[他誌掲載論文]

Journal of Agricultural and Food Chemistry, 2014, 62, 2790～2796.
より転載
Water-Based Extraction and Liquid Chromatography−Tandem Mass
Spectrometry Analysis of Neonicotinoid Insecticides and Their Metabolites
in Green Pepper/Tomato Samples
Takashi Iwafune1), Tomomi Ogino1), and Eiki Watanabe2)1)Agricultural Chemicals Inspection Station, Food and Agricultural Materials Inspection Center, 2-772

Suzuki-cho, Kodaira,Tokyo 187-0011, Japan
2)

Organochemicals Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kan-nondai,

Tsukuba, Ibaraki 305-8604, Japan・本論文の著作権は、American Chemical Society に帰属していますが、American Chemical Society の転載要件を満たしていることを確認の上転載しています.

Articlepubs.acs.org/JAFC

Water-Based Extraction and Liquid Chromatography−Tandem Mass
Spectrometry Analysis of Neonicotinoid Insecticides and Their
Metabolites in Green Pepper/Tomato Samples
Takashi Iwafune,† Tomomi Ogino,† and Eiki Watanabe*,§†Agricultural Chemicals Inspection Station, Food and Agricultural Materials Inspection Center, 2-772 Suzuki-cho, Kodaira,Tokyo 187-0011, Japan§
Organochemicals Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kan-nondai, Tsukuba, Ibaraki 305-8604, JapanS Supporting Information*

ABSTRACT: This paper proposes an environmentally friendly method involving water-based extraction of the samples, cleanupof the extracts by solid-phase extraction, and subsequent liquid chromatography coupled with tandem mass spectrometry, which
was used for simultaneous determination of seven hydrophilic neonicotinoid insecticides as well as their metabolites inagricultural samples. The eﬀects of sample matrix on detection of the target compounds were negligibly small. Mean recoveries
obtained at spiked concentrations between 0.01 and 1.00 mg/kg were 71.2−122.3% with relative standard deviations of≤7.5%. When the method was applied to crop samples sprayed with commercial formulations of the target compounds, theresidual concentrations of the compounds determined by the proposed method (0.015−0.27 mg/kg in green peppers and0.017−0.31 mg/kg in tomatoes) were equivalent to those determined by the oﬃcial Japanese method (0.017−0.26 mg/kg in
green peppers and 0.013−0.30 mg/kg in tomatoes).
KEYWORDS: water extraction, neonicotinoid insecticides, LC-MS/MS, agricultural samples■

the dispersive liquid−liquid microextraction method,8−10,23
which are available for successful extraction and cleanup withsmall volumes of organic solvents, could be reasonable in termsof reduction of organic solvents in sample preparation. The useof water as an extractant instead of an organic solvent can be an
important option for environmentally friendly analysis and can
be available for recovering hydrophilic pesticides and their polar
metabolites simultaneously. However, few multiresidue methods
based on water as an extractant have been developed.20,25
The aim of the current study was to develop a sample
preparation method involving water-based extraction andversatile SPE cleanup for simultaneous determination of sevenhydrophilic neonicotinoid insecticides, as well as some of the
major metabolites of nitenpyram and thiacloprid, in agricultural
samples by means of LC-MS/MS. To verify the applicability ofthe proposed sample preparation method, we compared
analytical results obtained using the proposed method forsamples prepared by spraying crops with several commercial
neonicotinoid insecticide formulations with results obtained bymeans of a reference method (the oﬃcial Japanese multiresidue
method18).

INTRODUCTION
Neonicotinoid insecticides, which have a high aﬃnity for insect
nicotinic acetylcholine receptors,1,2 are widely used to protect
crops against a broad range of pests, including aphids, whiteﬂy,
thrips, and mealybugs. The commerically available neonicotinoid
insecticides are acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam (Table 1).
Their high polarity2 and other physicochemical properties makethem useful for a wide range of application techniques, including
seed treatment, soil drench, and foliar and stem application.
Because some pesticides can be applied to crops up to the day
before harvest, the residual pesticide concentrations in crops
immediately after harvest may be relatively high.
Various methods for neonicotinoid insecticide residue analysis
have been reported.3−24 Imidacloprid and acetamiprid have been
analyzed by gas chromatography,3−5 and high-performance liquid
chromatography (HPLC) is useful for the analysis of neonicotinoid
insecticides in various matrices owing to the high polarity and low
volatility of these insecticides.2 The simultaneous determination ofmultiple neonicotinoid insecticides by HPLC coupled with diodearray or UV detection6−12 and by liquid chromatography coupledwith mass spectrometry (LC-MS)12−15 or with tandem mass
spectrometry (LC-MS/MS)10,16−24 has been reported.
Sample preparation, which is required for reliable results,
represents a bottleneck in pesticide residue analysis. Sample
preparation generally involves extraction with an organic solvent
followed by liquid−liquid partitioning and cleanup with a solidphase extraction (SPE) cartridge. Large volumes of hazardousorganic solvents are used, which presents a health risk to theanalyst and is not environmentally friendly. The quick, easy,
cheap, eﬀective, rugged, and safe (QuEChERS) method18,21 and© 2014 American Chemical Society■

