Article
pubs.acs.org/JAFC
Determination of Sulfoxaflor in Animal Origin Foods Using
Dispersive Solid-Phase Extraction and Multiplug Filtration Cleanup
Method Based on Multiwalled Carbon Nanotubes by
Ultraperformance Liquid Chromatography/Tandem Mass
Spectrometry
Chunyan Tian,† Jun Xu,*,† Fengshou Dong,† Xingang Liu,† Xiaohu Wu,† Huanhuan Zhao,‡ Chao Ju,†
Dongmei Wei,†,§ and Yongquan Zheng†
†
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural
Sciences, Beijing, 100193, P. R. China
‡
Department of Ecological Science and Engineering, College of Resources and Environmental Science, China Agricultural University,
Beijing, 100094, P. R. China
§
Department of Pesticide Science, College of Plant Protection, Shenyang Agricultural University, Shenyang, 110866, P. R. China
ABSTRACT: In the present study, a rapid analytical method was developed to determine the residue of sulfoxaflor in milk, pork,
eggs, porcine liver, porcine kidney, porcine fat, and chicken. The dispersive solid-phase extraction (d-SPE) and multiplug
filtration cleanup (m-PFC) based on multiwalled carbon nanotubes (MWCNTs) were compared for sulfoxaflor in the above
matrix and then detected by ultraperformance liquid chromatography coupled with tandem mass spectrometry. The analyte was
eluted within 5 min using a Waters Acquity UHPLC HSS T3 column under ESI+ conditions. The limits of detection were 1 μg
kg−1 for all of the matrices. Good linearities of sulfoxaflor were obtained in the range of 1−100 μg L−1, and the correlation
coefficients (R2) were higher than 0.9988 in all matrices. The average recoveries of the target compound were between 75.5% and
114.9%, and the intraday and interday relative standard deviation values were <14%. Both methods have purification ability.
While considering the cost of analysis and the applicability of the method, d-SPE was selected to purify the samples in the present
study. The method was successfully used to analyze the residue of sulfoxaflor in foods of animal origin.
KEYWORDS: sulfoxaflor, d-SPE, m-PFC, food of animal origin
■
INTRODUCTION
Currently, pesticides have become an essential part of
agriculture and are extensively used in preventing various
diseases. However, the wide use of pesticides may lead to
agrochemical residues on plants and accumulation in animal
products by consuming polluted grain, fodder, and forage.1 The
residual pesticides accumulated in the tissues of animals may
produce secondary toxicity in food of animal origin, such as
meat, milk, and eggs,2 threatening the health of humans
through the food chain. Therefore, to ensure the food safety
and the health of humans, the pesticide residues in foods of
animal origin must be monitored.
Sulfoxaflor, [methyl(oxo){1-[6-(trifluoromethyl)-3-pyridyl]ethyl}-λ6-sulfanylidene]cyanamide (Figure 1), is a novel
insecticide belonging to the sulfoximine class. Sulfoxaflor
mainly acts on the special binding site of the nicotinic
acetylcholine receptor (nAChR),3 which plays a central role
in the mediation of fast excitatory synaptic transmission in both
the insect and human central nervous system.4 Due to the
excellent insecticidal activity, sulfoxaflor has become one of the
most widely used insecticides on rice and wheat, which may
lead to residues on their straw and to the pollution of foods of
animal origin. Unfortunately, this residue may threaten the
health of humans because it can be bioaccumulated in the
human body and change the functions of the endocrine system
© 2016 American Chemical Society
Figure 1. Chemical structure of sulfoxaflor.
