ISSN: 0973-4945; CODEN ECJHAO

E-Journal of Chemistry
http://www.e-journals.net 2008, 5(S2), 1069-1080

Spectrophotometric and Conductometric

Determination of Clomiphene Citrate
and Nefazodone HCl
WAFAA S. HASSAN and MERVAT M. HOSNY

Analytical Chemistry Department,

Faculty of Pharmacy, Zagazig University, Zagazig, Egypt.
hassanwafaa76@yahoo.com

Received 30 December 2007; Accepted 20 February 2008

Abstract: Two accurate, rapid and simple spectrophotometric and

conductometric methods were developed for the determination of clomiphene
citrate (CMP) and nefazodone HCl (NFZ), the proposed methods depends
upon the reaction of ammonium reineckate with the two studied drugs to form
stable precipitate of ion-pair complexes, which was dissolved in suitable
solvent. The pink colored complexes were determined colorimetrically at 509,
523.6 nm, respectively. Using the conductometric titration, the studied drugs
could be evaluated in 50% (v/v) acetone in the range 60.02-540.18 and 63.3-443.1
g mL-1 for clomiphene citrate and nefazodone HCl, respectively. While for
spectrophotometric method the ranges were 0.2-1.8 and 0.2-1.6 mg mL-1 for
clomiphene citrate and nefazodone HCl respectively. Various experimental
conditions were studied. The results obtained showed good recoveries with
relative standard deviations of 0.759 and 0.552%. The proposed procedures
were applied successfully to the analysis of these drugs in their pharmaceutical
preparations and the results were favourably comparable with the official and
reference methods. The molar combining ratio reveal that (1:1) (drug : reagent)
ion associates were formed.
Keywords: Conductometric titration, Spectrophotometric determination, Clomiphene Citrate,
Nefazodone HCl.

Introduction
Clomiphene is used for induction of ovulation. It is a mixture of E and Z isomers of 2-{4-(2-
chloro-1,2-diphenylvinyl)phenoxy} triethylamine dihydrogen citrate. Different methods
were reported for its determination, either in pure or in dosage forms. It was determined by
spectrophotometric1-3, array-type DNA glass slide4, HPLC5-8, capillary electrophoresis9,
potentiometric10 and NMR methods11. Clomiphene was also determined in muco-adhesive
oral formulation of high permeability / high solubility drugs12.
1070 W. S. HASSAN et al.

Nefazodone hydrochloride belong to generation of antidepressant drugs, it appears to block