MATERIALS AND METHODS

Chemicals and Reagents. Certiﬁed neonicotinoid insecticide
standards, two major metabolites of nitenpyram [2-[N-(6-chloro3-pyridylmethyl)-N-ethylamino]-2-(methylimino)acetic acid (CPMA)
Received: November 26, 2013
Revised: February 27, 2014
Accepted: March 10, 2014
Published: March 10, 2014
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Articleall of >95% purity, were purchased from Wako Pure Chemical Industries(Osaka, Japan), Dr. Ehrenstorfer (Augsburg, Germany), and FlukaSigma-Aldrich (Steinheim, Germany), respectively. Pesticide analysis
grade and HPLC grade organic solvents, HPLC grade formic acid, andother analytical grade reagents were obtained from Kanto Chemical Co.
(Tokyo, Japan) or Wako Pure Chemical Industries. Pure water for
sample preparation and LC-MS/MS analysis was prepared in thelaboratory by means of a water puriﬁcation system (Milli-Q, Millipore
Corp., Bedford, MA, USA). ENVI-Carb II/PSA SPE cartridges (500 mg
of graphitized carbon black and 500 mg of ethylenediamine-N-propyl
silica gel) and ENVI-Carb/LC-NH2 SPE cartridges (500 mg ofgraphitized carbon black and 500 mg of aminopropyl silica gel) werepurchased from Supelco (Bellefonte, PA, USA).
Stock and Working Solutions. Stock solutions of CPMA in waterand the other target compounds in methanol were prepared, and thesolutions were stored in the dark at 4 and −20 °C, respectively.
Multicomponent working solutions (1, 10, and 100 mg/L) wereprepared by diluting each stock solution with 20:80 (v/v) methanol/
water at every recovery test and LC-MS/MS analyses, and the working
solutions were used as calibration standards and for spiking agricultural
samples.
Agricultural Samples. Green peppers and tomatoes were used asmodel agricultural crops. Green peppers and tomatoes were chopped
and homogenized by a home food processor (KC-D627, TWINBIRD
Corp., Niigata, Japan). For the preparation of spiked samples forrecovery tests, green peppers and tomatoes were grown on arable land of
the Japan Plant Protection Association (Miyazaki, Japan) without theuse of neonicotinoid insecticides. The absence of the target compounds
in the vegetables was conﬁrmed by LC-MS/MS prior to eachexperiment. For the recovery tests, a homogenized sample (5 g) was
spiked with 50 μL of the 1, 10, or 100 mg/L multicomponent working
solution (0.01, 0.10, or 1.00 mg/kg, respectively). The spiked samples
were exposed to the target compounds for 30 min prior to extraction.
In addition to the spike−recovery tests, we also conducted tests on
green peppers and tomatoes sprayed with commercial formulations of
the target compounds. The plants were grown in a plastic greenhouse on
arable land of the National Institute for Agro-Environmental Sciences
and, at the harvesting stage, were sprayed with a mixture of four
neonicotinoid insecticide formulations: Mospilan (water-soluble
powder), containing 20.0% acetamiprid (Nippon Soda Co., Tokyo,
Japan); Admire (water-soluble granules), containing 20% imidacloprid(Bayer Crop Science, Tokyo, Japan); Bariard (water-soluble granules),containing 30% thiacloprid (Bayer Crop Science); and Actara (watersoluble powder), containing 10% thiamethoxam (Syngenta Japan K.K.,
Tokyo, Japan), all diluted with water according to the manufacturers’
instructions. The samples were harvested at 1, 3, and 7 days after
spraying. After harvesting, the samples were chopped and homogenized
by a home food processor.
Sample Preparation. Proposed Water-Based Extraction Method.
A 5 g aliquot of homogenized sample was weighed into a 100 mL
centrifuge tube, and 25 mL of water was added to the tube. The sample
was shaken vigorously for 30 min on a shaker (SA-400, Yamato ScientiﬁcCo., Tokyo, Japan) and then centrifuged at approximately 1400g for 20
min. The sample mixture was suction-ﬁltered through a glass ﬁber ﬁlter(60 mm in diameter, GF-B, Kiriyama Glass Co., Tokyo, Japan), and thesolid residue on the ﬁlter was washed with 15 mL of water. The volumeof the extract was brought to exactly 50 mL with water, and then 2 mL
aliquots (equivalent to 0.2 g of sample) were added to 10 mL ofacetonitrile. The solution obtained by adding 2 mL aliquots to 10 mL ofacetonitrile was cleaned up according to the procedure established by
Kobayashi,16 as follows. The solution was loaded onto an ENVI-Carb II/
PSA SPE cartridge preconditioned with 5 mL of acetone and 5 mL ofn-hexane. The target compounds were eluted with 5 mL of acetonitrile/
toluene (3:1, v/v). The eluate was concentrated and evaporated todryness with a gentle stream of nitrogen. The residue was reconstituted
with 1 mL of 20:80 (v/v) methanol/water, and the resulting solution
was ﬁltered with a polytetraﬂuoroethylene membrane syringe-drivenﬁlter unit (0.45 μm, GL Sciences Inc., Tokyo, Japan).
Japanese Oﬃcial Method (Reference Method). To verify theapplicability of the proposed water extraction method, we used theTable 1. Neonicotinoid Insecticides and Metabolites
Analyzed in This Studya

