1. Introduction
White pepper (Piper nigrum L.) used as a spice worldwide
is obtained from the fully ripe berries of pepper plant.
Piperine [1], the main constituent of
white pepper, exhibited a
variety of pharmacological activities, e.g. antifungal [2], antidiarrhoeal
[3], anti-inflammatory [4], as well as 5-lipoxygenase and
cyclooxygenase-1 inhibitory activities [5]. Heat-reflux extraction
(HRE) is the most widely used traditional technique for the extraction
of piperine from this spice plant. However, HRE is laborious,
time consuming, and requires large amounts of volatile/hazardous
organic solvents. The benefit of using ultrasonic-assisted extraction
(UAE) in the extraction of organic compounds directly from
solid matrixes has already been demonstrated in recent years
[6–10]. Compared with traditional and other modern extraction
techniques, UAE is proposed as an alternative procedure for sample
pretreatment.
Recently, ionic liquids (ILs) have been used extensively in
areas of analytical chemistry, including electrochemistry, separation
science, mass spectrometry, and spectroscopy [11–18].
IL-assisted sample pretreatment techniques, such as liquid–liquid
extraction, liquid-phase microextraction, solid-phase microextraction
and aqueous two-phase systems extraction have also been
published [19–23]. However, there is no report about IL-based
∗ Corresponding author. Tel.: +86 571 88871031; fax: +86 571 88320961.
E-mail address:
xiaojicao@zjut.edu.cn (X. Cao).
ultrasonic-assisted extraction. The aim of the present paper is the
development of a rapid and effective IL-based ultrasonic-assisted
extraction approach for the extraction of bioactive piperine from
the spice plant “white pepper”.
2. Experimental
2.1. Chemicals
All chemicals involved in this study were at least of analytical
reagent grade. The ultrapure water was prepared with a
Milli-Q water purification system (18M , Millipore, Bedford, MA,
USA). Methanol used for UPLC analysis was of chromatographic
grade and purchased from Merck, Darmstadt, Germany. Standard
piperine used for UPLC–UV determinations was purchased from
Zhuokang Biological Technology Company (Shanghai, China). Ionic
liquids were gained from Merck, Darmstadt, Germany, and used as
received. The powder of white pepper was purchased from a local
store (Hangzhou, China). All samples were dried, milled, passed
through a stainless steel sieve and stored in closed desiccators at
4 â—¦C until use. The same batch of sample was used through this
study to be representative of variable hardness and density.
2.2. Apparatus
KQ-100DA and KQ-500 ultrasonic water baths (Kunshan,
Jiangsu, China) were used in the extraction step. The generators
of these ultrasonic water baths have frequency of 40 kHz.
0003-2670/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.aca.2009.03.029
48 X. Cao et al. / Analytica Chimica Acta 640 (2009) 47–51
An AcquityTM UPLC (Waters, Milford, MA, USA) equipped with
a binary solvent delivery system, an auto-sampler with a 10 L
sample loop, a PDA detector, a column oven, and a data station
running the Empower data software was from Waters. The
AcquityTM UPLC BEH C18 column (1.7 m, 50mm×2.1mm, i.d.)
equipped with a VanGuardTM Pre-Column (AcquityTM UPLC BEH,
C18, 5mm×2.1mm, 1.7 m) was used as the UPLC analytical column.
2.3. IL-based ultrasonic-assisted extraction
Ionic liquid-based ultrasonic-assisted extractionwas performed
in ultrasonic water baths (Model KQ-100DA and KQ-500, China).
1.0 g of dried sample powder was mixed with 10mL of different
IL solutions, and then the suspensions were ultrasonic
extraction. IL solutions were prepared by dissolving series of 1-
alkyl-3-methylimidazolium ionic liquids in deionized water at
the concentrations in the range of 0.5–3.0 mol L−1. The optimum
extraction conditionswere systematically studied in thiswork. The
suspensions obtained after ultrasound were cooled to room temperature
and filtered through a Busher funnel, then the filtrate was
diluted to 50mL with deionized water and filtered through the
0.22- m filter for the subsequent UPLC analysis.
