Volumetric and Acoustic Properties of Aqueous Carbohydrate

Article pubs.acs.org/jced

Volumetric and Acoustic Properties of Aqueous Carbohydrate− Polymer Solutions Mehdi Dadkhah Tehrani and Rahmat Sadeghi* Department of Chemistry, University of Kurdistan, Sanandaj, Iran ABSTRACT: Density and sound velocity for solutions of carbohydrates glucose, fructose and sucrose in water and in aqueous solutions of 10% w/w of polymers PPG400, PEG400, PEG4000, and PEG10000 were measured at T = (288.15, 293.15, 298.15, 303.15, and 308.15) K. From the measured experimental data, the isentropic compressibility values of the investigated solutions were determined and from which the values of the hydration numbers of the carbohydrates were calculated. Apparent molar volume and apparent molar isentropic compressibility of the carbohydrates in the investigated solutions were also determined and based of them the sweet properties of the carbohydrates were discussed. Finally, the infinite dilutions apparent molar properties for transfer of the carbohydrates from water to aqueous solutions of different polymers were studied and the results were discussed based on the different interactions exist in the solutions.

1. INTRODUCTION Carbohydrates are the most abundant biomolecules on the surface of the earth, which plays a key role in plant and animal life. Carbohydrates that contain one or more chiral centers have different enantiomer forms, which are distinguished by letters D (dextrorotatory) and L (levorotatory). Among the enantiomers, just form of D is found in nature and form of L is synthesized in the laboratory. Because of the structural diversity of carbohydrates molecules, they can interact with other biomolecules such as lipids, proteins, electrolytes and polymers. It has long been recognized that the mixture of aqueous solutions of some incompatible polymers or of some polymers and electrolytes forms a stable two-phase liquid system, where the only solvent is water. Both equilibrium phases have more than 50% water, and therefore, they are a gentle environment for the biomolecules and can provide a biocompatible media for separation of different biomolecules and thus these systems have a widespread use in biotechnology.1−3 One of the interesting and important properties of carbohydrates is that their aqueous solutions in the presence of polymer can form aqueous biphasic systems (ABS) with a carbohydrate-rich and a polymer-rich aqueous phases for which very little information has been reported in the literature.4,5 Because carbohydrates are of common occurrence in the biochemical, biological, chemical, and food industries, this type of ABS has the additional advantages in relative to the polymer−polymer or polymer−salt ABS. The mechanism of ABS formation is still to a large extent unknown at the molecular level and therefore, studying of the various thermodynamic properties of polymer-carbohydrate aqueous mixtures is necessary for elucidating of phase forming behavior of these systems and also for optimum design of industrial purification and separation process dealing with this type of ABS. Furthermore, these systems are very interesting as © XXXX American Chemical Society

they contain compounds derived from biomass. The volumetric and acoustical properties are important thermodynamics properties for investigation of these systems which can provide some unique information to extend our knowledge about the different interactions between their constituents. Although there is some reports in the literature about the volumetric and acoustic properties of carbohydrates in water,6−9 in aqueous electrolyte solutions,10−16 in aqueous ionic liquid solutions,17−19 and in aqueous amino acid solutions,20,21 as far as we know, there is no any information in the literature about the volumetric and acoustic properties of carbohydrates in aqueous solutions of water-soluble polymers. In this work, in order to obtain further information about the different interactions in aqueous polymer−carbohydrate systems, a comprehensive study of volumetric and compressibility properties at various temperatures (T = 288.15, 293.15, 298.15, 303.15, and 308.15 K) was performed for binary and ternary aqueous systems including: (i) glucose, fructose, and sucrose in water and (ii) glucose, fructose, and sucrose in aqueous solutions of 10% w/w of polymers PPG400, PEG400, PEG4000, and PEG10000. The selected compounds are the simplest carbohydrates and watersoluble polymers.

2. EXPERIMENTAL SECTION 2.1. Materials. The characteristics of the materials used in this work, are listed in the Table 1. All the materials were used without any further purification. Double distilled and deionized water that was used. Received: March 16, 2016 Accepted: July 19, 2016

A

DOI: 10.1021/acs.jced.6b00232 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

concentrated solutions, βsolute has the dominate contribution to the total value of βs and therefore similar to that of pure solute, the values of βs increase by increasing temperature. In Figure 2, the isentropic compressibilities for solutions of glucose, fructose and sucrose in pure water and those of sucrose in aqueous solutions of 10% w/w of PPG400, PEG400, PEG4000 and PEG10000 have been shown at T = 298.15 K. As can be seen, the isentropic compressibility of the investigated aqueous carbohydrate solutions follows the order: glucose > fructose ≫ sucrose, which is the same order of their hydrophobicity. Furthermore, in the presence of polymer the values of isentropic compressibility decrease and the abilities of the polymers in decreasing the isentropic compressibility follow the order: PPG400 > PEG400 > PEG4000 ≅ PEG10000. Since, compressibility of dilute aqueous solutions is mainly due to the effect of pressure on the bulk water, the values of βs decrease as the number of water molecules affected by the solutes increases. The hydration numbers of carbohydrates in 1 kg of pure

Table 1. Physical Properties of the Used Chemicals chemical

source

puritya (% w/w)

purification method

D(+)-glucose

Merck Merck Merck Merck Merck Merck Aldrich

≥0.995 ≥0.99 ≥0.98

no no no no no no no

D(−)-fructose

sucrose PEG400 PEG4000 PEG10000 PPG400 a

Declared by supplier.

2.2. Method of Measurement. All the solutions were prepared by mass on a Sartorius CP124S balance precisely within ±1 × 10−7 kg. Density and sound velocity of the solutions were measured by using a high precision vibratingtube analyzer and sound velocity measuring device, with automatic viscosity corrections (Anton Paar DSA 5000, Austria). It can measure the density in the range of (0 to 3) g·cm−3 and speed of sound from (1000 to 2000) m·s−1, simultaneously at temperatures from (273.15 to 343.15) K, with a pressure variation of (0 to 0.3) MPa at low frequency (approximately 3 MHz). Temperature of the cell is controlled by a Peltier device within a precision of ±1· 10−3 K. The calibration of the instrument was made with degassed and double distilled water and dry air at atmospheric pressure according to the instruction manual of the instrument.

water, nh, calculated from the equation nh =

55.51 m

(

1−

βs β° s

8

)

have been shown in Figure 3. In this figure, the values for glucose in aqueous solutions of 10% w/w of PEG400 have also been shown. As expected, the calculated values of nh decrease in the presence of polymer and also they decrease by increasing temperature. Furthermore, the values of hydration number for the investigated carbohydrates decrease in the order: sucrose ≫ fructose > glucose. Both of glucose and fructose are hexose monosaccharides and sucrose is a disaccharide. As can be seen, because of a cooperativity effect, sucrose has larger hydration number values than monosaccharides glucose and fructose. 3.2. Apparent Molar Volume. The measured density data were used to calculate the apparent molar volume, Vϕ, of the carbohydrates in the investigated solutions by the following equation:

