American Journal of Anal yt ical Chemistry, 2010, 1, 95-101
doi:10.4236/ajac.2010.13013 Published Online November 2010 (http://www.SciRP.org/journal/ajac)
Copyright © 2010 SciRes. AJAC
Development and Validation of Stability Indicating HPLC
Method for Simultaneous Estimation of Amoxicillin and
Clavulanic Acid in Injection
Durga Mallikarjuna Rao Tippa*, Narendra Singh
National P.G. College, Jaunpur, India
E-mail: tdmrao@yahoo.in
Received September 26, 2010; revised October 24, 2010; accepted October 27, 2010
Abstract
A simple, fast, precise, accurate and rugged stability indicating high performance liquid chromatography
(HPLC) method has been developed for simultaneous estimation of Amoxicillin and Clavulanic acid from
injectable dosage form. The stability indicating capability of the method was proven by subjecting the drugs
to stress conditions as per ICH recommended test conditions such as alkaline and acid hydrolysis, oxidation,
photolysis, thermal degradation and resolution of the degradation products formed therein. The separation
was obtained using a mobile phase composition at a ratio of 95:5 (v/v) of pH 5.0 buffer and methanol on In-
ertsil C18 column (250 × 4.0 mm, 4 μm) with UV detection at 220 nm at a flow rate of 1 ml/minute. The
photodiode array detector was used for stress studies. The order of elution of peaks was Clavulanic acid fol-
lowed by Amoxicillin. The linear calibration range was found to be 79.51 to 315.32 μg/ml for Amoxicillin
and 17.82 to 67.90 μg/ml for Clavulanic acid. The Amoxicillin and Clavulanic acid were found to be stable
in solution up to 24 hours. The method validation data showed excellent results for precision, linearity,
specificity, limit of detection, limit of quantification and robustness. The present method can be successfully
used for routine quality control and stability studies.
Keywords: Amoxicillin, Clavulanic Acid, HPLC, Stability Indicating
1. Introduction
Clavulanic acid is a novel beta-lactam compound which
was isolated from the culture fluid of Streptomyces cla-
vuligerus [1]. The compound is a potent inhibitor of a
large number of beta-lactamase enzymes, which are re-
sponsible for the resistance of many bacteria to beta-
lactam antibiotics [2]. In the presence of clavulanic acid,
beta-lactamase labile penicillins are protected from deg-
radation by cell-free beta-lactamase preparations and by
whole bacterial cultures [3].
Amoxicillin-Clavulanate potassium, a semi-synthetic
penicillin beta lactamase inhibitor combination drug, is a
widely used oral antibiotic [4]. Amoxicillin-Clavulanic
acid has been widely used as a prophylactic antibiotic in
abdominal and gynecological surgery [5]. It is effective
in the prevention of wound infections in operations in
which the most likely pathogens are gram-negative, an-
aerobic, or mixed bacteria [6]. Chemically, Amoxicillin
sodium is sodium (2S,5R.6R)-6-[®-(-)-2-Amino-2-(P-
hydroxyphenyl) acetamido]-3,3-dimethyl-7-oxo-4-thia-1-
azabicyclo[3.2.0] heptane-2-Carboxylate [7] and Clavu-
lanate potassium is potassium (2)-(2R,5R)-3-(2-hydro-
xyethylidene)-7-oxo-4-1-azabicyclo[3.2.0]-heptane-2-car-
boxylate [8]. Both of these drugs are official in pharma-
copoeias such as USP, BP etc. Several Amoxicillin and
Clavulanic acid combinations are available in market in
the form of tablet and suspension. In yester years in-
jectable formulation has also been developed.
Literature survey reveals that several HPLC methods
are reported for the determination of Amoxicillin [9-11]
and Clavulanic acid [12,13] individually. However, no
method is reported for simultaneous estimation of these
two drugs in injectable formulation by HPLC.
In the present investigation, a specific stability indi-
cating HPLC method is described for simultaneous esti-
mation of these two drugs in injectable dosage form.
