AE

DD

a

ARRAA

KFSDTAA(

1

tmd[h‘bmamnrsisish

k

0h

Fluid Phase Equilibria 355 (2013) 123–129

Contents lists available at SciVerse ScienceDirect

Fluid Phase Equilibria

jou rn al h om epage: www.elsev ier .com/ locate / f lu id

physicochemical study of SDS in aqueous solution of Furosemide:ffect of DMSO on surfactant-Furosemide interaction

. Kaushal, D.S. Rana, M.S. Chauhan, S. Chauhan ∗

epartment of Chemistry, Himachal Pradesh University, Shimla 171005, India

r t i c l e i n f o

rticle history:eceived 23 April 2013eceived in revised form 26 June 2013ccepted 28 June 2013vailable online 11 July 2013

eywords:urosemide

a b s t r a c t

Micellization behaviour of sodium dodecyl sulphate (anionic surfactant) has been studied in the presenceof Furosemide (cardiovascular drug) at two concentrations i.e. 0.001 and 0.002 M in 8.0 mol% aqueoussolution of dimethylsulphoxide using conductance (�), densities (d), velocities of sound (v) and viscosi-ties (�) studies in the temperature range 20–40 ◦C at an interval of 5 ◦C. The critical micelle concentration(cmc) of sodium dodecyl sulphate (SDS) was determined from the plots of specific conductance (�) ofSDS. The results showed that critical micelle concentration (cmc) values of surfactant decrease withincrease in [Furosemide] and increase with the rise in temperature. By using cmc data, various thermo-

o

DSMSOhermodynamic parameterspparent molar volume (�v)pparent molar adiabatic compressibility

� )

dynamic parameters like standard enthalpy of micellization (�Hm), standard entropy of micellization(�So

m) and standard free energy of micellization (�Gom), that have direct bearing on the consequences of

such interactions at the molecular level have been calculated. The apparent molar volume (�v) and appar-ent molar adiabatic compressibility (��) have also been computed using densities and velocities of sounddata. The above calculated parameters were found to be sensitive towards the interactions prevailing in

wate

� Furosemide–SDS–DMSO-

. Introduction

Surfactants are soluble amphiphiles which play an impor-ant role in applied and fundamental science. Above the critical

icelle concentration (cmc), they self-associate to form thermo-ynamically stable and non-covalent aggregates called micelles1,2]. The most important property of surfactant solution thatas significantly been used in pharmaceutical formulations is

Micellar Solubilisation’, especially with respect to increasing theio-availability of the drugs [3–6]. Micelles are widely used asembrane mimetic systems to characterize membrane proteins

nd peptides and as vehicles for drug delivery [7,8]. The core oficelle is formed by hydrocarbon chain and is hydrophobic in

ature while the outer polar head groups are hydrophilic and henceemain hydrated. Increase in solubility of non polar compound inurfactant medium is ascribed to their incorporation into their pal-sade layer or inner core of the micelles. However, compounds withome degree of polarity may be adsorbed at the micellar waternterface [9,10]. The micellar properties of these compounds in

olution are governed by a subtle and delicate balance of bothydrophobic and hydrophilic interactions. Presence of additives

∗ Corresponding author. Tel.: +91 177 2830803; fax: +91 177 2830775.E-mail addresses: chauhansuvarcha@rediffmail.com,

undanvashisht@gmail.com (S. Chauhan).

378-3812/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.fluid.2013.06.053

r systems.© 2013 Elsevier B.V. All rights reserved.

affects this balance by either changing the nature of solvent or byspecific interactions with the amphiphiles [11].

The colloidal properties of amphiphilic drugs are largely deter-mined by the nature of the aromatic ring system of their hydropho-bic moieties and such drugs are useful in probing the relationshipbetween the molecular architecture and the physicochemical prop-erties. In pharmacy, the interaction of small molecules with drugsis one of the most extensively studied areas. In this respect, a largenumber of drugs are interacting with surfactants [12–19].