2.4. Conventional reference extraction method
HRE was selected as the reference method for extraction of the
piperine. 1.0 g sample with 10mL of 75%methanol in a flask (50 mL)
were boiled for 2 h under the water-bath reflux. The suspensions
obtained after extraction were cooled to room temperature and filtered
through a Busher funnel, then the filtratewas diluted to 50mL
with deionizedwater and filtered through the 0.22- mfilter for the
subsequent UPLC analysis.
2.5. UPLC analysis and quantification
The diluted extracts were directly injected into liquid chromatography.
The mobile phase was eluent A, water and eluent B,
methanol. The elution started at 65% of eluent B for 2min, then
was increased to 90% of eluent B in 0.1 min and kept isocratic for
1min. At last, back to initial conditions in 0.1min, and the reequilibration
time was 1.9min. During the analysis, the column
was kept at 35â—¦C and the flow rate was 0.3mLmin−1. All chromatograms
were acquired at 343 nm and each injection volume
was 2 L.Under this condition, the piperinewas baseline separated.
The peak identification was carried out by comparing its retention
time with that of the corresponding peak in the standard piperine
solution. A comparison of the chromatogram of piperine obtained
from standard solution with that contained in an IL extract from
white pepper powder is shown in Fig. 1. No effects attributable to
the ILswere observed on peak resolution, elution order and elution
time.
3. Results and discussion
3.1. Screening of the IL-based extraction phase
The structure of ILs has significant influence on its physicochemical
properties, whichmight greatly affect the extraction efficiency
of target analyte [17]. In order to evaluate the performance of ionic
liquids incorporating the imidazolium cation (shown in Table 1) in
UAE process, the effects by changes in anion and the cation on the
extraction efficiency were investigated in this paper.
Due to the hydrophobicity of piperine, the hydrophobic interactions
between the piperine and the water phase containing ILs
Fig. 1. UPLC profile with UV detection of piperine in the [C4MIM][BF4] contained
white pepper powder extract and chemical structure of piperine. Insert: UPLC profile
of standard piperine (1mgmL−1) in mobile phase. Column: UPLC BEH C18. Mobile
phase: water-methanol. Flow rate: 0.3mLmin−1. UV detection at 343 nm.
Table 1
Chemical structures of studied ILs.
ILs Cations Anions
[C4MIM][PF6] PF6
−
[C4MIM][H2PO4] H2PO4
−
[C6MIM][BF4] BF4
−
[C4SO3HMIM]Br Br−
[C4MIM]Br Br−
[C4MIM][BF4] BF4
−
are the main driving force for extraction. It is well known that the
choice of anion determines water miscibility of ILs [24]. Thus, the
1-butyl-3-methylimidazolium ILs with four different anions (BF4
−,
Br−, H2PO4
−, PF6
−) were tested. As shown in Fig. 2, the extrac-
Fig. 2. Effect of ILs on the extraction efficiency of piperine from white pepper powder.
Pure water and 0.5M NaCl are selected as blank experiment. Sample: 1.0 g,
extractant volume: 10 mL, ultrasonic power: 500W, extraction time: 30 min. The
extraction efficiency is expressed as the observed values of piperine and the maximum
amount in curve was taken to be 100%.
X. Cao et al. / Analytica Chimica Acta 640 (2009) 47–51 49
Fig. 3. Effect of extraction time on the extraction efficiency of piperine from white
pepper powder. Sample: 1.0 g, concentration of selected IL ([C4MIM][BF4]): 1.5M,
extractant volume: 10 mL, ultrasonic power: 500W, The extraction efficiency is
expressed as the observed values of piperine and the maximum amount in curve
was taken to be 100%.
tion efficiency of the piperine was decreased from BF4
− to Br−
to H2PO4
− to PF6
− due to decreasing hydrophilicity of these four
anions. This result could be interpreted by the fact that the water
miscibility of four 1-butyl-3-methylimidazolium ILs decreases from
BF4
− to Br− to H2PO4
− to PF6
−.