All values were obtained from ref 2. b Major metabolite ofnitenpyram. c Not reported. d Major metabolite of thiacloprid.

and N-(6-chloro-3-pyridylmethyl)-N-ethyl-N′-methylformamidine(CPMF)], and a major metabolite of thiacloprid (thiacloprid amide),
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ArticleTable 2. Detection Parameters, Calibration Data, and Limits of Detection of Target Compounds
compound
CPMF
dinotefuran
CPMAnitenpyram
thiamethoxam
clothianidin
imidacloprid
thiacloprid
amide
acetamiprid
thiaclopridaretention
time (min)transition mass(m/z)atransition mass(m/z)bcone
voltage(V)collisionenergy (eV)

2.01
2.66
2.90
3.31
5.69
7.86
8.07
8.13

212 → 126
203 → 129
256 → 126
271 → 225
292 → 211
250 → 169
256 → 175
271 → 126

212 → 157
203 → 157
256 → 176
271 → 130292 → 181
250 → 132
256 → 209
271 → 228

20
12
20
10
17
13
22
25

33
26
25
31
26
24
25
25

8.62
9.74

223 → 126
253 → 126

223 → 90
253 → 56

20
25

32
36

calibration curve

linearity(μg/L)

correlationcoeﬃcient (r)limit ofdetection(μg/L)

y = 1015.23x − 36.43
y = 319.99x + 6.97
y = 271.39x − 0.90
y = 104.36x + 6.11
y = 224.32x + 6.14
y = 226.19x + 37.17
y = 188.91x + 1.54
y = 530.47x − 5.39

0.10−50.10−50.10−50.5−50.05−50.5−50.05−50.05−50.99970.99970.99970.99961.00000.99950.99980.9998

0.05
0.05
0.05
0.10
0.02
0.10
0.03
0.01

y = 1837.52x + 21.67
y = 2146.54x + 0.60

0.05−50.05−51.00001.00000.01
0.01

MS-MS transition used for quantiﬁcation. bMS-MS transition used for conformation.