both 5-HT2 receptors. Scientific literature reports spectrophotometric method13, voltammetric
technique14, HPLC methods for quantitative determination of nefazodone HCL in its metabolites
in human plasma and in pharmaceutical formulations15-17, and MS technique18-19. Nefazodone HCl
is not included in any pharmacopoeia. With its ever increasing use and the number of formulations
entering into the market, there is always a need for simple, sensitive, accurate, rapid analytical
method for the estimation of it in pure form and pharmaceutical preparations which can be easily
adapted for routine in quality testing laboratories. In the present study, two different techniques for
the simple and accurate determination of the two drugs mentioned above were investigated.
Ammonium reineckate was used to form ion-pair complex with many drugs
e.g. thioridazine20 and propranolol HCl21, the method based on precipitation of the ion-
associates formed from the reaction of the drugs with ammonium reineckate. IR was
reported to confirm the structure of the complex.
Experimental
Apparatus
The absorption spectra for all measurements were carried out using Shimadzu 260 recording
spectrophotometer equipped with 10mm quartz cells. A CONSORT nv, Model (Parklaan 36,
B2300 Tumhout, Belgium) was used. The measurement range was 1.010.0 S with
maximum error of 0.2%. The CONSORT nv model K410 dip-type cell was used with a
cell constant, Kcell, of 1.0.
Reagent
Analytical grade reagents and double distilled water were used to prepare all solutions.
Ammonium reineckate (Aldrich) was used. Clomiphene citrate pure drug and clomid
tablets, each tablet contains 50 mg of clomiphene citrate (Global Napi Pharmaceutical, under
License of Aventis Pharma S.A.E.). Nefazodone HCl pure drug and serzone tablets
(produced by Bristol-Myers Squibb Pharm.Ind.-Egypt), each tablet contains 200 mg of
nefazodone per tablet.
Preparation of sample solutions
Solution of 2 mg/mL was prepared by dissolving 50 mg drug in distilled water and made up
to 25 mL in a volumetric flask for spectrophotometric procedure. For conductometric
procedure, a stock standard solutions of 2.010-3 M nefazodone and clomiphene were
prepared by dissolving an exact weight of the pure analytical reagent grade drug in 70 mL
double distilled water, to which 0.01 M hydrochloric acid was added in a 100 mL measuring
flask. The mixture was warmed at 50C in water bath for 5 min and diluted to volume with
double distilled water. It was agitated by an electrical shaker for 5.0 min then cooled to room
temperature and diluted to volume with double distilled water.
Also 110-2 and 510-3 M ammonium reineckate (Aldrich) solutions were prepared by
dissolving appropriate weight in 100 mL double distilled water for spectrophotometric and
conductometric measurement respectively.
General procedures
Spectrophotometric procedure
Aliquots containing 0.2-1.8 and 0.2-1.6 mg/mL of clomiphene citrate and nefazodone HCl
respectively (Tables 1& 2) were quantitatively transferred into 10 mL measuring flasks. To each
flask 4.3 mL of reagent for clomiphene and nefazodone were added. Solutions of clomiphene
 Spectrophotometric Determination of Clomiphene Citrate 1071

were shaken well and left for 5 minute while that of nefazodone were left for 15 minute after
shaking well. Then the solutions were filtered, the precipitate was washed with water and
transferred with the appropriate solvent (acetonitrile for clomiphene citrate and acetone for
nefazodone HCl) to 10 mL measuring flasks. Solutions were shaken well and made up to volume
with the same solvent. Absorbance was measured at 509 and 523.6 against blank (Figure 1).
Table 1. Quantitative parameters for the spectrophotometric determination of clomiphene
citrate and nefazodone HCl using ammonium reineckate
Items Clomiphene citrate Nefazodone HCl
Beer's law range, mg/mL 0.2 1.8 0.2 1.6
Apparent molar absorptivity*, mol-1L cm-1 2.610 2 2.510 2
Sandell's sensitivity mg /mL per 0 .001A 4.3 10-5 4.9 10-5
egression equation
R
Intercept (a) 0.04 0.123
Slope (b) 0.000377 0.000166
Correlation Coefficient ( r) 0.9998 0.9999
Variance 0.57 0.30
Detection Limit 0.38 0.27
*Calculated on the basis of the molecular weight of the drug.
Table 2. Determination of clomiphene citrate and nefazodone HCl through complexation
with ammonium reineckate.

Clomiphene citrate Nefazodone HCl

Statistics
Taken, mg/mL Recovery, % Taken, mg/mL Recovery %
0.2 99.46 0.2 100.09
0.28 100.41 0.28 99.40
1.2 100.79 0.6 99.49
1.4 100.79 0.8 99.92
1.6 100.96 1.4 99.75
1.8 99.17 1.6 100.05
Mean*SD 100.260.761 99.950.55
N 6 6
SD 0.761 0.55
RSD 0.759 0.55
V 0.57 0.30
SE 0.31 0.22
*Mean of three different experiments.

