Simultaneous Spectrophotometric Determination of Naproxen and ...

Journal of Applied Chemical Research, Volume 17, 65-74 (2011)
Journal of
Applied
Chemical
Research
www.jacr.kiau.ac.ir
Simultaneous Spectrophotometric Determination of
Naproxen and Pantoprazole in Pharmaceutical
Dosage Form
S. N.Sloka, B.M. Gurupadayya*, Ch. A. Kumar
Department of Pharmaceutical Analysis, JSS College of Pharmacy, JSS University, Mysore 570
015, (KA), India.
(Received 25 March 2011; Final version received 15 April 2011)
Abstract
Two simple, but accurate, precise, reproducible, without separation and economical procedures for
simultaneous estimation of naproxen and pantoprazole in combined capsule dosage form have been
developed. One method employs solving of simultaneous equations using 262 nm and 289 nm as
two analytical wavelengths for both drugs in methanol. The other method is Q- value analysis based
on measurement of absorptivity at 262 nm and at isoabsorptive point 310 nm showing linearity in
concentration range of 10.0- 50.0 μg.ml -1 for naproxen and 8.0- 18.0 μg.ml-1 for pantoprazole. The
method was validated with respect to accuracy, precision, limit of detection and limit of quantitation.
The proposed method is recommended for routine analysis since it is rapid, simple, accurate and also
sensitive and without need to heat and organic solvent extraction.
Key words: Naproxen, Pantoprazole, Q- analysis, Simultaneous equation method.
Introduction
Naproxen [(+)-2-(6- methoxy-2 naphtyl)
propionic acid], is a non- steroidal antiinflammatory
drug that also presents analgesic
and antipyretic properties. Naproxen is
extensively used in the treatment of many
diseases e.g. Rheumatoid arthritis, acute gout
and primary dysmenorrhea[1].Similar other
non- steroidal, anti- inflammatory drugs, it
inhibits the biosynthesis of prostaglandins.
The United States Pharmacopeia [2] reports
high performance liquid chromatography
(HPLC) method for the determination of
naproxen tablets. Several analytical methods
have also been reported for the determination
of naproxen in pharmaceutical preparations
including UV-visible spectrophotomery [3-
5] spectrofluorimetry [6-8], phosphorimetry
[9,10], voltammetry [11], high-performance
liquid chromatography [12-14], capillary
* Corresponding author: Dr. .M. Gurupadayya, Professor, Department of Pharmaceutical Analysis, JSS College of Pharmacy, JSS
University, Mysore, S.S. Nagar, Mysore-570 015, Karnatakam India. Email: bm_guru2004@yahoo.co.in Fax:+91 821-2548359,
Cell: +91 9242886136.

