Article
pubs.acs.org/jced
Solubility of Trehalose in Water + Methanol Solvent System from
(293.15 to 313.15) K
Linjie Jiang,†,‡ Suye Li,†,‡,§ Jinxia Jiang,†,§ Yangang Liang,†,§ and Peng Wang*,†,‡
†
School of Chemical Engineering, and ‡Advanced Institute of Materials Science, Changchun University of Technology, Changchun,
Jilin 130012, People’s Republic of China
ABSTRACT: The solubility of trehalose in the water + methanol solvent
system was measured with the mole fraction of water ranging from 0.000 to
0.700, at temperatures from (293.15 to 313.15) K, using the gravimetric method.
Two kinds of crystals were collected and measured by differential scanning
calorimetry and X-ray diffraction to prove the change of crystal habit for
dihydrate trehalose from granular to powderlike at low water content. The
turning points of every solubility curve were the critical points of crystal habit
transition from the granular dihydrate trehalose (higher than the critical points)
to the powderlike dihydrate trehalose (lower than the critical points). The mole
fraction of the critical water content ranged from 0.160 to 0.250. The
combination version of the Jouyban−Acree and van’t Hoff models was used to
separately correlate the solubility data lower and higher than the critical points
by nonlinear surface fit. The root-mean-square deviation (rmsd) values for the
powderlike and the granular dihydrate trehalose solubility data were 1.4900·10−4 and 3.5919·10−4, respectively, which shows the
model correlated the data well.
■
INTRODUCTION
Trehalose, a nonreducing disaccharide which is widespread in
plants, animals and microbes, is formed by two glucose units
linked in an α,α-1,1-glycosidic linkage.1 Depending on the
given thermodynamic conditions, trehalose mainly has two
kinds of polymorphs: dihydrate and anhydrous forms.2 The
dihydrate trehalose can be easily obtained by crystallization
from supersaturated solutions and is the most stable one. There
are four different forms of anhydrous trehalose reported until
now.3 The β-form which is stable at room temperature and less
hydroscopic has been obtained when keeping the dihydrate
trehalose under vacuum at 130 °C for 4 h,4 or from the
transformation of dihydrate trehalose to anhydrous trehalose
using ethanol.3,5,6 The α-form which could be easily rehydrated
back to dihydrate trehalose has been observed when keeping
the dihydrate trehalose under vacuum at 85 °C for 4 h.4 The γform, the mixture of dihydrate and β-form trehalose, has been
shown by the shape of the calorimetric curve for the dihydrate
trehalose at 5 K·min−1 to 20 K·min−1.4 The ε-form has been
obtained still by thermal treatment according to Sussich’s
report.7
The importance of observing polymorphic forms and
solvated varieties has been recognized by most academic and
industrial research groups.8 In our previous work, we
determined the solubility of trehalose in a water + ethanol
solvent system, and a white flocculent suspension which is the
anhydrous form was observed in low water content. Most
researches simply involve water + methanol solvents and water
+ ethanol solvents to determine the solubility results.9 So it is
necessary to determine the solubility of trehalose in the water +
methanol solvent system.
© 2014 American Chemical Society
In this work, the solubility of trehalose in the water +
methanol solvent system was measured with the mole fraction
of water ranging from 0.000 to 0.700, at temperatures from
(293.15 to 313.15) K, using the gravimetric method. The
critical points of crystal habit transition were also recorded.
Below the critical points, the white flocculent suspension which
was distinguished from that higher than the critical points was
also observed in the water + methanol solvent system. This
phenomenon was very similar to that in the water + ethanol
solvent system observed in our previous work. In the water +
ethanol solvent system, the white flocculent suspension has
been proven to be the β-form of anhydrous trehalose, and the
crystals suspended in the higher water content solutions were
the dihydrate form.4,5 The combination version of the
Jouyban−Acree and van’t Hoff models was used to correlate
the solubility data at different temperatures and water content
by a nonlinear surface fit.
■
EXPERIMENTAL SECTION
Materials. Commercial food grade dihydrate trehalose was
obtained from Hayashibara Co., Ltd. (Okayama, Japan), and its
purity is higher than 98.0 % (mass fraction), and used without
further purification. The analytical reagent grade of methanol
used in our study is higher than 99.5 % (mass fraction) and the
other solvent used in this experiment was deionized water
which was prepared by Merck Millipore Mingche-D 24UV
Received: July 1, 2014
Accepted: November 13, 2014
Published: November 24, 2014
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ultrapure water system (electrical resistivity was 18.2 MΩ·cm at
25 °C).