3. RESULTS AND DISCUSSION In order to study the effect of water-soluble polymers on the volumetric and compressibility properties of carbohydrates in aqueous solutions, the density and sound velocity of solutions of carbohydrates glucose, fructose, and sucrose in water and in aqueous solutions 10% w/w of polymers PPG400, PEG400, PEG4000, and PEG10000 were measured at temperatures 288.15, 293.15, 298.15, 303.15, and 308.15 K. The measured density and sound velocity data have been reported in Table 2. 3.1. Isentropic Compressibility. Isentropic compressibil1 ∂V ity of solutions, βs, which is defined as βS = − V ∂P , can be

Vϕ =

1000 M (d ° − d ) + mdd° d

(2)

where M is the molecular mass of the carbohydrate, m is its molality, d° and d are densities of solvent and solution, respectively. In the case of ternary systems, polymer + water (aqueous solutions of 10% w/w of polymers) was taken as the solvent. As an example, Figure 4 shows the concentration dependence of apparent molar volume of glucose in pure water at different temperatures. The similar behavior was obtained for the other systems investigated in this work. As can be seen, the apparent molar volumes of the carbohydrates in the investigated aqueous solutions increase by increasing temperature and carbohydrate concentration (as those observed for aqueous electrolyte solutions28). The apparent molar volume of solutes in aqueous solutions can be considered as the sum of the intrinsic volume (positive contributions) of the solute and the volume contribution due to the solute−water interactions (negative contributions due to the electrostriction):8

( )S

calculated from the experimental density and sound velocity data by using the Laplace−Newton equation 1 βS = 2 (1) du where d and u are density and sound velocity, respectively. As shown in Figure 1, isentropic compressibility isotherms of aqueous glucose solutions decrease with increasing glucose concentration. Furthermore, at low carbohydrate concentrations, the values of βs decrease by increasing temperature. However, by increasing the concentration of carbohydrate, the temperature dependency of βs decreases so that at a specific carbohydrate concentration the isentropic compressibility isotherms are crossing and after that the values of βs increase by increasing temperature. The similar behaviors were obtained for the other systems investigated in this work. This is a common behavior for different aqueous solutions such as electrolytes,22 polymers,23−25 and ionic liquids.26,27 In aqueous solutions, βs can be considered as a sum of two contributions: βsolvent and βsolute. For the dilute solutions, βsolvent has the dominate contribution to the total value of βs and therefore at this concentration region the trends observed for temperature dependency are same as those for pure water. For the

Vϕ = Vintr + Vsolute − water

(3)

Overall the carbohydrates have small apparent molar volume due to extensive solute-water interactions.8 Increasing the values of Vϕ by increasing the carbohydrate molality may be related to the appearance of the solute−solute interactions in solution and therefore the liberation of structured water around the carbohydrate (decreasing the electrostriction).29 In addition, by increasing the temperature thermal kinetic energy B



Article

Table 2. Experimental Density, d, and Sound Velocity, u, Data of Solutions of the Investigated Carbohydrates in Water and in Aqueous Solutions of Various Polymers As a Function of Molality of Carbohydrate, m/(mol·kg−1), at Different Temperatures, T, and 845 hPaa m/(mol·kg−1)

T = 288.15 K

T = 293.15 K

T = 298.15 K

T = 303.15 K

T = 308.15 K

−3

−3

−3

−3

−3

10 d/ (kg·m−3)

u/ (m·s−1)

0.29209 0.48364 0.61638 0.97953 1.38773 1.85000 2.37871 2.98873 3.70006

1.018667 1.030776 1.038846 1.059739 1.081243 1.103582 1.126539 1.150244 1.174742

1485.76 1498.38 1507.04 1530.31 1555.59 1583.62 1613.59 1646.03 1681.16

0.17195 0.23149 0.29264 0.35487 0.48387 0.61711 0.75815 0.98057

1.027255 1.031127 1.035072 1.038980 1.046914 1.054876 1.063026 1.075373

1542.64 1546.50 1550.54 1554.45 1562.56 1570.88 1579.55 1593.04

0.17173 0.23160 0.29222 0.35463 0.48306 0.61722 0.75691 0.98013

1.028059 1.031960 1.035835 1.039763 1.047602 1.055685 1.063698 1.076119

1543.93 1547.84 1551.77 1555.76 1563.79 1572.38 1580.98 1594.65

0.17171 0.20170 0.26177 0.29225 0.48313 0.61694 0.75729 0.97990

1.028188 1.030136 1.034013 1.035977 1.047840 1.055782 1.063915 1.076203

1544.05 1546.02 1549.91 1551.98 1564.24 1572.54 1581.31 1594.81

0.11361 0.17199 0.29224 0.35548 0.48273 0.61769 0.75737 0.97979

1.016263 1.020142 1.027943 1.031965 1.039877 1.047997 1.056120 1.068575

1544.71 1548.36 1555.88 1559.81 1567.54 1575.61 1583.90 1596.98

0.17163 0.23122 0.29200 0.48254 0.61606 0.97866 1.38584 1.85058 2.37858 2.98084

1.011004 1.015033 1.019075 1.031390 1.039698 1.061056 1.083133 1.106016 1.129632 1.153680

1478.94 1483.23 1487.53 1500.94 1510.17 1534.74 1561.60 1588.90 1622.09 1655.53

10 d/ (kg·m−3)

u/ (m·s−1)

10 d/ (kg·m−3)

u/ (m·s−1)

10 d/ (kg·m−3)

