Solubility and Solution Thermodynamics of Gibberellin A4 in Different

Article pubs.acs.org/jced

Solubility and Solution Thermodynamics of Gibberellin A4 in Different Organic Solvents from 278.15 K to 333.15 K Gang Wu,† Yonghong Hu,*,† Pengfei Gu,† Wenge Yang,† Zhiwen Ding,† Chunxiao Wang,† and Yonggen Qian‡ †

State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, China Jiangsu Fengyuan Bioengineering Co. Ltd., Yancheng 224300, China

‡

ABSTRACT: Data on corresponding solid−liquid equilibrium of Gibberellin A4 (GA4) in different solvents is essential for a preliminary study of industrial applications. In this paper, the solid−liquid equilibrium of GA4 in water, methanol, ethanol, isopropanol, 1-butanol, acetonitrile, acetone, and ethyl acetate was explored in the temperatures (from 278.15 K to 333.15 K) under atmosphere pressure. For the temperature range investigated, the solubility of GA4 in the solvents increased with increasing temperature. From 278.15 K to 333.15 K, the solubility of GA4 in isopropanol is superior to other selected solvents. The modified Apelblat model, the Buchowski−Ksiazaczak λh model, and the ideal model were adopted to describe and predict the change tendency of solubility. Computational results showed that the modified Apelblat model has advantages than the other two models. In addition, the calculated thermodynamic parameters indicated that in each studied solvent the dissolution of GA4 is endothermic, nonspontaneous, and an entropy-driven process.

1. INTRODUCTION Gibberellic acids are acids of the carbocyclic family and classified as tetracyclic diterpenoid acids. At the present time, gibberellic acid is widely used to agricultural production as biological pesticides. Gibberellin A4 (Figure 1, C19H24O5, FW = 332.39,

explore more about separation processes such as the safety of operating and extractive crystallization. In this study, the solubility of gibberellin A4 in water, methanol, ethanol, isopropanol, 1-buutanol, acetonitrile, acetone, and ethyl acetate was measured in the temperature range from 278.15 K and 333.15 K under atmospheric pressure by the gravimetric method, and the solubility data was correlated to the modified Apelblat equation and λh equation. We can calculate thermodynamic parameters (including enthalpy, entropy, and Gibbs energy) by the van’t Hoff analysis and Gibbs equation. We expected to find out the best solvent in crystallization process of GA4 from the selected solvents according to experimental data. Besides, the analysis of thermodynamic properties would also help to determine the best temperature interval, which gave a variation tendency of solubility at different temperatures.3

2. EXPERIMENTAL SECTION 2.1. Materials and Apparatus. Gibberellin A4 (GA4) with a mass faction purity ≥0.980 was obtained from Jiangsu Fengyuan Bioengineering Co., Ltd. Its purity was measured by high performance liquid chromatography (HPLC type DIONEX P680 DIONEX Technologies). We measure the melting point by the melting point apparatus (HCRD-2C), which is from Chengdu Huacheng Instruments Co., Ltd. The double distilled water was produced by an ultrapure water system, which is from Shandong Flom Co., Ltd., in our laboratory. Other chemical reagents were

Figure 1. Chemical structure of gibberellin A4.

CAS RN = 468-44-0), a white power, is one of the gibberellic acids that is popularly used in agricultural production.1,2 As a biological pesticide, gibberellin A4 has a positive effect in fruit growing and also can increase the yield of crops. This work aims to provide some useful data to industrial production of the gibberellic acid chemistry. The solubility of the different organic solvents plays an important role in understanding the phase equilibria or solid−liquid equilibria in the research of crystallization or the liquid−liquid equilibria in extraction process. The purity is an important part of a chemical substance. Also, we want to research the solubility and thermodynamic property of gibberellin A4. Further, we can © 2015 American Chemical Society

Received: March 2, 2015 Accepted: June 12, 2015 Published: June 23, 2015 2104

DOI: 10.1021/acs.jced.5b00190 J. Chem. Eng. Data 2015, 60, 2104−2109

Journal of Chemical & Engineering Data

Article

where xi stand for the experimental solubility values, and xci represent the calculated solubility values. 3.1.1. Modified Apelblat Model. The change of temperatures on the solubility of GA4 has been fitted in with the following modified Apelblat model:6−8

