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New Analytical Methods
Simultaneous determination of acrylamide and 5hydroxymethylfurfural in heat processed foods employing EMR-Lipid as a new dispersive solid-phase extraction sorbent followed by liquid chromatography-tandem mass spectrometry Yousheng Huang, Chang Li, Huiyu Hu, Yuting Wang, Mingyue Shen, Shao-Ping Nie, Jie Chen, Maomao Zeng, and Ming-Yong Xie J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b05703 • Publication Date (Web): 06 Mar 2019 Downloaded from http://pubs.acs.org on March 6, 2019
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Journal of Agricultural and Food Chemistry
1
Simultaneous
determination
2
5-hydroxymethylfurfural
3
EMR-Lipid as a new dispersive solid-phase extraction sorbent
4
followed by liquid chromatography-tandem mass spectrometry
in
of
heat
acrylamide
processed
foods
and
employing
5 6
Yousheng Huang1, 2, Chang Li1, Huiyu Hu1, Yuting Wang1, Mingyue Shen1*,
7
Shaoping Nie1, Jie Chen3, Maomao Zeng3, Mingyong Xie1*
8 9
1State
Key Laboratory of Food Science and Technology, China-Canada Joint Lab of
10
Food Science and Technology (Nanchang), Nanchang University, 235 Nanjing East
11
Road, Nanchang 330047, China
12
2Jiangxi
13
3State
14
14122, China
Institute of Analysis and Testing, Nanchang 330029, China
Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 2
15 16
* Corresponding author:
17
Mingyue Shen, PhD
18
Tel.: 0791-88304447-8328
19
E-mail address:
[email protected] 20
Professor Mingyong Xie, PhD
21
Tel: +86 791 88305860
22
E-mail address:
[email protected] 1
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ABSTRACT: The goal of this study was to develop a method for simultaneous
24
determination of acrylamide (AA) and 5-hydroxymethylfurfural (5-HMF) in heat
25
processed foods by LC-MS/MS analysis. Several clean-up methods for QuEChERS
26
protocol were investigated and compared: (a) Dispersive solid phase extraction
27
(d-SPE) with Enhanced Matrix Removal-Lipid (EMR-Lipid); (b) d-SPE with PSA; (c)
28
without clean-up step; (d) clean-up with n-hexane. It's the first time that EMR-Lipid
29
sorbent has been used as d-SPE material to detect AA and 5-HMF in heat processed
30
foods, and among the four clean-up methods, EMR-Lipid method provided the best
31
clean-up of co-extracted matrix interferences and the highest extraction efficiency.
32
Validation experiments were carried out for the method of using EMR-Lipid as d-SPE
33
sorbent. Excellent linearity (R2 > 0.999) was achieved and the limits of detection
34
(LODs) of AA and 5-HMF were 2.5 μg/kg and 12.5 μg/kg, respectively. The
35
recoveries of AA and 5-HMF levels obtained were in the range of 87.3-103.3% and
36
83.2-104.3%, with precision (RSDs) of 1.2-6.8% and 1.4-7.4% (n=3), respectively.
37
The method is accurate and reliable and it was successfully applied to analyze the AA
38
and 5-HMF in 8 categories of Chinese heat processed foods.
39 40
KEYWORDS: EMR-Lipid; Acrylamide; 5-hydroxymethylfurfural; QuEChERS;
41
LC-MS/MS; Heat processed foods
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INTRODUCTION
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A series of chemical reactions occur during heat processing of food, including
44
Maillard reaction, caramelization and lipid oxidation, which may result in both
45
desired and undesired effects on food quality
46
5-hydroxymethylfurfural (5-HMF) are two important contaminants produced during
47
heat processing, and they are receiving increasing attention due to their potential
48
toxicity and wide occurrence
49
genotoxic compound and has also been classified as a probable human carcinogen
50
(Group 2A) by International Agency Research on Cancer (IARC) 4. It is formed in
51
food during heating processes such as baking, frying, grilling, and roasting, with the
52
major reaction between amino group of asparagine and carbonyl group of reducing
53
sugars during heating at temperature higher than 120 °C
54
serious risk to human health, but there are concerns in the potential genotoxic and
55
carcinogenic
56
5-chloromethylfurfural 2, 9. It is formed by the caramelization of sugars under thermal
57
treatment and acidic catalysis, and reducing sugars can also generate 5-HMF through
58
the formation of 3-deoxyglucosone
59
both AA and 5-HMF, it is necessary to develop a simultaneous determination method
60
to improve the efficiency of risk assessment and control the quality of heat processed
61
foods.
62 63
properties
2, 3.
of
1,
2.
Acrylamide (AA) and
AA has been demonstrated to be a neurotoxic and
its
metabolites
10, 11.
5-8.
