Potassium permanganate–glyoxal chemiluminescence system for flow
injection analysis of cephalosporin antibiotics: cefalexin, cefadroxil,
and cefazolin sodium in pharmaceutical preparations
Yuanyuan Sun, Yuhai Tang, Hong Yao, Xiaohui Zheng
Department of Chemistry, College of Science, Xi’an Jiaotong University, Xi’an 710061, PR China
Received 27 October 2003; received in revised form 2 February 2004; accepted 2 February 2004
Abstract
A sensitive flow injection chemiluminescence (FL-CL) method for the determination of cephalosporin antibiotics, was developed. The
method was based on that cephalosporin antibiotics could enhance the CL reaction of glyoxal and KMnO4 in sulfuric acid. Method developmentincluded the optimization of reagent concentrations and flow-rate. Under the optimized conditions, three cephalosporin antibiotics: cefalexin,cefadroxil, and cefazolin sodium, were determined. The detection limits of the method are 10 ng ml−1 cefalexin, 2 ng ml−1 cefadroxil, and2 ng ml−1 cefazolin sodium. The method was successfully applied to the determination of three cephalosporin antibiotics in pharmaceuticalpreparations. 2004 Elsevier B.V. All rights reserved. Keywords: Chemiluminescence; Flow injection; Cephalosporins; Pharmaceutical preparations
1. Introduction
cence reaction of cefadroxil with potassium permanganatein sulphuric acid, sensitized by quinine.
Cephalosporins, a kind of -lactam antibiotics with a
The present paper described a new flow injection CL
basic structure of 7-aminocephalosporanic acid, are widely
method for the determination of three cephalosporin an-
used to treat respiratory tract infection, prostatitis, urinary
tibiotics: cefalexin, cefadroxil, and cefazolin sodium. The
tract infection, skin, and soft tissues infection that often re-
method was based upon the enhancing effect of these an-
sult from encroachment of sensitive bacteria. Many methods
tibiotics on the CL reaction of glyoxal with potassium per-
have been reported for the determination of cephalosporins,
manganate in acid condition. Compared with the previous
reported chemiluminescence methods for cephalosporins
the present method shows lower detection limits
only few reports on chemiluminescence (CL) methods for
and wider calibration ranges. The method was applied to the
the determination of cephalosporins. Kubo et al.
determination of cefalexin, cefadroxil, and cefazolin sodium
ported a flow injection analysis method for the detection
in pharmaceutical formulations with satisfactory results.
of cephalothin. It was based on the direct chemilumines-cence reaction of -lactam antibiotics with luminol in thepresence of hexacyanoferrate(III) and hexacyanoferrate(II)
2. Experimental
in alkaline solution. Aly et al. veloped a flow in-jection chemiluminescent (FL-CL) method for the determi-
nation of cefadroxil monohydrate with a detection limit of50 ng ml−1. The method is based upon the chemilumines-
Analytical reagent grade chemicals and double distilled
water were used to prepare all solutions.
∗ Corresponding author. Tel.: +86-29-5275399; fax: +86-29-5275135.
Cefalexin, cefadroxil, and cefazolin sodium samples
E-mail address: tyh57@mail.xjtu.edu.cn (Y. Tang).
were purchased from National Institute for the Control of
0039-9140/$ – see front matter 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2004.02.012
Y. Sun et al. / Talanta 64 (2004) 156–159
KMnO4–cephalosporins solution. The calibration graphswere prepared by plotting the CL peak height against theconcentration of the cephalosporins. 2.3.2. Procedure for pharmaceutical preparations
Cefalexin capsules (250 mg per capsule), cefadroxil
tablets (250 mg per capsule) and cefazolin sodium for injec-
Fig. 1. Schematic diagram of the flow system for determination of
tion (500 mg per bottle), were purchased from local markets.
cephalosporins. (a): Glyoxal solution; (b): KMnO
Each sample stock solution was prepared by dissolving a
ple solution; (M): Manifold (P): Peristaltic pump; (V): Six-way injection
quantity of the mixed content, equivalent to 250 mg of this
valve; (F): Flow cell; (PMT): Photomultiplier tube; (HV): High voltage;
cephalosporin, from 10 capsules, tablets or bottles with
(COM): Computer; (W): Waste solution.
water. Before analysis, the stock solutions were diluted ap-propriately to ensure the concentration of each within the
Pharmaceutical and Biological Products (Beijing, China).
KMnO4 was obtained from Xi’an Chemical Reagent Fac-tory (Xi’an, China). Glyoxal was provided by ChemistryDepartment of Xi’an Jiaotong University. Dosage forms
3. Results and discussion
containing cefalexin, cefadroxil, and cefazolin sodium werepurchased from local markets. 3.1. Effect of different acid concentrations
The 1 × 10−3 mol l−1 KMnO4 working solution was pre-
pared by diluting appropriate 0.1 mol l−1 stock solution in
It was observed that the CL signal of KMnO
water. The 0.05 mol l−1 working solution was prepared by
system was stronger in acid solution than in neutral or ba-
diluting appropriate 1 mol l−1 glyoxal solution in water.
