November 2007
Chem. Pharm. Bull. 55(11) 1551—1556 (2007)
1551
Evaluation of N-Bromosuccinimide as a New Analytical Reagent for the
Spectrophotometric Determination of Fluoroquinolone Antibiotics
a
a
b
Hassan ASKAL, Ibrahim REFAAT, Ibrahim DARWISH, ,a,1) and Mostafa MARZOUQ
*
a Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Assiut University; Assiut 71526, Egypt: and
b Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Al-Azhar University; Assiut, 71524, Egypt.
Received January 21, 2007; accepted August 12, 2007
Analytical studies were carried out, for the first time, to evaluate the use of N-bromosuccinimide (NBS) as
an analytical reagent for the spectrophotometric determination of eleven therapeutically important fluoro-
quinolone antibiotics (FQA). The procedures involved the reaction of the FQA with NBS and subsequent meas-
urement of the excess NBS by its reaction with p-phenylenediamine (PDA) to give a violet colored product that
was measured at 530 nm. Different variables affecting the reaction (concentration of NBS, concentration of PDA,
pH of reaction medium, reaction time, and the diluting solvents) were carefully studied and optimized. The
molar ratio and mechanism of the reaction between each of the studied FQA with NBS were proposed using
UV–vis, IR, and NMR techniques. Under the optimum reaction conditions, the analytical method was developed
and validated. Beer’s law was obeyed in the general concentration range of 3—25 mg/ml. The assay limits of de-
tection and quantitation were 0.33—1.29 and 1.10—4.31 mg/ml, respectively. The precision of the method was
satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully
applied to the analysis of the investigated FQA in their pure and pharmaceutical dosage forms without interfer-
ence from the common excipients (label claim values were 99.85—100.17ꢀ0.13—0.59%). Interference from
ascorbic acid, that is co-formulated as a stabilizer for the ampoule form, was avoided by its pre-oxidation with
potassium bromate before applying the analytical procedure. The results obtained by the proposed method were
comparable with those obtained by the official and reported methods.
Key words fluoroquinolone antibiotic; N-bromosuccinimide; p-phenylenediamine; spectrophotometry; pharmaceutical analysis
Other equipment used included an electrothermal melting point apparatus
(Stuart Scientific Co., Florida, U.S.A.), an infrared spectrometer (IR 200-
91527, Shimadzu, Kyoto, Japan), and a 1H-NMR spectrometer (EM-360,
60 MHz, Varian Instrument Division, Palo, Alto, CA, U.S.A.).
Fluroquinolone antibiotics (FQA) are a class of important
synthetic antibacterial agents, which are active against Gram
positive and Gram negative bacteria.2) They are receiving a
significant attention due to their broad spectrum of activity,
Chemicals and Materials The following authentic standards were used
potency, variable indications and excellent pharmacokinetic after confirming their purity and compliance with the pharmaceutical re-
quirements. Amifloxacin (Sterling Winthrop Inc., U.S.A.), ciprofloxacin HCl
(Miles Inc. Pharmaceutical Division, West Haven, Germany), difloxacin HCl
(Abbott Laboratories, North Chicago, U.S.A.), enrofloxacin (Merck, Darm-
stadt, Germany), gatifloxacin (Bristol-Myers Squibb S.A.E., Cairo, Egypt),
profiles. Because of their therapeutic importance, numerous
analytical methods have been developed for their determina-
tions in pharmaceutical formulations and/or biological fluids;
comprehensive reviews for these methods were presented by
Carlucci G.3) and Belal F. et al.4) Spectrophotometry, because
of its inherent simplicity, low cost, and wide availability in
most quality control laboratories comprises the most widely
used technique for determination of FQA in bulk and phar-
maceutical dosage forms.5—15)
N-Haloimides have been used as effective analytical
reagents for the spectrophotometric determination of many
pharmaceutical compounds via oxidation or bromination of
these compounds.16—22) N-Bromosuccinimide (NBS), being
the most versatile one, is the most commonly used.17—22) The
use of NBS as an analytical reagent offered adequate sensi-
tivity and accuracy, in addition to the simplicity and low cost
of the analytical method. The use of NBS for the determina-
tion of FQA has not been reported yet. Therefore, the present
levofloxacin (Aventis Pharma S.A.E, Cairo, Egypt), lomefloxacin HCl
(Searle, Illinois, U.S.A.), norfloxacin HCl (Egyptian International Pharma-
ceutical Industries Co., Cairo, Egypt), ofloxacin (Daiichi, Tokyo, Japan), pe-
floxacin methanesulphonate (Rhone-Poulenc Rorer, Neuilly/Seine, France),
and sparfloxacin (Global Napi Pharmaceuticals, Cairo, Egypt). N-Bromo-
succinimide (NBS; Aldrich Co., Ltd., Gillingham-Dorst, Germany) was
0.5 mg/ml aqueous solution. Hydrochloric acid was obtained from El-Nasr
Pharmaceutical Chemicals Co. (Cairo, Egypt). p-Phenylenediamine (PDA;
Loba Chemie PVT. Ltd., Mumbai, India) was used at a concentration of
0.1 mg/ml in 0.01 M HCl solution. DC Alufolien, Kiesselgel 60 F254 pre-
coated TLC plates were purchased from E. Merck (Darmastadt, Germany).
All other chemicals and solvents used throughout this study were of analyti-
cal grade.
Pharmaceutical Dosage Forms The following pharmaceutical formu-
lations were obtained from the local markets and analyzed. Ciprofloxacin®
tablets (Amriya Pharmaceutical Industries, Alexandria, Egypt) are labeled to
contain 500 mg of ciprofloxacin HCl per tablet. Ciprofloxacin® intravenous
infusion (Amriya Pharmaceutical Industries, Alexandria, Egypt) is labeled
study was undertaken to evaluate NBS as an analytical to contain 200 mg of ciprofloxacin lactate per 100 ml infusion. Cipro® optic
reagent for the spectrophotometric determination of FQA.
The analytical procedure involved the treatment of the FQA
with NBS and subsequent measurement of the excess NBS
by its reaction with p-phenylenediamine (PDA) to give a vio-
let colored product that was measured at 530 nm.
drops (Chemical Industries Development Co., Giza, Egypt) are labeled to
contain 3.5 mg of ciprofloxacin HCl per 1 ml solution. Lomoxin® tablets
(Minapharm Egypt for Egyptian Group for Drug Trading, 10th Ramadan
City, Egypt) are labeled to contain 400 mg of lomefloxacin per tablet. Or-
chacin® eye drops (Minapharm Egypt for Egyptian Group for Drug Trading,
10th Ramadan City, Egypt) are labeled to contain 3 mg of lomefloxacin per
1 ml solution. Neofloxin® tablets (Alexandria Co., for Pharmaceuticals,
Alexandria, Egypt) are labeled to contain 400 mg of norfloxacin per tablet.
Conaz® tablets (Pharaonia Pharmaceuticals for Wockhardt Egypt, Alexan-
Experimental
Equipment An UV-1601 PC (Shimadzu, Japan), and a Lambda-3B
(Perkin-Elmer Corporation, Norwalk, U.SA.) ultraviolet–visible spectropho- dria, Egypt) are labeled to contain 400 mg of norfloxacin and 600 mg of
tometers with matched 1-cm quartz cells were used for all measurements. tinidazole per tablet. Ofloxacin® tablets (Sedico Pharmaceutical Co., 6th Oc-
∗ To whom correspondence should be addressed. e-mail: ia_darwish@yahoo.co.uk
© 2007 Pharmaceutical Society of Japan