Spectrophotometric determination of metronidazole and secnidazole in pharmaceutical preparations

Article abstract of DOI:10.1016/j.farmac.2004.06.001

A rapid and sensitive spectrophotometric method is proposed for determination of metronidazole and secnidazole. The method depends on the reduction of metronidazole and secnidazole molecule with zinc dust and hydrochloric acid flowed by diazotization and coupling with 8-quinolinol to give red colored chromogens easily measured spectrophotometrically which has λ_max = 500 nm. The experimental conditions were optimized and Berr's law was obeyed over the applicable concentration ranges both techniques were applied successfully to a wide variety of pharmaceutical preparations.

Full text of DOI:10.1016/j.farmac.2004.06.001

IL FARMACO 59 (2004) 843–846
www.elsevier.com/locate/farmac
Spectrophotometric determination of metronidazole
and secnidazole in pharmaceutical preparations
T. Saffaj *, M. Charrouf, A. Abourriche,Y. Abboud, A. Bennamara, M. Berrada
Laboratoire de Chimie Organique Biomoléculaire, Faculté des Sciences Ben M’Sik, Avenue Cdt D. El Harti, BP 7955, Casablanca, Morocco
Received 1 June 2004; accepted 9 June 2004
Available online 24 August 2004
Abstract
A rapid and sensitive spectrophotometric method is proposed for determination of metronidazole and secnidazole. The method depends on
the reduction of metronidazole and secnidazole molecule with zinc dust and hydrochloric acid flowed by diazotization and coupling with
8-quinolinol to give red colored chromogens easily measured spectrophotometrically which has kmax = 500 nm. The experimental conditions
were optimized and Berr’s law was obeyed over the applicable concentration ranges both techniques were applied successfully to a wide
variety of pharmaceutical preparations.
© 2004 Elsevier SAS. All rights reserved.
Keywords: Metronidazole; Secnidazole; Diazotization; 8-Quinolinol; Spectrophotometry
1. Introduction
ronidazole and secnidazole molecule with zinc dust and
hydrochloric acid flowed by diazotization and coupling with
8-quinolinol.
Metronidazole
(2-methyl-5-nitroimidazole-1-ethanol)
The scientific novelty of the present work is that the
reagents used in both the method are easily available and the
chemistry of these reagents is already well established. The
reactions involved with these reagents are simple, rapid and
sensitive in their range of determination compared with other
established methods. As metronidazole and secnidazole are
important class of imidazole compounds known for their
antiamebic and antiprotozoal activity, their determination in
pharmaceutical is of great importance.
and secnidazole (1-(2-methyl-5-nitroimidazole-1-yl)propan-
2-ol) are used as antiprotozoal, antiamebic and antibacterial
drugs [1]. Excellent reviews have been published on the
activity and pharmacokinetics of these drugs.
Several methods have been reported for determination of
metronidazole and secnidazole which includes potentiomet-
ric [2,3], polarographic [4,5], CPG [6], supercritical fluid
chromatography [7], TLC [8], HPLC [9–12], voltammetric
[13], derivative spectrophotometry [14–16], flow injection
analysis [17] and spectrophotometry [18–26]. Most of the
spectrophotometric methods reported suffer from the disad-
vantage, like narrow range of determination, requires heating
or extraction, long time for the reaction to complete, use of
non-aqueous systems, stability of the colored product
formed, etc.
2. Materiel and methods
2.1. Instrumentation
A Perkin-Elmer 551 UV-visible spectrophotometer with
1.0 cm matched cells was used.
This paper describes sensitive and simple spectrophoto-
metric method for the determination of metronidazole and
secnidazole in either pure form or in its pharmaceuticals
formulations. The method is based on the reduction of met-
2.2. Reagents
All chemicals used were of analytical-reagent grade.
8-Quinolinol was purchased from prolabo. Sodium nitrite
was purchased from prolabo. Metronidazole and secnidazole
* Corresponding author. Fax: +212-22-70-46-75.
E-mail address: saffajt@yahoo.fr (T. Saffaj).
0014-827X/$ - see front matter © 2004 Elsevier SAS. All rights reserved.
doi:10.1016/j.farmac.2004.06.001