Conductometric procedure
A suitable aliquot (up to 44.5 mL) of sample solution containing 2.5-30 mg of drug was
transferred to a 50 mL calibrated flask and made up to the mark with 50% (v/v) acetone
water mixture. The contents of the calibrated flask were transferred to a beaker and the
conductivity cell was immersed. 510-3 M ammonium reineckate solution was then added
from a micro burette and the conductance was measured subsequent to each addition of
1072 W. S. HASSAN et al.

reagent solution and after thorough stirring. The conductance was measured after 2 min of
each addition was corrected for dilution22 by means of the following equation, assuming that
conductivity is a linear function of dilution.
1 1 1 + 2
correct = obs
1
Where 1obs is the observed electrolytic conductivity, v1 is the initial volume and v2 is
the volume of reagent added.
A graph of corrected conductivity versus the volume of added titrant was constructed
and the end-point determined. 0.1 mL of 5 103 M ammonium reineckate is theoretically
equivalent to 0.633 and 0.30 mg of nefazodone and clomiphene respectively. The procedure
takes 1530 min in all.
0.7
Clomiphene
0.6 Nefazodone
nceAbsorba

0.5

0.4

0.3

0.2

0.1
450 500 550 600 650
nm
Figure 1. Absorption spectra of the complex formed through reaction of 1.6 mg/mL
clomiphene and nefazodone with ammonium reineckate.
Assay of pharmaceutical preparations
The contents of 20 tablets of each of the studied drugs were thoroughly ground. A
quantity equivalent to 50 mg drug was accurately weighed into a 100 mL volumetric
flask. The mixture was warmed at 50C in a water bath for 5.0 min, agitated by an
electrical shaker for another 5.0 min, cooled to room temperature and diluted to volume
with double distilled water, filtered and the procedures was completed as under the
general procedures.
Results and Discussion
Clomiphene citrate and nefazodone HCl were found to react with ammonium reineckate to
form stable ion pair complexes. These complexes are sparingly soluble in aqueous
solution, but are readily soluble in acetone or acetonitrile. Investigations were carried out
to establish the most favourable conditions for the ion pair complex formation of the two
drugs with ammonium reineckate to achieve sharp end point and/or maximum color
development, in the determination of the drugs the influence of some variables on the
reaction was tested as follow:
Conditions for spectrophotometric method
Effect of PH: The effect of PH on the precipitation of the drug-reineckate complexes was
studied, different buffers were tried, it was found that buffer had no effect on the reaction.
 Spectrophotometric Determination of Clomiphene Citrate 1073

Effect of reagent volume: 4 and 3 mL of 0.01 M ammonium reineckate solution were sufficient
to give best results with clomiphene citrate and nefazodone HCl, respectively (Figure 2).
0.6
Clomiphene
Nefazodone
0.5
Absorbance

0.4

0.3

0.2
1 2 3 4 5 6 7 8
Volume, mL
Figure 2. Effect of reagent volume on the absorbance of the complex formed with 1.2 and
1.4 mg/mL clomiphene citrate and nefazodone HCl, respectively.
Effect of solvent: Distilled water, acetone, (acetone : water), ethanol and acetonitrile were
tried. Acetonitrile and acetone were practically used to dissolve (clomiphene-reineckate) and
(nefazodone reineckate) complexes respectively.
Effect of precipitating time: 5 and 15 minute were sufficient to give complete precipitation,
increasing time than this had no effect on absorption (Figure 3).
Effect of temperature: Temperature had no effect on the absorbance, so experiments were
done at room temperature.
Composition of the complex: The stoichiometric ratio of the studied compounds to
reineckate in the complexes were determined by applying Job's method23, the results showed
that drugs and reagent react in (1:1) ratio, Figure 4.
Condition for conductometric method
Conductometric analysis can be used in many titration procedures when ionic solutions are
involved. As the conductance of a solution is related to the total ionic content, it can be
applied to follow reactions that result in a change in this quantity.
Conductance measurements are used successfully in quantitative titration of systems in
which the conductance of the solution varies before and after the equivalence point. In these
cases, the titration curve can be represented by two lines intersecting at the end point.
0.6
Clomiphene
Nefazodone
0.5
Absorbance

0.4

0.3

0.2
0 5 10 15 20 25 30
Time (min)
Time, min
Figure 3. Effect of precipitation time on the absorbance of the complex formed through
reaction of 1.2, 1.4 mg/mL clomiphene and nefazodone with ammonium reineckate.
1074 W. S. HASSAN et al.