With the same anion, the changes of alkyl chain length and substituted
groups on the alkyl chain of 1-alkyl-3-methylimidazolium
cations were evaluated. As shown in Fig. 2, increasing alkyl chain
length from propyl to butyl dramatically decreased the extraction
efficiency. This phenomenon could be attributed to the fact that
increasing the alkyl chain length from propyl to butyl decreases the
water miscibility of the ILs. Furthermore, the substituted groups
on the alkyl chain also have significant influence on the extraction.
The extraction efficiency of the IL terminated with sulfonic group on
the 1-alkyl chain is about 30% lower than that of IL without sulfoinc
group on the 1-alkyl chain due to changes in the water miscibility
and relative hydrogen bonding ability of the ILs [24]. Consideration
of the above results, the IL, [C4MIM][BF4], was selected for the
subsequent evaluation.
Fig. 4. Effect of concentration of selected IL ([C4MIM][BF4]) on the extraction efficiency
of piperine from white pepper powder. Sample: 1.0 g, extractant volume:
10 mL, ultrasonic power: 500W, extraction time: 30 min. The extraction efficiency
is expressed as the observed values of piperine and the maximum amount in curve
was taken to be 100%.
3.2. Optimization of the ILUAE process
The univariatemethodwas used in all instances for optimization
of the four parameters, which might extensively affect the extraction
step: extraction time, concentration of the [C4MIM][BF4] ion
liquid, ultrasonic power, and solid–liquid ratio. As shown in Fig. 3,
the extraction efficiency could reach to their maximum value at the
extraction time of 30min.
The concentration effect of the [C4MIM][BF4] ion liquidwas also
obvious. Results shown in Fig. 4 indicated that the extraction efficiency
could reach to the maximum value at the concentration of
2M.
When the ultrasonic power was tested at three different levels:
50W, 100Wand 500W, it was obvious that the suitable ultrasonic
power should be 500W(see Fig. 5a).
Additionally, the extraction efficiency increased when
solid–liquid ratio was changed from 1:5 to 1:15 as shown in
Fig. 5b. No significant change was observed when it was increased
to 1:20. Thus, a solid–liquid ratio of 1:15 was adopted in this study.
3.3. Comparison of the proposed ILUAE approach with the
conventional methods
The extraction efficiency of piperine from white pepper powder
reached 3.577% using the proposed ILUAE approach under opti-
Fig. 5. Effect of ultrasonic power (a) and solid–liquid ratio (b) on the extraction efficiency
of piperine fromwhite pepper powder with 2.0M[C4MIM][BF4] as extracting
phase. Sample: 1.0 g, extraction time: 30 min. The extraction efficiency is expressed
as the observed values of piperine and the maximum amount in curve was taken to
be 100%.
50 X. Cao et al. / Analytica Chimica Acta 640 (2009) 47–51
Table 2
Comparative study of extraction efficiency using different extraction methods.
Spike level (mgmL−1) Proposed methoda Conventional method
ILUAE([C4MIM][BF4], n = 3) Regular UAE(75% MeOH, n=3)b HRE (75% MeOH, n=3)c
Observed values Recovery yields (%) Observed values Recovery yields (%) Observed values Recovery yields (%)
Mean (mg g−1) RSDd (%) Mean RSD Mean (mg g−1) RSD (%) Mean RSD Mean (mg g−1) RSD (%) Mean RSD
0.05
35.77 0.87
93.50 1.30
19.60 2.14
95.74 2.41
19.50 2.62
100.56 3.51
0.10 98.70 2.56 93.60 4.12 94.85 1.23
0.20 96.44 0.59 103.80 0.51 91.81 0.83
a Operation under optimized conditions.
b The same operation conditions except the extracting phase.
c See Section 2 for operation conditions. The total extraction time is 2 h.
d Error, expressed as relative standard deviations.
mal conditions. Compared with the conventional HRE method, the
proposed approach could dramatically improve the extraction efficiency
of the piperine (from 1.950% to 3.577%) and reduce the total
extraction time (from 2 h to 30 min).