Both the drugs were subjected to stress studies and the
degradation products formed were separated from the
main peaks. The proposed validated stability indicating
96 D. M. R. TIPPA ET AL.
method can be used for routine quality control and sta-
bility studies of the subjected formulation.
2. Materials and Methods
2.1. Instrumentation
The high pressure liquid chromatographic (HPLC) sys-
tem was used of model Agilent 1100 series equipped
with binary pump (G1312A), auto sampler (G1316A),
thermo stated column compartment and variable wave-
length detector (G1314A) controlled by the Chem station
software. A HPLC system equipped with isocratic pump
(G1310a), rheodyne injector (7725i) and photodiode ar-
ray detector (G1315A) was used for degradation studies.
A column Inertsil C18 HPLC column (250 × 4.0 mm, 4 µm)
was used as a stationary phase.
2.2. Materials
Working standards of Amoxicillin trihydrate and Clavu-
lanate potassium with lithium of potencies 86.12% (on as
basis as Amoxicillin) and 42.11% (on as in basis as Cla-
vulanic acid). Potassium dihydrogen phosphate monohy-
drate, sodium hydroxide and ortho-phosphoric acid were
used of analytical reagent grade. HPLC grade methanol
manufactured by E. Merck was procured from commer-
cial source. HPLC grade water was obtained using mil-
lipore water purification system. Clavam 1.2 g (Amox-
icillin and Clavulanate potassium for injection) is a dry
powder injection contains Amoxicillin sodium equivalent
to 1 g of Amoxicillin and Clavulanate potassium equiva-
lent to 0.2 g of Clavulanic acid.
2.3. Methods
2.3.1. Chrom a to graphic Conditions
The analysis was carried out on binary HPLC system
using the column Inertsil C18 (250 × 4.0 mm, 4 µm) with
UV-detection of 220 nm at ambient temperature using
20 µl injection volume. For degradation studies, an iso-
cratic pump and a photodiode array detector were used.
2.3.2. Selection of Wavelength
The bands of peaks are showing the maximum detection
level for Amoxicillin in the range of 210 nm to 240 nm
and Clavulanic acid in the range of 210 nm to 230 nm. A
single wavelength has selected for estimation of Amox-
icillin and Clavulanic acid as 220 nm as both the peaks
have the significant response. Overlaid spectrum of
Amoxicillin and Clavulanic acid is given in Figure 1.
2.3.3. Mobi l e Phase
A degassed mixture of (95:5 v/v) pH 5.0 buffer (7.8 g of
sodium dihydrogen phosphate monohydrate was dis-
solved, diluted to 1000ml with water and adjusted the pH
to 5.0 ± 0.05 using dilute ortho-phosphoric acid solution)
and methanol.
Figure 1. Overlaid spectrum of Amoxicillin and Clavulanic acid.
Copyright © 2010 SciRes. AJAC
D. M. R. TIPPA ET AL.
Copyright © 2010 SciRes. AJAC
97
2.3.4. Stand ard Solution
Standard stock solution was prepared by dissolving
Amoxicillin trihydrate working standard equivalent to
100 mg of Amoxicillin and Clavulanate potassium work-
ing standard equivalent to 20 mg of Clavulanic acid in 60
ml of water and then diluted to 100 ml with the same
solvent. This stock solution was further diluted with wa-
ter to get a solution of concentration 200 μg/ml of
Amoxicillin and 40 μg/ml of Clavulanic acid. A typical
chromatogram is given in Figure 2.
2.3.5. Cali b ra t i on
Seven different concentration (79.51-315.32 μg/ml of
Amoxicillin and 17.82 to 67.90 μg/ml of Clavulanic acid)
of mixture of Amoxicillin and Clavulanic acid were pre-
pared for linearity studies. The responses were measured
as peak areas and plotted against concentration.
2.3.6. Estimation of Amoxicillin and Clavulanic Acid
from Injectable Formulation
Ten samples of Clavam 1.2 g were emptied completely
and mixed. The pooled powder sample equivalent to
about 20 mg of Clavulanic acid and 100 mg of Amox-
icillin was transferred to dried 100ml volumetric flask.