1.2
Clomiphene
Nefazodone
1
Absorbance
0.8

0.6

0.4

0.2

0
0 0.2 0.4 0.6 0.8 1
1/(1+2)
Figure 4. Continuous variation plot for 0.01M clomiphene citrate or nefazodone HCl and
0.01 M ammonium reineckate.
Investigations were carried out to establish the most favourable conditions for the ion
pair complex formation of nefazodone and clomiphene with ammonium reineckate to
achieve sharp end point and/or maximum colour development, in the determination of the
drug. The influence of some variables on the reaction has been tested as follow:
The optimum conditions for performing the titration in a quantitative manner were
elucidated as described below. Titrations in different media were attempted to obtain the
best results. Preliminary experiments in:
(i) Aqueous drug solution with aqueous reagent solution,
(ii) Ethanol drug solution with ethanol reagent solution,
(iii) Drug solution with reagent solution, both in ethanolwater (50%, v/v) mixture
(iv) Acetone drug solution with acetone reagent solution and
(v) Drug solution with reagent solution, both in acetonewater (50% v/v) mixture.
Preliminary experiments showed that procedure acetonewater (50% v/v) media was
the most suitable for successful results, because in other procedures precipitates were
formed which caused some errors.
The reagent concentration in each titration must be not less than ten times that of
the drug solution in order to minimize the dilution effect on the conductivity through the
titration. The optimum concentration of the reagent was 510 -3 M ammonium reineckate
in titration of the two studied drugs to achieve a constant and highly stable conductance
reading within 1-2 min of mixing. Concentrations less than these limits led to unstable
readings and more time was needed to obtain constant conductance values. On
increasing the temperature to 50C, no change in the conductance reading was observed,
whereas above which, the conductance value changed and so changed the shape of the
conductometric titration curve.
Representative titration curves are shown in (Figure 5). Two straight lines are obtained,
intersecting at the end-point, the first branch ascending and the second has conductance
values would remain constant or slightly increase after the equivalence point. The increase
of conductance may be attributed to the formation of ion-pair in solution as a result of the
complexation reaction. After the end-point, the titration curves indicate a constant or slightly
increase value of conductance, despite the excess of the reagent. This may be due to further
ionic condensation, leading to species of lower mobility.
 Spectrophotometric Determination of Clomiphene Citrate 1075

Conductivity 103, Sm-1

Volume of reineckate solution added, mL

Figure 5. Conductometric titration curves of (a) 6.5 mL (2.010-3M) NFZ and (b) 6.9 mL
(2.010-3M) CMP vs (5.0103) M ammonium reineckate.
The shape of the titration curve depends on all the species present during the titration
process and other factors such as viscosity, dielectric constant, solvation, ion-pair association
and proton transfer. The conductometric titrations of different volumes of 510-3 M
ammonium reineckate solution in acetone-water (50%, v/v) mixture was performed. The
results show an obvious maximum in the conductance curve at drug-reagent molar ratio of
(1:1). The reactions may be represented by the equations:
NFZ HCl + NH4 [Cr(NH3)2(CSN) 4] NFZ H[Cr(NH 3) 2(CSN)4 ] + NH 4Cl
The conductance of the titrated solution is mainly due to the drug cations and chloride
ions and partially to the hydrogen ions resulting from the dissociation of the protonated drug
cation. It was expected that the conductance values would remain constant or slightly
increase after the equivalence point. However, the conductance of the solution decreased.
This may be due to interaction of the protons available in the titration medium with the
added reagent. Measurements of the pH before and after reaching the end-point for
nefazodone and clomiphene, respectively, supporting the above assumption. The results
from the conductometic titrations are summariezed in Tables 3-4. The data show that
accurate results were obtained with good recoveries and low standard deviation values. The
optimum concentration ranges for determination of the two drugs were in the range of 63.3
443.1 and 60.02-540.18 g mL-1 for nefazodone and clomiphene respectively. At such
ranges, sharp inflections (Figure 5) and stable conductance reading were obtained.
Table 3. Analytical characteristic of conductometric procedure.
Parameters NFZ CMP
Optimum concentration, g mL-1 63.3-443.1 60.02-540.18
Shift or intercept of the regression line a 0.0699 0.0864
Slope of regression line 0.5044 0.7374
Correlation coefficient (r) 0.9998 0.9992
Relative standard deviation, % 1.90 2.08
a
Observed vs. theoretical; NFZ: Nefazodone HCl; CMF: Clomiphene citrate
In order to establish whether the proposed methods exhibit any fixed or proportional bias, a
simple linear regression24 of drug concentration (dependent variable) against the theoretical
values (independent variable) (6 points) were obtained using a programmable calculator.
1076 W. S. HASSAN et al.

