Spectrophotometric methods for the simultaneous determination of binary mixture of metronidazole and diloxanide furoate without prior separation

Journal of Advanced Research (2010) 1, 323–329

Cairo University

Journal of Advanced Research

ORIGINAL ARTICLE

Spectrophotometric methods for the simultaneous
determination of binary mixture of metronidazole
and diloxanide furoate without prior separation
Mohamed R. El-Ghobashy
a
b

a,*

, Nisreen F. Abo-Talib

b

Analytical Chemistry Department, Faculty of Pharmacy, Cairo University, Egypt
National Organization for Drug Control and Research (NODCAR), Cairo, Egypt

Received 26 October 2009; revised 1 March 2010; accepted 18 March 2010
Available online 30 June 2010

KEYWORDS
Metronidazole;
Diloxanide furoate;
Binary mixture;

Isosbestic point;
Ratio subtraction

Abstract Ratio subtraction and isosbestic point methods are two innovative spectrophotometric
methods for determining the concentrations of metronidazole (I) and diloxanide furoate (II) in a
mixture. Metronidazole was determined by direct spectrophotometric method at kmax 314.0 nm in
the presence of diloxanide furoate in the range of 4–24 lg mlÀ1 with a mean recovery percentage
of 99.83 ± 1.41. Two spectrophotometric methods were developed for the spectral resolution of
diloxanide furoate when present in mixture with metronidazole without preliminary separation.
The first method depends on measuring the absorbance at the isosbestic point at 277.2 nm in the
range of 5–30 lg mlÀ1 with a mean recovery percentage of 99.96 ± 1.47 for diloxanide furoate.
The second method is the ratio subtraction spectroscopic method for spectral isolation of diloxanide
furoate present in the mixture which can be measured at 251.2 nm in the range of 5–30 lg mlÀ1 with a
mean recovery percentage of 99.73 ± 1.33 for diloxanide furoate determination. The suggested procedures were validated using laboratory-prepared mixtures and were successfully applied for the
analysis of pharmaceutical preparations. The methods retained their accuracy and precision when
the standard addition technique was applied. The results obtained by applying the proposed methods
were statistically analyzed and compared with those obtained by the reported method.
ª 2010 Cairo University. Production and hosting by Elsevier B.V. All rights reserved.

* Corresponding author. Tel.: +202 33020604.
E-mail address: (M.R. El-Ghobashy).
2090-1232 ª 2010 Cairo University. Production and hosting by
Elsevier B.V. All rights reserved.
Peer review under responsibility of Cairo University.
doi:10.1016/j.jare.2010.06.001

Production and hosting by Elsevier

Introduction
Metronidazole and diloxanide furoate are formulated together

to be highly effective in the treatment of intestinal and extraintestinal amoebic infections. Metronidazole is less effective
against parasites in the bowel lumen and is, therefore, used
in combination with a luminal amoebicide, such as diloxanide
furoate in the treatment of invasive amoebiasis.
Metronidazole 2-methyl-5-nitroimidazole-1-ethanol [1]
was determined individually by short-wave length NIR


324
spectroscopy [2], voltammetry [3–5], NMR spectrometry [6],
gas chromatography [7] and HPLC methods either alone
[8–10] or in the presence of its metabolites [11,12] or in the
presence of its degradation product [13], in addition to its mixture with other drugs [14,15]. First derivative spectrophotometry was used for the determination of metronidazole in
mixture with ciprofloxacin [16].
Diloxanide furoate 2,2-dichloro-N-(4-hydroxyphenyl)N-methylacetamide [1] was determined individually by colorimetric method [17], in the presence of its degradation product
by derivative technique, derivative ratio, TLC-densitometry
[18] and HPLC [18,19] and in mixture with tinidazole and furazolidone by second derivative spectrophotometry [20].
The main problem of spectrophotometric binary mixture
analysis is the simultaneous determination of the two compounds in the same mixture without prior separation. One
spectrophotometric determination method has been used for
resolving such mixture with overlapping spectra, derivative
spectrophotometry [21] and HPLC [22].
The aim of this work is to develop new spectrophotometric
methods for resolving this mixture with spectral interfering
problems, without preliminary separation. The new methods
were very simple, did not require any computer programs
(derivative and derivative ratio) as metronidazole was determined by direct spectrophotometry and diloxanide furoate
was determined by simple mathematical calculation. Also the
method used did not require any sophisticated instrumentation,
such as HPLC, which requires solvents and time.