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T. Saffaj et al. / IL FARMACO 59 (2004) 843–846
were obtained as gifts from Aventis Pharma. All other re-
agents and solvents were of analytical-reagent grade.
2.3. Solutions
Accurately weighed (100 mg) metronidazole or secnida-
zole was transferred to a 100 ml beaker. Add 1 g of zinc dust
along with 20 ml 1 M hydrochloric acid. Stir well and wait
for 1 h at room temperature, filter and the filtrate was diluted
with water to 100 ml in a volumetric flask. The working
standard solution of the reduced metronidazole and secnida-
zole containing 100 µg ml–1 was prepared by further dilution.
A 1% 8-quinolinol solution in 1 M HCl and a 10% solution of
hydroxyde de sodium were kept in amber-glass volumetric
flasks.
A 1% sodium nitrite solution and a 2% sulfamic acid
solution were prepared separately in distilled water.
2.4. Procedure
Scheme 1. Reaction sequence for the formation of red azo colored product.
Aliquots of the working standard solution of reduced
metronidazole or reduced secnidazole were transferred into
10 ml calibrated flasks. One milliliter of 1 M HCl was added,
cool in an ice bath and add 1 ml of 1% NaNO2, stir the
solution for 2 min. Add 1 ml of 2% sulfamic acid, stir the
solution for 3 min and add 1 ml of 1% of 8-quinolinol. After
2 min made up to the mark with 10% of NaOH solution.
It was found that, 0.5–2 ml of 1 M HCl, 1–3 ml of 1%
NaNO2 solution, 1–3 ml of 1% 8-quinolinol solution were
necessary to achieve maximum color intensity.
The excess of nitrite sodium could be removed by the
addition of 1 ml of 2% sulfamic acid solution. An excess of
sulfamic acid has no effect on the color intensity of the
product formed.
2.5. Assay of pharmaceutical tablets
Twelve tablets were powdered and mixed thoroughly. An
amount equivalent to 100 mg of the drug was reduced as
mentioned in and the filtrate was made up to 100 ml and an
aliquot of this solution was treated as described above for
pure sample in both the method.
3.3. Quantification
Beer’s law is obeyed over the metronidazole concentra-
tion range of 1–17 µg/ml. Similarly, for secnidazole, Beer’s
law is obeyed over the concentration range of 1–15 µg/ml
The proposed procedure is validated by determining various
optical parameters, which are listed in Table 1.
3. Results and discussion
The spectrophotometric method for the determination of
metronidazole and secnidazole is based on the reduction of
the nitro to an amino group with zinc dust and hydrochloric
acid flowed by diazotization and coupling with 8-quinolinol
to give red colored product.
Table 1
Parameters for the spectrophotometric determination of metronidazole and
secnidazole
Parameters/characteristics
Color
Secnidazole
Red
Metronidazole
Red
3.1. Spectral characteristics and reaction mechanism
kmax (nm)
500
500
Stability (in days)
3
3
The absorption spectra of the red colored product with
kmax = 500 nm are shown in. The reagent blank has practi-
cally negligible absorption at this wavelength. The stochio-
metric equation derived was shown in Scheme 1.
Beer’s law range (µg ml–1
Molar absorptivity (l mol–1 cm–1
Regression equation a
Slop(a)
)
1–15
1.13104
1–17
0.90 × 104
)
0.058
0.0016
0.998
0.55
0.0516
0.0045
0.9985
0.73
Intercept (b)
3.2. Optimization of reactions conditions
Correlation coefficient
R.S.D.(%) b
The factors affecting color development, reproducibility,
sensitivity, and conformity with Beer’s law were investi-
gated.
a y = ax + b where x is the concentration of metronidazole or secnidazole in
µg ml–1
.
b five replicates.

T. Saffaj et al. / IL FARMACO 59 (2004) 843–846
845
Table 2
Determination of metronidazole and secnidazole in presence of excipients
Excipients
Amount (mg)
Recovery of MNZ a, % ( RSD b)
Recovery of SCN a, % ( RSD b)
100.4 0.40
Magnesium stearate
Carboxy methylcellulose
Lactose
40
50
30
30
50
50
50
50
30
99.5 0.52
100.5 0.30
99.7 0.66
99.1 0.70
99.8 0.55
Glucose
99.6 0.26
100.4 0.90
Sorbitol
100.1 0.70
100.5 0.75
Hypromellose
Povidone
100.3 0.45
99.6 0.85
101.5 0.38
100.6 0.48
Talc
99.6 0.80
99.9 0.26
Cellulose
98.9 0.90
100.3 0.50
a 10 µg ml–1 of metronidazole and secnidazole was taken.
b Average of five determination.
Table 3
Analysis of metronidazole in pharmaceutical preparation
Commercial formulations analyzed
Flagyl® 250
Content
Label claim (mg)
250/tablet
500/tablet
500/tablet
500
Recovery a, % ( RSD b)
99.5 ( 1.3)
Metronidazole
Metronidazole
Metronidazole
Metronidazole
Secnidazole
Flagyl® 500
98.2( 2.5)
Nidazol® 500
101.3( 1.8)
99.6( 1.5)
Synthetic mixture
Flagentyl® 500
500/tablet
500
100.7( 0.9)
99.3( 1.9)
Synthetic mixture
Secnidazole
a Average of five determination.
b Relative standard deviation.
3.4. Interference
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