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S. N. Sloka et al., J. Appl. Chem. Res., 17, 65-74 (2011)
electrophoresis [15,16], coulometry[17] and
oscilometric titration [18].
Pantoprazole sodium 5-(difluromethoxy)-2-
[[3,4- dimethoxy-2- pyridinyl) methyl]
sulfinyl]- 1H- benzimidazolesesquihydate,
proton- pump inhibitor, inhibits gastric acid by
blocking the H + / K + adenosine triphosphatese
enzyme system of the gastric parietal cell. It
is used for short- term treatment of erosion
and ulceration of the esophagus. Different
analytical methods are reported in the literature
for the assay of pantoprazole sodium in dosage
forms and in biological fluids including
spectrophotometry [19-24], TLC [25], and
HPTLC [26-28]. The present study involves
the simultaneous estimation of naproxen and
pantoprazole in combined dosage form.
Experimental
Instrumentation
UV- Visible spectrophotometer, model UV-
1700 (Shimadzu, Japan) having cells with 1-
cm light path. Shimadzu electronic balance
was used for weighing the samples. Naproxen
(96.7% purity) was provided by Strides
Arcolab, Bangalore, India and Pantoprazole
(98.5%) was suplied from Cresant therapeutics
limited, Hyderabad, India. All other chemicals
and solvents used were of analytical grade.
Preparation of standard stock solutions
A) Standard NAP stock solution (1mg/ml)
Pure form of naproxen powder (50.0mg) was
accurately weighed and transferred into 50 ml
volumetric flask and dissolved in methanol for
further it diluted by 50 ml methanol (1000μg/
ml). The stock solution is further diluted to get
the required working standard solutions.
B)Standard PANTO stock solution (1 mg.ml -1 )
Pure form of pantoprazole powder (50.0mg)
was accurately weighed and transferred to 50 ml
volumetric flask and dissolved in methanol. Then
the solution was diluted to 50 ml with methanol
to prepare stock solution (1000 μg.ml -1 ). The
stock solution is then diluted with methanol to
get the stock solution of concentration 10μg.ml -
1
. This stock solution is used for preparing the
working standard solutions.
Determination of Absorption Maxima
The working standard stock solutions of
naproxen and pantoprazole were scanned in
the range of 200- 400 nm against methanol as
a blank. Naproxen and pantoprazole showed
absorbance maxima at 262nm and 289nm
respectively. The overlain spectra (λ max
) of both
drugs was recorded (isoabsorptive point) at
310nm. When compared to other solvents, best
results were found when methanol was used as
solvent and very less interference was observed.
Calibration curves (linearity)
A) Calibration curve of naproxen
A calibration curve was plotted over a
concentration range of 10.0 – 50.0 μg.ml -1 ,
using the stock solution of concentration 1000
μg/ml. Accurately measured standard stock

S. N. Sloka et al., J. Appl. Chem. Res., 17, 65-74 (2011) 67
solution of naproxen (0.1, 0.2, 0.3, 0.4 and
0.5 ml) were transferred to a separate series of
10.0 ml of volumetric flasks and diluted to the
mark with methanol. The absorbance of each
solution was measured at 262 nm. Calibration
curve was constructed by plotting absorbance
versus concentrations at 262 nm. Each reading
is the average of three determinations.
Figure 1.Calibration graph of naproxen at λ 1
and λ 2
.
B) Calibration curve of pantoprazole
curve was plotted over a concentration range
of 8.0 – 18.0 μg/ml, using the stock solution of
concentration 100 μg/ml. Accurately measured
standard stock solution of pantoprazole (0.8,
1.0,1.2, 1.4, 1.6 and 1.8 ml) were transferred
to a separate series of 10.0ml of volumetric
flasks and diluted to the mark with methanol.
The absorbance of each solution was measured
at 289 nm. Calibration curve was constructed
by plotting absorbance versus concentrations
at 289 nm. Each reading is the average of three
determinations.
Method I (Simultaneous equation method)
Two wavelengths selected for the method are
262nm and 289nm that provide absorption
maximas of naproxen and pantoprazole
respectively in methanol. The stock solutions
of both drugs were measured at the selected
wavelengths and absorptivities (a, 1%, 1cm)
for both drugs at both wavelengths were
determined as mean of three independent
determinations. Data are represented in Figure
1 and 2 respectively.
Figure 2.Calibration graph of pantoprazole at λ 1
and λ 2
.
Concentrations in the sample were obtained
using following equations:
CX = A 2
ay 1
- A 1
ay 2
/ ax 2
ay 1
- ax 1
ay 2
Eq (i)
CY = A 1
ax 2
- Avax 1
/ ax 2
ay 1
- ax 1
ay 2
Eq (ii)
Where, A 1
and A 2
are the absorbances of
mixture at 262 nm and 289 nm respectively,ax 1
and ax 2
are absorptivites of naproxen at λ 1
and
λ 2
respectively and ay 1
and ay 2
are absorptivites
of pantoprazole at λ 1
and λ 2
respectively.CX
and CY are concentrations of naproxen and
pantoprazole respectively.
Method II (Absorption ratio or Q –analysis
method)
From the overlain spectrum of naproxen and
pantoprazole, two wavelengths were selected
one at 310 nm which is the isoabsorptive point
for both drugs and the other at 262 nm which is