Dissolved and diluted to 100mL with water. This stock
solution was further diluted with water to get a solution
of concentration 200 μg/mL of Amoxicillin and 40 μg/ml
of Clavulanic acid. 20 µl of each standard and test prepa-
rations were injected into the chromatography and the
responses were recorded.
2.4. Validation Parameters
The method validation was carried out as per ICH guide-
lines [14]. Various method validation parameters ascer-
tained are as follows.
2.4.1. Precision
Injection repeatability (System precision):
The injection repeatability was established by six rep-
licate injections of the standard solution containing both
the analytes of interest.
Sample repeatability (Method precision):
The sample repeatability was established by carrying
out the analysis of the analytes six times.
2.4.2. Specificity/Selectivity
Specificity of the method was evaluated by injecting the
blank, individual Amoxicillin, Clavulanic acid and sam-
ple solution prepared by spiking known impurities of
Amoxicillin and Clavulanic acid (i.e. , 6-Aminopenicil-
lanic acid and p-Hydroxyphenyl glycine) in sample at
1% level of test concentration and injected into HPLC
system to check the co-elution, if any, at the retention
time of Amoxicillin peak and Clavulanic acid peak.
2.4.3. Stress Testing (Forced Degradation)
To further confirm the stability indicating nature of the
analytical method, Amoxicillin and Clavulanate potas-
sium were subjected to stress testing as per ICH recom-
mended test conditions [15,16]. The drugs were subjected
Figure 2. A typical chromatogram of standard.
D. M. R. TIPPA ET AL.
Copyright © 2010 SciRes. AJAC
98
to acid hydrolysis by using 0.5M hydrochloric acid and
base hydrolysis by using 0.1N sodium hydroxide solu-
tion; oxidation by using 0.1%v/v solution of hydrogen
peroxide; thermal and photolysis.
The objective of stress study was to generate the deg-
radation products under various stress conditions. The
stress conditions varied both in terms of temperature and
time from moderate to extreme to achieve the appropri-
ate degradation. The spectral purity of the main peaks
was evaluated using photodiode array detector and
chemstation to verify that the degradation peaks are well
resolved from the main peaks.
2.4.4. Limit of Detection and Limit of Quantitation
The limit of detection (LOD) and the limit of quantita-
tion (LOQ) for Amoxicillin and Clavulanic acid were
determined.
2.4.5. Ruggedness (Intermediate Precision)
The ruggedness of the method was demonstrated by
analysis of the sample by using other column of same
brand with same specification and other instrument of
same brand and same configuration (Waters alliance
HPLC with Empower software). The percent relative
standard deviation (% RSD) of two sets of data indicates
the ruggedness of the method and t-test was performed.
2.4.6. Robus tness
The robustness of the method was determined as a meas-
ure of the analytical method capability to be unaffected by
small variations in method parameters. The different varia-
tions such as variation in flow rate by ± 0.2 ml/minute;
variation in wavelength by ± 2 nm, variation in tempera-
ture by ± 5˚C, variation in composition of mobile phase
± 5% absolute ( in terms of organic component) and
variation in pH of buffer by ± 0.2 units. At these changed
conditions, the standard and sample solutions were in-
jected. The system suitability was evaluated in each var-
ied condition. The amounts of Amoxicillin and Clavu-
lanic acid were calculated from sample solution in each
varied condition.
2.4.7. Stability of the Solution
A sample solution of Amoxicillin and Clavulanate potas-
sium for injection was prepared and analyzed initially
and also at different time intervals by keeping the solu-
tion at room temperature.
2.4.8. System Suitability Tests
System suitability was verified by injecting standard so-
lution on various days of the validation. The percent
RSD was verified from the replicate injections of stan-
dard solution. Various parameters such as tailing factor
and resolution between the peaks of Amoxicillin and
Clavulanic acid were obtained.