Glucose in Water 1.017625 1500.97 1.016335 1514.33 1.014826 1.029641 1513.04 1.028275 1525.93 1.026702 1.037656 1521.33 1.036240 1533.87 1.034620 1.058399 1543.58 1.056857 1555.20 1.055125 1.079760 1567.80 1.078087 1578.39 1.076245 1.101948 1594.67 1.100145 1604.16 1.098183 1.124767 1623.32 1.122847 1631.65 1.120786 1.148340 1654.38 1.146303 1661.43 1.144137 1.172710 1688.05 1.170559 1693.76 1.168296 Glucose in Aqueous Solutions of 10% w/w PEG400 1.025900 1553.15 1.024331 1562.18 1.022564 1.029746 1556.87 1.028151 1565.73 1.026366 1.033664 1560.73 1.032047 1569.43 1.030238 1.037543 1564.45 1.035903 1573.01 1.034074 1.045424 1572.22 1.043736 1580.47 1.041867 1.053333 1580.20 1.051601 1588.14 1.049691 1.061432 1588.53 1.059651 1596.15 1.057700 1.073697 1601.47 1.071848 1608.55 1.069837 Glucose in Aqueous Solutions of 10% w/w PEG4000 1.026670 1554.37 1.025065 1563.33 1.023267 1.030542 1558.13 1.028913 1566.92 1.027096 1.034389 1561.90 1.032738 1570.52 1.030898 1.038291 1565.70 1.036615 1574.15 1.034757 1.046080 1573.38 1.044359 1581.53 1.042461 1.054109 1581.60 1.052341 1589.41 1.050398 1.062071 1589.84 1.060258 1597.32 1.058277 1.074412 1602.95 1.072530 1609.91 1.070491 Glucose in Aqueous Solutions of 10% w/w PEG10000 1.026792 1554.51 1.025187 1563.43 1.023382 1.028727 1556.20 1.027107 1565.21 1.025294 1.032577 1560.10 1.030935 1568.78 1.029101 1.034527 1562.07 1.032873 1570.67 1.031030 1.046312 1573.60 1.044589 1581.88 1.042685 1.054202 1581.76 1.052431 1589.55 1.050485 1.062281 1590.15 1.060463 1597.62 1.058479 1.074490 1603.09 1.072607 1610.03 1.070562 Glucose in Aqueous Solutions of 10% w/w PPG400 1.014919 1554.22 1.013339 1562.21 1.011545 1.018769 1557.74 1.017170 1565.54 1.015357 1.026518 1564.89 1.024868 1572.39 1.023013 1.030510 1568.65 1.028833 1576.01 1.026955 1.038363 1576.08 1.036633 1583.11 1.034724 1.046430 1583.78 1.044658 1590.52 1.042697 1.054498 1591.73 1.052678 1598.16 1.050677 1.066872 1604.23 1.064985 1610.12 1.062921 Fructose in Water 1.010002 1494.40 1.008734 1507.97 1.007236 1.013994 1498.46 1.012689 1511.81 1.011161 1.018005 1502.56 1.016665 1515.69 1.015102 1.030211 1515.27 1.028763 1527.80 1.027103 1.038453 1524.11 1.036933 1536.18 1.035207 1.05967 1547.46 1.057916 1558.36 1.056019 1.081504 1572.94 1.079615 1582.54 1.077546 1.104263 1599.13 1.102197 1607.48 1.099942 1.127755 1630.78 1.125515 1637.59 1.123093 1.151662 1662.70 1.149245 1667.97 1.146655 C

u/ (m·s−1)

10 d/ (kg·m−3)

u/ (m·s−1)

1525.97 1537.11 1544.71 1565.21 1587.42 1612.19 1638.60 1667.24 1698.32

1.013115 1.024930 1.032809 1.053218 1.074241 1.096072 1.118584 1.141851 1.165923

1535.94 1546.62 1553.95 1573.64 1595.01 1618.83 1644.26 1671.83 1701.78

1569.75 1573.15 1576.70 1580.15 1587.33 1594.75 1602.41 1614.34

1.020575 1.024370 1.028220 1.032068 1.039824 1.047613 1.055588 1.067672

1575.96 1579.24 1582.61 1585.96 1592.92 1600.00 1607.40 1618.88

1570.79 1574.22 1577.67 1581.18 1588.30 1595.85 1603.45 1615.54

1.021284 1.025094 1.028881 1.032721 1.040390 1.048292 1.056136 1.068295

1576.82 1580.23 1583.45 1586.83 1593.69 1601.01 1608.29 1619.91

1570.89 1572.65 1576.06 1577.81 1588.60 1595.98 1603.71 1615.65

1.021398 1.023300 1.027088 1.029009 1.040607 1.048376 1.056332 1.068364

1576.98 1578.58 1581.88 1583.62 1594.02 1601.11 1608.56 1620.03

1568.66 1571.85 1578.45 1581.86 1588.69 1595.84 1603.15 1614.63

1.009553 1.013347 1.020965 1.024889 1.032618 1.040559 1.048501 1.060692

1573.65 1576.78 1583.05 1586.33 1592.91 1599.77 1606.80 1617.80

1519.76 1523.42 1527.14 1538.59 1546.53 1567.66 1590.65 1614.32 1642.98 1671.93

1.005535 1.009429 1.013338 1.025249 1.033290 1.053949 1.075318 1.097551 1.120529 1.143925

1529.92 1533.40 1536.90 1547.78 1555.34 1575.45 1597.31 1619.88 1647.15 1674.71



Article

Table 2. continued m/(mol·kg−1)

T = 288.15 K 10−3d/ (kg·m−3)

u/ (m·s−1)

3.66681

1.178118

1690.96

0.17187 0.23164 0.29267 0.35501 0.48352 0.61780 0.75821 0.98073

1.027509 1.031485 1.035489 1.039528 1.047640 1.055853 1.064204 1.076905

1543.51 1547.62 1551.88 1556.18 1564.88 1573.82 1583.07 1597.50

0.11339 0.17181 0.23144 0.29247 0.35480 0.48363 0.61793 0.75722

1.024397 1.028330 1.032294 1.036306 1.040301 1.048443 1.056660 1.064925

1540.51 1544.60 1548.78 1553.08 1557.30 1566.11 1575.15 1584.42

0.11407 0.17207 0.23162 0.35483 0.48307 0.61750 0.75726 0.97998

1.024546 1.028461 1.032430 1.040451 1.048552 1.056797 1.065046 1.077698

1540.87 1545.02 1549.22 1557.76 1566.53 1575.57 1584.83 1599.25

0.17199 0.23169 0.29269 0.35509 0.48406 0.61855 0.75826 0.98031

1.020426 1.024422 1.028446 1.032511 1.040696 1.048990 1.057325 1.070088

1549.28 1553.28 1557.36 1561.62 1569.89 1578.49 1587.34 1601.23

0.09036 0.12173 0.15375 0.25383 0.32449 0.51561 0.72903 0.97360 1.25221 1.57329 1.94767

1.010864 1.014832 1.018819 1.030977 1.039250 1.060407 1.082254 1.105099 1.128743 1.153122 1.178478

1475.39 1478.47 1481.61 1491.45 1498.33 1516.83 1537.29 1559.88 1585.22 1613.01 1643.78