In a previous paper [20], we have discussed the drug–surfactantinteractions in aqueous solutions. In continuation with our previ-ous physicochemical studies, in this present paper, we have studiedthe interaction between Furosemide with sodium dodecyl sul-phate (SDS) in 8.0 mol% aqueous solution of dimethylsulphoxide(DMSO). Furosemide is often classified as a loop diuretic due toits predominant action in the nephron, where the drug interfereswith the tubular re-absorption of sodium on Henle’s loop [21].Dimethylsulphoxide (DMSO) is recognized as good non-aqueoussolvent with moderate dielectric constant (ε = 46.7). DMSO is animportant reactant and a “super solvent”, being highly polar andhaving excellent electron-donor properties [22,23]. DMSO dis-solves a tremendous array of organic molecules, carbohydrates,polymers, peptides, even many inorganic salts and gases. Mixtures

of DMSO and water are of considerable importance as chemicalreaction medium and in biomedical applications [24,25]. Hydrogenbonds are formed between water hydrogen sites and the oxy-gen sites of DMSO; these mixtures are strongly associated and

1 se Equilibria 355 (2013) 123–129

e[

2

2

[FDCwwdwaf

2

dcwwtftwsw(Tiraawa

3

3

aFcucTfbXXvbs6rstoc

24 D. Kaushal et al. / Fluid Pha

xhibit non-ideal behaviour, especially in their transport properties26–29].

. Experimental

.1. Materials

Furosemide from Aventis Pharma Ltd. and was used as received20]. Sodium dodecyl sulphate of AR grade was obtained from SDine Chem. Ltd., and was purified as described in the literature [30].MSO of AR grade with purity > 99.5% was supplied by SD Finehem. Ltd. and was used without further purification. Ordinary tapater of conductivity range 3–5 × 10−6 S cm−1 at 25 ◦C was distilledith the help of Millipore (Elix) distillation unit, which was furtheristilled in the presence of alkaline potassium permanganate. Theater so obtained has conductivity value 1–4 × 10−7 S cm−1 at 25 ◦C

nd pH in the range 6.5–7.0. Water of these specifications was usedor all sample preparation and the calibration of the instruments.

.2. Apparatus and measurements

Conductivity measurements were carried out with a calibratedigital conductivity metre (CM 180 Elico Ltd.) using a dip typeonductivity cell. The reproducibility of the individual point wasithin ±2% of conductivity unit. The solution under investigationas taken in the jacketed measuring cell. A high precision water

hermostat fitted with a digital temperature controlled device usedor all experimental measurements was supplied by Narang Scien-ific Works (NSW) – New Delhi. The temperature of thermostatas maintained within ±0.1 ◦C over the entire temperature range

tudied. Density and sound velocity measurements of the solutionere run on a high precision density and sound velocity analyzer

DSA-5000). DSA was calibrated before use with deionized water.he measurements were performed between 20 and 40 ◦C at annterval of 5 ◦C. The temperature was maintained to ±0.001 ◦C. Theeproducibility of speed of sound and density data was ±0.5 m s−1

nd ±5 × 10−6 kg m−3 respectively over the entire concentrationnd temperature range of measurements. Viscosity measurementsere carried out with a jacketed Ostwald viscometer. The precision

chieved in viscosity measurement was ±0.01%.

. Results and discussion

.1. Conductometric measurements

The micellization behaviour of SDS was studied in 8.0 mol%queous solution of DMSO containing 0, 0.001 and 0.002 Murosemide. The cmc values were determined from the plots of spe-ific conductance (�) versus [SDS] at different temperatures by thesual conductivity procedure [31,32]. The dependence of � on SDSoncentration has been reported in Table S1 (supplementary data).he variation of � versus [SDS] has been depicted in Fig. 1. It is clearrom these graphs that � value increases almost linearly with [SDS]ut with definite break points. The temperature dependence ofcmc values of SDS has been presented in Fig. 2 which shows that thecmc values increase linearly with increase in temperature. The cmcalues of SDS in 8.0 mol% aqueous solution of DMSO are found to beetween 8.0 and 9.4 mM at different temperatures which decreaseharply on addition of drug i.e. the cmc values lie in the range.4–8.35 and 5.5–7.3 mM for 0.001 M and 0.002 M [Furosemide]espectively, which is much lower than the cmc of aqueous SDS

olution (8 mM) at 298 K. An increase in cmc value upon the addi-ion of DMSO is identified with the inhibitory effect of this additiven micellization of SDS [33]. The cmc data reported suggest thatounter ion binding on the micellar surface is very weak in presence