5-HMF does not pose a
5-sulfoxymethylfurfural
and
Since most of heat processed foods contain
In recent years, conventional methods for quantitation of AA and 5-HMF include gas chromatography (GC)
12, 13,
high-performance liquid chromatography (HPLC) 3
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14-16,
65
chromatography-tandem mass spectrometry (LC-MS/MS)
66
methods, LC-MS/MS was used as a powerful technique for the determination of AA
67
and 5-HMF alone or simultaneously in various food samples with high detection
68
sensitivity and without the derivatization step. However, to the authors’ best
69
knowledge, only one paper with regard to the simultaneous determination of AA and
70
5-HMF in food matrix (seafood) has been published
71
clean-up step was excluded for reducing recovery of 5-HMF by approximately 70%,
72
which could result in more matrix interference, decreased column lifetime and
73
increased instrument maintenance. Considering the necessities of purification of
74
extracts and lots of other heat processed foods containing AA and 5-HMF
75
simultaneously,
76
determination methods and broaden their application in more categories of food
77
matrices.
gas
chromatography-mass
further
studies
spectrometry
are
necessary
(GC-MS)
25.
to
17-19
20-24.
and
liquid
Among these
Moreover, in that study, the
investigate
simultaneous
78
The QuEChERS (acronym of quick, easy, cheap, effective, rugged and safe)
79
method, including extraction and dispersive solid phase extraction (d-SPE) clean-up
80
step, has been developed and used for the extraction of AA or 5-HMF in the last few
81
years
82
difference of AA and 5-HMF in polarity and solubility, the ability of d-SPE sorbent to
83
clean up interfering compounds from food matrices without sacrifice of target
84
compounds’ recoveries is very important for the simultaneous determination of AA
85
and 5-HMF. Primary secondary amine (PSA) is a well-known sorbent employed in
17, 20, 25, 26.
For the complexity of food matrices such as high lipids and the
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the QuEChERS method when removal of lipids from food matrices is necessary 27, 28,
87
but the fact that addition of PSA could reduce the recovery of AA and 5-HMF was
88
also reported by researchers 20, 25. Moreover, several new d-SPE sorbents such as sol–
89
gel hybrid methyltrimethoxysilane–tetraethoxysilane and magnetic graphene sol–gel
90
hybrid were used in the analysis of AA in heat processed food in recent years
91
However, the effectiveness of d-SPE sorbents to clean up co-extracts for the
92
simultaneous determination of AA and 5-HMF in food matrices has never been
93
investigated before.
17, 29.
94
Due to the high-fat content of most heat processed foods, it is important to remove
95
lipids from the extract before LC-MS/MS analysis. Recently, a vendor introduced a
96
unique product known as “Enhanced Matrix Removal-Lipid” (EMR-Lipid). The
97
manufacturer claims that lipids are removed selectively by EMR-Lipid from
98
QuEChERS extracts of fatty foods such as avocado and animal tissues, without loss of
99
target substance , such as pesticides, veterinary drugs, or PAHs
30-32.
Preliminary
100
results with the novel sorbent material EMR-Lipid are promising for removing
101
unwanted matrix interferences from the extract without loss of the target compounds
102
33-36.
103
property interests, but the extraction mechanism is said to involve both size exclusion
104
and hydrophobic interactions. Lipids with long-chain hydrocarbons are trapped via
105
association with the EMR-Lipid structure. AA and 5-HMF are hydrophilic molecules,
106
which may be separated from interfering compounds such as lipids in heat processed
107
foods by EMR-Lipid, similar to pesticides determined in fatty foods. It could be a
The composition of EMR-Lipid has not been disclosed yet due to intellectual
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good try to select EMR-Lipid as d-SPE sorbent of QuEChERS method. However, to
109
the authors' best knowledge, no previous study has been reported for using
110
EMR-Lipid sorbent as d-SPE material to detect AA and 5-HMF.
111
Taking all these points into account and considering the importance of
112
simultaneous determination of AA and 5-HMF, the objective of the present study is to
113
develop a convenient, sensitive and accurate quantitative method for the simultaneous
114
determination of AA and 5-HMF in heat processed foods. The performance of d-SPE
115
with EMR-Lipid was compared with those of three other clean-up methods (d-SPE
116
with PSA, without clean-up step and clean-up with n-hexane) in QuEChERS protocol.
117
Moreover, the finally selected method was validated and used to assess the levels of
118
AA and 5-HMF in eight different categories of heat processed foods in China.
119
MATERIALS AND METHODS
120
Samples
121
Eight categories of commercially available foods including fried potato chips,
122
biscuits, bread, deep-fried stick (you-tiao), fried peanuts, fried fragrant taro, fried
123
chips made with rice and peanuts (yueliangba) and coffee beverage were purchased
124
from local supermarkets in Nanchang, Jiangxi Province, China. Number of samples
125
(Sample ID) for each category is shown in Supplementary Table 1. All the samples
126
were ground into powder by a homogenizer and stored at -20ºC before analysis.