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S. N. Sloka et al., J. Appl. Chem. Res., 17, 65-74 (2011)
λ max
of naproxen (Figure 3).
The method employs Q - values and the
concentrations of drugs in sample solution
were determined using the following formula:
For Naproxen:
For Pantoprazole:
Figure 3.The curve showing the isobestic point at 310 nm.
The absorbances of the sample solutions
prepared in a similar manner as in the previous
method were measured and the absorptivity
values for both drugs at the selected
wavelengths were also calculated and are
represented in Figures 4 and 5 respectively.
Where,
Figure 4. Calibration graph of naproxen at λ 1
and
isobestic point.
Figure 5. Calibration graph of pantoprazole at λ 1
and
isobestic point.
A= Absorbance of sample at isoabsorptivity point,a1
and a2 = Absorptivites of naproxen and pantoprazole
respectively at isoabsorptive point.
Application of proposed method for the
determination of naproxen and pantoprazole in
capsules
Ten capsules dosage form (Arthopan)
manufactured by Cresant Therapeutics,
Hyderabad, India were used.Each capsule
contains naproxen 250 mg and pantoprazole
50 mg. The contents of the capsules were
weighed and mixed thoroughly. For analysis
of the drug, a standard addition method was
used. To bring the two drugs in the linearity

S. N. Sloka et al., J. Appl. Chem. Res., 17, 65-74 (2011) 69
range the quantity of powder equivalent to 5
mg of naproxen and 5mg of pantoprazole was
weighed and dissolved in 30.0 ml of methanol
and sonicated for 10 min. Then the solution
was filtered through whatman filter paper no.
41 and then final volume of the solution was
made up to 50.0 ml with methanol to get a stock
solution containing 100 μg/ml of naproxen
and 100 μg.ml -1 of pantoprazole. Appropriate
aliquots of naproxen and pantoprazole within
the Beer’s law limit were taken. In Method
I, the concentration of both naproxen and
pantoprazole were determined by measuring
the absorbance of the sample at 262 nm and 289
nm. Values were substituted in the respective
formula to obtain concentrations.Results of
capsule analysis are shown inTable 1.
Table 1.Analysis of Capsule Formulation for naproxen by Method I and Method II.
S. No Naproxen
METHOD I
METHOD II
mg/ capsule % Purity mg/ capsule % Purity
1. 243.09 97.24 245.98 98.39
2. 240.05 96.02 248.09 99.2
3. 232.59 93.03 246.69 98.67
Mean 238.57±0.31193 246.69±0.6199
% RSD 2.26 0.43
RSD = Relative Standard Deviation
For Method II, the concentrations of both
naproxen and pantoprazole were determined
by measuring absorbance of the sample
at 262 nm and 310 nm and values were
substituted in the respective formula to obtain
concentrations. Results of capsule analysis are
shown inTable 2.
Table 2.Analysis of Capsule Formulation for pantoprazole by Method I and Method II.
S. No Pantoprazole
METHOD I
METHOD II
mg/ capsule % Purity mg/ capsule % Purity
1. 19.09 95.45 18.99 94.95
2. 19.49 97.45 19.01 95.5
3. 19.54 97.7 19.09 95.45
Mean 19.49 19.01
% RSD 1.27±0.1424 0.28± 0.03055
RSD = Relative Standard Deviation.
(Each capsule contains 250.0mg of naproxen and 20.0mg of pantoprazole)