or cause some other diseases.5 Casida et al. reported that
neuroactive insecticides may be associated with Parkinson’s and
Alzheimer’s diseases.6 Several methods have been reported for
the determination of sulfoxaflor residues in vegetables, fruits,
and soils,7 and for the stereoselective determination of
sulfoxaflor in cereals.8 However, there is no literature available
on analytical methods for the determination of sulfoxaflor
residues in foods of animal origin.9
Received:
Revised:
Accepted:
Published:
2641
January 19, 2016
March 8, 2016
March 11, 2016
March 11, 2016
DOI: 10.1021/acs.jafc.6b00285
J. Agric. Food Chem. 2016, 64, 2641−2646
Article
Journal of Agricultural and Food Chemistry
Table 1. Optimized UHPLC-MS/MS Acquisition Method Parametersa
a
compound
mol formula
mol wt
ion source
CV (V)
quantification ion transition
CE 1 (eV)
confirmatory ion transition
CE (eV)
Sulfoxaflor
C10H10F3N3OS
277.27
ESI+
22
278 → 174
13
278 → 154
23
CV: cone voltage. CE: collision energy.
The target compound was analyzed on a triple-quadrupole mass
spectrometer (TQD, Waters Corp., Milford, MA, USA) equipped with
an electrospray ionization (ESI) source. MS/MS detection was
conducted on positive ionization mode, and the monitoring conditions
were optimized for sulfoxaflor. Nitrogen (99.95%) and argon
(99.999%) were used as the nebulizer gas and collision gas,
respectively, with a pressure of 2 × 10−3 mbar in the T-wave cell.
The typical conditions were as follows: the capillary voltage was set at
3.0 kV, and the source temperature and desolvation temperature were
held at 150 and 350 °C, respectively. Nitrogen was used for the cone
and desolvation gas flows at 50 and 550 L/h, respectively. MassLynx
software (version 4.1) was used for instrument control and data
acquisition. Multiple reaction monitoring (MRM) mode was used for
sulfoxaflor analysis. All of the parameters for the MRM transitions,
cone voltage, and collision energy were optimized to obtain the
highest sensitivity and resolution (Table 1).
Sample Preparation. Blank samples, including milk, pork, eggs,
porcine liver, porcine kidney, porcine fat, and chicken, were purchased
from a supermarket and were not contaminated by the target
compound. These samples were chopped and mixed thoroughly in an
Ultra-Turrax homogenizer (IKA-Werke, Staufen, Germany) and then
stored in the dark at less than −20 °C until analysis. The final method
for the recovery study was as follows: approximately 10 g blank
samples (including milk, pork, eggs, porcine liver, porcine kidney,
porcine fat, and chicken) were weighed into 50 mL Teflon centrifuge
tubes and were spiked with an appropriate volume of standard solution
at three different concentrations. Then, the tubes were vortexed for 30
s and stood for 2 h in room temperature to ensure that the samples
interacted evenly with the target pesticide. Next, 10 mL of acetonitrile
was added to the tubes. The tubes were then capped and shaken
violently for 5 min. Afterward, 4 g of MgSO4 and 1 g of NaCl were
added (4 g of NaCl was added for the milk sample), and the samples
were vortexed immediately for 1 min and centrifuged at 4000 rpm for
5 min to obtain the supernatant. An appropriate volume of the
obtained upper layer was purified as described in the next section and
was filtered through 0.22 μm nylon syringe filters and transferred to
autosampler vials for UPLC-MS/MS analysis.
Purification by Two Methods. To ensure good recoveries, the
cleanup effects of the traditional d-SPE sorbents and the three types of
m-PFC columns were compared in the current study.
The d-SPE Purification Procedure. An aliquot of 1.5 mL of the
supernatant was transferred into a 2 mL single-use centrifuge tube
containing a suitable amount of sorbent (50 mg of C18 for eggs,
chicken, milk, and porcine fat; 30 mg of C18 + 20 mg of PSA + 10 mg
of GCB for porcine liver and porcine kidney) and 150 mg of MgSO4,
and the tubes were again shaken for 1 min and centrifuged for 5 min at
5000 rpm. Finally, the supernatant was filtered through 0.22 μm nylon
syringe filters and was transferred to autosampler vials for UPLC-MS/
MS analysis.