In order to further demonstrate the use of ILs, the proposed
approach was compared with the regular UAE process. Results
shown in Table 2 indicated that the extraction efficiency of regular
UAE (1.960%)was almost equal to that provided by the conventional
HRE method; and it was still much lower than that obtained by the
ILUAE approach. This means that the proposed IL-based UAE procedure
has great potential to be a rapid and effective approach for
extraction of the piperine from the spice white pepper.
3.4. Analytical performance of the proposed method
To evaluate the proposed IL-based UAE approach, some
parameters such as linearity, reproducibility, and recovery were
determined under the optimized conditions. Calibration curves
were obtained by dissolving the standard piperine to mobile phase
at seven concentrations in the range of 1–1000 gmL−1under
the same UPLC conditions for white pepper powder extraction.
Linear regression equation and correlation coefficient is
y = 6.22×106x−8.93×103 and 0.9994, respectively. The limit
of detection (LOD) and the limit of quantification (LOQ) were
0.2mgL−1 and1mgL−1, respectively. The reproducibility studywas
carried out on repetitive extractions (1.0 g sample for each) with
both the proposed and the conventional approaches. As seen in
Table 2, the relative standard deviation (RSD) obtained by the proposed
approach is 0.87%. To evaluate the accuracy of the present
method, standard solution of piperine was added to white pepper
powder samples, at three levels 0.05, 0.10 and 0.20mgmL−1.
Processed under the proposed IL-based UAE approach, satisfactory
results were found, with recovery values between 93.5% and 98.7%
(shown in Table 2), not related to the spiking level. Moreover, the
calculatedRSDvalueswere lower than5%at all spiking levels, which
indicated that the present method was credible.
4. Conclusion
A green and effective method based on the IL-based ultrasonicassisted
extraction has been developed for the extraction of
piperine from white pepper powder. Compared with conventional
HRE and regular UAE extraction, the proposed approach provides
higher extraction efficiency, and obviously reduced extraction time.
Moreover, due to the efficiency and good reproducibility, the procedure
could also be proposed for the daily quality evaluation in
both government agency and food companies.
White pepper (Piper nigrum L.) used as a spice worldwide
is obtained from the fully ripe berries of pepper plant. Piperine
[1], the main constituent of white pepper, exhibited a
variety of pharmacological activities, e.g. antifungal [2], antidiarrhoeal
[3], anti-inflammatory [4], as well as 5-lipoxygenase and
cyclooxygenase-1 inhibitory activities [5]. Heat-reflux extraction
(HRE) is the most widely used traditional technique for the extraction
of piperine from this spice plant. However, HRE is laborious,
time consuming, and requires large amounts of volatile/hazardous
organic solvents. The benefit of using ultrasonic-assisted extraction
(UAE) in the extraction of organic compounds directly from
solid matrixes has already been demonstrated in recent years
[6–10]. Compared with traditional and other modern extraction
techniques, UAE is proposed as an alternative procedure for sample
pretreatment.
Recently, ionic liquids (ILs) have been used extensively in
areas of analytical chemistry, including electrochemistry, separation
science, mass spectrometry, and spectroscopy [11–18].
IL-assisted sample pretreatment techniques, such as liquid–liquid
extraction, liquid-phase microextraction, solid-phase microextraction
and aqueous two-phase systems extraction have also been
published [19–23]. However, there is no report about IL-based
∗ Corresponding author. Tel.: +86 571 88871031; fax: +86 571 88320961.
E-mail address: xiaojicao@zjut.edu.cn (X. Cao).
ultrasonic-assisted extraction. The aim of the present paper is the
development of a rapid and effective IL-based ultrasonic-assisted
extraction approach for the extraction of bioactive piperine from
the spice plant “white pepper”.