Fig. 1. Plot of � vs. concentration of SDS in 8.0 mol% aqueous solution of DMSOcontaining (a) 0, (b) 0.001 and (c) 0.002 M Furosemide at different temperatures.

of DMSO. Such a state of affair is consistent with the fact that Na+

is preferentially more solvated; such an effect of the additive isattributed to dehydration of micelle surface as a result of strongintermolecular interactions, and reduction in counter ion bindingresulting from its preferential solvation with DMSO as compare towater. It is believed that, the micellar surface undergoes extensivedehydration upon addition of DMSO because of relatively strong

intermolecular interactions in water–DMSO solvent system. As aresult, the electrostatic repulsion between the polar head groups ofSDS molecules gets enhanced and inhibits the further aggregation.Also, from our previous studies, we found that addition of DMSO

D. Kaushal et al. / Fluid Phase Equilibria 355 (2013) 123–129 125

290 295 300 305 310 315

1.0

1.2

1.4

1.6

1.8X C

MC ,

104

T(K)

drug conc0

0.001M 0.002M

Fc

iDmwv

3

ihzmb

e

�

wltzf

�

�

spwpm

o −1 o −1 −1

TC

ig. 2. Plot of Xcmc vs. temperature of SDS in 8.0 mol% aqueous solution of DMSOontaining different concentrations of Furosemide.

ncrease the cmc [34,35]. With the addition of drug to the solution,MSO get attached to Furosemide preferentially, because this drugolecule has many charged centres which can interact with DMSOith the help of hydrogen bonding resulting the decrease in cmc

alues due to the solubilization of drugs in the micellar core.

.2. Thermodynamics of micelle formation of SDS

In order to derive further information about drug–surfactantnteractions, various thermodynamic parameters of micellizationave been calculated and examined such as enthalpy of micelli-ation (�Ho

m), free energy of micellization (�Gom) and entropy of

icellization (�Gom) of SDS which was determined as described

elow:The standard enthalpy of micellization �Ho

m is given by thequation [36,37].

Hom = −RT2

[d ln(Xcmc)

dT

]P

(1)

here d(ln Xcmc)/dT was determined as the slope of the straightine obtained by plotting lnXcmc against T and subjecting the datao a least–squares treatment. The standard free energy of micelli-ation and entropy of micellization have been estimated from theollowing equations [38,39].

Gom = RT ln(Xcmc) (2)

Gom = �Ho

m − T�Som (3)

The values obtained from the above relation have also beenummarized in Table 1. The variation of �Ho

m and �Som with tem-

erature is shown in Fig. 3. Examining the data reported in Table 1,e find that �Ho

m value of SDS is negative over the entire tem-erature range studied. This observation appears to suggest thaticellization of SDS, which is found to be spontaneous process,

able 1mc ×10−3, Xcmc ×10−4 (in mole fraction) �Ho

m , �Gom and �So

m values for SDS in 8.0 mol%

T (K) Cmc, ×103 Xcmc, ×104 �Hom kJ mol

0 0.001 0.002 0 0.001 0.002 0 0.