The m-PFC Cleanup Procedure. One milliliter of the supernatant
was transferred into a 2 mL single-use centrifuge tube and purified
with the three types of m-PFC columns. The nanotubes were installed
on the syringe, and the syringe needle was kept under the surface of
the extract. To obtain the ideal purification effects, the syringe piston
was pulled and pushed 3 times to let the extracts pass through the
sorbents and interact with the sorbents thoroughly. The obtained
liquid was filtered through a 0.22 μm filter membrane. The extract was
placed into UPLC vials for chromatographic analysis.
Method Validation. The traditional validation procedure was used
to estimate the performance of the developed method, and the
following parameters were included in the validation procedure:
specificity, linearity, limit of quantification (LOQ), precision, and
accuracy.18
Animal matrices are considerably complicated as they are rich
in fat, protein, and some other lipophilic compounds that are
easily coextracted with the target analytes.10 Thus, it is
extremely difficult to effectively purify the samples.11 d-SPE is
the most commonly used cleaning-up method in pesticide
residue analysis because it is convenient and requires only a
small amount of sorbents. Besides, it is reported that MWCNTs
can effectively remove interferences for they are hollow
graphene cylinders which make them outstanding candidates
for purifying samples.12 The multiplug filtration cleanup (mPFC) is a kind of cartridge packed with MWCNTs, PSA, GCB,
C18, and some other materials.13,14 It has excellent adsorption
ability in cleaning up complex matrix due to the increased
contact time and area between sorbents and matrix.15−17
Considering the complex characteristics of animal origin foods,
both d-SPE and m-PFC were selected and used to purify these
matrices in the present study.
The aim of this study is to establish an analytical method for
sulfoxaflor in foods of animal origin by combining d-SPE and
m-PFC. The purification performances of d-SPE and m-PFC
were also compared. To the best of our knowledge, this is the
first report of an analytical method for the determination of
sulfoxaflor in foods of animal origin.
■
EXPERIMENTAL SECTION
Chemicals and Materials. Sulfoxaflor standard (purity, 99.7%)
was provided by the Dow Chemical Company (Shanghai, China).
HPLC grade acetonitrile was purchased from Sigma-Aldrich
(Steinheim, Germany); NaCl, MgSO4, and formic acid (FA) of
analytical grade were provided by Beihua Fine Chemical Co. (Beijing,
PRC). Ultrapure water was obtained from a Milli-Q system (Bedford,
MA, USA). Primary secondary amine (PSA, 40 μm), graphitized
carbon black (GCB, 40 μm), octadecylsilane (C18, 40 μm), and three
kinds of m-PFC columns (IC-NN1510-S, IC-NN1510-C, and ICNN1010-V) were purchased from Agela Technologies Inc. (Beijing,
China). To filter the concentrated extracts, 0.22 mm nylon syringe
filters (Tengda, Tianjin, PRC) were used.
The standard stock solution (100 mg L−1) of sulfoxaflor was
prepared in pure acetonitrile. Standard working solutions at 1, 5, 10,
50, 100, and 500 μg L−1 were prepared by diluting the stock solution
with acetonitrile. Accordingly, the matrix-matched standard solutions
were obtained (1, 5, 10, 50, 100, and 500 μg L−1) by adding an
appropriate volume of blank sample extract (eggs, chicken, pork,
porcine liver, porcine kidney, porcine fat, and milk) to each serially
diluted standard solution. All solutions were stored in the refrigerator
in the dark at 4 °C, and no degradation of the working standard
solutions occurred during 3 months’ storage.
Instrumentation. The chromatographic analysis of sulfoxaflor was
performed on a Waters ACQUITY UHPLC system (Milford, MA)
equipped with a Waters ACQUITY UPLC binary solvent manager, an
ACQUITY UPLC manager, and a Waters Acquity UHPLC HSS T3
column (2.1 mm × 100 mm, 1.8 μm particle size). The column
temperature was kept at 40 °C to reduce the viscosity. The
temperature of the sample manager was held at 5 °C, and the
injection volume was 10 μL. The mobile phase was composed of
acetonitrile and 0.2% (v/v) formic acid (FA) in ultrapure water as
solvents A and B, respectively, with a flow rate of 0.3 mL/min. The
gradient elution program was as follows: 0−0.5 min, 10−90% A; 0.5−
3.9 min, retain 90% A; 3.9−4.0 min, 90−10% A; 4.0−5.0 min, retain
10% A, equilibration of the column.