2. Experimental
2.1. Chemicals
All chemicals involved in this study were at least of analytical
reagent grade. The ultrapure water was prepared with a
Milli-Q water purification system (18M , Millipore, Bedford, MA,
USA). Methanol used for UPLC analysis was of chromatographic
grade and purchased from Merck, Darmstadt, Germany. Standard
piperine used for UPLC–UV determinations was purchased from
Zhuokang Biological Technology Company (Shanghai, China). Ionic
liquids were gained from Merck, Darmstadt, Germany, and used as
received. The powder of white pepper was purchased from a local
store (Hangzhou, China). All samples were dried, milled, passed
through a stainless steel sieve and stored in closed desiccators at
4 â—¦C until use. The same batch of sample was used through this
study to be representative of variable hardness and density.
2.2. Apparatus
KQ-100DA and KQ-500 ultrasonic water baths (Kunshan,
Jiangsu, China) were used in the extraction step. The generators
of these ultrasonic water baths have frequency of 40 kHz.
0003-2670/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.aca.2009.03.029
48 X. Cao et al. / Analytica Chimica Acta 640 (2009) 47–51
An AcquityTM UPLC (Waters, Milford, MA, USA) equipped with
a binary solvent delivery system, an auto-sampler with a 10 L
sample loop, a PDA detector, a column oven, and a data station
running the Empower data software was from Waters. The
AcquityTM UPLC BEH C18 column (1.7 m, 50mm×2.1mm, i.d.)
equipped with a VanGuardTM Pre-Column (AcquityTM UPLC BEH,
C18, 5mm×2.1mm, 1.7 m) was used as the UPLC analytical column.
2.3. IL-based ultrasonic-assisted extraction
Ionic liquid-based ultrasonic-assisted extractionwas performed
in ultrasonic water baths (Model KQ-100DA and KQ-500, China).
1.0 g of dried sample powder was mixed with 10mL of different
IL solutions, and then the suspensions were ultrasonic
extraction. IL solutions were prepared by dissolving series of 1-
alkyl-3-methylimidazolium ionic liquids in deionized water at
the concentrations in the range of 0.5–3.0 mol L−1. The optimum
extraction conditionswere systematically studied in thiswork. The
suspensions obtained after ultrasound were cooled to room temperature
and filtered through a Busher funnel, then the filtrate was
diluted to 50mL with deionized water and filtered through the
0.22- m filter for the subsequent UPLC analysis.
2.4. Conventional reference extraction method
HRE was selected as the reference method for extraction of the
piperine. 1.0 g sample with 10mL of 75%methanol in a flask (50 mL)
were boiled for 2 h under the water-bath reflux. The suspensions
obtained after extraction were cooled to room temperature and filtered
through a Busher funnel, then the filtratewas diluted to 50mL
with deionizedwater and filtered through the 0.22- mfilter for the
subsequent UPLC analysis.
2.5. UPLC analysis and quantification
The diluted extracts were directly injected into liquid chromatography.
The mobile phase was eluent A, water and eluent B,
methanol. The elution started at 65% of eluent B for 2min, then
was increased to 90% of eluent B in 0.1 min and kept isocratic for
1min. At last, back to initial conditions in 0.1min, and the reequilibration
time was 1.9min. During the analysis, the column
was kept at 35â—¦C and the flow rate was 0.3mLmin−1. All chromatograms
were acquired at 343 nm and each injection volume
was 2 L.Under this condition, the piperinewas baseline separated.
The peak identification was carried out by comparing its retention
time with that of the corresponding peak in the standard piperine
solution. A comparison of the chromatogram of piperine obtained
from standard solution with that contained in an IL extract from
white pepper powder is shown in Fig. 1. No effects attributable to
the ILswere observed on peak resolution, elution order and elution
time.
3. Results and discussion
3.1. Screening of the IL-based extraction phase
The structure of ILs has significant influence on its physicochemical
properties, whichmight greatly affect the extraction efficiency
of target analyte [17]. In order to evaluate the performance of ionic
liquids incorporating the imidazolium cation (shown in Table 1) in
UAE process, the effects by changes in anion and the cation on the
extraction efficiency were investigated in this paper.
Due to the hydrophobicity of piperine, the hydrophobic interactions
between the piperine and the water phase containing ILs
Fig. 1. UPLC profile with UV detection of piperine in the [C4MIM][BF4] contained
white pepper powder extract and chemical structure of piperine. Insert: UPLC profile
of standard piperine (1mgmL−1) in mobile phase. Column: UPLC BEH C18. Mobile
phase: water-methanol. Flow rate: 0.3mLmin−1. UV detection at 343 nm.