293 8.00 6.40 5.50 1.43 1.15 0.986 −5.7 −298 8.35 6.80 5.90 1.50 1.22 1.060 −5.9 −303 8.65 7.25 6.40 1.55 1.30 1.150 −6.1 −308 9.10 7.79 6.85 1.63 1.40 1.230 −6.3 −1313 9.40 8.35 7.30 1.68 1.50 1.310 −6.5 −1

Fig. 3. Plot of (a) �Hm (kJ mol ) and (b) �Sm . (J K mol ) of SDS vs. tempera-ture in 8.0 mol% aqueous solution of DMSO containing different concentrations ofFurosemide.

because �Gom < 0 over the entire temperature range, is energy

driven. The �Hom and �Go

m values are decreased in the presence ofDMSO, i.e., �Ho

m < 0 become more negative and �Som > 0 become

less positive, suggesting that the process of micellization of SDStends to be energy driven in the presence of DMSO. However, thesmaller �So

m values of SDS in 0.001 M Furosemide in the presence ofDMSO might be due to the decrease in hydrophobic hydration at thehydrocarbon–water interface. In other words, it might be expectedthat SDS molecules are getting solubilized in 0.001 M Furosemide inthe presence of DMSO, inhibiting the process of micellization. How-ever, since the value of �So

m is practically insensitive to Furosemideconcentration, it can be considered indicative of relatively exten-

sive interaction of Furosemide with SDS in the presence of DMSO.In the absence of Furosemide, therefore, we expect that reductionin hydrophobicity at the water hydrocarbon interface is relativelysmall, explaining the large �So

m > 0 values of SDS. Thus, we find

DMSO containing 0, 0.001 and 0.002 M Furosemide.

−1 �Gom kJ mol−1 �So

m JK−1 mol−1

001 0.002 0 0.001 0.002 0 0.001 0.002

9.3 −10.0 −21.6 −22.1 −22.5 54.1 43.8 42.69.6 −10.3 −21.8 −22.3 −22.7 53.4 42.7 41.49.9 −10.7 −22.1 −22.5 −22.9 52.8 41.7 40.20.2 −11.0 −22.3 −22.7 −23.1 52.0 40.5 39.00.6 −11.4 −22.6 −22.9 −23.3 51.4 39.4 37.9

1 se Equilibria 355 (2013) 123–129

tiric

3

sd

v

�

wpa�rocastttsbw

3

8bbeaS2

�

�

wmocv�aatts

sfsbs

t

26 D. Kaushal et al. / Fluid Pha

hat micellization of SDS becomes an energy driven process as wencrease the Furosemide concentration. Finally, since �Go

m valuesemain practically independent of temperature, this observations found to suggest that both �Ho

m and �Som vary in a mutually

orresponding manner rendering �Gom constant.

.3. Viscometric studies

The viscosities of SDS in the presence of 8.0 mol% aqueousolution of DMSO containing 0, 0.001 and 0.002 M Furosemide atifferent temperatures ranging from 293 to 313 K.

The viscosity parameter is further used to calculate the relativeiscosity, �r which was calculated using the relation

r = �

�o

here � is the viscosity of solution and �o is the viscosity of theure solvent. Typical plots between �r versus SDS concentrationsre given in Supplementary Fig. S1. From these plots, it is clear thatr value of surfactants initially increases very slowly up to the cmcange. However, a relatively large increase in �r value is noticed toccur as surfactant concentration exceeds its cmc. In addition, thehange that is observed to occur in these plots with temperaturend Furosemide concentration in the presence of DMSO is con-idered to largely originate from the change in the aggregation ofhe surfactant molecules in the presence of DMSO. In other words,his observation is speculated as resulting from various competi-ive interactions between different interacting components in theolutions described earlier. Similar observation has been reportedy Greener et al. [40] in respect of anionic surfactant with gelatine,hich is indicative of micellization region.

.4. Volumetric and compressibility measurements

The density (d) and speed of sound (v) data for SDS in.0 mol% DMSO at different concentrations of Furosemide haveeen reported in Tables S2 and S3 (supplementary data) and haveeen used to calculate the apparent molar volume (�v) and appar-nt molar adiabatic compressibility, (��) values of SDS in DMSOnd in drug–DMSO systems over a wide concentration range ofDS, 2–14 mmol kg−1 and at different temperatures ranging from93–313 K at interval of 5 K from the relation [41].