3. Results and Discussion
3.1. Precision
The values of the relative standard deviation of six repli-
cate injections of the standard solution containing both
the analytes of interest lie well within the limits (% RSD
2.0), indicating the injection repeatability of the
method. The values of the percent relative standard de-
viation for sample repeatability also lie well within the
limits (% RSD 2.0) indicating the sample repeatability
of the method. The results are given in Table 1.
3.2. Specificity/Selectivity
There was no interference from the blank and also from
the impurities (i.e., 6-Aminopenicillanic acid and p-Hydro-
xyphenyl glycine) at the retention time of Amoxicillin
and Clavulanic acid peaks. The peak purity data shows
the peaks are pure and there was no co-eluting peak at
the retention time of Amoxicillin peak and Clavulanic
acid peaks.
Table 1. Compiled data of method precision and rugged-
ness.
% Assay of
Amoxicillin
% Assay of
Clavulanic acid
S. No.
I II I II
1. 99.25 99.10 103.41 103.72
2. 98.81 99.50 106.94 103.41
3. 99.11 99.29 102.71 102.81
4. 100.21 100.10 102.41 102.79
5. 98.71 101.57 106.14 100.39
6. 101.72 101.65 102.01 99.97
Mean. 99.85 99.41 104.19 101.94
SD 1.851 1.751 1.944 1.740
% RSD 1.87 1.75 1.85 1.69
Overall Mean.99.49 104.015
Overall SD 1.801 1.842
Overall % RSD1.81 1.77
I-Method Precision, II-Ruggedness.
D. M. R. TIPPA ET AL.
99
3.3. Stress Testing (Forced Degradation)
The % degradation of Amoxicillin in acid hydrolysis,
base hydrolysis, oxidation, thermal and photolytic was
6.65, 6.21, 5.01, 13.12 and 8.59 respectively. The %
degradation of Clavulanic acid in acid hydrolysis, base
hydrolysis, oxidation, thermal and photolytic was 23.21,
14.41, 0.00, 17.80 and 10.21 respectively. Peak purity
was also found to be passed. The peaks of the degrada-
tion products were well resolved from the peaks of the
main component. The results of the stress studies are
tabulated in Tables 2(a) and 2(b).
3.4. LOD and LOQ
The LOD and LOQ for Amoxicillin and Clavulanic acid
were found to be 3.98 μg/ml and 12.06 μg/ml for Amox-
icillin and 7.13 μg/ml and 21.62 μg/ml for Clavulanic
acid, respectively.
3.5. Ruggedness (Intermediate Precision) &
Robustness
The percent relative standard deviation (% RSD) of two
sets of data indicates the ruggedness of the method. Fur-
ther, the t-test was performed on the data and the differ-
ence was found to be not significant. The compiled data
of method precision and ruggedness are given in Table 1.
The method is not affected by the deliberate variations
such as flow rate, wavelength, mobile phase composition,
temperature and pH.
3.6. Linearity
Calibration curve obtained by the least square regression
analysis between average peak area and concentration
showed linear relationship with a correlation coefficient
of 0.9998 0.9994 for Amoxicillin and Clavulanic acid
respectively over the calibration ranges tested.
The linear calibration range was found to be 79.51 to
315.32 μg/ml for Amoxicillin and 17.82 to 67.90 μg/ml
for Clavulanic acid. The linearity of the calibration
curves indicated the suitability of the method over a wide
range of concentration of both the actives.
Linear regression least square fit data obtained from
the calibration curves are given in Tables 3(a) and 3(b).
3.7. System Suitability and Stability of
Analytical Solution
The tailing of Amoxicillin and Clavulanic acid were in
the range of 0.96-0.99 and 1.07-1.14 respectively. The %
Table 2. (a) Forced degradation for Amoxicillin.