0.09050 0.12190 0.15392 0.18696 0.25459 0.32536 0.39885 0.51658

1.027333 1.031260 1.035195 1.039205 1.047221 1.055336 1.063557 1.076150

1540.12 1543.13 1546.17 1549.31 1555.68 1562.22 1569.04 1579.86

T = 293.15 K 10−3d/ (kg·m−3)

u/ (m·s−1)

T = 298.15 K 10−3d/ (kg·m−3)

u/ (m·s−1)

T = 303.15 K 10−3d/ (kg·m−3)

Fructose in Water 1.175942 1696.47 1.173338 1700.11 1.170575 Fructose in Aqueous Solutions of 10% w/w PEG400 1.026123 1553.84 1.024518 1562.71 1.022714 1.030062 1557.78 1.028423 1566.46 1.026589 1.034028 1561.80 1.032353 1570.24 1.030485 1.038029 1565.86 1.036317 1574.10 1.034418 1.046065 1574.08 1.044279 1581.88 1.042314 1.054200 1582.58 1.052345 1589.98 1.050316 1.062489 1591.39 1.060564 1598.35 1.058469 1.075066 1605.09 1.073028 1611.31 1.070831 Fructose in Aqueous Solutions of 10% w/w PEG4000 1.023017 1550.99 1.021412 1559.99 1.019612 1.026915 1554.89 1.025280 1563.67 1.023443 1.030844 1558.87 1.029175 1567.42 1.027308 1.034816 1562.91 1.033106 1571.25 1.031208 1.038781 1566.94 1.037041 1575.06 1.035107 1.046855 1575.28 1.045041 1582.99 1.043045 1.055001 1583.86 1.053121 1591.11 1.051055 1.063178 1592.63 1.061225 1599.43 1.059092 Fructose in Aqueous Solutions of 10% w/w PEG10000 1.023161 1551.36 1.021555 1560.34 1.019749 1.027051 1555.28 1.025408 1564.04 1.023572 1.030985 1559.26 1.029308 1567.79 1.027436 1.038917 1567.33 1.037171 1575.42 1.035234 1.046943 1575.62 1.045128 1583.30 1.043126 1.055114 1584.23 1.053226 1591.47 1.051153 1.063295 1593.00 1.061341 1599.79 1.059200 1.075850 1606.72 1.073790 1612.80 1.071552 Fructose in Aqueous Solutions of 10% w/w PPG400 1.019018 1558.44 1.017380 1566.10 1.015529 1.022975 1562.22 1.021298 1569.67 1.019414 1.026965 1566.11 1.025254 1573.34 1.023340 1.030982 1570.07 1.029235 1577.04 1.027282 1.039101 1577.94 1.037281 1584.55 1.035266 1.047310 1586.08 1.045414 1592.23 1.043335 1.055574 1594.48 1.053612 1600.20 1.051457 1.068185 1607.55 1.066096 1612.55 1.063834 Sucrose in Water 1.009894 1491.08 1.008671 1504.89 1.007217 1.013837 1494.04 1.012590 1507.70 1.011118 1.017798 1497.04 1.016530 1510.57 1.015037 1.029882 1506.38 1.028548 1519.52 1.026998 1.038103 1512.97 1.036727 1525.84 1.035138 1.059134 1530.68 1.057642 1542.76 1.055956 1.080848 1550.19 1.079246 1561.47 1.077458 1.103563 1571.89 1.101844 1582.23 1.099956 1.127074 1596.09 1.125240 1605.44 1.123248 1.151325 1622.67 1.149376 1630.91 1.147284 1.176549 1652.12 1.174484 1659.12 1.172292 Sucrose in Aqueous Solutions of 10% w/w PEG400 1.025991 1550.72 1.024432 1559.87 1.022677 1.029897 1553.59 1.028321 1562.60 1.026545 1.033810 1556.51 1.032213 1565.39 1.030424 1.037797 1559.52 1.036179 1568.26 1.034366 1.045761 1565.64 1.044100 1574.09 1.042267 1.053838 1571.85 1.052140 1580.06 1.050261 1.062010 1578.39 1.060272 1586.38 1.058358 1.074535 1588.77 1.072733 1596.29 1.070768 D

T = 308.15 K

u/ (m·s−1)

10−3d/ (kg·m−3)

u/ (m·s−1)

1702.54

1.167687

1703.93

1570.12 1573.64 1577.25 1580.94 1588.31 1595.99 1603.94 1616.29

1.020700 1.024560 1.028440 1.032341 1.040179 1.048122 1.056209 1.068484

1576.17 1579.50 1582.91 1586.43 1593.45 1600.77 1608.34 1620.08

1567.48 1570.97 1574.52 1578.14 1581.77 1589.29 1597.00 1604.89

1.017625 1.021428 1.025262 1.029132 1.033000 1.040881 1.048830 1.056813

1573.55 1576.87 1580.25 1583.68 1587.14 1594.27 1601.61 1609.12

1567.83 1571.30 1574.87 1582.10 1589.58 1597.34 1605.24 1617.59

1.017758 1.021551 1.025387 1.033127 1.040956 1.048927 1.056918 1.069173

1573.90 1577.20 1580.60 1587.47 1594.59 1602.00 1609.44 1621.19

1572.25 1575.61 1579.07 1582.61 1589.68 1597.00 1604.57 1616.23

1.013482 1.017340 1.021233 1.025147 1.033067 1.041075 1.049138 1.061425

1577.04 1580.20 1583.43 1586.80 1593.50 1600.44 1607.60 1618.68

1516.88 1519.60 1522.34 1530.93 1536.98 1553.19 1571.12 1591.05 1613.28 1637.73 1664.85

1.005552 1.009435 1.013339 1.025251 1.033353 1.054085 1.075500 1.097905 1.121111 1.145055 1.169977

1527.28 1529.82 1532.45 1540.73 1546.51 1562.03 1579.22 1598.39 1619.73 1643.25 1669.34

1567.50 1570.11 1572.81 1575.57 1581.13 1586.89 1592.94 1602.50

1.020699 1.024570 1.028440 1.032377 1.040246 1.048208 1.056272 1.068638

1573.80 1576.26 1578.84 1581.48 1586.85 1592.42 1598.26 1607.38



Article

Table 2. continued m/(mol·kg−1)

T = 288.15 K 10−3d/ (kg·m−3)

u/ (m·s−1)