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S. N. Sloka et al., J. Appl. Chem. Res., 17, 65-74 (2011)
Method validation
Linearity
The linearity of an analytical method is its
ability to elicit test results that are directly or
by a well-defined mathematical transformation
proportional to the concentration of analyte
in samples within a given range. The range
of analytical method is the interval between
upper and lower level of analyte including
levels that have been demonstrated to be
determined with precision and accuracy using
the method. The linear response of naproxen
and pantoprazole were determined by analysing
three independent levels of the calibration
curve in the range of 10.0-50.0 μg.ml -1 and 8.0
– 18.0 μg/ml -1 respectively for naproxen and
pantoprazole in triplicate.
(10μg.ml -1 ) for six times and analysed as per
the proposed method. Percentage relative
standard deviation (%RSD).
B)Intermediate precision (Reproducibility)
It expresses within the laboratory variations
as on different days analysis or experiment
within the laboratory. Variation of results
within the same day is called intra- day
precision and variation of results amongst
days called inter- day precision. The intra-day
precision (C.V) was determined for standard
solutions of naproxen (10.0-50.0 μg/ml -1 )
and pantoprazole (8.0- 18.0 μg.ml -1 ) for three
times on the same day. The inter-day precision
(C.V) was determined for standard solutions
of naproxen and pantoprazole for three days.
Precision
The precision is the measure of either the degree
of reproducibility or repeatability of analytical
method. It provides an indication of random
error. The precision of an analytical method
is usually expressed as the standard deviation,
relative standard deviation or coefficient of
variance of a series of measurements.
A)Repeatability (Precision on replication)
It is a precision under a same condition
(Same analyst, same apparatus, short interval
of time and identical reagents) using same
sample. Method precision of experiment was
performed by preparing the standard solution
of naproxen (10μg/ml -1 ) and pantoprazole
Accuracy (% Recovery)
Accuracy of an analysis is determined by
systemic error involved. It is defined as closeness
of agreement between the actual (true) value
and analytical value, obtained by applying test
method for a number of times. Accuracy may
often be expressed as % recovery by the assay
of known, added amount of analyte (Table 3). It
is the measure of the exactness of the analytical
method. The recovery experiments were carried
out in triplicate by spiking preciously analysed
samples of the capsules (naproxen 10μg.
ml-1and pantoprazole 8μg/ml -1 ) with three
different concentrations of standards (naproxen
10, 20,30 μg.ml -1 and pantoprazole 8, 10, 12
μg.ml -1 ).

S. N. Sloka et al., J. Appl. Chem. Res., 17, 65-74 (2011) 71
Table 3.Recovery studies.
S. No Naproxen Pantoprazole
Amount Standard
Amount of % Recovery Amount Standard Amount of % Recovery
added
(µg/ml)
Sample Added
(µg/ml)
added (µg/ml) Sample Added
(µg/ml)
1. 10 10 99.43 2 8 101.27
2. 20 10 100.2 4 8 100.57
3. 30 10 98.09 6 8 99.45
Limit of Detection
It is the lowest amount of analyte in a sample that
can be detected but not necessarily quantified
LOQ = 10 × N/S
Where, N is the standard deviation of the peak
areas of the drug and S is the slope of the
under the stated experimental conditions. corresponding calibration curve.
Limits of detection can be calculated using
following equation as per ICH guidelines.
LOD = 3.3 × N/S
Where, N is the standard deviation of the peak
areas of the drug and S is the slope of the
corresponding calibration curve.
Results and Discussion
The overlain spectra of naproxen and
pantoprazole exhibit λ max
at 262 nm and 289
nm repectively which are quite separated from
each other. The optical characteristics are
given in Table 4.
Limit of Quantification
It is the lowest concentration of analyte in
Additionally one isoabsorptive point was
observed at 310 nm. This wavelength was
a sample that can be determined with the selected for simultaneous estimation of
acceptable precision and accuracy under
stated experimental conditions. Limit of
naproxen and pantoprazole for Q- value
anlaysis and it is assumed to be sensitive to
quantification can be calculated using wavelength. The optical characteristics are
following equation as per ICH guidelines. given in Table 5.
Table 4.Linear regression analysis data with their respective values for Method I.
Method I
Parameter
Naproxen
Pantoprazole
262 nm 289 nm 262 nm 289 nm
Beer’s law limits (µg/ ml) 10.0 -50.0 10.0 -50.0 8.0- 18.0 8.0- 18.0
Molar absorptivity 5.62 x10 3 1.336 x 10 3 9.153 x 10 3 1.567 x 10 3
(L.mol -1 .cm -1 )
Correlation coefficient (R) 0.998 0.998 0.996 0.999
Sandell’s sensitivity (µg.cm -2 ) 0.040 0.172 0.041 0.0245