Experimental

M.R. El-Ghobashy and N.F. Abo-Talib
Chemicals and reagents
All chemicals were of analytical grade and the solvents were of
spectroscopic grade. Methanol, (E-Merck, Darmstadt,
Germany).
Standard solutions
Stock solutions
Metronidazole (I) and diloxanide furoate (II) stock solutions
(1 mg mlÀ1) were prepared by weighing accurately 100 mg of
each powder into two separate 100 ml volumetric flasks. Methanol (50 ml) was added, shaken for a few minutes and completed to volume with the same solvent.
Working solutions
Four micro litres of the stock solution of (I) and 5 ml of the
stock solution (II) were accurately transferred into two separate 50 ml measuring flasks and diluted to the mark with methanol to get a final concentration of 80 lg mlÀ1 and 100 lg mlÀ1
of (I) and (II), respectively.
Laboratory-prepared mixtures
Accurate aliquots equivalent to (40–100 lg) of (I) were transferred from its working solution (80 lg mlÀ1) into a series of
10 ml volumetric flasks and portions equivalent to (50–
150 lg) of (II) from its working solution (100 lg mlÀ1) were
added to the same flasks and volumes were completed to mark
with methanol and mixed well.

Apparatus
Procedures
Spectrophotometer: SHIMADZU UV-1601 PC, dual beam
UV–visible spectrophotometer with two matched 1 cm quartz
cells, connected to an IBM compatible personal computer
(PC) and an HP-600 inkjet printer. Bundled UV-PC personal
spectroscopy software version (3.7) was used to process the

absorption and the derivative spectra. The spectral band width
was 0.2 nm with wavelength scanning speed of 2800 nm minÀ1.
Materials
Pure samples
Metronidazole and diloxanide furoate were kindly supplied by
Egyptian Int. Pharmaceutical Industries Co., E.I.P.I.CO. 10th
of Ramadan City, Area B1 P.O. 149, Egypt. Their purity was
found to be 99.84 ± 1.26 and 100.50 ± 0.71, respectively,
according to the manufacturer’s direct spectrophotometric
method (personal communication).
Market samples
Furazole tablets (E.I.P.I.CO.); batch no. 080435. It was labeled
to contain 200 and 250 mg metronidazole and diloxanide furoate, respectively, per tablet.
Furazole suspension (E.I.P.I.CO.); batch no. 074135. It was
labeled to contain 200 and 100 mg metronidazole and diloxanide furoate, respectively, per 5 ml.

Isosbestic spectrophotometric method
Linearity: aliquots from (I) and (II) working solutions (80 lg ml
À1
of (I) and 100 lg mlÀ1 of (II), respectively) equivalent to 40–
240 lg of (I) and 50–300 lg of (II) were transferred into two separate sets of 10 ml volumetric flasks and completed to the mark
with methanol. The zero order absorption spectra were recorded for both drugs using methanol as a blank; then the
absorbance was measured at 314.0 nm for (I) and 277.2 nm
(Aiso) for (I) and (II). Two calibration curves were constructed
for each drug relating the absorbance at the selected wavelength
to the corresponding drug concentrations and the regression
equations were computed.
Assay of laboratory-prepared mixtures: Absorbance of the
spectra of laboratory-prepared mixtures containing different
ratios of (I) and (II) were measured at 314.0 nm corresponding

to the contents of (I) only, and at 277.2 nm (Aiso) corresponding to the total content of (I) and (II) in the mixture. The concentration of (I) alone and the total concentration of the two
drugs were calculated from their corresponding regression
equations; then by subtraction of (I) concentration from the
total mixture concentration, yielding the actual concentration
of (II) in the mixture.
Ratio subtraction spectrophotometric method
Linearity: Aliquots containing 50–300 lg from (II) working
solution (80 lg mlÀ1) were transferred into a series of 10 ml
volumetric flasks then completed to volume with methanol;