Table 1. Properties of the Compounds Evaluated properties material

molar mass

mass fraction purity

analysis method

source

−1

g·mol

gibberellin A4 332.39

0.980

water methanol ethanol isopropanol 1-butanol acetonitrile acetone ethyl acetate

double distilled 0.995 0.997 0.997 0.990 0.999 0.995 0.997

18.02 32.04 46.07 60.06 74.12 41.05 58.08 88.11

ln x = A +

HPLC Jiangsu Fengyuan Bioengineering Co. Ltd. HPLC our laboratory HPLC Shenbo Chemical Industry HPLC Shenbo Chemical Industry HPLC Shenbo Chemical Industry HPLC Shenbo Chemical Industry HPLC Shenbo Chemical Industry HPLC Shenbo Chemical Industry HPLC Shenbo Chemical Industry

B + C ln(T /K) (T /K)

(2)

where T stand for the absolute Kelvin temperature, A, B, and C represent the model parameters, and x represent the mole fraction solubility of GA4 in aqueous solutions. The factors A and B represent the variation in the solution activity coefficient and take an indication of the effect of nonideal solution of solute solubility, and the factor C represent the temperature effect upon the fusion enthalpy, which is a deviation of heat capacity(ΔCp).9,10 The regression curve parameters of modified Apelblat model are listed in Table 3. The average absolute deviations (RAD) are listed in Table 3−5. The relative average deviations (RAD) are expressed as

used without further purification. The detailed information on the materials used in the experiment is listed in Table 1. An analytical balance (model: BSA224S) was bought from Sartorius Scientific Instruments (Beijing) Co., Ltd., with the accuracy of ±0.01 mg. The smart water-circulating thermostatic bath (model: DC-2006) was bought by Ningbo Scientz Biotechnology Co., Ltd., with the accuracy of ±0.1 K. 2.2. Methods. The solid (GA4) were put into the melting point apparatus, and then raise the temperature. The temperature was recorded when the solid had been melted. The melting points were measured five times. The melting points were 474.15 K, 475.15 K, 475.65 K, 477.65 K, and 478.15 K, respectively. So, the melting point temperature is 476.15 K (u(T) = 0.85 K). The method for solubility measurement was similar to that described in the literature.4,5 The excess GA4 and 8 mL of organic solvent was added into a 10 mL glass test tube with a stopper, and all of the glass test tubes were maintained in a required temperatures thermostatic bath, which was stirred continuously by a magnetic stirrer. To ensure the solution reached the solid− liquid equilibrium, the stirring was continuous for more than 24 h. Also, the temperature was maintained and the stirring was turned off for at least 6 h to ensure that the undissolved solids settle down at the bottom of the glass test tube. Then, 1 mL of upper clear saturated solution was taken by pipet gun and transferred into a 5 mL beaker quickly, which had been weighed. The beaker was measured with the solution immediately and then the beaker was put into a dryer at room temperature. The sampling was measured weekly until the weight had no change. To check the repeatability of the solubility determination, each experiment was repeated at least three times. And in the same way, three samples were measured for each solvent at different temperatures and the mean value was used to calculate the mole fraction solubility.

RAD =

1 N

N

∑ i=1

xi − xci xi

(3)

3.1.2. Buchowski−Ksiazaczak λh Model. The Buchowski− Ksiazaczak λh model was requested to describe the solution behavior by Buchowaski first. The λh equation would fit the experimental data with two parameters λ and h. The λh equation is defined as follows: ⎡ 1 ⎡ λ(1 − x) ⎤ 1 ⎤ ln⎢1 + − ⎥ ⎥ = λh⎢ ⎣ ⎦ (Tm/K) ⎦ x ⎣ (T /K)

(4)

where x is the mole fraction solubility of GA4, T is the experimental Kelvin temperature, and Tm is the standard melting Kelvin temperature.11−13 The parameters of λ and h are presented in Table 4. 3.1.3. Ideal Model. The ideal model is a universal equation for (solvent + solute) equilibrium which based on thermodynamic principles.14 The equation is defined as ln xγ =

ΔdissocH ⎛ 1 1⎞ − ⎟ ⎜ R ⎝ Tm T⎠

(5)

when the solution is an ideal solution (γ = 1), and then we have some transformations, as follows: def

