to know theefficiency of extraction and cleanup procedures. Thecontrol samples of brinjal fruits were spiked at 0.50,0.25, and 0.05 mgkg−1 and processed by following themethodology as described above. The mean recoveriesof thiacloprid were found to range from 87.59 to91.26 % for brinjal fruits (Table 1). Therefore,the results have been presented as such without apply-ing any correction factor. The precision of the methodwas determined by repeatability studies of the methodand expressed by the RSD values. The RSD for re-peatability ranged from 2.86 to 4.08 % for brinjalfruits for thiacloprid at different spiking levels asshown in Table 1.

Half-scale deflection was obtained for 50 ngthiacloprid which could be easily identified from thebaseline, as 10 ng of the compound produced 10 %deflection which can be measured. When 50 g ofbrinjal fruits was extracted, cleaned up, and final vol-ume made to 5 mL, 20 μL (200 mg) of sample wheninjected did not produce any background interference.

Thus, LOQ was found to be 0.05 mgkg−1 and LODbeing 0.017 mgkg−1.

Persistence of thiacloprid in brinjal

The overall results of the analysis of brinjal fruitsfollowing the third application of thiacloprid at 180and 360 g a.i. ha−1 are presented in Table 3. The meaninitial deposits of thiacloprid were 0.48 and 1.05 mgkg−1 on the fruits following third application ofthiacloprid at minimum effective and double the ef-fective dosages, respectively. These deposits dissipat-ed to 0.11 and 0.22 mgkg−1 after 1 day respectivelythereby showing a loss of about 77.08 and 79.05 %following application of thiacloprid at 180 and 360 ga.i. ha−1. These residues reached below the detectablelimit of 0.05 mgkg−1 in 3 and 5 days, respectively, andthereby showing 100 % loss following application ofthiacloprid at both the dosages (Table 2).

The above findings revealed that higher rate ofapplication of thiacloprid resulted in higher initial de-posits. As with the other insecticides, the residues ofthiacloprid on brinjal declined with time and a fairlyhigh rate of dissipation was observed. These resultsare in agreement with those of Omirou et al. (2009)who studied the thiacloprid residues on greenhousetomato following the application of thiacloprid(Calypso 480 SC) at 30 and 60 mlha−1. The initialdeposits of thiacloprid were 0.74 and 1.56 mgkg−1 atsingle and double doses, respectively. Residues weredissipated to 0.07 and 0.23 mgkg−1 after 20 days.Similarly, Kooner et al. (2010) reported that averageinitial deposits of thiacloprid on tomato were 0.16 and0.29 mgkg−1, respectively, following three applica-tions of the combination mixture (flubendiamide24 % + thiacloprid 24 %) 480 SC with respect tothiacloprid at 48 and 96 g a.i. ha−1. Residues of

Fig. 4 Calibration curve ofdifferent concentrations ofthiacloprid

Table 1 Recovery and repeatability (RSD) for thiacloprid inspiked brinjal fruit samples at different levels

Level of fortification(mgkg−1)

Mean recovery(%)a

SD RSD (%)

0.50 87.59 2.66 3.04

0.25 91.26 3.72 4.08

0.05 90.56 2.59 2.86

a Number of replicates at each level (n=3) all made under thesame conditions on the same day

SD standard deviation, RSD relative standard deviation

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thiacloprid dissipated below LOQ of 0.01 mgkg−1 in 5and 7 days at single and double dosages, respectively.Dubey et al. (2008) reported that thiacloprid residuesdissipated rapidly and did not accumulate in apple andtea. The initial deposit of thiacloprid on apple fruitswas found to be 1.62 mgkg−1 following application ofthiacloprid (Calypso 240 SC) at 120 g a.i. ha−1 inSolan. These residues were dissipated to 0.24 mgkg−1 after 10 days of application. In tea, initial de-posits were found to be 2.30 and 4.80 mgkg−1 follow-ing application of thiacloprid at 30 and 60 g a.i. ha−1.These residues were dissipated to 0.21 and 0.42 mgkg−1 after 10 days. Yun-long et al. (2007) studied theresidues of thiacloprid on medical herbs marjoram,thyme, and camomile. Thiacloprid (480 g a.i. L−1)was sprayed at 0.12 L in 400 L water hm−2 whencamomile was in the flowering phase and marjoramand thyme were approximately 15 cm in height.Thiacloprid residues in marjoram, thyme, and camo-mile persisted beyond 10, 14, and 14 days, but noresidues were detected after 14, 21, and 21 days, re-spectively. Dikshit et al. (2006) studied the residues oncotton at harvest time during 2001–2003. Thiaclopridwas sprayed at 30, 120, and 240 g a.i. ha−1 at thesquare bud to fruiting stage of the cotton crop.Residues of thiacloprid were non-detectable in cottonseed and lint samples at harvest. The absence of resi-dues of thiacloprid in seed oil ensured its consumption

without association of any residues risk. Kumar et al.(2010) reported thiacloprid residues on cardamom fol-lowing application of thiacloprid 240 SC at 25 and50 g a.i. ha−1. The residues of thiacloprid in green andcured cardamom capsule were found to be belowdetectable limit at harvest time.