Analysis of metronidazole and diloxanide furoate in binary mixture

325

a 100 ml beaker, sonicated in 20 ml methanol for 10 min and
filtered into a 100 ml volumetric flask. The residue was washed
three times using 20 ml methanol each time and the volume
was completed to the mark with methanol. Aliquots of 0.5, 1
and 1.5 ml were separately transferred to 10 ml volumetric
flask and diluted with methanol. The general procedures under
linearity were followed.
The validity of the methods was assessed by applying the
standard addition technique.
Furazole suspension: Furazole (0.5 ml) suspension was accurately transferred into a 100 ml beaker, sonicated in 20 ml
methanol for 10 min and filtered into a 100 ml volumetric flask.
The residue was washed using 20 ml methanol and the volume
was completed to the mark with methanol. Aliquots of 0.2, 0.4
and 0.6 ml (for analysis of metronidazole) and 0.5, 1 and 1.5 ml
(for analysis of diloxanide furoate) were separately transferred

to 10 ml volumetric flasks and diluted with methanol. The general procedures under linearity were followed.
The validity of the methods was assessed by applying the
standard addition technique.

the spectra of the prepared standard solutions were scanned. A
calibration curve was constructed relating the absorbance of
zero order spectra of (II) at kmax 251.2 nm to the corresponding concentrations and the regression equation was computed.
Aliquot equivalent to 40 lg from the (I) working solution
(100 lg mlÀ1) was transferred into 10 ml volumetric flask and
completed to volume with methanol to be used as a divisor
(4 lg mlÀ1).
Assay of laboratory-prepared mixtures: Absorbance of the
spectra of laboratory-prepared mixtures containing different
ratios of (I) and (II) was scanned; then the (absorbance at each
wavelength) was divided by the spectrum of 4 lg mlÀ1of standard (I) (divisor) to obtain division spectra and the absorbance
in the plateau region (the constant) was subtracted. By multiplication of the obtained spectra (absorbance at each wavelength) by the spectrum of the divisor the original curves for
direct determination of (II) at 251.2 nm were obtained and
the concentration was calculated from the corresponding
regression equation.
Assay of pharmaceutical formulations

Results and discussion
Furazole tablets: Ten Furazole tablets were accurately weighed
and finely powdered. A portion equivalent to 8 mg of (I) and
10 mg of (II) was weighed. The powder was transferred into

Analytical methods for the determination of binary mixture
without previous separation were of interest. Metronidazole

Fig. 1 Zero order absorption spectra of 20 lg mlÀ1 of metronidazole (_____), 20 lg mlÀ1 of diloxanide furoate (- - - - -) and (1:1) mixture

containing 10 lg mlÀ1 of each (. . . . . ..) using methanol as a blank.

Table 1

Method validation for the determination of pure sample of metronidazole and diloxanide furoate by the proposed methods.

Parameter

Accuracy mean ± SD
Precision repeatabilitya
Intermediate precisionb
Concentration range (lg mlÀ1)

Isosbestic spectrophotometry

Ratio subtraction spectrophotometry

Metronidazole

Diloxanide furoate

Diloxanide furoate

99.83 ± 1.41
100.07 ± 0.76
99.95 ± 0.82
4–24

99.96 ± 1.47
99.93 ± 0.48

100.05 ± 0.60
5–30

99.73 ± 1.33
99.87 ± 0.52
100.11 ± 0.59
5–30

a
The intraday (n = 3), average of three concentrations (4, 12, 24 lg mlÀ1) for metronidazole and (5, 15, 25 lg mlÀ1) for diloxanide furoate
repeated three times within the day.
b
The interday (n = 3), average of three concentrations (4, 12, 24 lg mlÀ1) for metronidazole and (5, 15, 25 lg mlÀ1) for diloxanide furoate
repeated three times in three successive days.