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Journal of Agricultural and Food Chemistry
Chemicals and Materials
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AA, 5-HMF, 13C3-AA and 13C6-HMF were purchased from Sigma-Aldrich (USA).
129
HPLC-grade acetonitrile, methanol, n-hexane and formic acid were obtained from
130
Merck Company (Darmstadt, Germany). Distilled water used for extraction and as
131
HPLC mobile phase was purchased from Watsons Water Co., Ltd (Guangzhou,
132
China). Sodium chloride (NaCl) and anhydrous magnesium sulphate (MgSO4) were
133
obtained from Sinopharm chemical reagent co.ltd (Shanghai, China). Bond Elut
134
EMR-Lipid was purchased from Agilent Technologies (Santa Clara, USA) consisting
135
of 1 g EMR-Lipid material in a 15 mL polypropylene tube and 2 g EMR-Polish salts
136
(anhydrous MgSO4:NaCl, 4:1, w/w) in a second 15 mL centrifuge tube. PSA and
137
anhydrous MgSO4 for QuEChERS were purchased from Agilent Technologies
138
(Shanghai, China).
139
Standards Preparation
140
Stock solutions of AA, 5-HMF,
13C
3-AA
and
13C
6-HMF
were prepared by
141
weighing 10 mg of each analyte into a 10 mL volumetric flask and adding water to
142
obtain the final volume of 10 mL. The mixed working standard solutions were
143
obtained by dilution of stock solutions with water.
144
LC-MS/MS Analysis
145
An Agilent 1200 Series high performance liquid chromatograph (HPLC) system
146
(Agilent Technologies Inc, USA) equipped with a binary pump, a solvent degasser, an
147
autosampler and a thermostatically controlled column apartment was used for 7
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chromatographic analysis. Separation of the analytes was achieved on a Synergi
149
Hydro-RP column (150 × 2 mm i.d., 4 µm, Phenomenex, USA) with a column
150
temperature of 30 °C. The binary solvent system consisted of acetonitrile (A) and
151
0.1% (V/V) aqueous formic acid solution (B). The gradient profile of the binary pump
152
was started at 95% B (0 min), decreased to 20% B from 0 to 1.0 min, then maintained
153
at 20% B from 1.0 min to 3 min, finally, back to 95% B at 3.1 min, and equilibrating
154
for 5 min. The flow rate was 0.3 mL/min, and the injection volume was 5.0 μL.
155
The MS/MS detection was performed on an Agilent 6410 Triple Quadrupole mass
156
spectrometer (QQQ) (Agilent Technologies, USA), and the electrospray ionization
157
(ESI) source was operated in positive mode and data was acquired using multiple
158
reaction monitoring (MRM) mode. Each standard solution (1.0 μg/mL) was directly
159
injected into the QQQ to obtain the optimal parameters of precursor ion, product ion,
160
fragmentor voltage and collision energy (CE) (Table 1). The dwell time for all MRM
161
transitions of the analytes was set to 40 ms. The other working parameters of the mass
162
spectrometer were as follows: nebulizer gas: nitrogen; drying gas temperature: 350℃;
163
drying gas flow rate: 10 L/min; nebulizer pressure: 40 psi; capillary voltage: 4000 V.
164
Both MS1 and MS2 quadrupoles were maintained at unit resolution. MassHunter
165
Workstation (version B.01.03) (Agilent, Lake Forest, CA, USA) was used to control
166
the LC-MS/MS system and process the data.
167
Sample Preparation
168
1.0 g of ground sample was weighed into a 50 mL centrifuge tube, and spiked with
169
internal standards of 13C3-AA (250 μg/kg) and 13C6-HMF (1000 μg/kg), then 3 mL of 8
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distilled water was added. After standing for 20 min, 10 mL of acetonitrile was added
171
to sample and the mixture was then shaken by an IKA Vortex Genius 3 shaker (IKA,
172
Staufer, Germany) for 2 min. Then four versions of clean-up methods were compared:
173
(a) d-SPE with EMR-Lipid. The tubes were centrifuged at 4400 g for 5 min by an
174
Anke TDL-5-A low-speed centrifuge (Anke, Shanghai, China). Then 5.0 mL of the
175
supernatant was collected and added into a 15 mL d-SPE tube containing EMR-Lipid
176
sorbent and 3 mL water. Subsequently, the mixture was shaken vigorously for 1 min
177
and then centrifuged at 4400 g for 5 min. After that, the above extract (5 mL) was
178
transferred to a 15 mL EMR-Polish tube containing 2 g salts (anhydrous MgSO4:
179
NaCl, 4:1, w/w). The mixture was shaken vigorously for 1 min and then centrifuged
180
at 4400 g for 5 min. 2.0 mL of supernatant was transferred into a 10 mL glass test
181
tube.