0.05984 0.09067 0.12183 0.15400 0.18690 0.25463 0.32465 0.39923

1.024277 1.028194 1.032082 1.036026 1.039995 1.048022 1.056085 1.064400

1538.36 1541.30 1544.38 1547.38 1550.51 1556.92 1563.60 1570.62

0.09037 0.12186 0.15387 0.18657 0.25440 0.32529 0.39896 0.51608

1.028307 1.032202 1.036137 1.040110 1.048145 1.056294 1.064542 1.077070

1541.57 1544.46 1547.54 1550.68 1557.15 1563.86 1570.86 1581.80

0.07503 0.10613 0.15415 0.18706 0.25451 0.32577 0.40040 0.51749

1.018269 1.022199 1.028158 1.032163 1.040212 1.048477 1.056864 1.069465

1544.39 1547.26 1551.78 1554.67 1560.83 1567.27 1573.97 1584.47

T = 293.15 K 10−3d/ (kg·m−3)

u/ (m·s−1)

T = 298.15 K 10−3d/ (kg·m−3)

u/ (m·s−1)

T = 303.15 K 10−3d/ (kg·m−3)

Sucrose in Aqueous Solutions of 10% w/w PEG4000 1.022925 1549.01 1.021353 1558.17 1.019580 1.026816 1551.86 1.025225 1560.91 1.023435 1.030682 1554.78 1.029071 1563.69 1.027265 1.034605 1557.66 1.032973 1566.44 1.031150 1.038551 1560.64 1.036900 1569.28 1.035058 1.046534 1566.78 1.044843 1575.14 1.042967 1.054550 1573.12 1.052819 1581.23 1.050908 1.062818 1579.85 1.061048 1587.67 1.059099 Sucrose in Aqueous Solutions of 10% w/w PEG10000 1.026928 1552.03 1.025333 1561.05 1.023541 1.030801 1554.85 1.029187 1563.75 1.027378 1.034714 1557.79 1.033079 1566.54 1.031252 1.038662 1560.79 1.037008 1569.40 1.035163 1.046652 1566.97 1.044959 1575.30 1.043077 1.054755 1573.36 1.053020 1581.43 1.051105 1.062957 1580.07 1.061184 1587.07 1.059232 1.075419 1590.55 1.073584 1597.90 1.071579 Sucrose in Aqueous Solutions of 10% w/w PPG400 1.016922 1553.95 1.015342 1561.96 1.013550 1.020832 1556.67 1.019231 1564.54 1.017419 1.026755 1560.98 1.025126 1568.63 1.023288 1.030737 1563.77 1.029086 1571.34 1.027230 1.038740 1569.63 1.037048 1576.91 1.035157 1.046955 1575.75 1.045222 1582.80 1.043293 1.055295 1582.21 1.053517 1588.97 1.051553 1.067825 1592.20 1.065998 1598.54 1.063982

T = 308.15 K

u/ (m·s−1)

10−3d/ (kg·m−3)

u/ (m·s−1)

1565.85 1568.47 1571.09 1573.72 1576.45 1582.07 1587.91 1594.10

1.017621 1.021460 1.025275 1.029145 1.033039 1.040916 1.048828 1.056988

1572.05 1574.58 1577.15 1579.63 1582.24 1587.68 1593.27 1599.19

1568.56 1571.15 1573.81 1576.58 1582.23 1588.09 1594.28 1603.91

1.021561 1.025385 1.029244 1.033140 1.041022 1.049020 1.057116 1.069416

1574.67 1577.18 1579.75 1582.34 1587.77 1593.42 1599.36 1608.60

1568.41 1570.90 1574.81 1577.40 1582.79 1588.39 1594.33 1603.48

1.011556 1.015410 1.021255 1.025180 1.033077 1.041182 1.049410 1.061788

1573.43 1575.82 1579.58 1582.03 1587.19 1592.61 1598.31 1607.08

The combined standard uncertainties in molality, density, speed of sound, temperature, and pressure were 2 × 10−5 mol.kg−1, 0.15 kg·m−3, 0.5 m· s−1, 0.005 K, and 10 hPa, respectively.

a

Figure 1. Plot of isentropic compressibility, βs, for solutions of glucose in water at different temperatures: ○, 288.15 K; × , 293.15 K; ▲, 298.15 K; ◇, 303.15 K; □, 308.15 K.

Figure 2. Plot of isentropic compressibility, βs, for solutions of glucose, fructose and sucrose in pure water and those of sucrose in aqueous solutions of 10% w/w of PPG400, PEG400, PEG4000 and PEG10000 at T = 298.15. ○, glucose in pure water; ▲, fructose in pure water; × , sucrose in pure water; △, sucrose in PPG400(aq); ◇, sucrose in PEG400(aq); □, sucrose in PEG4000(aq); + , sucrose in PEG10000(aq).

of water molecules is increased and then their interactions with carbohydrate molecules are weakened. This phenomenon leads to irregular carbohydrate hydration layer and finally, the release of a number of water molecules around the carbohydrate molecules which reduces the pressure on these molecules and increasing the volume of the carbohydrate. As can be seen from

Figure 3, the calculated values of the hydration number decrease by increasing both the temperature and carbohydrate E



Article

apparent molar volume than monosaccharides glucose and fructose. Although glucose and fructose have a same molecular mass (constitutional isomers), the values of Vϕ for glucose are larger than those for fructose. This can be attributed to this fact that fructose because of the higher hydrophilicity has a stronger interaction with water and therefore more electrostriction than glucose. As can be seen from Figure 3, the calculated values of the hydration numbers for fructose are larger than those for glucose. The apparent specific volume, vϕ = Vϕ/M, is an important parameter which distinguishes the sweeteners on the basis of their taste qualities in aqueous solutions.30 The four basic taste ranges have been defined on the basis of vϕ values, that is, salt (vϕ < 3.3 × 10−4 m3·kg−1), sour (3.3 × 10−4 < vϕ < 5.2 × 10−4 m3·kg−1), sweet (5.2 × 10−4 < vϕ < 7.1 × 10−4 m3·kg−1), and bitter (7.1 × 10−4 < vϕ < 9.3 × 10−4 m3·kg−1).31 As can be seen from Figure 6, the vϕ values for the studied saccharides in pure water and in the investigated polymer solutions follow the order: glucose > sucrose > fructose and they fall within the sweet taste range. Figure 6 also shows that there is a good agreement between our experimental apparent specific volume data and those taken from the literature. The infinite dilution apparent molar volumes, V0Φ, which provide valuable information about the solute−solvent interactions, were obtained by least-squares fitting of the following relation to VΦ data:

Figure 3. Plot of hydration number, nh, for glucose, fructose and sucrose in pure water. ○, glucose at 298.15 K; ▲, fructose at 298.15 K; □, sucrose at 308.15 K; × , sucrose at 298.15 K; ◇, sucrose at 288.15 K; + , glucose in PEG400(aq) at 298.15 K.