326

M.R. El-Ghobashy and N.F. Abo-Talib

can be determined by direct measurement of absorbance at
314.0 nm, while the absorption spectra of diloxanide furoate
and metronidazole showed severe overlap, which makes the
determination of diloxanide furoate concentration in the mixture more difficult (Fig. 1). By applying the proposed techniques to the spectral data of the mixture, both diloxanide
furoate and metronidazole concentrations could be determined
without any interference.

in the mixture could be calculated, without any interference, at
314.0 nm. Thus the concentration of (II) could be calculated by
subtraction.

A linear correlation was obtained between the absorbance
values and the corresponding concentrations of both drugs at
their corresponding wavelengths. The regression equations
were:

Isosbestic spectrophotometric method

Aiso ¼ 0:0134C þ 0:0204 r ¼ 0:9994 at 277:2 nm
A ¼ 0:0324C þ 0:0024 r ¼ 0:9995 at 314:0 nm

Erram and Tipnis [23] developed the isosbestic spectrophotometric method. This method was used for simultaneous determination of (I) and (II) in their binary mixtures. At the
isosbestic point the mixture of drugs acts as a single component and gives the same absorbance value as pure drug. Thus,
by measuring the absorbance value at the chosen isosbestic
point 277.2 nm (Aiso) (Fig. 1), the total concentration of both
(I) and (II) could be calculated, while the concentration of (I)

where A is the absorbance, C is the concentration of the drug
in lg mlÀ1 and r is the correlation coefficient.
The proposed method was applied for the determination of
(I) and (II) in bulk powder: satisfactory results were obtained
(Table 1).
The laboratory-prepared mixtures were analyzed by
the isosbestic method. The method is valid for determining
the drug in laboratory-prepared mixtures as shown in
(Table 2).

Table 2

Determination of metronidazole and diloxanide furoate in laboratory-prepared mixtures by the proposed methods.

Mixture no.

1
2
3
4
5
6

Claimed taken (lg mlÀ1)

Isospestic spectrophotometry

Ratio subtraction
spectrophotometry

Metronidazole

Metronidazole

Diloxanide furoate

Diloxanide furoate

Recoverya%
at 314 nm

Recoverya% at
277.2 nm

Recoverya% at 251.2 nm

101.61
98.71
101.57
97.30
100.77
98.18

99.00
97.26
100.86
97.45
100.29
97.07

99.08
100.52
99.35
98.95
100.26
99.47

10
10
10
5
15
5

Mean ± SD
a

Diloxanide
furoate

8
10
5
8
8
10

99.69 ± 1.86

98.66 ± 1.65

99.61 ± 0.64

Average of three determinations.

Fig. 2 Division spectra of laboratory prepared mixtures of diloxanide furoate (X) and metronidazole (Y) using 4 lg mlÀ1 of
metronidazole (Y’) as a divisor and methanol as a blank.


Analysis of metronidazole and diloxanide furoate in binary mixture

327

Ratio subtraction spectrophotometric method

concentration from the corresponding regression equation
could be calculated. This can be summarized as follows:

The method was applied for determination of mixture of (II)
and (I) when the spectrum of (I) extended than the other
(II), as shown in (Fig. 1). The determination of (II) could be
achieved by scanning the zero order absorption spectra of
the laboratory-prepared mixtures (I and II) in methanol, then
dividing them by a carefully chosen concentration (4 lg mlÀ1)
of standard (I) (I0 = divisor) to produce a new ratio spectra
that represents II/I0 + constant, as shown in (Fig. 2); then,
subtraction of the absorbance values of these constants (I/I0 )
in plateau as shown in (Fig. 3) followed by multiplication of
the obtained spectra by (I0 ) the divisor as shown in (Fig. 4); finally, the original spectra of (II), which are used for direct
determination of (II) at 251.2 nm, could be obtained and the