Japanese oﬃcial method26 as a reference method as follows. Acetonitrile(50 mL) was added to 20 g of homogenized sample, and the slurry was
extracted for 3 min with a high-speed homogenizer (Polytron PT2100,
Kinematica AG, Lucerne, Switzerland). The sample mixture wassuction-ﬁltered, and the solid residue on the ﬁlter was extracted again
with 20 mL of acetonitrile. The volume of the combined extracts wasbrought to exactly 100 mL with acetonitrile, and 20 mL aliquots of theextract (equivalent to 4 g of sample) were mixed with 10 g of sodium
chloride and 20 mL of 0.5 M phosphate buﬀer (pH 7). The resulting
mixture was shaken vigorously for 10 min and then allowed to stand forabout 10 min. After the aqueous phase was discarded, the acetonitrile
phase was dried with anhydrous sodium sulfate and ﬁltered, and theﬁltrate was concentrated and evaporated to dryness with a gentle streamof nitrogen. The residue was reconstituted in 2 mL of acetonitrile/
toluene (3:1, v/v), and the resulting solution was loaded onto an ENVICarb/LC-NH2 SPE cartridge preconditioned with 10 mL of acetonitrile/
toluene (3:1, v/v). After the target compounds were eluted with
20 mL of acetonitrile/toluene (3:1, v/v), the eluate was concentrated.
The residue was reconstituted in 10 mL of acetone. The resulting
solution was concentrated, and 5 mL of acetone was added to theresidue. The acetone was evaporated under a gentle stream of nitrogen.
After the residue was reconstituted with 1 mL of methanol, the solution
was diluted ﬁve times with methanol/water (20:80, v/v) and ﬁlteredthrough a polytetraﬂuoroethylene membrane syringe-driven ﬁlter unit.
Evaluation of Matrix Eﬀects. To evaluate matrix eﬀects, we used
the proposed water extraction method and the reference method
described above to prepare cleaned up extracts of nonspiked samples.
The cleaned up extracts were dissolved in 1 mL of methanol/water(20:80, v/v), and then 0.04 μg of each target compound was added tothe extracts. Matrix eﬀects were evaluated according to a method
described in an earlier paper,27 and the magnitude of the eﬀects wascalculated by means of the following equation:

an electrospray ionization (ESI) interface. For all compounds, the MS
instrument was operated in the ESI positive-ion mode at a desolvation
temperature of 350 °C and a source temperature of 120 °C and at an ESI
voltage of 3.9 kV. Nitrogen was used as the desolvation gas at a ﬂow rateof 600 L/h. For collision-induced dissociation, argon gas was used as thecollision gas at a pressure of 4.5 × 10−3 mbar in the collision cell. Mass
spectrometric detection was performed in multiple reaction monitoring
mode. The multiple reaction monitoring transitions were selected andtuned by direct syringe pump infusion of a 5.0 mg/L standard solution ofeach compound prepared in methanol/water 20:80 (v/v) into thespectrometer at a ﬂow rate of 10 μL/min. The dwell time for eachtransition was 300−600 ms. Optimized MS/MS transitions as well as
speciﬁc cone voltages and collision energies are summarized in Table 2.
Under the chromatographic conditions described, calibration graphs
were constructed by plotting peak areas versus concentrations. Excellent
linearity and regression coeﬃcient (r) were achieved for all of the target
compounds in this study (Table 2). The limit of detection for eachcompound was determined as the lowest concentration of eachcompound that gave a signal-to-noise ratio of at least 3.

■

RESULTS AND DISCUSSION
Optimization of LC-MS/MS Conditions. To achieve good
separation of the target compounds with high sensitivity, we
analyzed all samples using a slightly modiﬁed version of the LC
gradient program reported by Kobayashi.16 This gradient
program resulted in good sensitivity and peak shape for all of
the target compounds. We optimized the MS parameters andmultiple reaction monitoring transitions for the maximum
abundance of fragmented ions under ESI positive-ion modeconditions by infusing standard solutions of the target compounds
into the mass spectrometer (Table 2). Full-scan spectra were
measured for selection of the most abundant m/z values. For eachtarget compound, the addicted ion [M + H]+ was determined as aprecursor ion. The optimal collision energy for each target
compound was selected, which yielded the most abundant production by dissociation of each precursor ion in the collision cell.
Matrix Eﬀects. Matrix eﬀects have been widely studied andare recognized as a source of error in quantitative LC-ESI-MS/MS
analysis of food samples.28 Matrix eﬀects result from competition
between matrix ions and analyte ions in the sprayed solution foraccess to the droplet.29 Depending on the environment in which
ionization and ion evaporation take place, this competition caneither suppress or enhance the eﬃciency of analyte ion formation.30
We evaluated matrix eﬀects on the results of analysis of thetarget compounds in green peppers and tomatoes by means of
the proposed water-based extraction method and the reference
method (Figure 1). For all of the target compounds, the⎡ peak area of standards in cleaned up extract⎤
matrix effect (%) = ⎢− 1⎥⎦⎣ peak area of standards in pure solvent
× 100