Half-life of thiacloprid

The degradation kinetics of the thiacloprid in brinjalwas determined by plotting residue concentrationagainst time, and the maximum squares of correlationcoefficients found were used to determine the equa-tions of best fit curves (Fig. 5). The persistence of anyinsecticide is generally expressed in terms of half-life(T1/2) or DT50 i.e. time for disappearance of insecticideto 50 % of its initial concentration. The dissipation ofthiacloprid on brinjal did not follow first-order kinet-ics. Half-life (T1/2) of thiacloprid calculated as perHoskins (1961) was observed to be 0.47 and 0.50 days,respectively, when applied at 180 and 360 g a.i. ha−1

(Table 2). Kooner et al. (2010) also observed the half-life values of thiacloprid on tomato fruits to be 1.18and 0.95 days following application of thiacloprid(flubendiamide 24 % + thiacloprid 24 %, 480 SC) at48 and 96 g a.i. ha−1, respectively. Similarly, Dubey etal. (2008) reported that the half-life values ofthiacloprid on apple fruits were 4.1–4.6 and 3.8–

Table 2 Residues of thiacloprid(in milligram per kilogram) inthe fruits of brinjal

BDL below determination limit(<0.05 mgkg−1), T1/2 half-life(days)

Days after thirdapplication

180.0 g a.i. ha−1 360.0 g a.i. ha−1

Replicates Mean±SD % dissipation Replicates Mean±SD % dissipation

Before thirdapplication

BDL BDL – BDL BDL –BDL BDL

BDL BDL

0 0.51 0.48±0.05 – 0.97 1.05±0.07 –0.51 1.07

0.43 1.10

1 0.14 0.11±0.03 77.08 0.22 0.22±0.01 79.050.09 0.22

0.11 0.21

3 BDL BDL 100.00 0.11 0.10±0.01 90.48BDL 0.09

BDL 0.10

5 BDL BDL – BDL BDL 100.00BDL BDL

BDL BDL

T1/2 0.47 0.50

Environ Monit Assess (2013) 185:7935–7943 7941

4.1 days following the application of thiacloprid at 120and 240 g a.i. ha−1, respectively, for four locations. Ongreen tea shoots, the half-life valueswere around 3.3 daysafter application of thiacloprid at 30 and 60 g a.i. ha−1.Yun-long et al. (2007) observed that the biexponentialmodel is more suitable than the first-order function todescribe the decline of thiacloprid in fresh marjoram,fresh thyme, and dried camomile flowers with half-lifeof 1.1, 0.7, and 1.2 day, respectively.

Risk assessment of thiacloprid on brinjal

The use of pesticides on food crops leads to unwantedresidues, which may constitute barriers to exportersand domestic consumptions when they exceed maxi-mum residue limit (MRL). Theoretical maximum res-idue contributions (TMRCs) were calculated andcompared with maximum permissible intake (MPI)to evaluate the risk to the consumer for the thiaclopridon brinjal fruits. The prescribed acceptable daily in-take (ADI) of thiacloprid is 0.01 mg−1kg−1bodyweight−1day−1. The MPI was obtained by multiplyingthe ADI with the weight of average Indian person

(55 kg) (Mukherjee and Gopal 2000). MPI was calcu-lated to be 550 μgperson−1day−1. Taking 80 g asvegetable consumption for an Indian balance diet(Anonymous 1999) and maximum residues on brinjalfruits, the TMRC values on 0 day are found to be 38.8and 40.8 μg−1person−1day−1, respectively, for averageand maximum residues observed in the case ofrecommended dose (Table 3). Both the values are lessas compared to ADI; hence, the insecticide will notcause any adverse effect after consumption of suchbrinjal fruits.

These studies, therefore, suggest that the use ofthiacloprid at the minimum and maximum effectivedosages does not seem to pose any hazards to theconsumers if a waiting period of 1 day is observed.Kooner et al. (2010) also reported that a waiting periodof 5 days is required for safe consumption of tomatofruit after application of combination formulation offlubendiamide 24 % + thiacloprid 24 % (480 SC) at200 gha−1. Dubey et al. (2008) suggested a waitingperiod of 10 and 3 days, respectively, for apple fruitsand tea following application of thiacloprid for thesafe consumption of thiacloprid-treated apple and

Fig. 5 Semi-logarithmgraph showing dissipationkinetics of thiacloprid resi-dues on brinjal fruits

Table 3 Theoretical maximum residue contribution (TMRC) in brinjal fruits

Days afterapplication

ADI for 55 kg person(μgperson−1day−1)

Thiacloprid 180.0 g a.i. ha−1

Average residues inbrinjal fruits (mgkg−1)

TMRC (μgperson−1 d−1)

Maximum residues inbrinjal fruits (mgkg−1)

TMRC (μgperson−1day−1)

0 550 0.48 38.8 0.51 40.8

1 550 0.11 8.8 0.14 11.2

3 550 BDL 0 BDL 0

ADI acceptable daily intake, TMRC theoretical maximum residue contribution, BDL below determination limit (0.05 mgkg−1 )

7942 Environ Monit Assess (2013) 185:7935–7943

tea. Omirou et al. (2009) reported that thiaclopridresidues were below EU MRLs (0.50 mgkg−1) after2 days of the application of the pesticides.

Conclusions

The average initial deposits of thiacloprid were ob-served to be 0.48 and 1.05 mgkg−1 on the brinjal fruitfollowing third application of thiacloprid at minimumeffective and double the effective dosages, respective-ly. Half-life values for thiacloprid following three ap-pl ica t ions at recommended and double therecommended dosages on brinjal fruits were observedto be 0.47 and 0.50 days, respectively. Even 0 daybrinjal fruit consumption is safe at both the dosages.A waiting period of 1 day is suggested to reduce therisk before consumption of brinjal fruits.

Acknowledgments The authors are thankful to the Professorand Head, Department of Entomology, PAU, Ludhiana for pro-viding the necessary research facilities. Financial assistanceprovided by Indian Council of Agricultural Research, NewDelhi and Bayer CropScience India Ltd., Mumbai, India is alsogratefully acknowledged.

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