V = M

d+ [do − d]

mddo(4)

� = �V ̌ + [ ̌ − ˇo]mdo

(5)

here m is the molality of the solution, M is the relative molarass of SDS, d is the density of the solution and do is the density

f the solvent system. ̌ and ˇo are the adiabatic compressibilityoefficient of the solution and solvent calculated as: ̌ = 1/v2d;

is the sound velocity of solution. However, these values ofv and �� are subject to error as high as ±0.2 × 10−5 m3 mol−1

nd ±5 × 10−3 m3 mol−1 TPa−1 respectively. Both these propertiesre highly sensitive to the extrinsic experimental conditions and,herefore, are suggested to be relevant to extract the informa-ion, especially with regards to the existence of solute–solute andolute–solvent intermolecular interactions.

The effect of DMSO on �v and �� values of SDS has been pre-ented in Figs. 4 and 5. The dependence of �v parameter as aunction of SDS concentration at different temperatures has beenummarized in Table 2; however the effect of these solvents have

een investigated from the view point of co-solvent effect on watertructure.

From Fig. 4, we find that there are four important features inhe �v values of SDS: (i) the �v value increases relatively more

Fig. 4. Plot of �v vs. concentration of SDS in (a) 0, (b) 0.001 M and (c) 0.002 MFurosemide in 8.0 mol% aqueous solution of DMSO at different temperatures.

significantly with the increase in SDS concentration both in 0 and0.001 M aqueous solutions of Furosemide (Fig. 4a and b) than in theabsence of DMSO, the corresponding values in 0.002 M Furosemideare found to decrease (Fig. 4c); (ii) the effect of temperature isseen to increase the �v value over the entire temperature rangestudied (iii) �v value decreases substantially with the concentra-tion of SDS in 0.002 M and (iv) there is a substantial decrease inthe magnitude of �v value of SDS in the presence of DMSO. These

observations are found to indicate the effect of DMSO when com-pared with those reported previously; however, the effect can berationalized, in terms of the strength of intermolecular interactionsbetween water and DMSO which diminish the hydrophobic effect

D.

Kaushal

et al.

/ Fluid

Phase Equilibria

355 (2013)

123–129

127

Table 2Apparent molar volume, �v (m3 mol−1) and adiabatic molar compressibility, �� (m3 mol−1 TPa−1) of SDS (103, mol kg−1) in 8.0 mol% aqueous solution of DMSO containing different concentrations of Furosemide at differenttemperatures.

[Drug] [SDS], ×103 mol kg−1 �v , ×105/m3 mol−1 �� , ×102/m3 mol−1 TPa−1

293 298 303 308 313 293 298 303 308 313

(0)

2 14.9 15.3 16.3 16.8 17.1 −17.30 −14.08 −12.20 −11.35 −10.393 18.3 18.6 19.4 19.6 19.8 −9.68 −7.52 −5.60 −5.10 −2.834 19.6 19.9 20.5 20.7 21.1 −7.43 −5.79 −3.92 −3.76 −1.425 20.9 21.1 21.5 21.7 22.1 −4.29 −2.99 −1.52 −1.45 0.816 22.0 22.2 22.7 22.8 22.8 −2.13 −1.03 0.24 0.31 2.037 21.9 22.1 22.6 22.6 23.0 −0.99 −0.03 1.33 1.11 3.088 21.2 21.4 21.8 21.8 22.4 −2.26 −1.43 −0.13 −0.47 1.879 21.6 21.7 22.1 22.1 22.5 −0.28 0.44 1.41 1.33 2.97

10 22.0 22.1 22.6 22.4 22.8 1.05 1.71 2.64 2.51 3.8711 22.0 22.1 22.4 22.4 22.9 0.40 0.99 2.03 1.71 3.5112 22.3 22.4 22.8 22.7 23.1 1.50 2.05 3.00 2.73 4.3113 22.8 22.9 23.2 23.2 23.6 2.68 3.20 3.98 3.86 5.2214 22.8 22.9 23.3 23.2 23.6 2.98 3.46 4.27 4.08 5.34