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DOI: 10.1021/acs.jafc.6b00285
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Article
Journal of Agricultural and Food Chemistry
Blank samples (milk, pork, eggs, porcine liver, porcine kidney,
porcine fat, and chicken) were analyzed to confirm the absence of
interfering peaks at the retention time under the same conditions. To
verify the linearity of the method, standard solutions and matrixmatched standard solutions were analyzed in triplicate at six different
concentrations (from 1 to 500 μg L−1). The following parameters can
be obtained from the linear regression: slope, intercept, standard
deviation, and correlation coefficient (Table 2). LOQ refers to the
lowest spike level of the validation meeting the method performance
acceptability criteria (recoveries within the range 70−120%, with an
associated repeatability RSDr ≤ 20%). The matrix-induced signal
suppression/enhancement (SSE) was dependent on the slope ratio of
the matrix-matched calibration curve/pure solvent calibration curve.
Spike recoveries were used to verify the accuracy and precision. Five
replicates of the spiked samples at three different concentrations (1,
10, and 100 μg L−1) for milk, pork, eggs, porcine liver, porcine kidney,
porcine fat, and chicken were performed on three different days. The
compound was extracted and purified in accordance with the above
procedure. The precision for the repeatability, expressed as the relative
standard deviation (RSD), was determined by the intraday and
interday assays.
The stability of sulfoxaflor was determined in the solvent and in the
matrix. The stability of the stock solutions was tested monthly by
injection of a newly prepared working solution. The stability of the
spiked samples (10 mg L−1) for sulfoxaflor was evaluated monthly, and
all of the samples used in the stability test were stored at −20 °C.
Table 2. Calibration Equations, R2, LOD, LOQ, and Matrix
Effect of Each Pesticide
matrix
acetonitrile
milk
eggs
chicken
pork
porcine liver
porcine
kidney
porcine fat
regression
equation
y = 331.93x
4214.9
y = 212.13x
301.59
y = 222.42x
2084.9
y = 182.37x
1665
y = 199.95x
669.26
y = 237.81x
1160.8
y = 266.05x
817.29
y = 260.07x
3433
R
2
slope of
matrix/slope
of solventa
matrix
effectb
(%)
LOQ
(μg/
kg)
+
0.99
1
+
0.9999
0.63
−37
1
+
0.999
0.67
−33
1
+
0.9988
0.55
−45
1
+
0.9994
0.60
−40
1
+
0.9996
0.72
−28
1
+
0.9999
0.80
−20
1
+
0.9996
0.78
−22
1
■
RESULTS AND DISCUSSION
Optimization of the UPLC-MS/MS Parameters. The
multireaction monitoring mode (MRM) was used for the
analysis of sulfoxaflor, and higher intensities were obtained
under positive ESI mode. [M + H] + was chosen as the
precursor ion, and the two most abundant MRM transitions
were selected to quantify and identify the target compound.
The optimized MS/MS parameters for sulfoxaflor are listed in
Table 1.
In addition, to obtain excellent retention behavior, two types
of columns (UPLC BEH C18 and UPLC HSS T3) were tested
in our study; however sulfoxaflor exhibited good retention
behavior only on the UPLC HSS T3 column (1.8 μm, 100 mm
× 2.1 mm).
a
Slope ratio = matrix/ACN. bMatrix effect (%) = ((slope matrix/slope
solvent) − 1) × 100.
Figure 2. Typical UPLC-MS/MS MRM chromatograms of sulfoxaflor in (A) standard solution (1 μg L−1), (B) blank egg, milk, and porcine kidney,
and (C) egg, milk, and porcine kidney spiked at 1 μg L−1.