Table 1
Chemical structures of studied ILs.
ILs Cations Anions
[C4MIM][PF6] PF6
−
[C4MIM][H2PO4] H2PO4
−
[C6MIM][BF4] BF4
−
[C4SO3HMIM]Br Br−
[C4MIM]Br Br−
[C4MIM][BF4] BF4
−
are the main driving force for extraction. It is well known that the
choice of anion determines water miscibility of ILs [24]. Thus, the
1-butyl-3-methylimidazolium ILs with four different anions (BF4
−,
Br−, H2PO4
−, PF6
−) were tested. As shown in Fig. 2, the extrac-
Fig. 2. Effect of ILs on the extraction efficiency of piperine from white pepper powder.
Pure water and 0.5M NaCl are selected as blank experiment. Sample: 1.0 g,
extractant volume: 10 mL, ultrasonic power: 500W, extraction time: 30 min. The
extraction efficiency is expressed as the observed values of piperine and the maximum
amount in curve was taken to be 100%.
X. Cao et al. / Analytica Chimica Acta 640 (2009) 47–51 49
Fig. 3. Effect of extraction time on the extraction efficiency of piperine from white
pepper powder. Sample: 1.0 g, concentration of selected IL ([C4MIM][BF4]): 1.5M,
extractant volume: 10 mL, ultrasonic power: 500W, The extraction efficiency is
expressed as the observed values of piperine and the maximum amount in curve
was taken to be 100%.
tion efficiency of the piperine was decreased from BF4
− to Br−
to H2PO4
− to PF6
− due to decreasing hydrophilicity of these four
anions. This result could be interpreted by the fact that the water
miscibility of four 1-butyl-3-methylimidazolium ILs decreases from
BF4
− to Br− to H2PO4
− to PF6
−.
With the same anion, the changes of alkyl chain length and substituted
groups on the alkyl chain of 1-alkyl-3-methylimidazolium
cations were evaluated. As shown in Fig. 2, increasing alkyl chain
length from propyl to butyl dramatically decreased the extraction
efficiency. This phenomenon could be attributed to the fact that
increasing the alkyl chain length from propyl to butyl decreases the
water miscibility of the ILs. Furthermore, the substituted groups
on the alkyl chain also have significant influence on the extraction.
The extraction efficiency of the IL terminated with sulfonic group on
the 1-alkyl chain is about 30% lower than that of IL without sulfoinc
group on the 1-alkyl chain due to changes in the water miscibility
and relative hydrogen bonding ability of the ILs [24]. Consideration
of the above results, the IL, [C4MIM][BF4], was selected for the
subsequent evaluation.
Fig. 4. Effect of concentration of selected IL ([C4MIM][BF4]) on the extraction efficiency
of piperine from white pepper powder. Sample: 1.0 g, extractant volume:
10 mL, ultrasonic power: 500W, extraction time: 30 min. The extraction efficiency
is expressed as the observed values of piperine and the maximum amount in curve
was taken to be 100%.
3.2. Optimization of the ILUAE process
The univariatemethodwas used in all instances for optimization
of the four parameters, which might extensively affect the extraction
step: extraction time, concentration of the [C4MIM][BF4] ion
liquid, ultrasonic power, and solid–liquid ratio. As shown in Fig. 3,
the extraction efficiency could reach to their maximum value at the
extraction time of 30min.
The concentration effect of the [C4MIM][BF4] ion liquidwas also
obvious. Results shown in Fig. 4 indicated that the extraction efficiency
could reach to the maximum value at the concentration of
2M.
When the ultrasonic power was tested at three different levels:
50W, 100Wand 500W, it was obvious that the suitable ultrasonic
power should be 500W(see Fig. 5a).
Additionally, the extraction efficiency increased when
solid–liquid ratio was changed from 1:5 to 1:15 as shown in
Fig. 5b. No significant change was observed when it was increased
to 1:20. Thus, a solid–liquid ratio of 1:15 was adopted in this study.