ðII þ IÞ=I0 ¼ II=I0 þ I=I0 ¼ II=I0 þ constant
II=I0 þ constant À constant ¼ II=I0
II=I0 Â I0 ¼ II
The constant can be determined directly from the curve
(II + I)/I0 by the straight line which is parallel to the wavelength axis in the region where (I) is extended. The correct
choice of the divisor is fundamental, as, if the concentration
of the divisor increases or decreases, the resulting constant value will be proportionally decreased or increased [24].
A linear correlation was obtained between the absorbance
and the corresponding concentration of (II) at its corresponding wavelength: the regression equation was:

Fig. 3 Division spectra of laboratory prepared mixtures of diloxanide furoate (X) and metronidazole (Y) using 4 lg mlÀ1 of
metronidazole (Y0 ) as a divisor and methanol as a blank after subtraction of the constant.

Fig. 4 The zero order absorption spectra of diloxanide furoate obtained by the proposed ratio subtraction method for the analysis of
laboratory prepared mixtures after multiplication by the divisor (Y0 ).


328

M.R. El-Ghobashy and N.F. Abo-Talib

Table 3 Determination of metronidazole and diloxanide furoate in their pharmaceutical preparations by the proposed methods and
application of standard addition technique.
Product

Isosbestic spectrophotometry

Ratio subtraction spectrophotometry

Founda (%) ± SD Added Founda Recovery (%) Founda (%) ± SD Added Founda Recovery (%)
Metronidazole in Furazole tablets
(batch no. 080435)

100.23 ± 0.62

4
8
12

3.94
8.03
11.77

98.50
100.38
100.23 ± 0.62
98.08
98.99 ± 1.23

4
8
12

3.94
8.03
11.77

98.50
100.38
98.08
98.99 ± 1.23

5
10
15

4.98
9.81
14.68

99.60
98.10
98.97 ± 0.23

97.87
98.52 ± 0.94

5
10
15

4.96
9.86
14.80

99.20
98.60
98.67
98.82 ± 0.33

4
8
12

3.95
7.87
11.90

98.75
98.38
98.69 ± 0.54
99.17
98.77 ± 0.40

4
8
12

3.95
7.87
11.90

98.75
98.38
99.17
98.77 ± 0.40

5
10
15

4.98
10.01
14.72

99.60
100.10
99.13 ± 0.49
98.13
99.28 ± 1.02

5
10
15

4.97
9.96
15.08

99.40
99.60
100.53
99.84 ± 0.60

Mean ± SD
Diloxanide furoate in Furazole tablets
(batch no. 080435)
99.04 ± 0.98
Mean ± SD
Metronidazole in Furazole suspension
(batch no. 074135)
98.69 ± 0.54
Mean ± SD
Diloxanide furoate in Furazole
suspension (batch no. 074135)

99.20 ± 0.66

Mean ± SD
a

Average of three determinations.

Table 4 Statistical comparison of the results obtained by applying the proposed methods and the direct spectrophotometric

manufacturer method for the analysis of pure metronidazole and diloxanide furoate.
Manufacturer method

Ratio subtraction spectrophotometry

Isosbestic spectrophotometry

Diloxanide furoate

Metronidazole

Diloxanide furoate

Diloxanide furoate

Metronidazole

100.50
0.71
6
0.504
–
–

99.84
1.26
6
1.588
–
–

99.73
1.33
6
1.769
1.251
3.510

99.96
1.47
6
2.161
0.816
4.288

99.83
1.41
6
1.988
0.013
1.252

*

Value

Mean
SD
n
Variance

t-Test (2.228)*
F value (5.05)*

The values in parenthesis are corresponding to the theoretical values of t and F (P = 0.05).