2643
DOI: 10.1021/acs.jafc.6b00285
J. Agric. Food Chem. 2016, 64, 2641−2646
Article
Journal of Agricultural and Food Chemistry
Figure 3. Effect of different kinds of sorbents for targeted compounds in different matrices at the 10 μg L−1 level (n = 3); error bars represent the
relative standard deviation (RSD) of three replicates.
Purification by the m-PFC Method. m-PFC is a novel
purification method that uses MWCNTs, PSA, GCB, and
MgSO4. The contact time and area between sorbents and
samples are increased and the purification efficiency is
improved compared to other purification methods. Qin et
al.12 successfully used the m-PFC method to purify wheat,
spinach, carrot, apple, citrus, and peanut samples. To compare
the purification effects with the d-SPE method, three types of
m-PFC columns (IC-NN1510-S, IC-NN1510-C, and ICNN1010-V) were used in the present study. IC-NN1010-V
and IC-NN1510-S are composed of MgSO4 and MWCNTs,
IC-NN1510-C consists of PSA, GCB, MWCNTs, and MgSO4,
and the results are shown in Figure 3.
The Purification Performance of the Two Methods. As
shown in Figure 3, regardless of the sorbents used on pork,
chicken, porcine fat, and porcine liver, the recoveries and RSD
were acceptable. However, for eggs, one type of m-PFC column
(IC-NN1010-V) did not give satisfactory recoveries and RSDs.
Acceptable recoveries and RSDs for milk were not obtained on
two types of m-PFC columns (IC-NN1010-V and IC-NN1510S). For porcine kidney, unsatisfactory recoveries were obtained
with two types of m-PFC columns (IC-NN1510-S and ICNN1510-C).
Although both cleaning-up methods were acceptable for
purifying these matrices, taking the cost of analysis and the
applicability of the method into consideration, d-SPE was
selected to purify the samples of foods of animal origin in the
present study. The purifying effects of these sorbents are
evaluated in the next section.
Matrix effects. Matrix effects were first described by Kebarle
and Tang,24 who defined them as the effects caused by the
presence of coextractives.25,26 The presence of coextractives
may have positive or negative effects on the chromatographic
response of the analyte, depending on the level of ion
suppression or enhancement.27 In the present work, the effects
caused by the matrices (including milk, pork, eggs, porcine
liver, porcine kidney, porcine fat, and chicken) were studied by
comparing the slope ratio in the calibration curve using the
matrix-free solution and the matrix extract solution. The
parameters related to the matrix effects are summarized in
Table 2. In terms of the decrease or increase in the slope
percentage, different matrix effects were described as follows: a
slope between −20% and +20% indicated mild signal
suppression or enhancement; a slope between −50% and
−20% and between +20% and +50% indicated a medium effect;
and a strong effect of signal suppression or enhancement was
indicated if the slope was below −50% or above +50%.10 As is
indicated in Table 2, distinct signal suppression was observed
To obtain satisfactory peak shape and appropriate retention
time, we also modified the mobile phase, which had a
significant impact on the peak shape and retention time.
Acetonitrile−water and acetonitrile−0.2% formic acid aqueous
solutions were evaluated for their elution ability, and the
acetonitrile−0.2% formic acid aqueous solution resulted in
better performance. This mobile phase was used throughout
this study. The retention time of sulfoxaflor was approximately
2.19 min, and there were no interference peaks near the
retention time of the target compound (Figure 2).
Optimization of the Extraction and Purification
Procedure. Optimization of the Extraction Procedure. The
extraction solvent has great significance in extracting the target
analytes for pesticide residue analysis. In many studies,
acetonitrile (ACN) was evaluated as the extraction solvent
because of its lesser coextraction of matrix components and
higher recoveries.7,8,19 However, for some compounds,
acetonitrile with formic acid (FA) was also used for extracting
pesticides from various samples.20 To obtain satisfactory
recoveries, three different extraction solvents (ACN, ACN−
0.1% FA, and ACN−0.2% FA) were tested in this study. ACN
had the best extraction efficiency among the three extraction
solvents. One gram of NaCl and 4 g of MgSO4 were added in
the organic extract to enhance the organic phase separation
from the inorganic phase and to absorb water in the solvent,
respectively.