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S. N. Sloka et al., J. Appl. Chem. Res., 17, 65-74 (2011)
Regression equation (Y) Y = 0.020X + Y= 0.004X + Y = 0.022X+ Y = 0.04 X+ 0.001
Y= bX+a
0.016 0.004
0.004
Slope, b 0.020 0.004 0.022 0.04
Intercept, a 0.016 0.004 0.004 0.001
Relative standard deviation% 1.88 2.71 2.43 0.77
Limit of detection (µg/ ml) 0.70 0.126 0.825 0.247
Limit of quantification (µg /ml) 2.1 0.378 2.475 0.741
Y= absorbance, X=concentration in µg/ml -1
Table 5.Linear regression analysis data with their respective values for Method II.
Method II
Parameter
Naproxen
Pantoprazole
262 nm 310 nm 262 nm 310 nm
Beer’s law limits (µg/ ml) 10.0 -50.0 10.0 -50.0 8.0- 18.0 8.0- 18.0
Molar absorptivity
5.62 x10 3 1.036 x 10 3 9.153 x 10 3 3.450 x 10 3
(L.mol -1 .cm -1 )
Correlation coefficient (R) 0.998 0.999 0.996 0.999
Sandell’s sensitivity (µg.cm -2 ) 0.040 0.22 0.041 0.11
Regression equation (Y)
Y= bX+a
Y = 0.020 X +
0.016
Y = 0.009 X -
0.000
Y = 0.022 X +
0.004
Y = 0.004 X +
0.002
Slope, b 0.020 0.009 0.022 0.004
Intercept, a 0.016 0.000 0.004 0.002
Relative standard deviation% 1.88 1.11 2.43 1.29
Limit of detection (µg /ml) 0.70 0.366 0.825 0.470
Limit of quantification (µg/ ml) 2.1 1.098 2.475 1.41
Y= absorbance, X=concentration in µg/ml -1
Standard calibration curves for naproxen and
pantoprazole were linear with correlation
coefficients(r) values 0.996- 0.999 at all
selected wavelengths and the values are
average of three readings with standard
deviation in the range of 0.0030 – 0.0121.
The calibration curves were repeated three
times in a day and the average % RSD was
found to be 1.11- 2.71 % for naproxen and
2.43- 0.77 % for pantoprazole at all the
selected wavelengths, similarly the method
was repeated for three days and the average
% RSD was found to be 1.15% for naproxen
and 2.58% for pantoprazole. The accuracy of
the method was confirmed by recovery studies
from capsule at three different levels of
standard additions. Recovery in the range of
98.0 – 101.27 % justifies the accuracy of the
method. The LOD values were found to be 0.7,
0.126, 0.366 and 0.83, 0.25, 0.47 for naproxen
and pantoprazole respectively at 262 nm, 289
nm and 310nm. The LOQ values were found
to be 2.1, 0.378, 1.098 and 2.475, 0.741, 1.41
for naproxen and pantoprazole respectively at
262 nm, 289 nm and 310nm. Based on various
optical andvalidation parameters, method II is

S. N. Sloka et al., J. Appl. Chem. Res., 17, 65-74 (2011) 73
more sensitive and reliable method compared
to method I.
Conclusion
All these factors lead to the conclusion that
the proposed method is accurate, precise,
simple, sensitive, and rapid and can be applied
successfully for the estimation of naproxen and
pantoprazole in pharmaceutical formulation
without any interference.
Acknowledgement
The authors are thankful to Strides Arcolab for
providing samples of pure drug of naproxen
and Cresant therapeutics Ltd for pantoprazole.
The authors are also thankful to Dr.H.G.
Shivakumar, Principal of JSS College of
Pharmacy for his encouragement to carry out
this work.
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