(0.001)

2 18.4 18.7 19.0 19.4 19.6 −8.82 −7.36 −5.70 −3.97 −2.793 21.2 21.1 21.6 21.7 22.0 −3.33 −1.87 −0.54 −0.35 0.574 22.2 22.4 22.6 22.3 23.0 0.87 1.63 1.95 1.81 3.095 22.9 23.1 23.2 23.3 23.6 2.57 3.56 2.92 3.04 4.166 23.3 23.5 23.7 23.9 24.0 3.44 4.22 4.27 5.00 5.467 23.1 23.4 23.6 23.9 23.7 3.97 4.92 5.23 5.89 6.008 22.8 23.0 23.2 23.3 23.5 4.22 4.77 5.33 5.69 6.119 23.1 23.2 23.4 23.5 23.7 4.86 5.33 5.79 6.17 6.45

10 22.9 23.1 23.3 23.4 23.6 5.01 5.43 5.91 6.27 6.5911 22.9 23.1 23.2 23.4 23.5 4.86 5.30 5.67 6.12 6.4212 23.0 23.2 23.3 23.5 23.6 4.94 5.37 5.72 6.17 6.6413 23.1 23.3 23.4 23.5 23.7 5.21 5.62 6.01 6.37 6.7814 23.4 23.5 23.6 23.8 23.9 6.37 6.70 6.96 7.43 7.61

(0.002)

2 27.3 27.4 27.7 27.8 28.0 10.25 12.08 12.32 11.98 12.383 25.6 25.8 25.8 25.9 26.2 7.98 8.41 8.71 9.67 9.634 25.6 25.6 25.8 25.8 25.9 7.58 8.02 8.38 9.07 8.945 25.5 25.5 25.5 25.6 25.9 7.52 7.95 8.14 8.65 8.896 25.0 25.1 25.4 25.5 25.7 7.02 7.61 8.04 8.35 8.657 25.0 25.1 25.3 25.4 25.6 7.10 7.68 8.07 8.35 8.648 24.9 25.0 25.2 25.3 25.4 7.13 7.74 8.03 8.29 8.519 25.0 25.0 25.2 25.3 25.4 7.26 7.77 8.10 8.35 8.55

10 24.9 25.0 25.1 25.2 25.4 7.20 7.76 8.03 8.29 8.5211 24.6 24.8 24.9 25.0 25.2 7.00 7.56 7.81 8.10 8.3212 24.6 24.7 24.8 24.9 25.1 7.06 7.48 7.77 7.99 8.2113 24.8 24.9 25.0 25.1 25.2 7.51 7.90 8.18 8.41 8.6214 24.9 25.0 25.1 25.2 25.4 7.82 8.17 8.45 8.67 8.91

128 D. Kaushal et al. / Fluid Phase Equilibria 355 (2013) 123–129

Fig. 5. Plot of �� vs. concentration of SDS in (a) 0, (b) 0.001 M and (c) 0.002 MF

orabSttt

Stm

Fig. 6. Representative plot of �v vs. concentration of SDS for different concentrationsof Furosemide in 8.0 mol% aqueous solution of DMSO at 303 K.

mission, New Delhi for their financial assistance under the majorresearch project (F.No. 32-237/2006(SR)) and Dr. D.S. Kothari Post

urosemide in 8.0 mol% aqueous solution of DMSO at different temperatures.

f the alkyl chain of SDS [42,43]. Such an effect of DMSO is alsoeflected in the �� values of SDS which have been presented in Fig. 5s a function of SDS concentration; the �� value remains negativeelow 9 mM concentration of SDS, i.e., in the pre–micellar region ofDS in the absence of Furosemide; in the presence of Furosemidehe �� value, however, tends to be positive over the entire concen-ration region of SDS at all temperatures which may be attributedo the hydrophobic interactions between SDS and Furosemide.