Optimization of the d-SPE Method. The sorbent is another
factor that affects the residue analysis. Currently, d-SPE is the
most commonly used cleaning-up procedure as it requires only
a small amount of sorbent.21,22 d-SPE usually contains PSA,
C18, and GCB. It is well-known that PSA can remove various
polar organic acids, fatty acids, some sugars, and polar pigments
from nonpolar samples.22 C18 extracts nonpolar and mediumpolar compounds from polar samples, and GCB removes
hydrophobic interaction-based compounds, such as chlorophyll
and carotenoids.19,23 In this study, we have evaluated the effects
of traditional dispersive sorbents (including PSA, GCB, C18,
and GCB) for the cleanup of samples of foods of animal origin.
Three sorbent combinations (150 mg of MgSO4 + 50 mg of
PSA, 150 mg of MgSO4 + 50 mg of C18, 150 mg of MgSO4 +
20 mg of PSA + 30 mg of C18) were used to evaluate the effects
on cleaning up eggs, pork, chicken, and milk. Three other
sorbent combinations (150 mg of MgSO4 + 50 mg of PSA + 10
mg of GCB, 150 mg of MgSO4 + 50 mg of C18 + 10 mg of
GCB, 150 mg of MgSO4 + 20 mg of PSA + 30 mg of C18 + 10
mg of GCB) were used to find suitable sorbents for purifying
porcine liver and porcine kidney.
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DOI: 10.1021/acs.jafc.6b00285
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Journal of Agricultural and Food Chemistry
Table 3. Recoveries (n = 15, Percent) and RSDr and RSDR for the Target Compounds from Different Matrices at Three Spiked
Levelsa
Intraday (n = 5)
day 1
matrix
milk
eggs
chicken
pork
porcine liver
porcine kidney
porcine fat
a
day 2
day 3
spiked level (μg kg−1)
av recovery (%)
RSDr (%)
av recovery (%)
RSDr (%)
av recovery (%)
RSDr (%)
interday (n = 15)RSDR (%)
1
10
100
1
10
100
1
10
100
1
10
100
1
10
100
1
10
100
1
10
100
91.5
101.7
96.2
81.4
114.9
114.1
76.2
104.7
99.5
100.2
100.4
102.5
97.2
94.6
101.8
100.6
97.8
101
82.1
82.6
99.4
11.5
8.5
2.0
4.6
4.2
2.4
7.0
3.2
1.6
6.9
2.8
4.2
4.1
5.7
3.0
5.4
4.3
3.0
7.4
7.0
3.2
94.5
106.5
91.1
86.7
104.9
97.5
94.9
93.6
101.3
92.6
111.6
89.9
102.5
91.6
104.5
81.1
91.6
103.4
82.8
96.9
84.6
7.5
7.7
4.5
12
1.6
3.3
12.2
6.6
4.8
3.3
6.3
3.1
5.5
5.3
7.6
2.8
5.5
4.7
12.0
12.7
4.5
109.7
106.1
92.0
91.0
110.5
86.9
101.4
95.5
100.9
105.1
106.6
103.8
75.5
77.5
86.1
79.4
84.1
91.6
87.7
99.7
102.0
4.0
2.8
4.7
12.2
2.6
13.6
5.3
7.8
6.7
3.7
9.0
4.1
5.5
8.3
2.6
5.8
6.5
4.5
13.6
9.5
3.3
11.3
7.1
4.6
11.4
4.7
11.5
13.8
8.2
4.2
7.2
7.9
7.4
13.7
10.6
9.8
12.1
8.2
6.6
11.8
13.1
8.9
RSDr intraday, the relative standard deviation for repeatability (n = 5); RSDR interday, the relative standard deviation for reproducibility (n = 15).
for sulfoxaflor in seven matrices. The matrix effects in all of the
studied matrices ranged from −45% to −20%. The incomplete
removal of fat, fatty acids, phospholipids, and pigments was
responsible for the occurrence of the signal suppression or
enchancement.28 The true reason and mechanism responsible
for the matrix effects are not completely understood and should
be further researched. Therefore, in order to acquire more
accurate results, calibration was performed for sulfoxaflor using
the external matrix-matched standards to eliminate the matrix
effect.