A =

ΔdissocH 1 × R Tm

def

B = −

ΔdissocH R

(6)

We can get eq 7

3. RESULTS AND DISCUSSION 3.1. Solubility Data and Correlation Models. The saturated mole fraction solubility (x) of GA4 in water, methanol, ethanol, isopropanol, 1-butanol, acetonitrile, acetone, and ethyl acetate over the temperature in the range of 278.15 K to 333.15 K was recorded in Table 2. These are shown in Figure 2. The relative deviations (RD) between the experimental values and the calculated values are also presented in Table 2. The RD is defined as follows: x − xci RD = i xi (1)

ln x = A +

B T

(7)

where x is the mole fraction solubility of GA4, T is the Kelvin temperature in corresponding. The parameters of A and B are recorded in Table 5. 3.2. Thermodynamic Parameters. The van’t Hoff analysis is a common method in the thermodynamic field. The standard molar dissolution enthalpy (ΔsolnH0m) is expressed as ⎛ ∂ln x ⎞ Δsoln Hm0 = −R × ⎜ ⎟ ⎝ ∂(1/T ) ⎠ 2105

(8) DOI: 10.1021/acs.jced.5b00190 J. Chem. Eng. Data 2015, 60, 2104−2109


Article

Table 2. Mole Fraction Solubilities, x, of GA4 in Different Organic Solvents with the Temperature Range from 278.15 K to 333.15 K under 0.1 MPaa T

100x

K

a

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

0.0009 0.0012 0.0017 0.0021 0.0028 0.0034 0.0044 0.0053 0.0061 0.0073 0.0092 0.0120

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

4.6570 5.0966 5.5927 6.3657 7.0533 7.4272 8.0533 8.8152 9.3331 10.0583 10.9745 12.0779

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

0.0809 0.0911 0.1067 0.1179 0.1327 0.1592 0.1874 0.2171 0.2565 0.2726 0.3184 0.3873

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

6.9068 7.4513 7.7496 8.5934 9.1604 9.6862 10.2519 10.9526 11.9738 12.3285 13.1368 14.0276

T

100RD eq 2 water −21.41 −9.58 −3.88 −0.25 3.76 2.21 7.97 4.79 −1.56 −5.03 −3.50 2.67 methanol −1.11 −1.71 −1.75 2.12 3.51 0.14 −0.14 0.73 −1.52 −1.81 −0.65 1.52 ethanol 1.09 −0.47 1.66 −2.14 −4.39 −0.16 1.91 2.24 4.40 −4.04 −3.07 1.91 isopropanol 0.29 0.71 −2.40 1.10 0.80 −0.17 −0.91 −0.58 2.16 −0.93 −0.49 0.28

eq 4

100x

K

eq 7

100RD eq 2

−4.61 1.02 2.47 2.94 4.63 1.51 6.39 2.78 −3.54 −6.37 −3.64 4.03

−3.33 1.94 3.12 3.36 4.85 1.58 6.34 2.64 −3.71 −6.52 −3.69 4.15

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

5.8815 6.1264 6.7402 7.2298 7.6158 7.9769 8.3567 8.7226 9.3133 10.0278 10.8891 11.9046

−1.69 −2.06 −1.91 2.12 3.63 0.35 0.11 0.98 −1.33 −1.72 −0.73 1.22

−0.28 −1.24 −1.57 2.07 3.32 −0.15 −0.45 0.45 −1.73 −1.88 −0.55 1.84

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

0.3906 0.4573 0.5294 0.6469 0.7763 0.9065 1.0773 1.2364 1.3508 1.4933 1.6788 1.8842

10.05 5.28 4.58 −1.30 −5.17 −1.93 −0.29 0.06 2.69 −5.01 −2.78 3.66

11.90 6.64 5.43 −0.87 −5.11 −2.15 −0.69 −0.41 2.28 −5.29 −2.78 4.06

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

5.2979 5.6971 5.9557 6.4481 6.9201 7.5864 8.0128 8.6170 9.1703 9.8267 10.5994 11.1910

−0.37 0.33 −2.54 1.16 1.00 0.12 −0.58 −0.27 2.38 −0.85 −0.62 −0.14

1.27 1.22 −2.24 0.99 0.51 −0.56 −1.33 −0.95 1.92 −1.00 −0.32 0.74

278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15

1.0515 1.1811 1.3432 1.5653 1.7201 1.9455 2.1150 2.3853 2.6497 2.9870 3.2476 3.5657