The effect of Furosemide concentration on �v and �� values ofDS can be seen in Figs. 6 and 7; however, these are the representa-

ive plots indicating the effect of Furosemide concentration on the

agnitude of these parameters at 303 K.

Fig. 7. Representative plot of �� vs. concentration of SDS for different concentrationsof Furosemide in 8.0 mol% aqueous solution of DMSO at 303 K.

4. Conclusion

In summary, we can say that addition of non-aqueous solventi.e. DMSO has a profound influence on the micellar properties ofionic surfactant and it leads to the formation of charged com-plex between DMSO and Furosemide preferentially due to thesolubilization of drugs in the micellar core, which is reflected byconductometric, volumetric and viscometric studies. Moreover thefree energy of micellization �Go

m becomes more negative withincrease in temperature as well as with increase in Drug concen-tration which support the above observations.

Acknowledgements

S. Chauhan and D.S. Rana thanks the University Grant Com-

Doctoral Fellowship, respectively. D. Kaushal thanks CSIR NewDelhi for her financial assistance.

se Equ

A

t

R

[

[

[

[

[

[[[

[

[[

[

[

[[[

[[[[[

[[

[[[

[

[[[

[

D. Kaushal et al. / Fluid Pha

ppendix A. Supplementary data

Supplementary data associated with this article can be found, inhe online version, at http://dx.doi.org/10.1016/j.fluid.2013.06.053.

eferences

[1] K.P. Das, D.K. Chattoraj, Physico-chemical studies of surfactants in solution andat interface, in: A.K. Biswas (Ed.), Frontiers of Applied Chemistry, Narosa Press,New Delhi, 1989, pp. 166–208.

[2] F. Akhtar, Md.A. Hoque, Md.A. Khan, J. Chem. Thermodyn. 40 (2008) 1082–1086.[3] O. Cudina, J. Brboric, I. Jankovic, K. Karljikovic-Rajic, S. Vladimirov, Colloids Surf.

B: Biointerfaces 65 (2008) 80–84.[4] K.G.H. Desai, A.R. Kulkarni, T.M. Aminabhavi, J. Chem. Eng. Data 48 (2003)

942–945.[5] D. Attwood, A.T. Florence, Surfactant Systems: The Chemistry, Pharmacy and

Biology, Chapman and Hall, New York, 1983.[6] M. Enache, E. Volanschi, J. Pharm. Sci. 100 (2) (2011) 558–565.[7] S.S. Sham, S. Shobana, L.E. Townsley, J.B. Jordan, J.Q. Fernandez, O.S. Andersen,

D.V. Greathouse, J.F. Hinton, Biochemistry 42 (2003) 1401–1409.[8] A.S. Narang, D. Delmarre, D. Gao, Int. J. Pharm. 345 (2007) 9–25.[9] C.O.R. Yagui, H.W.L. Hsu, A. Pessoa- Jr., L.C. Tavares, J. Pharm. Pharmaceut. Sci.

8 (2005) 147–163.10] E.J. Fendler, J.H. Fendler, Catalysis in Micellar and Macromolecular Systems,

Academic Press, New York, 1975.11] Kabir-ud-Din, M.D.A. Al-Ahmadi, A.Z. Naqvi, M. Akram, Colloid J. 71 (4) (2009)

498–502.12] V.M. Rao, M. Nerurkar, S. Pinnamaneni, F. Rinaldi, K. Raghavan, Int. J. Pharm.

319 (2006) 98–106.13] Md.S. Ali, K. Anjum, J.M. Khan, R.H. Khan, Kabir ud-Din, Colloids Surf. B: Bioin-

terfaces 82 (1) (2011) 258–262.14] M.J. Ruiz-Angel, S. Carda-Broch, M.C. Garcia-Alvarez-Coque, J. Chromatogr. A

1217 (11) (2010) 1786–1798.15] J.B. Rosenholm, Colloids Surf. A 354 (1–3) (2010) 197–203.16] L.J. Waters, T. Hussain, G.M.B. Parkes, J. Chem. Thermodyn. 53 (2012) 36–41.17] X. Ren, X. Mao, L. Cao, K. Xue, L. Si, J. Qiu, A.D. Schimmer, G. Li, Eur J. Pharm. Sci.