Method Validation. Linearity and LOQ. The above
optimized method was used to analyze the residue of
sulfoxaflor. Calibration curves were made based on different
matrices at concentrations from 1 μg L−1 to 50 μg L−1 for
sulfoxaflor. The standard solution curves, regression equations,
and coefficients (R2) of all the matrix-matched curves are listed
in Table 2. The linearity (R2 ≥ 0.99) obtained for sulfoxaflor in
the different matrices was satisfactory. The LOQ in the present
study was 1 μg kg−1 for all matrices, which is far below the
Codex’s maximum residue analysis (0.1 mg/kg in eggs and
chicken, and 0.2 mg/kg in milk).
Accuracy and Precision. The accuracy and precision were
determined to assess the performance of the method by spiking
blank samples (N = 5) at three different concentrations (1, 10,
and 100 μg L−1) (Table 3). The accuracy of the method was
assessed by the recoveries, and the precision was evaluated by
repeatability (RSDr) and reproducibility (RSDR) studies. The
RSDr (intraday precision) was measured by comparing the
standard deviation of the recovery percentages of the fortified
samples analyzed on the same day. The RSDR (interday
precision) was assessed by analyzing spiked samples on three
different days. As is listed in Table 3, the mean recovery values
ranged from 75.5% to 114.9% for milk, pork, eggs, porcine liver,
porcine kidney, chicken, and porcine fat. The RSDr and RSDR
ranged from 1.6% to 13.6% and 4.6% to 13.8%, respectively.
The data were in accordance with the EU guidelines for
pesticide analysis.29
Application to Real Samples. The effectiveness and
applicability of the proposed method were further investigated
by determining the sulfoxaflor residues in 210 animal origin
food samples. The 210 animal origin food samples include
pork, porcine liver, porcine kidney, porcine fat, eggs, chicken,
and milk, which were all collected from the main producing
areas of China (including Shandong, Jiangsu, Sichuan, Zhejiang,
Hebei, Guangdong, Henan, Hunan, Hubei, Beijing, Anhui,
Xinjiang, Ningxia, and Inner Mongolia). The sulfoxaflor
residues in all the animal origin food samples were below the
LOQ, which are far below the MRLs setted by CAC (0.1 mg/
kg in chicken and eggs, 0.2 mg/kg in milk) and USA (0.01 mg/
kg in chicken and eggs, 0.15 mg/kg in milk).
A quick and simple analytical method for the determination
of sulfoxaflor in foods of animal origin was established and
validated in the present study. The samples were purified by
both d-SPE and m-PFC. However, d-SPE was selected because
of the lower cost. Under the optimized conditions, the analyte
was eluted within 5 min and outstanding recovery, linearity,
LOQ, precision, and accuracy were obtained. The satisfactory
results obtained from the real samples confirmed the reliability
and efficacy of this proposed method for routine pesticide
residue monitoring in animal origin food samples.
■
AUTHOR INFORMATION
Corresponding Author
*Phone: 86-10-62815938. Fax: 86-10-62815938. E-mail:
xujun1977927@163.com.
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J. Agric. Food Chem. 2016, 64, 2641−2646
Article
Journal of Agricultural and Food Chemistry
Funding
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This work was supported by the Nature Science Foundation of
China (NSFC, 31371968).
Notes
The authors declare no competing financial interest.
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DOI: 10.1021/acs.jafc.6b00285
J. Agric. Food Chem. 2016, 64, 2641−2646