sic solution. Four different acids (i.e. HCl, HNO
The 1.0 mg ml−1 standard solutions of cefalexin, ce-
fadroxil, and cefazolin sodium were daily prepared by
2SO4) of different concentrations, as the mediums for
dissolving 0.2500 g of each in water and diluting with water
4, over the range of 0.1–2 mol l−1 were tested. The
results showed maximum CL intensity was obtained with
to 250 ml. The standard solutions were stored in the refrig-
erator and protected from light. The testing solutions were
2SO4. The effect of H2SO4 on the CL reaction
prepared by appropriate dilution of these standard solutionswith water before used. 3.2. Effect of KMnO4 concentration
The effect of 1 × 10−4–1 × 10−2 mol l−1 KMnO4 on
ws the schematic diagram of the flow injection
the CL intensity was examined. The CL intensity contin-
chemiluminescence system. One peristaltic pump was used
ued to increase with increasing KMnO4 concentration up to
1.0×10−3 mol l−1. The experimental results showed that 1×
other peristaltic pump was used to pump glyoxal solutions.
10−3 mol l−1 could give rise to the larger CL response and
All components were connected with PTFE tubing (0.8 mm
lower background signal. Larger concentration of KMnO4
i.d.) in the flow system. Reagent solutions were injected into
could lower the CL intensity. Thus, 1×10−3 mol l−1 KMnO4
the flow system by a six-way injection valve. A photomul-
tiplier tube was used to detect the CL. The CL signal wasrecorded with IBM-compatible computer, which was em-ployed an IFFL-D model flow-injection CL analysis systemsoftware (Xi’an Ruike Electronic Equipment Corporation,Xi’an, China).
A series of working solutions of three cephalosporin
antibiotics with different concentrations were prepared bydiluting respective concentrated standard solutions. KMnO4solution in sulfuric acid was mixed with the cephalosporinssolution in a manifold prior to reaching the six-way injec-
Fig. 2. Effect of H2SO4 concentration of KMnO4 on the CL inten-
tion valve. Glyoxal solution was injected into the flow cell
sity. Conditions: cefalexin, 0.1 g ml−1; glyoxal, 0.05 mol l−1; KMnO4,
by the six-way injection valve to combine with the mixed
Y. Sun et al. / Talanta 64 (2004) 156–159
eters of the calibration curves and the calculated detectionlimits (S/N = 3).
In order to assess the selectivity of the proposed method,
the effect of some common inorganic ions and organiccompounds was studied by preparing solutions containing0.1 g ml−1 of cefalexin. It was considered not to interfereif a foreign material caused a relative error of less than±5% during the determination of 0.1 g ml−1 cefalexin. The results showed that no interference had been foundwhen including up to a 1000-fold Na+, K+, Mg2+, Ba2+,
Fig. 3. Effect of glyoxal concentration on the CL intensity. Conditions:
cefalexin, 0.1 g ml−1; KMnO4, 1 × 10−3 mol l−1.
acid, 500-fold carbowax, 100-fold Zn2+, five-fold Al3+,and two-fold CO 2−
3.3. Effect of glyoxal concentration
The effect of 0.02–0.15 mol l−1 glyoxal on the CL inten-
Following the procedure detailed in the pro-
sity was examined. The CL intensity continued to increase
posed method was applied to the determination of cefalexin,
with increasing glyoxal concentration up to 0.05 mol l−1.
cefadroxil and cefazolin in pharmaceutical formulations.
The experimental results (showed the CL intensity
The results were listed in and agreed well with
continued to increase with increasing glyoxal concentration
up to 0.05 mol l−1. When the glyoxal concentration is be-yond 0.05 mol l−1, the intensity of the CL signal is trending
stable. In this work, 0.05 mol l−1 glyoxal was selected.
It was reported that KMnO4 could react with some
3.4. Calibration curves, detection limits, and precisions
reductants in the presence of formaldehyde to produce1O 1
g), a complex oxygen molecule of single
The method allowed the determination of 0.01–1 g ml−1
state, which could transform into 3O2 (3 g), a triplet state
cefalexin, 0.01–1 g ml−1 cefadroxil, and 0.1–5 g ml−1 ce-
oxygen. During the transformation, it could produce CL and
fazolin sodium. The relative standard deviations for 11 repli-
the formaldehyde could accelerate oxidation reaction rate
cate measurements of cefalexin, cefadroxil, and cefazolin
Thus it was assumed that the cephalosporins could
sodium were 1.1, 1.3, and 1.5%, respectively, when their
also react with KMnO4 to produce CL and the CL reaction
concentrations were at 0.1 g ml−1. the param-
Table 1Calibration curves of the studied cephalosporins
Regression equation Y = a + b
a Y = a + b X where Y is the concentration in 0.1 g ml−1 and X is the CL intensity.
Table 2Determination results of cephalosporins in samples
Cefazolin sodium for injection (No.: B02082916)
Y. Sun et al. / Talanta 64 (2004) 156–159
Based on the above discussions, the possible reaction
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This work was financially supported by Xi’an Jiaotong
Contracepção de emergência: nova pauta do judiciário brasileiro RESUMO: O presente artigo versa sobre a legalidade da distribuição dos contraceptivos de emergência no Brasil. São analisadas decisões judiciais que restringem a distribuição do medicamento, por considerá-lo abortivo, bem como apontadas referências legais que prevêem seu uso enquanto método contraceptivo. Conclui
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