36 (4-5) (2009) 401–411.

[[

[

ilibria 355 (2013) 123–129 129

18] S.S. Dhondge, S.P. Zodape, D.V. Parnate, J. Chem. Thermodyn. 48 (2012)207–212.

19] S.K. Mehta, K.K. Bhasin, A. Kumar, S. Dham, Colloids Surf. A 278 (2006) 17–25.20] S. Chauhan, M.S. Chauhan, D. Kaushal, V.K. Syal, J. Jyoti, J. Sol. Chem. 39 (2010)

622–638.21] V.K. Ahluwalia, M. Chopra, Medicinal Chemistry, Anubha Printers, Noida, 2008,

pp. 21,265.22] X.Q. Yang, L.J. Yang, K.M. Huang, W.Y. Tian, H. Shang, J. Sol. Chem. 39 (2010)

849–856.23] M. Chalaris, S. Marinakisa, D. Dellis, Fluid Phase Equilib. 267 (2008) 47–60.24] Z.W. Yu, P.J. Quinn, Biosci. Rep. 14 (1994) 259–281.25] G. Hernandez-Perni, H. Leuenberger, Eur. J. Pharm. Biopharm. 61 (2005)

201–213.26] T.M. Aminabhavi, B. Gopalakrishna, J. Chem. Eng. Data 40 (1995) 856–861.27] B.C. Gordalla, M.D. Zeidler, Mol. Phys. 74 (1991) 975.28] R. Ludwig, T.C. Farrar, M.D. Zeidler, J. Phys. Chem. 98 (1994) 6684–6687.29] E.S. Baker, J. Jones, J. Phys. Chem. 89 (1985) 1730–1735.30] S. Chauhan, M.S. Chauhan, P. Sharma, D.S. Rana, A. Umar, Fluid Phase Equilib.

337 (2013) 39–46.31] K.Y. Mya, A. Sirivat, A.M. Jamieson, J. Phys. Chem. B 107 (2003) 5460–5466.32] Y. Moroi, H. Takagaki, S. Nagadome, Y. Hirata, G. Sugihara, J. Colloid Int. Sci. 149

(1992) 252–255.33] M.S. Chauhan, G. Kumar, A. Kumar, S. Chauhan, Colloids Surf. 166 (2000) 51–57.34] M.F. Fox, K.P. Whittingliani, J. Chem. Soc. Faraday Trans. I 71 (1975) 1407–1412.35] M.S. Chauhan, G. Kumar, A. Kumar, K. Sharma, S. Chauhan, Colloids Surf. A 180

(2001) 111–119.36] J.M. Del Rio, C. Pombo, G. Prieto, V. Mosquera, F. Sarmiento, J. Colloid Int. Sci.

172 (1995) 137–141.37] M.S. Bakshi, J. Incl. Phenom. Macrocycl. Chem. 36 (2000) 39–54.38] H.N. Singh, S.M. Saleem, R.P. Singh, J. Phys. Chem. 84 (1980) 2191–2194.39] S.K. Mehta, K.K. Bhasin, R. Chauhan, S. Dham, Colloids Surf. A 255 (2005)

153–157.40] J. Greener, B.A. Contestable, M.D. Bale, Macromolecules 20 (10) (1987)

2490–2498.

41] M. Alauddin, N.P. Yao, R.E. Verrall, J. Phys. Chem. 92 (1988) 1301–1307.42] L.G. Lonescu, T. Tokuhiro, B.J. Czemiawski, E.S. Smith, K.L. Mittal (Eds.), Solution

Chemistry of Surfactants, vol. 1, Plenurn Press, New York, 1979, pp. 487–496.43] T. Tokuhiro, L.G. Ionescu, K.L. Mittal (Eds.), Solution Chemistry of Surfactants,

vol. 1, Plenurn Press, New York, 1979, pp. 497–506.