Apparatus and Procedures. The gravimetric method was
also used to measure the solubility of trehalose. The procedures
were the same as we used in our previous work.5 In our
experiments, different amounts of water and methanol were
added in the crystallizer which was maintained at a constant
temperature by a thermostatic water bath (Shanghai Laboratory
Instrument Works Co., Ltd. 501A, China), and then excess
trehalose weighed by a analytical balance (0.1 mg precision)
was added. The mixed solution was stirred fully with a magnetic
stirring apparatus (IKA, RCT B S25, Germany) for 2 h which
was the reasonable equilibrium time according to our research
on the dissolution equilibrium time of trehalose. Also the time
for the dissolution of dihydrate trehalose at the water content
below and above the critical points was less than 2 h. The
suspension was settled for 20 min, and then about 3 mL of clear
liquor with no visible particles was weighed. The sample was
dried during 24 h at 60 °C. In this paper, the molecular weight
of dihydrate trehalose was used to calculate the solubility of
trehalose. Every experimental point was measured at least three
times, and represented by the average value. For the above
experiments, the relative expanded uncertainty of measurement
was estimated to be 7 %. Calorimetric measurements were
carried out with a PerkinElmer Diamond differential scanning
calorimeter (DSC), and the underlying scan rate was 10 K·
min−1. X-ray diffraction (XRD) patterns were obtained with D/
MAX-2200PC X-ray diffractometer at room temperature. The
samples were scanned in the range of 2θ from 10° to 30° at a
scanning rate of 1°·min−1.
Models and Calculations. The combination version of the
Jouyban−Acree and van’t Hoff models proposed by A. Jouyban
and W. E. Acree Jr.10 was used to correlate the solubility data of
trehalose in the binary water + methanol solvent system at
different temperatures, and its expression can be written as
follows,11−13
Figure 1. Experimental and correlated mole fraction solubility of
trehalose (xA) versus mole fraction of water in a water + methanol
solvent system (x1) at different solvent compositions and temperatures.
⎛
⎛
B ⎞
B ⎞
ln(xA ) = x1⎜A1 + 1 ⎟ + (1 − x1)⎜A 2 + 2 ⎟
⎝
⎠
⎝
T
T⎠
x (1 − x1)
+ 1
[J0 + J1(2x1 − 1) + J2 (2x1 − 1)2 ]
T
(1)
where x1 is the mole fraction of water in mixed solvent, in
solute-free basis, xA is the calculated solubility of trehalose in
mole fraction according to the selected model, A1, B1, A2, B2, J0,
J1, and J2 terms are the model parameters obtained by nonlinear
surface fit of the solubility at different temperatures and water
content.
Equation 2 was used to calculate the root-mean-square
deviation (rmsd).
Figure 2. Experimental and correlated logarithm mole fraction
solubility of trehalose (ln(xA)) versus mole fraction of water (x1) in
water + ethanol and water + methanol solvent system. (a) Water +
ethanol, (b) water + methanol: pink □―, T = 293.15 K; black ○ 
, T = 298.15 K; red △―, T = 303.15 K; green ▽―, T = 308.15
K; blue ◇―, T = 313.15 K.
N
rmsd =
∑i = 1 (xical − xiexp)2
N
(2)
where N is the number of the experimental solubility data,
superscript cal is the calculated values and exp is the
experimental one.
that the solubility of trehalose increases with the mole fraction
of water and temperature. To clearly show the difference of
solubility curves below and above the critical water content, the
curves of ln(xA) versus x1 were plotted as shown in Figure 2b.
From Figure 2b, it can be seen that there were the turning
points (x1 = 0.160 to 0.250) for every curve corresponding to
the critical mole fraction of water that increased with
temperature. After filtration, the white flocculent suspension
■
RESULTS AND DISCUSSION
The 2D scatter plot of trehalose solubility and calculated
solubility curves in water + methanol solvent system from
(293.15 to 313.15) K is shown in Figure 1. Figure 1 showed
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Table 1. Experimental solubility xAexp (mole fraction) of
trehalose in water + methanol solvent system at mole
fraction of water x1 lower and higher than the turning point
at different temperatures Ta
lower than the turning point
x1
mol/mol
10
higher than the turning point
3
x1
103xAexp
mol/mol
mol/mol
xAexp
mol/mol
T = 293.15 K
0.000
0.050
0.080
0.100
0.140
0.150
0.349
0.394
0.526
0.534
1.164
1.708
0.000
0.050
0.100
0.150
0.171
0.313
0.446
0.587
1.084
1.945
0.000
0.050
0.101
0.151
0.190
0.379
0.403
0.728
0.874
2.051
0.000
0.100
0.150
0.200
0.211
0.339
0.674
1.019
1.860
2.077
0.000
0.100
0.150
0.200
0.240
0.383
0.719
1.139
1.982
3.171
0.200
0.300
0.400
0.499
0.600
0.700
1.445
1.582
2.439
3.977
6.828
11.022
0.181
0.201
0.301
0.400
0.500
0.600
0.700
1.906
1.844
2.111
3.240
5.194
8.746
14.102
0.201
0.300
0.400
0.501
0.600
0.701
2.455
2.777
4.084
7.156
11.805
18.955
0.220
0.300
0.400
0.500
0.600
0.700
3.132
3.829
5.670
9.563
15.890
25.228
0.250
0.300
0.400
0.500
0.600
0.700
4.499
5.294
8.105
13.653
22.704
33.315
T = 298.15 K
T = 303.15 K
Figure 3. Spectrograms of DSC: (a) granular dihydrate trehalose part
and (b) powderlike dihydrate trehalose part.