182
(b) d-SPE with PSA. The prepared mix of QuEChERS pouch, composed of 4.0 g of
183
MgSO4 and 1.0 g of NaCl, was added to the 50 mL tube containing acetonitrile/water
184
extract and the mixture was shaken vigorously for 2 min. The tube was then
185
centrifuged at 4400 g for 5 min. For the clean-up step, 5.0 mL supernatant was
186
transferred to a centrifuge tube containing 250 mg of PSA and 750 mg of anhydrous
187
MgSO4. The tube was then shaken vigorously for 1 min and centrifuged at 4400 g for
188
5 min. 2.0 mL of supernatant was transferred into 10 mL a glass test tube.
189
(c) Without clean-up step. The extraction method was the same as version b and the
190
clean-up step was skipped. 2.0 mL of supernatant was transferred into a 10 mL glass
191
test tube. 9
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(d) Clean-up with n-hexane. The extraction method was the same as version b with
193
a different clean-up step described as follows. Instead of clean-up with PSA, 5 mL
194
n-hexane was added to the tube of 5.0 mL supernatant, then the mixture was vortexed
195
for 1 min and centrifuged at 4400 g for 5 min, afterward, the n-hexane layer was
196
discarded. The lower layer of acetonitrile (2 mL) was transferred into a 10 mL glass
197
test tube.
198
For each version, the solution of extract in the 10 mL glass test tube was dried by a
199
gentle nitrogen stream in a water bath at 40 ℃, then residue was re-dissolved in 1.0
200
mL water and filtered through a 0.22 μm PES membrane (Anpel, Shanghai, China),
201
for analysis by LC–MS/MS. The extraction and clean-up method for each sample was
202
carried out in triplicate. The detailed workflow for the best method (version a) is
203
shown in Fig.1.
204
Analyte loss during extraction (ALDE)
205
The extraction efficiency was evaluated by ALDE. As analytes and their internal
206
standards had the same behavior during sample preparation, 13C3-AA (250 μg/kg) and
207
13C
208
Then peak areas of internal standards in extracted sample solution were compared to
209
those of internal standard solution at the same concentrations (n=3). The ALDE was
210
calculated as the following formula:
211
ALDE (%) = 1 -
6-HMF
(1000 μg/kg) were added to fried potato chips before sample preparation.
(
peak areas of internal standards in extracted sample solution peak area of internal standard solution
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× 100.
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Validation of the method
213
Validation experiments were carried out for the method of using EMR-Lipid as
214
d-SPE sorbents. Calibration curves were built by standard solutions at six different
215
concentration levels (5, 10, 20, 50, 100, 200 ng/mL for AA and 20, 40, 80, 200, 400,
216
800 ng/mL for 5-HMF), containing the internal standards at 50 ng/mL and 200
217
ng/mL, respectively. Each standard solution was analyzed three times and the average
218
peak area ratio between analyte and internal standard was plotted against the
219
corresponding concentration ratio of analyte to internal standard. Recovery of
220
analytes in eight different food categories was obtained by analyzing samples spiked
221
with standard containing AA (25, 100, 200 and 500 μg/kg) and 5-HMF (400, 800 and
222
2000 μg/kg) and their internal standards (250 μg/kg for AA and 1000 μg/kg for
223
5-HMF), and each recovery level was determined in triplicate. The recovery for AA
224
and 5-HMF was calculated as follows:
225
Recovery (%) =the amount of analytes added × 100.
226
The amount of analytes tested was calibrated by the calibration curves mentioned
227
above.
228
Statistical Analysis
the amount of analytes tested
229
Analysis of variance (ANOVA) was performed using SPSS software (version
230
19.0). The results were subjected to Tukey's test and P-value < 0.05 was considered
231
statistically significant.
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RESULTS AND DISCUSSION
233
LC-MS/MS Optimization
234
The instrument parameters were optimized based on previous studies on the 20, 25.
235
analysis of AA and 5-HMF
Positive electrospray mode was proved to be the
236
most sensitive mode for the analytes and internal standards. All parameters were
237
optimized to obtain the strongest responses for the ion [M+H]+ of analytes. For LC
238
separation, a Synergi Hydro-RP column (150 × 2 mm; 4 µm) was selected. Its
239
property of polar endcapping enabled to provide acceptable retention and peak shape
240
for both AA and 5-HMF. In the final method, 95% aqueous solution containing 0.1%
241
formic acid and 5% acetonitrile was used as initial mobile phase for elution. The
242
chromatograms of analytes and internal standards are shown in Fig.2. Considering the
243
co-extract in the sample, a stronger mobile phase with high percentage of acetonitrile
244
was necessary to avoid the accumulation and eventually peak co-elution in the
245
following analysis.