Table 4. The intra-day accuracy and precision data for the studied drugs obtained by
conductometric method.

NFZ CMP
Taken Found Recovery RSD Er Taken Found Recovery RSD Er
g mL-1 g mL-1 % % % g mL-1 g mL-1 % % %
63.3 63.62 100.50 0.46 0.50 60.02 59.96 99.90 0.43 -0.10
126.6 126.09 99.60 0.53 -0.40 120.4 119.14 98.95 0.81 -1.05
189.9 188.48 99.25 0.84 -0.75 180.06 179.16 99.50 0.70 -0.50
253.2 251.35 99.27 0.90 -0.73 300.1 298.00 99.30 0.92 -0.70
316.5 313.81 99.15 0.43 -0.85 420.14 419.72 99.90 0.52 -0.1
443.1 442.21 99.80 0.72 -0.20 540.18 540.72 100.10 0.64 0.10
a
Average value of six determinations.
Quantification
Calibration graphs with good linearity were obtained as recorded before. The linear
regression equations were also calculated. Correlation coefficient, intercept and slope values
for the calibration data calculated, detection limit was also evaluated and recorded in Table
1. The Validity of the proposed methods was assessed by its application to the determination
of the two drugs in their pharmaceutical preparations Tables 5-7. Student's t-test (at 95 %
confidence level) was applied to the results obtained compared with that obtained when
applying the official method for clomiphene citrate or reference one for nefazodone HCl, the
results showed that it didn't differ significantly and there are no systematic differences
between the proposed and official or reference methods. The results of different statistical
treatment of the data are shown in Table 8.
Table 5. Application of the proposed spectrophotometric method for the analysis of
clomiphene citrate drug in dosage form
Claimed
Authentic added, Recovery,
Commercial product amount,
mg/mL %
mg/mL
0.28 --- 101.17
Clomid tablets --- 0.2 100.79
Each tablets contain 50 mg --- 0.6 99.02
clomiphene citrate per tablet --- 0.8 101.12
--- 1.2 101.67
Mean*SD 100.651.14
N 4
SD 1.14
RSD 1.13
V 1.29
SE 0.57
*Mean of three different experiments.
 Spectrophotometric Determination of Clomiphene Citrate 1077

Table 6. Determination of nefazodone HCl in its pharmaceutical preparation by using

spectrophotometric method.