3.3. Comparison of the proposed ILUAE approach with the
conventional methods
The extraction efficiency of piperine from white pepper powder
reached 3.577% using the proposed ILUAE approach under opti-
Fig. 5. Effect of ultrasonic power (a) and solid–liquid ratio (b) on the extraction efficiency
of piperine fromwhite pepper powder with 2.0M[C4MIM][BF4] as extracting
phase. Sample: 1.0 g, extraction time: 30 min. The extraction efficiency is expressed
as the observed values of piperine and the maximum amount in curve was taken to
be 100%.
50 X. Cao et al. / Analytica Chimica Acta 640 (2009) 47–51
Table 2
Comparative study of extraction efficiency using different extraction methods.
Spike level (mgmL−1) Proposed methoda Conventional method
ILUAE([C4MIM][BF4], n = 3) Regular UAE(75% MeOH, n=3)b HRE (75% MeOH, n=3)c
Observed values Recovery yields (%) Observed values Recovery yields (%) Observed values Recovery yields (%)
Mean (mg g−1) RSDd (%) Mean RSD Mean (mg g−1) RSD (%) Mean RSD Mean (mg g−1) RSD (%) Mean RSD
0.05
35.77 0.87
93.50 1.30
19.60 2.14
95.74 2.41
19.50 2.62
100.56 3.51
0.10 98.70 2.56 93.60 4.12 94.85 1.23
0.20 96.44 0.59 103.80 0.51 91.81 0.83
a Operation under optimized conditions.
b The same operation conditions except the extracting phase.
c See Section 2 for operation conditions. The total extraction time is 2 h.
d Error, expressed as relative standard deviations.
mal conditions. Compared with the conventional HRE method, the
proposed approach could dramatically improve the extraction efficiency
of the piperine (from 1.950% to 3.577%) and reduce the total
extraction time (from 2 h to 30 min).
In order to further demonstrate the use of ILs, the proposed
approach was compared with the regular UAE process. Results
shown in Table 2 indicated that the extraction efficiency of regular
UAE (1.960%)was almost equal to that provided by the conventional
HRE method; and it was still much lower than that obtained by the
ILUAE approach. This means that the proposed IL-based UAE procedure
has great potential to be a rapid and effective approach for
extraction of the piperine from the spice white pepper.
3.4. Analytical performance of the proposed method
To evaluate the proposed IL-based UAE approach, some
parameters such as linearity, reproducibility, and recovery were
determined under the optimized conditions. Calibration curves
were obtained by dissolving the standard piperine to mobile phase
at seven concentrations in the range of 1–1000 gmL−1under
the same UPLC conditions for white pepper powder extraction.
Linear regression equation and correlation coefficient is
y = 6.22×106x−8.93×103 and 0.9994, respectively. The limit
of detection (LOD) and the limit of quantification (LOQ) were
0.2mgL−1 and1mgL−1, respectively. The reproducibility studywas
carried out on repetitive extractions (1.0 g sample for each) with
both the proposed and the conventional approaches. As seen in
Table 2, the relative standard deviation (RSD) obtained by the proposed
approach is 0.87%. To evaluate the accuracy of the present
method, standard solution of piperine was added to white pepper
powder samples, at three levels 0.05, 0.10 and 0.20mgmL−1.
Processed under the proposed IL-based UAE approach, satisfactory
results were found, with recovery values between 93.5% and 98.7%
(shown in Table 2), not related to the spiking level. Moreover, the
calculatedRSDvalueswere lower than5%at all spiking levels, which
indicated that the present method was credible.
4. Conclusion
A green and effective method based on the IL-based ultrasonicassisted
extraction has been developed for the extraction of
piperine from white pepper powder. Compared with conventional
HRE and regular UAE extraction, the proposed approach provides
higher extraction efficiency, and obviously reduced extraction time.
Moreover, due to the efficiency and good reproducibility, the procedure
could also be proposed for the daily quality evaluation in
both government agency and food companies.