246
Evaluation of different clean-up methods
247
The objective was to develop a QuEChERS pre-treatment method with suitable
248
clean-up method to extract AA and 5-HMF from various heat processed foods that
249
would be compatible with subsequent LC-MS/MS analysis. As starting points in the
250
method development, an addition of water was necessary to facilitate AA and 5-HMF
251
extraction from food samples, followed by the addition of acetonitrile as an
252
appropriate extraction solvent. In this study, several clean-up methods were 12
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investigated, including two d-SPE methods using EMR-Lipid product and PSA as
254
d-SPE sorbent materials respectively and a method of liquid-liquid extraction by
255
adding n-hexane. Samples without clean-up step were also compared. EMR-Lipid is a
256
novel clean-up sorbent for dispersive solid phase extraction employed for highly
257
selective matrix removal, especially for high-fat samples, incorporated in an initial
258
QuEChERS-based extraction step
259
efficiency of different clean-up methods were evaluated by using fried potato chips as
260
representative matrix. The results were discussed in the following text.
30, 31, 37.
The extract cleanliness and extraction
261
Extract cleanliness. Firstly, as an attempt to estimate the extract cleanliness of
262
different clean-up methods, full-scan total ion chromatograms (TICs) of potato chip
263
extracts obtained from different clean-up methods were overlapped for comparison
264
purposes. As shown in Fig.3, TICs obtained from the same potato chip matrix showed
265
that d-SPE with EMR-Lipid was the most effective clean-up method with minimum
266
amounts of matrix interferences existing in the final extract compared to other three
267
versions of clean-up method. Several studies also found that EMR-Lipid method was
268
more effective to clean up co-extracts during the determination of pesticide residues
269
and environmental contaminants in food matrix 34, 36. Compared with TICs of extracts
270
obtained by methods of clean-up with n-hexane and without clean-up step, the TIC of
271
the extract pretreated with PSA was close to that of the extract pretreated with
272
EMR-Lipid, which showed that the cleaning ability of PSA was comparable to that of
273
EMR-Lipid. PSA is a commonly used sorbent in QuEChERS method to remove fatty
274
acids, sugars and some pigments. Dunovska et al.
38
reported that PSA significantly
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reduced the matrix co-extracts (mainly free fatty acids) during the determination of
276
AA in food. However, we found that the utilization of PSA resulted in the loss of
277
analytes in the extraction step, especially for 5-HMF, as described below.
278
Moreover, as shown in Fig.3, it was obvious that co-extractive impurities of peak 1
279
and peak 2 are co-eluted with AA (1.9 min) and 5-HMF (3.9 min), which may cause
280
matrix effect and affect accuracy of determination. However, their peak areas in
281
EMR-Lipid method were minimum compared to those in other methods. For the
282
LC-MS/MS analysis of AA (Fig.4A), an interference peak having the retention time
283
of about 1.4 min was found, which could be the interference of amino acid valine
284
generating m/z 72 product ion in samples typically analyzed for AA
285
interference peak area of extracts obtained by clean-up method of n-hexane and
286
without clean-up step were higher than that of extracts obtained by d-SPE methods
287
(PSA and EMR-Lipid), showing the impurity was not removed sufficiently by method
288
of n-hexane or without the clean-up step.
39.
The
289
Extraction efficiency. In order to evaluate extraction efficiency, the peak area of
290
analytes in the same fried potato chip pretreated with four clean-up methods was
291
compared in Figure 4, and ALDE was also calculated. For AA, as shown in Fig.4A-B,
292
the peak area of AA in sample pretreated with EMR-Lipid is higher than those in
293
samples pretreated with other clean-up methods, and the ALDE of EMR-Lipid
294
method was less than those of other clean-up methods, demonstrating the use of
295
d-SPE with EMR-Lipid has the best extraction efficiency. The extract cleanliness of
296
d-SPE with PSA was close to that of the EMR-Lipid method as described above, 14
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however, PSA resulted in a 20% rise of analyte loss during extraction of AA
298
compared to EMR-Lipid, which was in agreement with previous study 20. Moreover,
299
although d-SPE sorbents have not been used in the method of n-hexane and without
300
clean-up step, the ALDE of these two methods were still higher than that of the
301
EMR-Lipid method.
302
For 5-HMF, the results were similar to those of AA. As shown in Fig.4C-D, the
303
peak area of 5-HMF in sample pretreated with EMR-Lipid is also higher than those in
304
samples pretreated with other clean-up methods, and the ALDE of EMR-Lipid
305
method was less than those of other clean-up methods. It was notable that the highest
306
ALDE (94%) was obtained when d-SPE with PSA was used, so most of 5-HMF was
307
lost when clean-up with PSA. Qin et al.
308
the 5-HMF loss by approximately 70% during extraction. For this reason, the clean-up
309
step of QuEChERS extraction was excluded in his study. Therefore, PSA is not a
310
suitable sorbent to clean up the matrix interferences for 5-HMF analysis.