LC-MS/MS Analysis. LC-MS/MS analysis was carried out with an
HPLC system (Alliance 2695 series, Waters, Milford, MA, USA)equipped with a pump, a degasser, an autosampler, and a column oven.
The target compounds were separated on an Atlantis T3 analyticalcolumn (50 mm × 2.1 mm i.d., 3.5 μm particle size) ﬁtted with an
Atlantis T3 guard column Atlantis T3 (10 mm × 2.1 mm i.d., 3.5 μm
particle size), both from Waters. The column oven temperature was kept
at 30 °C. The injection volume was 10 μL, and the ﬂow rate was 0.2 mL
min−1. Mobile phases A and B were methanol and 5 mM ammonium
acetate containing 0.1% formic acid, respectively. A gradient mobile wasused, with the A:B ratio varied as follows: 0 min, 20:80; 5 min, 20:80;
10 min, 95:5; 13 min, 95:5; 13.5 min, 20:80; 25 min, 20:80.
The MS/MS system (Quattro Micro API, Micromass, Manchester,UK) was a triple-quadrupole tandem mass spectrometer equipped with
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ArticleTable 3. Recoveries of Target Compounds from Artiﬁcially
Spiked Agricultural Samples Using the Proposed Water-Based
Extraction Method (n = 4)
green pepper

tomatoacompound
CPMF

dinotefuran

CPMAnitenpyram

thiamethoxam

clothianidin

imidacloprid

thiacloprid amide

acetamiprid

thiacloprid

Figure 1. Matrix eﬀects in the proposed water-based extraction method
and the reference method.

spiked concentration recovery RSD(mg/kg)
(%)
(%)
0.01
0.10
1.00
0.01
0.10
1.00
0.01
0.10
1.00
0.01
0.10
1.00
0.01
0.10
1.00
0.01
0.10
1.00
0.01
0.10
1.00
0.01
0.10
1.00
0.01
0.10
1.00
0.01
0.10
1.00

88.6
71.2
106.1
112.8
81.8
100.7
88.8
82.3
100.1
94.3
83.5
95.0
90.0
84.0
102.8
110.7
85.0
105.2
106.2
97.2
103.9
87.2
81.9
96.4
86.8
81.7
101.4
82.7
79.0
98.0

6.4
5.0
0.7
4.3
4.0
0.4
2.3
7.5
0.8
3.1
4.7
0.8
4.0
5.4
0.4
1.9
2.9
0.5
2.4
6.0
0.3
3.2
5.6
2.1
2.9
5.1
0.2
2.6
6.1
1.1

recovery RSDa
(%)
(%)
99.8
75.9
85.0
96.9
77.1
93.1
93.0
80.2
97.6
121.7
96.6
104.5
104.6
85.7
100.2
104.0
87.0
108.0
122.3
96.2
100.5
105.1
86.5
98.7
100.6
82.8
102.2
100.1
81.9
101.3

6.7
6.4
3.5
4.7
6.2
1.9
4.5
6.9
1.9
4.1
4.3
1.6
4.4
6.8
2.1
4.5
7.4
2.2
2.0
6.5
1.8
2.5
6.3
1.1
1.5
6.6
1.4
1.5
5.5
1.0

a

Relative standard deviation.

magnitude of the matrix eﬀect was between −1.7 and +12.6%;
this result indicates that for all the combinations of target
compounds and matrices in this study, there was no substantial
signal suppression or enhancement (matrix eﬀect within ±20%)that interfered with accurate determination by LC-MS/MS
analysis according to the criteria explained by Mol et al.31 On thebasis of our results, we performed calibration of the target
compounds with external standards diluted with 20:80 (v/v)
methanol/water. Some studies21,32,33 on the QuEChERS
method reported that matrix-matched calibration was performed
because there was substantial signal suppression and enhancement for the combinations of some pesticides and matrices. On
the other hand, matrix eﬀects in the proposed method were notsigniﬁcant; therefore, the target compounds in this study could
be analyzed with good precision by calibration with external
standards. From the viewpoint of calibration of the target
compounds without matrix-matched standards, the proposed
method might have an advantage over the QuEChERS method.
Precision and Accuracy of the Proposed Water-Based
Extraction Method. We conducted recovery tests on samples
spiked with the target compounds at three concentrations (0.01,
0.10, and 1.00 mg/kg; Table 3). The recoveries and relative
standard deviations were in the range of 71.2−112.8 and ≤7.5%,
respectively, except for the recoveries of imidacloprid (122.3 ±
2.5%) and nitenpyram (121.7 ± 4.9%) in tomato samples spiked