concentration. In Figure 5, the apparent molar volume for glucose, fructose and sucrose in pure water and those for sucrose in aqueous solutions of 10% w/w of PPG400, PEG400, PEG4000, and PEG10000 have been shown at T = 298.15 K. The values of Vϕ of all the investigated carbohydrates in aqueous solutions increase in the presence of polymer. Because of the polymer−water hydrogen bond interactions, hydrogen bond interactions between water and carbohydrate molecules are weakened which results in the reduction of water molecules around the carbohydrate molecules and therefore increasing Vϕ. As expected, sucrose which is a disaccharide has a larger

VΦ = V Φ0 + bv m

(4)

where bv is respective experimental slope. The calculated values of V0Φ and bv for the investigated systems are given in Table 3. In Table 3, VΦ0 values of the investigated carohydrates in pure water have been compared with the values reported in the literature at 298.15 K and a fairly good agreement has been obtained. V0Φ and bv are indicative of solute−solvent and solute−solute interactions, respectively. The values of bv

Figure 4. Plot of apparent molar volume, Vϕ, of glucose in water as a function of molality at different temperatures: ○, 288.15 K; × , 293.15 K; ▲, 298.15 K; ◇, 303.15 K; □, 308.15 K. F



Article

Figure 5. Apparent molar volume of glucose and fructose in pure water (a) and those of sucrose in pure water and in aqueous solutions of 10% w/w of PPG400, PEG400, PEG4000, and PEG10000 (b) at 298.15 K. ○, glucose in pure water; ▲, fructose in pure water; × , sucrose in pure water; △, sucrose in PPG400(aq); ◇, sucrose in PEG400(aq); □, sucrose in PEG4000(aq); + , sucrose in PEG10000(aq).

Figure 6. (a) Apparent specific volume of glucose, fructose and sucrose in pure water at 298.15 K: ○, glucose (this work); △, fructose (this work); □, sucrose (this work); ●, glucose (ref 35); ▲, fructose(ref 35); × , sucrose (ref 36). (b) Apparent specific volume of sucrose in pure water and in aqueous solutions of 10% w/w of PPG400, PEG400, PEG4000, and PEG10000 at 298.15 K: × , sucrose in pure water; △, sucrose in PPG400(aq); ◇, sucrose in PEG400(aq); □, sucrose in PEG4000(aq); + , sucrose in PEG10000(aq).

aqueous polymer solution) − V0Φ (carbohydrate in pure water), and are also given in Table 3. Table 3 shows that the calculated values of ΔV0Φ are positive and decrease by increasing the temperature. Furthermore, the values of ΔV0Φ for sucrose are larger than those for glucose and fructose. Our experiments show that aqueous PPG−carbohydrate systems form aqueous two-phase system and therefore the investigated carbohydrates have a soluting-out effect on the aqueous PPG solutions. However, aqueous PEG−carbohydrate systems cannot form aqueous two-phase systems (soluting-in effect). So, in the aqueous PPG-carbohydrate systems, positive values of ΔV0Φ can also be attributed to the repulsive force due

increase by addition of polymer as well as by decreasing temperature. The larger positive values of bv in the aqueous polymer solutions than pure water suggest that the carbohydrate−carbohydrate interactions increase in the presence of polymer. The strong attractive interactions between the polymers and water molecule induce the dehydration of carbohydrates molecules and therefore increase the carbohydrate-carbohydrate interactions. Table 3 shows that the carbohydrates molecules are larger in size in aqueous polymer solutions than in pure water. The infinite dilution apparent molar volumes of transfer, ΔV0Φ, defined as V0Φ (carbohydrate in G


110.9501 111.4906 111.9656 112.4080 112.7876

111.0412 111.5721 112.0654 112.4946 112.9000

110.9357 111.4793 111.9704 112.4099 112.8104

110.8924 111.4421 111.9455 112.4094 112.8356

109.4397 110.1094 110.7893 111.09b 110.8c 111.04e 111.4367 112.0221

288.15 293.15 298.15 303.15 308.15

288.15 293.15 298.15 303.15 308.15

288.15 293.15 298.15 303.15 308.15

288.15 293.15 298.15 303.15 308.15

288.15 293.15 298.15

H

303.15 308.15

303.15 308.15

110.8799 111.4414 111.9510 111.7a 111.87b 111.89e 112.4020 112.8175

106 V0Φ/m3·mol−1

288.15 293.15 298.15

T/K

0.4660 0.4453

0.6155 0.5487 0.5049

0.9090 0.8581 0.8103 0.7600 0.7244

0.9696 0.9012 0.8500 0.8134 0.7937

0.9131 0.8572 0.8016 0.7781 0.7492

0.9500 0.8886 0.8524 0.8169 0.7575

0.5377 0.5179

0.6447 0.6007 0.5620

106 bv/kg·m3·mol−2

0.124 0.118

−1.7772 −1.5295

0.3552 0.3311

0.4845 0.4347 0.3894

0.4504 0.3987 0.3560 0.3213 0.2899

0.4885 0.4321 0.4201 0.3937 0.3690

0.4779 0.4342 0.4044 0.3685 0.3395

0.4598 0.4083 0.3875 0.3456 0.3228

0.2502 0.2323

1014 bk / kg·m3 ·mol−2·Pa−1

0.087 −1.4266 0.077 −1.2344 Glucose in Aqueous Solution 10% w/w PEG400 0.0702 0.112 −1.7018 0.0492 0.102 −1.4591 0.0147 0.092 −1.2736 0.0060 0.082 −1.0887 −0.0300 0.072 −0.9435 Glucose in Aqueous Solution 10% w/w PEG4000 0.1613 0.111 −1.7216 0.1307 0.102 −1.4849 0.1145 0.093 −1.2864 0.0927 0.084 −1.1061 0.0826 0.075 −0.9506 Glucose in Aqueous Solution 10% w/w PEG10000 0.0558 0.113 −1.7452 0.0379 0.103 −1.4965 0.0194 0.094 −1.3145 0.0079 0.084 −1.1396 −0.0071 0.074 −0.9899 Glucose in Aqueous Solution 10% w/w Ppg400 0.0125 0.116 −1.6395 0.0007 0.106 −1.4019 −0.0055 0.097 −1.1976 0.0074 0.088 −1.0214 0.0181 0.078 −0.8641 Fructose in Water 0.141 −2.7836 0.136 −2.4128 0.130 −2.0701 −2.17c −2.14f

