The Determination of Surface Tension of Traditional Chinese Medicine Tablet

doi:10.4236/jmp.2012.312236

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Journal of Modern Physics, 2012, 3, 1878-1881

http://dx.doi.org/10.4236/jmp.2012.312236 Published Online December 2012 (http://www.SciRP.org/journal/jmp)

The Determination of Surface Tension of Traditional

Chinese Medicine Tablet

Xiaolu Zhang, Hao Zhang, Ke Liang, Er’jia Zhu, Ruisi Yan, Hui Yang, Zaiyou Tan*

School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou, China

Email: *[email protected]

Received September 27, 2012; revised October 26, 2012; accepted November 4, 2012

ABSTRACT

In this paper we aimed to determine the surface tension of traditional Chinese medicine (TCM) tablet and tried to pro-

vide a key reference parameter to control tablet film coating quality. Using contact angle tester, the Chinese medicine

tablet, a famous Fufang Danshen tablet CP as a model example, was determined by Zisman critical surface tension

method. Our study showed that the critical surface tension of Fufang Danshen tablet CP was determined to be 18.00

dyne/cm. The Zisman method, hence, can determine successfully the critical surface tension of Chinese medicine tablet

and will become an effective manner to control tablet film coating quality.

Keywords: Surface Tension; Contact Angle; The Zisman Critical Surface Tension Method; Fufang Danshen Tablet CP;

Chinese Medicine

1. Introduction

Film coating is a process which involves the deposition

of a membrane consisting of polymer, plasticizer, col-

ourant and possibly other additives onto the surface of a

pharmaceutical dosage form, typical a tablet or a granule.

Over the past two decades, there has been a dramatic

increase in the use of this process in China. The reasons

for file coating are many and varied. They include [1]: 1)

To improve product appearance, odour and taste and to

aid swallowing. 2) To aid identification and hence de-

crease the risk of confusion, especially when patients

have to take several preparations. 3) To protect the active

ingredient against heat, light and moisture. 4) To separate

incompatible active ingredients present in the preparation.

5) To prevent dust formation during subsequent packing

on high-speed packing lines. 6) To control the release of

an active ingredient by use of either a coating with

pH-dependence solubility or a coating that acts as a dif-

fusion membrane. Compared to the conventional sugar

coat, the film coat is relatively thin typically 10 - 100 μm.

Although the technology involved in the application of

such a thin coating to a substrate is not new, having

precedents in both the paints and adhesive technologies,

problems do occur resulting in a number of film defects.

These can either affect the visual appearance of the

coated tablet or, more importantly, result in the loss of

continuity of the film and thus affect the release of the

active ingredient from the preparation. Therefore, look-

ing for the reference factor of quality control of film

coating of tablet is necessary.

One of the requirements of tablet film coating is that

good adhesion of the coat to the tablet must be achieved.

The properties of the coating formulation as well as those

of the tablet can influence adhesion. The prerequisite for

good adhesion is the spreading of the atomized droplets

over the surface of the tablet and limited penetration of

the coating solution into pores of the tablet. Both of these

are controlled by the surface tension of the tablet and the

coating. The surface tension of solid surface can be de-

termined using: Owen’s method [2], Van Oss’s [3] method

and Zisman’s method [4]. The both of Owen’s and Van

Oss’s must depend on accurate interaction energy pa-

rameters of all components to determine the surface ten-

sion of TCM tablet but it is difficult owing to the ingre-

dients of the tablet extracting from various herbs are

complicate. So we make an experiment in order to find

out the surface tension of CTM tablet by Zisman’s me-

thod.

Zisman and his associates found that when the cosine

of the contact angle, was plotted versus the surface ten-

sion for a homologous series of liquids spread on a sur-

face such as Teflon (polytetrafluoroethylene), a straight

line resulted. The line can be extrapolated to cosθ = 1,

that is, to a contact angle of zero, signifying complete

wetting. The surface tension at cosθ = 1 was given the

term critical surface tension and the symbol γc, Zisman

concluded that γc was characteristic for each solid. We

should try to find out such γc of film coating of TCM

*Corresponding author.

X. L. ZHANG ET AL. 1879

tablet as a characteristic parameter to control tablet coat-

ing quantity. In this paper, we will report the traditional

Chinese medicine tablet, a famous Fufang Danshen tablet

CP [5] as a model example, was determined using contact

angle tester by Zisman critical surface tension method.

2. Instruments and Reagents

2.1. Instruments

The JZ8002 electronic balance (Shanghai Balance In-

strument Factory); GZX-9240MBE significant number of

blast oven (Shanghai Xun Bo Industrial Co., Ltd. Medi-

cal Equipment Factory); JC2000C1 contact angle meas-

uring instrument (Shanghai Zhong Chen Technology Co.,

Ltd.).

2.2. Reagents

Pure water (Guangdong Pharmaceutical University); For-

mamide (Sino Pharmaceutical and Chemical Reagent Co.,

Ltd., AR); Glycol (Guangzhou Chemical Reagent Fac-

tory, AR); Butanol (J & K, AR).

3. The Contact Angle Measurements

3.1. Preparation of Fufang Danshen Tablet CP

and the Test Liquids

We prepare the Fufang Danshen tablet CP by weighing

the formulation 400 mg and Repressing them into 2 mm

thickness and smooth surface tablet for sparing according

to Chinese Pharmacopoeia as a model tablet study and

design several test liquids (pure water, formamide, glycol,

butanol etc.) system.

3.2. Measurements of Contact Angle of Fufang

Danshen Tablet CP

Pretreatment: Place 5 ml water, Butanol, glycol, for-

mamide in the Petri dish, respectively and then put the

Petri dish in closed desiccators. The tablets employed to

test were located in the closed desiccators for 48 h until

the surface was saturated under the steam of the test liq-

uid.