Label claim,
Commercial product Found, %
mg/mL
0.20 100.30
0.28 99.61
Serzone tablets
0.40 101.35
0.60 100.70
MeanSD 100.490.728
N 4
SD 0.728
RSD 0.725
V 0.529
SE 0.364
*Mean SD (mean of three different experiments)
**
Theoretical values for t and F-values at five degree of freedom.
Table 7. Application of the proposed conductometric method to the determination of the
studied drugs in dosage forms.
Sample Reported or official method Conductometric method
Serzone Tablets (200 mg NFZ/tablet)
X SDa 99.80 0.58 99.70 0.58
t-value b 0.27
F-value b 1.0
Clomid Tablets (50 mg CMP/tablet)
X SDa 99.67 0.64 99.82 0.73
t-value b 0.35
F-value b 1.30
*Mean SD (mean of three different experiments)
**
Theoretical values for t and F-values at five degree of freedom and 95 % confidence limit.
Table 8. Determination of clomiphene citrate and nefazodone HCl through complexation
with ammonium reineckate using Spectrophotometric method compared with official and
reference one.
Clomiphene citrate Nefazodone HCl
Statistics Official Spectro- Conduc- Spectro- Conduc-
Reference
method photometric tometric 13 photometric tometric
Method
method method method method
Mean*,p=0.05 99.56 99.60 99.95 99.10 99.61 100.26
N 6 6 5 6 6 4
V 0.57 0.32 0.45 0.304 0.452 0.32
SD 0.81 0.552 0.673 0.74 0.761 0.57
t-test ** 1.56 (2.306) 0.12(2.306) 2.14 (2.262) 0.743(2.262)
F-test ** 1.80 (5.41) 1.69(5.41) 0.148 (5.19) 1.45(5.19)
*Mean SD (mean of three different experiments)
**
Theoretical values for t and F-values at five degree of freedom and 95 % confidence limit.
1078 W. S. HASSAN et al.

IR spectra (Figure 6&7) show that complexation between clomiphene citrate and ammonium
reineckate (amonium tetra thiocyanate diamine chromate) took place through ion pairing to
produce clomiphene reineckate. IR chart of the resulting complex not only contain bands due to
the reineckate part such as 3314, 3237 cm-1 NHs and 2077 cm-1 SCN, but also enclose a band at
3442 NH of clomiphene. Moreover, The absence of C=O absorption band at 1731 cm-1 and the
broad OH absorption band at 3250-2500 cm-1 propose the absence of the citrate anion from the
complex. As a conclusion from the above data, the complex is ion pair where protonated
clomiphene replaces the ammonium cation of ammonium reineckate with a molar ration (1:1).
In the same way, IR spectra were analyzed to verify the structure of the complex formed
between nefazodone HCl and ammonium reineckate. Again the complex is ion pairing
between protonated nefazadone and reineckate with a molar ration (1:1). The IR spectrum of
complex shows bands characteristic for functional groups of both parts of the salt, such as:
1. Presence of amidic C=O at 1678 cm-1 confirms the presence of nifazadone in the complex.
2. Presence of two bands at 3295, 3236 cm-1NHs, in addition to the very characteristic
band at 2076 cm-1 SCN authenticates the presence of reineckate in the complex.

Figure 6. IR spectra of (a) ammonium reineckate, (b) Clomiphene citrate and

(c) Clomiphene citrate and ammonium reineckate complex.
 Spectrophotometric Determination of Clomiphene Citrate 1079

Figure 7. IR spectra of (a) ammonium reineckate, (d) Nefazodone HCl, and (e) Nefazodone
HCl and ammonium reineckate complex.
Accuracy and precision
In order to determine the accuracy and precision of the proposed method, solutions
containing six different concentrations of each drug were prepared and six replicate
determinations were carried out for the pure form and the pharmaceutical preparation of the
drugs under investigation. The analytical results obtained from this investigation are
summarized in Table 4. The relative standard deviation (RSD %) as precision and
percentage relative error (Er %) as accuracy of the suggested method was calculated. The
percentage relative error calculated using the following equation:
Er % = [(found added) / added] 100
The intra-day precision and accuracy results are shown in Table 4. These results of
accuracy and precision show that the proposed method have good repeatability and
reproducibility.
1080 W. S. HASSAN et al.

Conclusions
The proposed methods have the advantages of being simple, rapid, accurate, highly
reproducible and time saving, thereby encouraging its applications in quality control of these
drugs in their pure form and in pharmaceutical preparations; conductometric method has the
advantage over the spectrophotometric one of being more sensitive.
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