25
also found that the addition of PSA made
311
Taking these results into account, it was found that clean-up method using
312
EMR-Lipid as d-SPE sorbent enabled to guarantee good extraction efficiency while it
313
could also ensure efficient and robust clean-up to remove unwanted matrix
314
interferences, especially lipids, from the extract, while increasing the overall
315
performance of the method. Therefore, EMR-Lipid was chosen as clean-up sorbent
316
for AA and 5-HMF determination in the heat processed foods. Validation experiments
317
were carried out for the selected method.
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Method Validation
319
Linearity and sensitivity. Considering the different levels of AA and 5-HMF in
320
most of the samples, different linear range of these two analytes was obtained.
321
Excellent linearity was achieved with a correlation coefficient (R2) >0.999 for both
322
AA and 5-HMF. The limits of detection (LOD) and quantification (LOQ) based on a
323
signal-to-noise ratio (S/N) of 3:1 and 10:1 were determined. In our study, the LODs of
324
AA and 5-HMF were 2.5 and 12.5 μg/kg, while the LOQs of AA and 5-HMF were
325
8.3 and 41.5 μg/kg, respectively.
326
Recovery and precision. As shown in Table 2, observed recoveries of AA and
327
5-HMF were in the range of 87.3-103.3% and 83.2-104.3% in 8 categories of heat
328
processed food samples, with RSDs ranging from 1.2% to 6.8% and 1.4% to 7.4%,
329
respectively. In comparison with the previous studies reported
330
precision of this analytical method were satisfactory.
20, 25,
the recovery and
331
Comparison with previous studies. As shown in Table 3, the LOD obtained in the
332
current study using EMR-Lipid as d-SPE sorbent is compared with those published in
333
previous studies using other preparation methods such as SPE and QuEChERs with or
334
without d-SPE. For AA, the sensitivity of this developed method is higher than the
335
results obtained using d-SPE with hybrid sol–gel MTMOS–TEOS and SPE with
336
mixture of C18, SCX and SAX sorbents 17, 21, and is comparable to that of QuEChERs
337
without d-SPE clean-up step
338
d-SPE sorbent gives the lowest LOD, as finally only 50 μL acetonitrile was added to
339
re-dissolve the residue for LC-MS/MS analysis, which highly concentrated analytes in
20.
The method using Fe3O4@G-TEOS-MTMOS as
16
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340
sample solutions
For 5-HMF, the sensitivity of this developed method is
341
comparable to those of the SPE method with HLB and ENV+
342
sensitivity of this developed method is lower than the results of QuEChERs without
343
d-SPE clean-up step used for simultaneous determination of AA and 5-HMF in
344
seafood matrix 25. As the clean-up step was excluded in that study, it could result in
345
more matrix interference, decreased column lifetime and increased instrument
346
maintenance. In our study, the proposed QuEChERS with EMR-Lipid as d-SPE
347
sorbent offered a simple approach to efficiently clean up co-extracts for the
348
simultaneous determination of AA and 5-HMF in a variety of heat-processed foods.
349
Analysis of real samples
19, 24.
Moreover, the
350
The developed method was applied to determine levels of AA and 5-HMF in a
351
variety of commercially available heat processed foods in the Chinese market. Eight
352
categories of frequently-consumed foods including fried potato chips, biscuits, bread,
353
you-tiao, fried peanuts, fried fragrant taro, yueliangba and coffee beverage were
354
analyzed. The mean levels, minimum values and maximum values of AA and 5-HMF
355
in 8 categories of foods are shown in Table 4. AA was detected in the samples at
356
concentrations ranging from < LOD to 633.3 μg/kg and the levels fluctuated wildly
357
even if in the same category except for bread and coffee beverage. The mean AA
358
levels of 8 categories of food samples were in the order of potato chip > fragrant taro
359
chip > biscuit > yueliangba > you-tiao > bread > peanut > coffee beverage. Among all
360
food samples analyzed, the AA levels of 4 samples (two potato chip samples, one
361
biscuit sample and one fragrant taro chip sample) exceeded 300 μg/kg, while AA 17
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362
levels were below the LOD in 9 samples (one biscuit sample, three peanut sample and
363
all of coffee beverage samples). 18 samples (36% of total) contained AA at
364
concentrations of 100-300 μg/kg, while 19 samples (38% of total) contained AA at
365
concentrations lower than 100 μg/kg. These AA levels of potato chip, biscuit, peanut,
366
bread and you-tiao were in agreement with the previous studies reported
367
Taking potato chip as an example, we found the AA concentrations ranged from 44.8
368
μg/kg to 633.3 μg/kg with a mean value of 251.0 μg/kg, slightly lower than those
369
reported by Oroian et al. 43 in Romanian, ranging from 18 μg/kg to 1782 μg/kg, with a
370
mean value of 600 μg/kg. Bertuzzi et al.