Measure: The measurements were conducted through

the way of sessile drops with a computerized JC2000A

contact angle goniometer (Shanghai Balance Instrument

Factory). When the JC2000A contact angle goniometer

was operated, the production of the sessile drops was

yielded by performing the processes as follows:

1) Control the temperature to be 25˚C.

2) The infusion needle of the instrument was coated

with paraffin to ensure that the droplet is always in the

needle position.

3) Placing the needle near the surface, the correspond-

ing volume of liquid was squeezed out of the syringe.

4) Squeezing a drop of tested liquid on the tablet sur-

face, focusing camera 5 s latter.

5) Recorded every 5 seconds until 30 seconds and test

10 times for each test liquid Contact angle was measured

using the JC2000A, which takes a video image of the

drop and uses goniometer to determine and calculate.

6) Then select the mean value as the θ.

Each measurement should be finished less than 1 min to

minimize the effects of evaporation of the liquids. It was

found experimentally that the contact angle remained

constant within this operating time. An advancing con-

tact angles was measured in this way. Each number in the

Table 1 is the mean value of at least 10 single measure-

ments. The results and images are shown in Figure 1.

4. Results and Discussion

To characterize the TCM tablet, the surface tensions of

several liquids and their contact angles on the model Fu-

fang Danshen tablet CP were determined at 25˚C, as

showed in the following Table 1.

Plot cosθ versus γ, they appear to fit nicely the Zisman

principle, producing a straight line that extrapolates to

cosθ corresponding to a critical surface tension of γc =

18.00 dyne/cm as shown in Figure 1. From the results

obtained, the liquid in the tablet would be expected to the

best wet on the model tablet. For a more exact calcula-

tion of the critical surface tension γc, least-squares linear

regression analysis can be applied to yield:

cos0.0029 1.0522,0.9859.







  (1)

According to the above critical surface tension of Fu-

fang Danshen tablet CP which was tested to be 18.00

dyne/cm, we prepared 3 batches of film control release

coated tablets of Fufang Danshen. The results of release

rate and the release profiles of 3 batches of tablets were

exhibited in the Table 2 and Figure 2.

The results showed that the released rate and the veri-

fication of 3 batches which were good agreement on the

quality requirements of control drug release formula-

tions.

5. Conclusion

Although one frequently desires to determine the relative

Table 1. Contact angles of liquids and surface tension of

Fufang Danshen tablets CP at 25˚C.

Surface tension Contact angle cosθ

Water 72.8 31.43 0.845

Formamide 58.2 28.4 0.876

Glycol 48 22.14 0.922

Butanol 24.6 11.6 0.98

X. L. ZHANG ET AL.

1880

Surface Tension of FufangDanshen Tablet CP b

Zisman Method

y = -0.0029x + 1.0522

= 0.9859

0.82

0.84

0.86

0.88

0.9

0.92

0.94

0.96

0.98

1.02

0 102030405060

Surface Tension (Dyne/cm)

cosθ

7080

Figure 1. Surface tension of F ufang Danshen tablets CP by Zisman method.

Table 2. Drug release with different batches.

Time (h) 1 2 3

2 21.4 22.7 19.5

4 42.1 45.5 39

6 57.3 62.1 54.2

8 73.6 76.2 70.7

10 83.4 84.9 79.2

12 87.8 89.7 84.1

100

0246810

Release Time(h)

Amount Release(%)

1214

Figure 2. Release profile of verification test.

efficiencies of wetting agents, it is difficult to measure

directly the contact angle of a solid surface. As a result of

these difficulties, our experimental tests have indicated

Zisman’ method can be used to measure the critical sur-

face tension of the TCM tablet in industry. To ensure the

quantity control the TCM tablet, we suggest Zisman’s

method can be used for estimating the ability of a wetting

agent or file coating on the surface of the tablet and the

application property of such products are ordinary deter-

mined by subjective evaluation. More importantly, Zis-

man’s method can be applied to the surface tension of

solid which was constituted with various components. It

is difficult for other indirect methods such as the Owen’s

method and Van Oss’s method to determine the surface

X. L. ZHANG ET AL. 1881

tension of solid owing to they must depend on accurate

interaction energy parameters of each component. How-

ever, in order to ensure accessing accurate surface ten-

sion values, the nature of the surface materials should be

poorly hygroscopic. Meanwhile, the humidity of experi-

mental environment must be controlled. The surfaces of

tested samples should be saturated by the tested liquid

during experiment procedure. This job calls for patience.

REFERENCES

[1] D. Ganderton and J. Trevor, “Advances in Pharmaceutical

Science,” Academic Press, London, Vol. 6, 1992, pp. 65-

66.

[2] D. K. Owens and R. C. Wendt, “Estimation of the Surface

Free Energy of Polymers,” Journal of Applied Polymer

Science, Vol. 13, No. 8, 1969, pp. 1741-1747.

doi:10.1002/app.1969.070130815

[3] C. J. Van Oss, M. K. Chaudhury and R. J. Good, “Inter-

facial Lifshitz-van der Waals and Polar Interactions in

Macroscopic Systems,” Chemical Reviews, Vol. 88, No. 6,

1988, pp. 927-941. doi:10.1021/cr00088a006

[4] W. A. Zisman, “Contact Angle, Wettability and Adhesion

in Advances in Chemistry Series,” American Chemical

Society, Vol. 9, No. 43, 1964, p. 513.

[5] “Chinese Pharmacopoeia,” The Medicine Science and Tech-

nology Press of China, Beijing, 2010, pp. 904-905.