1014 K0Φ/m3·mol−1·Pa−1 0.3295 0.2970 0.2707

Glucose in Water 0.117 0.107 0.097

106 E0Φ/m3·mol−1·K−1 −2.2166 −1.9079 −1.6467 −1.76a

106 ΔV0Φ/m3·mol−1

0.5771 0.5060 0.4491 0.4052 0.3703

0.4714 0.4114 0.3322 0.2870 0.2445

0.4949 0.4229 0.3602 0.3204 0.2838

0.5148 0.4488 0.3730 0.3379 0.2909

1014 ΔK0Φ/m3·mol−1·Pa−1

Table 3. Infinite Dilution Apparent Molar Properties, V0Φ and K0Φ, Empirical Constants, bv and bK, and Infinite Dilution Apparent Molar Properties of Transfer, ΔV0Φ and ΔK0Φ, for Carbohydrate in Water and in Aqueous Polymer Solutions at Different Temperatures

Journal of Chemical & Engineering Data Article


106 V0Φ/m3·mol−1

109.5325 110.2499 110.9200 111.5682 112.0523

109.4886 110.1561 110.8362 111.4680 112.0640

109.5008 110.1552 110.8472 111.4768 112.0775

109.2966 110.0386 110.7432 111.4109 112.0393

209.7435 210.6323 211.4409 211.6a 211.91b 211.12d 211.87e 212.1946 212.8864

210.0330 210.9052 211.6687 212.3892 212.8927

210.1042 210.9456

T/K

288.15 293.15 298.15 303.15 308.15

288.15 293.15 298.15 303.15 308.15

288.15 293.15 298.15 303.15 308.15

288.15 293.15 298.15 303.15 308.15

288.15 293.15 298.15

303.15 308.15

288.15 293.15 298.15 303.15 308.15

288.15 293.15

Table 3. continued

I

1.8998 1.8072

2.0260 1.6657 1.8138 1.7235 1.8221

1.1252 1.0801

1.3419 1.2559 1.1869

0.9684 0.9083 0.8550 0.8052 0.7545

0.8538 0.8352 0.7568 0.7349 0.6933

0.9713 0.9175 0.8476 0.8199 0.7836

0.7847 0.7075 0.6671 0.6104 0.6546


106 E0Φ/m3·mol−1·K−1

1014 K0Φ/m3·mol−1·Pa−1

0.4210 0.3904

0.2894 0.2728 0.2277 0.1945 0.0063

0.0928 0.1405 0.1307 0.1315 0.0302

0.144 −1.4229 0.131 −1.1503 Sucrose in Aqueous Solution 10% w/w PEG400 0.189 −1.7614 0.166 −1.3923 0.144 −1.1383 0.122 −0.8523 0.099 −0.6401 Sucrose in Aqueous Solution 10% w/w PEG4000 0.174 −1.7862 0.162 −1.4212

Fructose in Aqueous Solution 10% w/w PEG400 0.155 −2.0872 0.141 −1.7714 0.127 −1.5200 0.113 −1.2663 0.099 −1.0608 Fructose in Aqueous Solution 10% w/w PEG4000 0.0489 0.140 −2.0794 0.0467 0.135 −1.7673 0.0469 0.129 −1.4985 0.0313 0.124 −1.2476 0.0419 0.118 −1.0200 Fructose in Aqueous Solution 10% w/w PEG10000 0.0611 0.139 −2.1702 0.0458 0.134 −1.8647 0.0579 0.130 −1.5980 0.0401 0.125 −1.3426 0.0554 0.120 −1.1313 Fructose in Aqueous Solution 10% w/w Ppg400 −0.1430 0.152 −2.0580 −0.0708 0.145 −1.7425 −0.0460 0.137 −1.4685 −0.0258 0.130 −1.2234 0.0172 0.122 −1.0151 Sucrose in Water 0.183 −2.5801 0.170 −2.1464 0.157 −1.7513 −1.78a −1.86d


1.1789 1.0294

1.1203 0.9689 0.9772 0.8493 0.8058

0.6162 0.5870

0.7881 0.7281 0.6628

0.5447 0.4765 0.4251 0.3774 0.3502

0.5885 0.5317 0.4905 0.4356 0.3998

0.5112 0.4359 0.3922 0.3372 0.2782

0.5041 0.4361 0.4084 0.3518 0.3209

1014 bk / kg·m3 ·mol−2·Pa−1

0.7938 0.7252

0.8186 0.7541 0.6130 0.5706 0.5102

0.7256 0.6703 0.6016 0.5538 0.5144

0.6134 0.5481 0.4721 0.4346 0.3982

0.7042 0.6455 0.5716 0.5296 0.5095

0.6964 0.6414 0.5500 0.5109 0.4687

1014 ΔK0Φ/m3·mol−1·Pa−1

Journal of Chemical & Engineering Data Article


to the sharing of hydrophilic hydration cosphere of carbohydrate and hydrophobic hydration cosphere of PPG. In the case of carbohydrates in PEG aqueous solutions, because of the preferential carbohydrate−PEG interactions, the electrostriction of water in the hydration cosphere of carbohydrate may be reduced and therefore, these systems show the positive values of ΔV0Φ. The temperature dependence of V0Φ was expressed by the following equation:

0.9447 0.8420 0.7353 0.6611 0.6190

0.7544 0.6834 0.5642 0.5294 0.4798

0.6178 0.5573 0.5439

Article

Data taken from ref 33. bData taken from ref 11. cData taken from ref 8. dData taken from ref 17. eData taken from ref 12. fData taken from ref 34.

⎛ ∂V 0 ⎞ EΦ0 = ⎜ Φ ⎟ = b + 2c(T − T °) ⎝ ∂T ⎠ P

(6)

where T° = 288.15 K. The obtained infinite dilution apparent molar isobaric expansibilities, E0Φ, are also given in Table 3. As can be seen, the positive values of E0Φ decrease by increasing ⎛ ∂E 0 ⎞ ∂ 2V 0 temperature (the negative values of ⎜ ∂Tϕ ⎟ = ∂T 2Φ ) and at ⎝ ⎠P P the same condition they follow the order: sucrose > fructose >

( )

glucose. Because V Φ0 2

∂CP0 ∂P

( )

∂ 2V Φ0

( ) , a negative value of

= −T

T

∂T 2

P

2

( ) ∂

∂T

seems to associate with a structure-breaking solute and

P

a positive one is associated with a structure-making solute.32 All solutes investigated in this work are structure-breakers based on ∂ 2V Φ0

( ) . Furthermore, at a same condition, the magnitude of ( ) and therefore structure-

the negative values of

∂T 2

P ∂ 2V Φ0 ∂T 2

P

breaker property of the investigated carbohydrates follows the order sucrose > glucose > fructose. 3.3. Apparent Molar Isentropic Compressibility. Apparent molar isentropic compressibilities of the solutes, KΦ, which defined as K Φ = −

∂VΦ ∂P S

( ) , were calculated from the

experimental density and sound velocity data according to the following equation: KΦ =