1-butanol −2.23 −2.93 1.57 3.16 2.72 1.47 −0.01 −2.11 −2.12 −1.47 −0.14 1.69 acetonitrile 4.92 0.22 −4.41 −2.16 −0.53 −0.48 2.39 2.83 −0.62 −2.03 −0.85 0.98 acetone 0.90 0.98 −1.73 −0.86 −0.82 1.38 −0.07 0.33 −0.27 −0.13 0.73 −0.50 ethyl acetate 0.25 −1.11 −0.81 2.32 0.00 0.90 −1.83 −0.52 −0.44 1.41 −0.05 −0.28

eq 4

eq 7

1.34 −1.13 1.94 2.56 1.48 −0.10 −1.64 −3.52 −3.03 −1.65 0.58 3.45

3.27 −0.01 2.34 2.44 0.98 −0.86 −2.49 −4.32 −3.61 −1.85 0.89 4.37

−8.36 −8.34 −9.00 −3.44 0.47 1.97 5.47 5.94 1.98 −0.65 −1.35 −1.98

−6.77 −7.33 −8.49 −3.35 0.27 1.57 4.99 5.45 1.56 −0.87 −1.27 −1.46

1.48 1.24 −1.69 −0.97 −1.02 1.16 −0.28 0.17 −0.36 −0.12 0.82 −0.31

3.25 2.25 −1.30 −1.09 −1.50 0.48 −1.05 −0.54 −0.88 −0.31 1.09 0.56

−1.18 −2.02 −1.27 2.23 0.19 1.28 −1.33 −0.03 −0.04 1.61 −0.15 −0.80

0.68 −0.85 −0.69 2.33 −0.06 0.79 −1.96 −0.65 −0.53 1.37 −0.02 −0.16

The relative standard uncertainty is U(x) = 2 %. The standard uncertainty u are u(T) = 0.05 K, u(p) = 2 KPa.

⎞ ⎛ ∂ln x Δsoln Hm0 = −R × ⎜ ⎟ ⎝ ∂(1/T − 1/Tmean) ⎠

where the parameter of R represents universal gas constant (8.314 J·mol−1·K−1) and T represent the corresponding absolute Kelvin temperature. Also the standard molar dissolution enthalpy can be valid for the mean temperature.15,16 Therefore, we can get eq 9

(9)

where the parameter of Tmean is 305.65 K, which represents the mean temperature of the temperature range. Figure 3 2106



Article

Table 3. Parameters of the Modified Apelblat Model for GA4 in the Different Organic Solvents at Temperature Range from 278.15 K to 333.15 K solvent

A

B

C


−154.13 −11.61 −144.23 −16.82 −105.99 154.27 −41.97 −3.53

3153.16 −920.44 4003.90 −359.97 3727.36 −9508.05 690.03 −1776.61

23.35 2.11 21.80 2.74 15.95 −22.33 6.49 0.95 ∑(102 RAD) = 15.36

102 RAD 5.55 1.39 2.29 0.90 1.80 1.87 0.72 0.83

Table 4. Parameters of the λh Model for GA4 in the Different Organic Solvents solvent

100λ

h

102 RAD


0.47 31.51 3.62 17.67 11.63 15.37 16.55 16.07

884477.30 4230.75 72508.16 4601.36 6099.03 15730.20 5607.86 11523.83 ∑(102 RAD) = 17.34

3.66 1.49 3.57 0.86 1.87 4.08 0.80 1.01

Table 5. Parameters of Ideal Model for GA4 Solubility in the Different Organic Solvents at Temperature Range from 278.15 K to 333.15 K solvents

A

B

102 RAD


3.51 2.58 2.75 1.64 1.34 3.74 1.72 2.89

−4190.31 −1569.59 −2781.42 −1202.66 −1168.85 −2565.16 −1306.12 −2071.47 ∑(102 RAD) = 18.03

3.77 1.29 3.97 1.09 2.28 3.61 1.19 0.83

According the Gibbs equation, we can get the equation of mole entropy of solution (ΔsolnG0m) and the equations of contribution of enthalpy and entropy to standard Gibbs energy.18 The research of the %ξH and %ξS is aimed at comparing the relative contribution to the ΔsolnG0m by entropy and enthalpy in the solution process Δsoln Sm0 = %ξH = Figure 2. Mole fraction solubility (x) of GA4 versus temperature (T) in the selected organic solvents: (a) ☆, water; × , ethanol; +, acetonitrile; ▽, ethyl acetate; (b)◇, isopropanol; ○, methanol; (c) △, 1-butanol; □, acetone.