A ¼ 0:0726C þ 0:0452 r ¼ 0:9997
where A is the absorbance of (II) at 251.2 nm, C is the concentration of (II) in lg mlÀ1 and r is the correlation coefficient.
The proposed method was applied for the determination of
(II) in bulk powder and satisfactory results were obtained see
(Table 1).
The laboratory-prepared mixtures were analyzed by the ratio subtraction method at 251.2 nm. The method is valid for
determining the drug in laboratory-prepared mixtures as
shown in (Table 2).
The proposed methods were successfully applied for the
analysis of both drugs in pharmaceutical dosage form and
the results are shown in (Table 3).
The validity of the proposed methods was assessed by
applying the standard addition technique. The results obtained
were reproducible with low relative standard deviation as
shown in (Table 3).
A statistical comparison of the results obtained by the two
proposed methods and the manufacturer’s method for pure
drugs is shown in Table 4. The values of the calculated t and
F are less than the tabulated ones, which reveals that there is
no significant difference with respect to accuracy and precision

between the proposed methods and the manufacturer’s
procedure.
Conclusion
The aim of this work is to develop simple and new methods for

the simultaneous determination of metronidazole and diloxanide furoate. The isosbestic spectrophotometric and ratio subtraction spectrophotometric methods could be applied to the
simultaneous determination of metronidazole and diloxanide
furoate either in their pure powder form or in their combined
preparations. The results demonstrate the usefulness of the
methods, which are simple, safe, sensitive, precise, accurate,
inexpensive and non-polluting. So, the proposed methods
could be used in routine and quality control analysis of metronidazole and diloxanide furoate in pharmaceutical preparations containing them.
References
[1] O’Neil MJ, Smith A, Heckelman PE, Budavari SB. Merck index.
14th ed. Darmstadt: Merck Sharp & Dohme Corp.; 2006.


Analysis of metronidazole and diloxanide furoate in binary mixture
[2] Zhao L, Dou Y, Mi H, Ren M, Ren Y. Non-destructive
determination of metronidazole powder by using artificial neural
networks on short-wavelength NIR spectroscopy. Spectrochim
Acta A Mol Biomol Spectrosc 2007;66(4-5):1327–32.
[3] Bartlett PN, Ghoneim E, El Hefnawy G, El-Hallag I.
Voltammetry and determination of metronidazole at a carbon
fiber microdisk electrode. Talanta 2005;66(4):869–74.
[4] Lu S, Wu K, Dang X, Hu S. Electrochemical reduction and
voltammetric determination of metronidazole at a nanomaterial
thin film coated glassy carbon electrode. Talanta 2004;63(3):
653–7.
[5] O¨zkan SA, O¨zkan Y, S
ß entu¨rk Z. Electrochemical reduction of
metronidazole at activated glassy carbon electrode and its
determination in pharmaceutical dosage forms. J Pharm
Biomed Anal 1998;17(2):299–305.
[6] Salem AA, Mossa HA, Barsoum BN. Application of nuclear

magnetic resonance spectroscopy for quantitative analysis of
miconazole,
metronidazole
and
sulfamethoxazole
in
pharmaceutical and urine samples. J Pharm Biomed Anal
2006; 41(2):654–61.
[7] Ho C, Sin DWM, Wong KM, Tang HPO. Determination of
dimetridazole and metronidazole in poultry and porcine tissues
by gas chromatography-electron capture negative ionization
mass spectrometry. Anal Chim Acta 2005;530(1):23–31.
[8] Xia X, Li X, Zhang S, Ding S, Jiang H, Shen J. Confirmation of
four nitroimidazoles in porcine liver by liquid chromatography–
tandem mass spectrometry. Anal Chim Acta 2007;586(12):394–8.
[9] Ding T, Xu J, Shen C, Jiang Y, Chen H, Wu B, Zhao Z, Li G,
Zhang J, Liu F. Determination of three nitroimidazole residues
in royal jelly by high performance liquid chromatography–
tandem mass spectrometry. Chin J Chromatogr 2006;24(4):
331–4.
[10] Go´mez MJ, Petrovic´ M, Ferna´ndez-Alba AR, Barcelo´ D.
Determination of pharmaceuticals of various therapeutic
classes by solid-phase extraction and liquid chromatography–
tandem mass spectrometry analysis in hospital effluent
wastewaters. J Chromatogr A 2000;1114(2):224–33.
[11] Fraselle S, Derop V, Degroodt JM, Van Loco J. Validation of a
method for the detection and confirmation of nitroimidazoles
and the corresponding hydroxy metabolites in pig plasma by
high performance liquid chromatography–tandem mass
spectrometry. Anal Chim Acta 2007;586(1–2):383–93.