1000(βsd° − βs°d) mdd°

+

Mβs d

(7)

Figure 7 shows the concentration dependence of KΦ for glucose in pure water at different temperatures. The similar behavior was obtained for the other systems investigated in this work. The apparent molar isentropic compressibilities of the solutes have negative values and become less negative by increasing the temperature and carbohydrate molality. The negative values of KΦ indicate that the water molecules in the hydration layer of the solutes are more compact than bulk water molecules. By increasing the temperature or carbohydrate concentration, the carbohydrate−water interactions are weakened (decreasing the electrostriction), and therefore, the water molecules in the hydration layer of the solutes become more compressible and then the values of KΦ increase. In Figure 8, the apparent molar isentropic compressibility for glucose, fructose, and sucrose in pure water and those for sucrose in aqueous solutions of 10% w/w of PPG400, PEG400, PEG4000, and PEG10000 have been shown at T = 298.15 K. The values

a

209.8052 210.6766 211.4876 212.2262 212.9255 288.15 293.15 298.15 303.15 308.15

2.1938 2.0835 1.9526 1.8773 1.7978

209.8202 210.6622 211.4572 212.1584 212.8392 288.15 293.15 298.15 303.15 308.15

(5)

and from which the infinite dilution apparent molar expansibilities, E0ϕ, were obtained as

0.9560 0.8798 0.8105 0.7358 0.6652

1.1528 1.0209 1.0698 0.8687 0.8293

211.7305 212.4483 213.1195 298.15 303.15 308.15

2.2899 2.1913 2.0680 2.0434 1.9585

106 V0Φ/m3·mol−1

1.6973 1.6248 1.5504

0.3502 0.3063 0.2857

Sucrose in Aqueous Solution 10% w/w PEG4000 0.151 −1.1334 0.139 −0.8655 0.127 −0.6063 Sucrose in Aqueous Solution 10% w/w PEG10000 0.1370 0.175 −1.8256 0.1070 0.163 −1.4630 0.0769 0.151 −1.1871 0.0164 0.139 −0.8934 0.0054 0.127 −0.6705 Sucrose in Aqueous Solution 10% w/w Ppg400 0.1220 0.180 −1.6354 0.1214 0.168 −1.3044 0.1073 0.156 −1.0159 0.0842 0.144 −0.7617 0.0917 0.132 −0.5312

0.9853 0.9122 0.7570

V Φ0 = a + b(T − T °) + c(T − T °)2

T/K

Table 3. continued



106 E0Φ/m3·mol−1·K−1

1014 K0Φ/m3·mol−1·Pa−1

1014 bk / kg·m3 ·mol−2·Pa−1

1014 ΔK0Φ/m3·mol−1·Pa−1


J



Article

Figure 7. Plot of apparent molar isentropic compressibility, Kϕ, of glucose in water as a function of molality at different temperatures: ○, 288.15 K; × , 293.15 K; ▲, 298.15 K; ◇, 303.15 K; □, 308.15 K.

Figure 8. (a) Apparent molar isentropic compressibility of glucose, fructose and sucrose in pure water at 298.15 K: ○, glucose (this work); △, fructose (this work); □, sucrose (this work); ●, glucose (ref 36); × , sucrose (ref 36). (b) Apparent molar isentropic compressibility of sucrose in pure water and in aqueous solutions of 10% w/w of PPG400, PEG400, PEG4000 and PEG10000 at 298.15 K. × , sucrose in pure water; △, sucrose in PPG400(aq); ◇, sucrose in PEG400(aq); □, sucrose in PEG4000(aq); + , sucrose in PEG10000(aq).

of Kϕ of all the investigated carbohydrates in aqueous solutions increase in the presence of polymer and the ability of PPG in increasing of Kϕ is larger than PEGs. At concentrated solutions the values of Kϕ for the investigated systems decrease in the order: sucrose > glucose > fructose. Figure 8 also shows that there is a good agreement between our experimental apparent molar isentropic compressibility data and those taken from the literature. The infinite dilution apparent molar isentropic compressibilities, K0Φ, were obtained by least-squares fitting of the following relation to KΦ data:

K Φ = K Φ0 + bK m

where bK is respective experimental slope. The calculated values of K0Φ and bK for the investigated systems are also given in Table 3. In Table 3, K0Φ values of the investigated carohydrates in pure water have been compared with the values reported in the literature at 298.15 K and a fairly good agreement has been obtained. Similar to bv, the values of bK are positive and increase by addition of polymer as well as decreasing temperature. At a same condition, the values of bK for the investigated corbohydrates follow the order: sucrose > fructose > glucose which is similar to that obtained for the hydration number. For all the studied carbohydrates, K0Φ have negative values and become less negative as temperature increases or polymer is

(8) K



Article

added. At low and high temperatures, the values of K0Φ for the investigated corbohydrates respectively follow the orders: glucose > sucrose > fructose and sucrose > glucose > fructose. The infinite dilution apparent molar isentropic compressibilities of transfer, ΔK0Φ = K0Φ (carbohydrate in aqueous polymer solution) − K0Φ (carbohydrate in pure water), have positive values and decrease by increasing the temperature. Furthermore, the obtained values of ΔK0Φ decrease in the order: sucrose > fructose > glucose and the values of ΔK0Φ for transfer of carbohydrates from pure water to aqueous PPG solutions are larger than those to aqueous PEG solutions.

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4. CONCLUSIONS 0 The standard partial molar volumes, VΦ , and isentropic compressibilities, K0Φ, of carbohydrates sucrose, fructose, and glucose in water and in aqueous solutions 10% w/w of polymers PPG400, PEG400, PEG4000, and PEG10000 were measured at temperatures 288.15, 293.15, 298.15, 303.15, and 308.15 K. The variations of V0Φ and K0Φ with temperature and their transfer properties from water to aqueous solutions of the investigated polymers have also been reported. It was found that both of ΔV0Φ and ΔK0Φ have positive values and decrease by increasing the temperature and that for sucrose are larger than those of glucose and fructose. The values of ΔK0Φ and ΔV0Φ for transfer of the carbohydrates from pure water to aqueous PPG solutions, respectively, are larger and smaller than those to aqueous PEG solutions. The concentration dependence of βs, the obtained values of nh, E0Φ, and bK for the investigated solutes follow the order sucrose > fructose > glucose. Finally, the obtained negative values for

∂ 2V Φ0

( ) ∂T 2

show that all the solutes

P

investigated in this work are structure-breakers and structurebreaker property of them follows the order sucrose > glucose > fructose.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +98 8733624133. Fax: +98 8733660075. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

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Volumetric and Acoustic Properties of Aqueous Carbohydrate

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