Mode of Degradation Condition % Assay % Degradation w. r. t control Peak purity data
Control No treatment 101.80 - 998.31
Acid 0.5 N HCl (2 hrs) 97.10 6.65 998.64
Base 0.1 N NaOH (0 hrs) 96.42 6.21 992.71
Oxidation 0.1% v/v H2O2 (0 hrs) 98.21 5.01 998.63
Thermal 50˚C (3 hrs) 88.92 13.12 998.39
Photolytic UV-light (3 hrs) 95.21 8.59 998.78
Table 2. (b) Forced degradation for Clavulanic acid.
Mode of Degradation Condition % Assay % Degradation w. r. t control Peak purity data
Control No treatment 101.27 - 999.21
Acid 0.5 N HCl (2 hrs) 78.91 23.21 999.90
Base 0.1 N NaOH (0hrs) 87.72 14.41 999.43
Oxidation 0.1% v/v H2O2 (0 hrs) 108.44 - 998.40
Thermal 50˚C (3 hrs) 84.21 17.80 999.10
Photolytic UV-light(3 hrs) 91.39 10.21 999.11
Copyright © 2010 SciRes. AJAC
D. M. R. TIPPA ET AL.
Copyright © 2010 SciRes. AJAC
100
Table 3. (a) Linearity of response for Amoxicillin.
S. No. Conc. (μg/ml) Peak area
1. 79.51 2322.80
2. 118.70 3458.52
3. 158.21 4674.12
4. 197.67 5767.28
5. 236.81 6972.31
6. 276.21 8067.69
7. 315.32 9187.91
Slope. 29.18
Intercept 43.34
Correlation Coefficient 0.9998
Table 3. (b) Linearity of response for Clavulanic acid.
S. No. Conc. (μg/ml) Peak area
1. 17.82 610.35
2. 26.11 708.51
3. 34.38 1226.31
4. 42.80 1509.10
5. 51.09 1820.12
6. 59.58 2095.61
7. 67.90 2485.09
Slope. 35.44
Intercept 26.14
Correlation Coefficient 0.9994
RSD for five replicate injections of standard was found
in the range of 0.03-0.05 for Amoxicillin peak and 0.13-
0.31 for Clavulanic acid peak. Resolutions between the
peaks were found in the range of 12.01-13.21. The reso-
lution, tailing factor and % RSD values are given in Ta-
ble 4.
The peaks of Amoxicillin and Clavulanic acid were
found to be symmetrical and well defined, free from
tailing. The elution order was Clavulanic acid first at
retention time of about 5.3 minutes followed by Amox-
icillin at retention time of about 7.5 minutes. The sensi-
tivity of the method using the said method was found to
be good. The total run time of each analysis is about 12
minutes, which is rapid and economical considering the
Table 4. System suitability.
% RSD Tailing factor
ExperimentR Amoxicillin
peak
Clavulanic
acid peak
Amoxicillin
peak
Clavulanic
acid peak
Method
precision 12.010.04 0.13 0.99 1.14
Stress study13.210.05 0.29 0.96 1.12
Linearity12.320.03 0.14 0.99 1.14
Ruggedness12.600.03 0.31 0.96 1.07
R-Resolution between Amoxicillin and Clavulanic acid peaks.
stability indicating nature of the method. The sample
solutions were found to be stable up to 24 hours.
4. Conclusions
The analytical method is simple, specific, rugged and
stability indicating. Hence it can be used for routine
quality control analysis as well as stability studies of
injection and might be useful for other pharmaceutical
dosage forms. The developed method is stability indi-
cating and it is LOD and LOQ values are in the range
of 3.98 μg/ml and 12.06 μg/ml for Amoxicillin and
7.13 μg/ml and 21.62 μg/ml for Clavulanic acid. This
method is sensitive and superior to the published meth-
ods since those are neither stability indicating nor LOD
and LOQ values are estimated at low level.
5. Acknowledgements
The help rendered by T.D.P.G College for providing the
facilities of their laboratory at Jaunpur, Uttar Pradesh
was gratefully acknowledged. The author also thanks to
Dr. A. N. Thakur, M.Sc, Ph.D. Professor, Department of
Physics, and T.D.P.G. College for his support.
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