T = 308.15 K
T = 313.15 K
a
The standard uncertainty for temperature is u(T) = 0.05 K, the
relative standard uncertainty for solvent mole fraction of water is
ur(x1) = 0.02, and the relative expanded uncertainty for the solubility is
Ur(xAexp) = 0.07 for all the solubility data.
Table 2. Model Parameters Fitted from Experimental
Trehalose Solubility Data
A1
B1
A2
B2
J0
J1
J2
Adj. R2
Figure 4. Spectrograms of XRD: (a) granular dihydrate trehalose part
and (b) powderlike dihydrate trehalose part.
below the critical points was powder−like, while above those, it
was granular. And the two kinds of crystals were determined by
DSC and XRD measurements. The spectrograms are shown in
Figures 3 and 4. From Figure 3 panels a and b, the first
endothermic peaks which appeared around 100 °C were
attributed to the dehydration of dihydrate trehalose.6 And the
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lower than the turning point
higher than the turning point
−41.25
5.899·104
−4.655
−9.985·102
−8.604·104
−6.292·104
−2.592·104
0.9583
15.28
−5.356·103
10.46
−4.520·103
−1.821·103
1.945·103
−2.004·103
0.9982
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Figure 5. Experimental and correlated mole fraction solubility of trehalose (xA) versus mole fraction of water (x1) in the water + methanol and water
+ ethanol solvent systems at 308.15 K. (A) Below the critical points and (B) above the critical points: black ■ , water + ethanol; red ○―, water
+ methanol.
XRD spectrograms between the powder-like and granular
trehalose crystals obtained in water + methanol solvent system
might be the different crystal habit of them. So the trehalose we
obtained below the critical points was still dihydrate trehalose
only with a different crystal habit from that above the critical
points.
To get the theoretical values of solubility of two kinds of
crystals accurately, we divided the solubility data into two parts
from the turning points and correlated the data using the
combination version of the Jouyban−Acree and van’t Hoff
models, respectively. The Adj. R2 (adjusted coefficient of
determination) and correlated parameters are listed in Table 2.
All of the experimental solubility data are listed in Table 1. The
rmsd values for the powder-like dihydrate trehalose part and
the granular dihydrate trehalose part were 1.4900·10−4 and
3.5919·10−4, respectively, which shows a good mathematical
representation of the experimental solubility data of trehalose in
water + methanol solvent system. In Table 2, it was obvious
that the combination version of the Jouyban−Acree and van’t
Hoff models was more suitable for the data above the
boundary.
A comparison between the solubility curves of trehalose in
water + ethanol and water + methanol solvent systems is shown
in Figure 2. From Figure 2, at the same temperature, the critical
water content in water + methanol system was higher than that
in the water + ethanol system with relatively low critical water
content (x1 = 0.040 to 0.050).5 It also can be seen that the
solubility curves below the critical points in the water +
methanol solvent system increased with temperature, while that
in the water + ethanol solvent system decreased with
temperature. This indicates that the influence of polymorphism
(in water + ethanol solvent system) and crystal habit (in water
+ methanol solvent system) on solubility behaviors of trehalose
could be different. From Figure 5, the solubility data of
trehalose in the water + methanol solvent system is higher than
that of trehalose in the water + ethanol solvent system above
the critical points, but the data intersected below the critical
points. The comparison of critical points between the two
Figure 6. Comparison of critical points between water + methanol and
water + ethanol solvent systems.
range of the first peak temperature varied from 91 to 103 °C
because of the purity of the crystals.14 So the powderlike and
the granular trehalose crystals obtained in water + methanol
solvent system were both dihydrate forms. The last
endothermic peaks in Figure 3 panels a and b around 215 °C
were due to the melting of the β-form of anhydrous trehalose.