%ξS =

shows the curves of GA4 with the parameters of ln x and (1/T − 1/Tmean).17 Then the equation of mole Gibbs energy (ΔsolnG0m) is Δsoln Gm0 = − RTmean × intercept

Δsoln Hm0 − Δsoln Gm0 Tmean |Δsoln Hm0|

|Δsoln Hm0| + |T ·Δsoln Sm0|

|T ·Δsoln HS0| |Δsoln Hm0| + |T Δsoln Sm0|

ΔsolnH0m,

ΔsolnS0m,

(11)

× 100% (12)

× 100% (13)

ΔsolnG0m,

The values of %ξH, and %ξS are listed in Table 6. 3.3. Chart Analysis. According Table 2 and Figure 2, we can find that the solubility of GA4 in different solvents is function of

(10) 2107



Article

Table 6. Thermodynamic Parameters of Dissolution of GA4 in the Different Organic Solvents at the Mean Temperature solvents

ΔsolnHom kJ mol


−1

34.49 13.05 21.84 9.93 9.38 22.48 10.67 17.19

ΔsolnSom

ΔsolnGom

%ξH

−1

kJ mol−1

%

%

25.90 6.50 16.10 5.84 6.32 11.84 6.47 9.89

80.06 66.57 79.19 70.81 75.42 67.88 71.79 70.19

19.94 33.43 20.81 29.19 24.58 32.12 28.21 29.81

J mol

−1

K

28.09 21.45 18.78 13.39 10.00 34.81 13.71 23.88

%ξS

solvents. From 278.15 K to 333.15 K, the solubility of GA4 in isopropanol is superior to other selected solvents. (2) The solubility data could be successfully correlated using three equations (van’t Hoff, modified Apelblat, and the λh), and the modified Apelblat fit the data best. (3) According the thermodynamic parameters of van’t Hoff analysis and Gibbs equation, the dissolution process of GA4 is endothermic and nonspontaneous.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This research work was financially supported by Jiangsu Province Agricultural Science and Technology Innovation Fund projects (CX(14)2057), Jiangsu Province Science and Technology Support Plan (BE2014386), Agricultural Science and Technology Achievements Transformation Projects (2014GB2C100317), and Major Projects Supported by the Natural Science Foundation of the Jiangsu Higher Education Institutions (14KJA180001).

■

Figure 3. van’t Hoff plot of the mole fraction solubility (ln x) of GA4 in the selected organic solvents against (1/T − 1/Tmean) with a straight line to correlate the data: (a) ☆, water; × , ethanol; +, acetonitrile; ▽, ethyl acetate; (b) ◇, isopropanol; ○, methanol; △, 1-butanol; □, acetone.

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temperature, whereas the solubility increase with the temperature rising. According Table 6 and Figure 3, the thermodynamic parameters of ΔsolnH0m and ΔsolnG0m are both positive value. Moreover, the main contributor to the standard molar Gibbs energy of solution is the enthalpy during the dissolution because all values of %ξH are ≥66.57 %. All of those mean that the dissolution of GA4 is endothermic, nonspontaneous, and entropy-drive process. According Table 6, the value of ΔsolnG0m which GA4 in the isopropanol is the minimum value among the table. It consistent with our experimental results. And the value of ΔsolnS0m which GA4 in the methanol is bigger than the value which GA4 in 1-butanol and acetone. It proves that the solubility of GA4 in methanol is bigger at high temperature.

4. CONCLUSIONS We can make the following conclusions from Table 2−6 and Figure 1−3: (1) In the temperature range 278.15 K and 333.15 K, the solubility of GA4 in different solvents is increasing with the temperature raising, but the increment is different in different 2108



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Solubility and Solution Thermodynamics of Gibberellin A4 in Different

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