371
ranging from 92 μg/kg to 1722 μg/kg, with a mean value of 803 μg/kg. It was notable
372
that the AA levels were below the LOD in 5 coffee beverage samples. Andrzejewski
373
et al.
374
those in ground coffee and instant coffee, ranging from 6 to 16 ng/mL (close to the
375
LOD). The AA loss in brewed coffee may be due to the dilution and brewing of
376
coffee. Moreover, to the best of our knowledge, no data about levels of AA in fragrant
377
taro chip and yueliangba was reported before, and our data could provide useful
378
information for the consumption and risk assessment of these foods.
44
42
20, 29, 40-43.
reported AA levels of potato chip in Italy
reported the levels in brewed coffee (coffee beverage) were much less than
379
The 5-HMF was detected in all the samples at concentrations ranging from 0.3 to
380
56.3 mg/kg and the levels also fluctuated wildly even if in the same category (Table
381
4). It was necessary that some samples containing high concentrations of 5-HMF
382
deserved an additional dilution of the extract before LC-MS/MS analysis in order to
383
obtain a response able to be quantified within the linear calibration range. The mean 18
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5-HMF levels of 8 categories of food samples were in the order of yueliangba >
385
coffee beverage > bread > biscuit > potato chip > fragrant taro chip > peanut >
386
you-tiao. Among all food samples analyzed, the 5-HMF levels of 8 samples (two
387
biscuit samples, one bread sample, two yueliangba samples and three coffee beverage
388
samples) exceeded 10 mg/kg. 32 samples (64% of total) contained 5-HMF at
389
concentrations of 1.0-10 mg/kg, while 10 food samples (20% of total) contained
390
5-HMF at concentrations lower than 1.0 mg/kg. These 5-HMF levels of potato chip,
391
biscuit, bread and coffee were in the same order of magnitude as those reported by
392
previous studies
393
concentrations ranged from 7.3 mg/kg to 23.5 mg/kg with a mean value of 5.2 mg/kg,
394
similar to those found by Ameur et al. 47, which ranged from 0.5 mg/kg to 74.6 mg/kg
395
with a mean value of 24.1 mg/kg, and slightly lower than those reported by
396
Delgado-Andrade et al. 48, which ranged from 3.1 mg/kg to 182.5 mg/kg with a mean
397
value of 14.4 mg/kg. Moreover, as mentioned above, to the best of our knowledge, no
398
data about levels of 5-HMF in you-tiao, peanut, taro chip and yueliangba was reported
399
before, and our data could provide useful information for the consumption and risk
400
assessment of these foods.
2, 19, 45-48.
For instance, for biscuits, we found the 5-HMF
401
402
ABBREVIATIONS USED
403
AA, Acrylamide; 5-HMF, 5-hydroxymethylfurfural; GC, gas chromatography; HPLC,
404
high-performance liquid chromatography; GC-MS, gas chromatography-mass 19
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405
spectrometry; LC-MS/MS, liquid chromatography–tandem mass spectrometry;
406
QuEChERS, acronym of quick, easy, cheap, effective, rugged and safe; d-SPE,
407
dispersive solid phase extraction; PSA, Primary secondary amine; EMR-Lipid,
408
Enhanced Matrix Removal-Lipid; ALDE, Analyte loss during extraction.
409
ACKNOWLEDGEMENTS
410
The authors acknowledge the financial supports from the National Key Research
411
and Development Program of China (2017YFC1600405).
412
Notes
413
414 415 416 417 418
The authors declare no conflicts of interest.
Supporting Information The Supporting Information is available free of charge on the ACS Publications website at http://pubs.acs.org. The sample ID and levels of AA and 5-HMF for each heat processed food sample (Supplementary Table 1)
419
20
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Figure captions
581
Figure 1. Schematic diagram of the best extraction method (version a)
582
Figure 2. LC-MS/MS chromatograms of analytes and internal standards
583
Figure 3. Overlapped total ion chromatograms of potato chip extracts obtained with
584
different clean-up methods
585
Figure 4. Overlapped LC-MS/MS chromatogram and ALDE of different clean-up
586
methods (A. Overlapped LC-MS/MS chromatogram of AA in the same fried potato
587
chip; B. ALDE of AA calculated via the peak area of 13C3-AA; C. Overlapped
588
LC-MS/MS chromatogram of 5-HMF in the same fried potato chip; D. ALDE of
589
5-HMF calculated via the peak area of 13C6-HMF)
29
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Figure 1
591 592
30
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593
Journal of Agricultural and Food Chemistry
Figure 2
594 595
31
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Figure 3
597 598
32
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Page 33 of 39
599
Journal of Agricultural and Food Chemistry
Figure 4
600
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Tables
603
Table 1. Mass spectrometric settings for MRM of the analytes and internal standards Compounds
Precursor ion
Product ion
Fragmentor(eV)
CE(eV)
75
58
40
10
72
55 (Q)
40
10
72
44 (C)
40
20
133
86
75
15
127
81 (C)
75
15
127
53 (Q)
75
20
13C
3-AA
AA 13C
6-HMF
5-HMF
604 605
Q: quantification ion; C: confirmation ion.