[12] Jessa MJ, Barrett DA, Shaw PN, Spiller RC. Rapid and selective
high-performance liquid chromatographic method for the
determination of metronidazole and its active metabolite in

[13]

[14]

[15]

[16]

[17]
[18]

[19]

[20]

[21]

[22]

[23]

[24]

329
human plasma, saliva and gastric juice. J Chromatogr B Biomed
Appl 1996;677(2):374–9.

Bempong DK, Manning RG, Mirza T, Bhattacharyya L. A
stability-indicating HPLC assay for metronidazole benzoate. J
Pharm Biomed Anal 2005;38(4):776–80.
Akay C, O¨zkan SA, S
ß entu¨rk Z, Cevheroglu S. Simultaneous
determination of metronidazole and miconazole in
pharmaceutical dosage forms by RP-HPLC. Farmaco 2002;
57(11):953–7.
Vega E, Dabbene V, Nassetta M, Sola´ N. Validation of a
reversed-phase LC method for quantitative analysis of
intravenous admixtures of ciprofloxacin and metronidazole. J
Pharm Biomed Anal 1999;21(5):1003–9.
Vega E, Sola´ N. Quantitative analysis of metronidazole in
intravenous admixture with ciprofloxacin by first derivative
spectrophotometry. J Pharm Biomed Anal 2001;25(3-4):523–30.
Al-Khannam SM, Belal F. Spectrophotometric determination of
diloxanide furoate in dosage forms. Il Farmaco 2001;56:677–81.
Hasan NY, Elkawy MA, Elzeany BE, Wagieh NE. Stability
indicating methods for the determination of diloxanide furoate.
J Pharm Biomed Anal 2002;28(2):187–97.
Gadkariem EA, Belal F, Abounassif MA, El-Obeid HA,
Ibrahim KEE. Stability studies on diloxanide furoate involving
effect of pH, temperature, gastric and intestinal fluids. Il
Farmaco 2004;59(4):323–9.
Prasad CV, Sripriya V, Saha RN, Parimoo P. Simultaneous
determination of tinidazole, furazolidone and diloxanide furoate
in a combined tablet preparation by second-derivative
spectrophotometry. J Pharm Biomed Anal 1999;21(5):961–8.
Galal SM, Bedair MM, El-Sayed MA. Derivative
spectrophotometric determination of antiprotozoal drugs in

two- component tablet preparation. J Pharm Belg 1991;46(5):
315–9.
Mishal A, Sober D. Stability indicating reversed-phase liquid
chromatographic determination of metronidazole benzoate and
diloxanide furoate as bulk drug and in suspension dosage form.
J Pharm Biomed Anal 2005;39(3–4):819–23.
Erram SV, Tipnis HP. Simple spectrometric analysis of
propranolol hydrochloride and hydrochlorothiazide from
combined pharmaceutical dosages. Indian Drugs 1994;31(2):
65–8.
El-Bardicy MG, Lotfy HM, El Sayed MA, El-Tarras MF. Smart
stability-indicating
spectrophotometric
methods
for
determination of binary mixtures without prior separation. J
AOAC Int 2008;91(2):299–310.