From Figure 3, the DSC spectrogram of the powderlike
dihydrate trehalose was similar to that of the granular one
except for the residue in Figure 3a at 125 °C. The reason was
that the transformed trehalose contained some α-form of
anhydrous trehalose,6 while after the dehydration of the
powderlike dihydrate trehalose, only β-form anhydrous
trehalose was generated. In addition, from Figure 4, the XRD
spectrogram of the granular dihydrate trehalose agreed with
that in the literature.4 Except for the differences at the range of
21° to 23° of 2θ, the XRD spectrograms of the two kinds of
crystals were similar. The cause of the discrepancy of DSC and
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(5) Wang, P.; Jiang, J.; Jia, X. a.; Jiang, L.; Li, S. Solubility of trehalose
in water + ethanol solvent system from (288.15 to 318.15) K. J. Chem.
Eng. Data 2014, 59, 1872−1876.
(6) Verhoeven, N.; Neoh, T. L.; Furuta, T.; Yamamoto, C.; Ohashi,
T.; Yoshii, H. Characteristics of dehydration kinetics of dihydrate
trehalose to its anhydrous form in ethanol by DSC. Food Chem. 2012,
132, 1638−1643.
(7) Sussich, F.; Cesàro, A. Transitions and phenomenology of α,αtrehalose polymorphs interconversion. J. Therm. Anal. Calorim. 2000,
62, 757−768.
(8) Garnier, S.; Petit, S.; Coquerel, G. Dehydration mechanism and
crystallisation behaviour of lactose. J. Therm. Anal. Calorim. 2002, 68,
489−502.
(9) Zou, F.; Zhuang, W.; Wu, J.; Zhou, J.; Liu, Q.; Chen, Y.; Xie, J.;
Zhu, C.; Guo, T.; Ying, H. Experimental measurement and modelling
of solubility of inosine-5′-monophosphate disodium in pure and mixed
solvents. J. Chem. Thermodyn. 2014, 77, 14−22.
(10) Jouyban, A.; Shayanfar, A.; Acree, W. E., Jr Solubility prediction
of polycyclic aromatic hydrocarbons in non-aqueous solvent mixtures.
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various temperatures. J. Chem. Eng. Data 2012, 57, 2848−2854.
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of 2-butyl-3-benzofuranyl 4-(2-(diethylamino)ethoxy)-3,5-diiodophenyl ketone hydrochloride (amiodarone HCl) in ethanol + water and Nmethyl-2-pyrrolidone + water mixtures at various temperatures. J.
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solvent systems is shown in Figure 6. The critical points in the
water + methanol solvent system increased with temperature,
while that in the water + ethanol solvent system had little
change basically.
■
CONCLUSIONS
The solubility of trehalose with the mole fraction of water
ranging from 0.000 to 0.700 at different temperatures was
determined using the gravimetric method in the water +
methanol solvent system, and the solubility curves increased
with water content and temperature. The analysis of DSC and
XRD spectrograms showed that the two kinds of crystals
suspended in the solution were both dihydrate forms in
different crystal habit. The critical points of crystal habit
transition from the granular dihydrate trehalose to the
powderlike one were from 0.160 to 0.250 (mole fraction of
water in solvent). The solubility curves lower and higher than
the critical points were different. Comparing with the solubility
curves of trehalose in the water + ethanol solvent system, the
critical water content increased obviously. The critical points in
the water + methanol solvent system had an obvious growth
trend with temperature, while it was almost invariable in the
water + ethanol solvent system. The solubility data of trehalose
in the water + methanol solvent system was higher than that of
trehalose in the water + ethanol solvent system above the
critical points, but the data intersected and had the opposite
trend below the critical points due to the different effect of
polymorphism and crystal habit on solubility behaviors of
trehalose. We used the combination version of the Jouyban−
Acree and van’t Hoff models to separately fit the solubility data
below and above the crystal habit transition points by nonlinear
surface fit. The adj. R2 values for the powderlike and the
granular dihydrate trehalose were 95.83 % and 99.82 %,
respectively, which showed the model correlated the solubility
data well especially for the latter. The rmsd values for the data
lower and higher than the turning points were 1.4900·10−4 and
3.5919·10−4, respectively.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail: [email protected]. Tel.: +86-431-85717211.
Author Contributions
§
S.L., J.J., and Y.L. contributed equally to this work.
Funding
This work was financially supported by Changchun University
of Technology Foundation for Scientific Research and
Development (LG06).
Notes
The authors declare no competing financial interest.
■
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