at 0.01 mg/kg. For most of the target compounds, the recoveries
and relative standard deviations were within the criteria speciﬁed
in Japanese and European guidelines for validation of pesticide
residue analysis methods (70−120 and <20%, respectively).34,35
These results are indicative of the good precision and accuracy ofthe proposed water-based extraction method. Although the watersolubility and octanol−water partition coeﬃcients of CPMA,
CPMF, and thiacloprid amide have not been reported, thesemetabolites are thought to be at least as hydrophilic as therespective parent compounds. Xiao et al.20 reported that
neonicotinoid insecticides in bovine tissues can be recovered
almost completely by means of extraction with pressurized purewater. Our results conﬁrmed that the hydrophilic neonicotinoid
insecticides and their metabolites targeted in this study could be
extracted into water and recovered, suggesting that the proposed
environmentally friendly water-based extraction method ispotentially useful for the analysis of hydrophilic pesticides suchas neonicotinoid insecticides and related metabolites.
Applicability of the Proposed Method to Samples
Sprayed with Commercial Insecticide Formulations. We
evaluated the relationship between the analytical results obtainedby means of the proposed water-based extraction method and thereference method with green pepper and tomato samples that
had been sprayed with four commercial neonicotinoid insecticide
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ArticleFigure 2. Relationship between residue concentrations in green pepper andtomato samples determined by the proposed water-based extraction
method and by the reference method: (○) acetamiprid; (□) clothianidin(a metabolite of thiamethoxam); (△) imidacloprid; (●) thiacloprid; (■)
thiamethoxam. Each point is the average of four replicate determinations.
The dotted line corresponds to a perfect correlation (y = x).

Figure 3. Chromatograms of target compounds obtained from tomato
samples harvested 7 days after being sprayed with mixtures of theinsecticide formulations by the proposed water-based extraction method(A) and by the reference method (B).

formulations (Figure 2). Acetamiprid, imidacloprid, thiacloprid,thiamethoxam, and clothianidin (a metabolite of thiamethoxam)
were detected at >0.01 mg/kg in the samples. The residual
concentrations of the target compounds in the green pepper
samples determined by means of the proposed method and thereference method were 0.015−0.27 and 0.017−0.26 mg/kg, andthose in the tomato samples were 0.017−0.31 and 0.013−0.30 mg/kg,
respectively. The residual concentration of thiacloprid amide in
the samples was <0.01 mg/kg. Figure 3 shows chromatograms oftarget compounds obtained from green pepper and tomato
samples harvested 7 days after being sprayed with mixtures of theinsecticide formulations. The slopes of the simple linear
regression equations describing the relationship between thepesticide concentrations detected by means of the proposed
method and the reference method were approximately 1;
speciﬁcally, the slope for the green pepper samples was 0.95
(r = 0.98) and that for the tomato samples was 0.98 (r = 0.99),

indicating that the concentrations detected by means of the two
methods were equivalent. Our results suggest that the proposed
method can be also applicable for spraying crops and market
samples with hydrophilic pesticides.
The proposed environmentally friendly water-based extraction
method for agricultural samples here demonstrates that (1) the
consumed volume of organic solvent (25 mL per sample) ismuch less than the volume consumed by the oﬃcial Japanesemultiresidue method (150 mL per sample) and (2) it has simple
procedures without liquid−liquid partitioning and can simultaneously and suitably recover hydrophilic pesticides as well aspolar metabolites such as CPMA and CPMF that cannot be
simultaneously recovered by the oﬃcial Japanese multiresidue
method. To secure food safety, this proposed method could be
utilized for regular monitoring of neonicotinoid insecticides andtheir metabolites in high water content crops, such as green
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peppers and tomatoes, and for monitoring before shipment ofthese crops.

■

ASSOCIATED CONTENT

S Supporting Information*

Residue concentrations in green pepper and tomato samples
sprayed with formulations 1, 3, and 7 days after insecticide
application determined by the proposed method and by thereference method (n = 4). This material is available free of charge
via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author*(E.W.) Phone: +81 29 838 8306. Fax: +81 29 838 8199. E-mail:eikiw@aﬀrc.go.jp.
Notes

The authors declare no competing ﬁnancial interest.

■

ACKNOWLEDGMENTS■

REFERENCES

We thank Takahiro Ara and Hiroshi Yamagushi (National
Institute for Agro-Environmental Sciences) for their support in
the growth of crop samples sprayed with commercial
formulations of pesticides. We also thank Yutaka Takagi (Japan
Plant Protection Association) for providing blank samples forrecovery tests.

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