606
Table 2. Recoveries and RSDs of AA and 5-HMF in 8 categories of heat processed
607
food samples (n=3) Sample
Potato chips
Biscuits
Bread
You-tiao
Peanut
Taro chips
AA
5-HMF
Spiked(μg/kg)
Recovery(%)
RSD (%)
Spiked(μg/kg)
Recovery(%)
RSD (%)
25
90.9
4.7
--
--
--
100
95.7
2.0
400
98.9
5.8
200
95.8
4.0
800
88.6
6.2
500
98.3
4.7
2000
84.3
3.8
25
94.5
6.7
--
--
--
100
96.3
4.9
400
104.3
2.2
200
92.3
1.9
800
98.7
4.0
500
98.1
3.0
2000
91.3
6.8
25
88.7
5.2
--
--
--
100
94.3
4.6
400
90.4
5.4
200
89.7
3.3
800
83.4
7.4
500
99.8
3.1
2000
86.3
6.3
25
103.3
6.8
--
--
--
100
87.8
4.6
400
96.3
5.7
200
88.7
2.0
800
102.3
4.5
500
92.8
1.2
2000
91.5
3.6
25
87.3
2.9
--
--
--
100
92.7
4.0
400
98.9
5.8
200
94.7
1.8
800
100.9
5.1
500
96.4
2.5
2000
91.0
3.5
25
101.9
3.3
--
--
--
34
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Yueliangba
100
88.7
4.7
400
88.7
5.5
200
89.0
5.5
800
101.3
3.2
500
90.6
3.9
2000
85.7
5.5
25
94.6
3.3
--
--
--
100
96.3
5.3
400
86.9
3.9
200
93.5
1.5
800
96.7
1.4
500
88.6
4.1
2000
83.2
6.6
25
100.6
3.8
--
--
--
Coffee
100
97.7
2.4
400
87.8
2.9
beverage
200
89.5
2.5
800
83.8
6.9
500
88.0
2.7
2000
84.9
3.4
608
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Table 3. LOD of AA and 5-HMF in the current study compared to other studies Sample
Sample preparation method
LOD of AM (μg/kg)
LOD of 5-HMF (μg/kg)
Detector
Reference
Potato chip, biscuit, bread,fragrant taro chip, yueliangba, you-tiao, peanut and coffee beverage
d-SPE with EMR-Lipid
2.5
12.5
LC-MS/MS
Current study
Fried potato, fried eggplant, minnan and gorrasa
d-SPE with hybrid sol–gel MTMOS–TEOS
9.1-12.8
/
GC-MS
Omar et al.17
Boiled potato, fried potato with bright-fleshed, sweet potato, cheese snack, banana chips, fried eggplant, bread and potato chips
d-SPE with Fe3O4@G-TEOS-MTMOS
0.061-2.89
/
GC-MS
Rashidi Nodeh et al.29
SPE with mixture of C18, SCX and SAX sorbents
5
/
LC-MS/MS
Bortolomeazzi et al. 21
Dried fruits and edible seeds
QuEChERs without d-SPE clean-up step
2
/
LC-MS/MS
De Paola et al.20
Baby Foods
SPE with HLB
/
5
LC-MS/MS
Gökmen et al.24
Biscuits, breakfast cereals, orange juice, honey and jam
SPE with ENV+
/
12
GC-MS
Teixido et al.19
Thermally processed seafood
QuEChERs without d-SPE clean-up step
0.22
0.27
LC-MS/MS
Qin et al.25
Roasted coffee
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Journal of Agricultural and Food Chemistry
Table 4. Levels of AA and 5-HMF in 8 categories of heat processed food samples Food groups
n
Potato chip
9
AA (μg/kg)
5-HMF (mg/kg)
Meana
Minimum
Maximum
Mean
Minimum
Maximum
251.0
44.8
633.3
3.9
0.8
9.3
345.5
5.2
0.7
23.5
Biscuit
13
119.8
N.D.b
Bread
6
12.6
10.5
14.4
6.2
1.1
12.2
You-tiao
5
112.2
50.3
161.9
1.2
0.6
2.3
Peanut
4
5.3
N.D.
21.1
1.5
0.3
3.3
Fragrant taro
4
206.4
48.5
425.0
2.8
1.3
6.6
Yueliangba
4
114.6
19.4
200.0
21.3
1.7
56.3
Coffee beverage
5
N.D.
N.D.
N.D.
10.2
1.4
23.2
a For
statistical analysis, N.D. samples were assigned as zero.
b N.D.:
Not detected (lower than the limit of detection).
614
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Graphic for table of contents
616
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