Int J Pharm Pharm Sci, Vol 7, Issue 6, 152-157Original Article



1Chemistry Department, Faculty of Science, Zagazig University, Zagazig, 44519, Egypt, 2Ismailia Chemical Laboratory, Forensic Medicine Authority, Justice Ministry, Egypt

Received: 09 Mar 2015 Revised and Accepted: 05 Apr 2015


Objective: Simple and sensitive an extractive-spectrophotometric method have been developed for the determination of four important antihistaminic drugs, namely desloratadine (DSL), chlorpheniramine maleate (CPM), diphenhydramine hydrochloride (DPH) and fexofenadine (FXO).

Methods: This method is based on the formation of colored ion-pair complexes between the basic nitrogen of the drugs and halofluorescein dyes, namely rose bengal (RB) dye in weak acidic medium. The formed complexes were extracted with dichloromethane measured spectrophotometrically at 550 nm.

Results: The reaction conditions were optimized to obtain the maximum color intensity. Beer’s law was obeyed with a good correlation coefficient (0.9963-0.9975) in the concentration ranges 1-6, 4-18, 6-16 and 2-22 µg/ml for DSL, CPM, DPH and FXO, respectively. The composition ratio of the ion-pair complexes was found to be 1:1 as established by Job’s method.

Conclusion: The proposed method was successfully extended to pharmaceutical preparations. Excipients used as additive in commercial formulations did not interfere in the analysis. The proposed method can be recommended for quality control and routine analysis where time, cost effectiveness and high specificity of analytical technique are of great importance.

Keywords: Desloratadine, Chlorpheniramine maleate, Diphenhydramine hydrochloride, Fexofenadine, Rose Bengal, Ion-pair complexes, Spectrophotometry.


Desloratadine (DSL, fig. 1), 4-(8-chloro-5,6-dihydro-11H-benzo-[5,6]cyclohepta [1,2b]pyridin-11-ylidene)-1-piperidine. DSL is a selective peripheral H1 receptor antagonist, devoid of any substantial effect on the central and autonomic nervous systems [1, 2]. Desloratadine exhibits qualitatively similar pharmacodynamic activity with a relative oral potency in animals, two to three-fold greater than its parent analogue loratadine, probably due to a higher affinity for histamine H1 human receptors [3].

Several analytical methods have been reported for the determination of DSL in biological samples and applied in pharmacokinetics studies. These methods include liquid chromatography [4-6] and High-performance liquid chromatographic method [7]. However, DSL was determined in pharmaceutical preparations using a spectrophotometric and spectrofluorometric [8-12].

Chlorpheniramine maleate (CPM, fig. 1), ((3-(4-chloro-phenyl)-N,N-dimethyl-3-(2-pyridyl)propylaminemonomaleate) 1), chemical structure is showed in (fig. 1c). Chlorpheniramine maleate is an antihistamine drug that is widely used in phamarceutical preparations for symptomatic relief of common cold and allergic diseases [13]. Chlorpheniramine maleate was determined in pharmaceutical dosage forms and plasma samples by chromatographic [14-24], spectrophotometric [25-28] and electrochemical methods [29, 30].

Diphenhydramine hydroch loride (DPH, fig. 1), is an antihistamine drug having the chemical name 2-(diphenylmethoxy)-N,N-dimethylethylamine hydrochloride. It is usually administered orally and may be used by intramuscular or intravenous injection in severe allergies and applied topically for local allergic reactions. Several published methods have been developed for the determination of DPH in pharmaceutical preparations and in biological fluids including: spectrophotometry [31–34], flow injection analysis [35], gas chromatography [36], atomic absorption spectrometry [37], high performance liquid chromatography [38], Liquid chromatography [39] and capillary electrophoresis [40–42].

Fexofenadine (FXO, fig.1) is, chemically, 2,2-dimethyl-4(1-hydroxy-4-{hydroxy diphenylmethyl-1-piperidinyl}butyl)benzoaceticacid. FXO is a highly selective peripheral histamine H1 receptor antagonist used in the treatment of allergic diseases such as allergic rhinitis and chronic urticaria. Fexofenadine is the active derivative of the antihistamine terfenadine, with no antichrolinergic or alpha 1-adernergic receptor-blocking effects and without severe cardiac side effects of terfenadine [43, 44]. Several methods for the determination of fexofenadine hydrochloride in pharmaceutical formulations and biological fluids have been reported including chromatographic methods [45–52], spectrophotometry [53–58], spectrofluorometry [59], potentiometry [60], and capillary electrophoresis [61].

The proposed method is dedicate to study the formation of a ion-pair complex between each of the studied drugs and rose bengal dye in an attempt to develop a simple, sensitive and accurate extraction-free spectrophotometric method for the determination of DSL, CPM, DPH and FXO drugs in their pharmaceutical preparations.



All the absorbance spectral measurements were made using spectroscan 80 D double-beam UV/Visible spectrophotometer (Biotech Sedico, Scientific Equipment Distribution, Ltd. Nicosia, Cyprus), with wavelength range 190 nm ~ 1100 nm, spectral bandwidth 2 nm, with 10 mm matched quartz cells. An Orion Research Model 601 A/digital analyzer, pH-meter with a combined saturated calomel glass electrode was used for pH measurements, water bath and hot plate.


All chemicals and reagents were of pharmaceutical or analytical grade and all solutions were prepared fresh daily. They are included drugs under investigation: desloratadin (DSL) chlorpheniramine (CPM), diphenhydramine (DPH) and fexofenadine (FXO) that supplied from Egyptian International Pharmaceutical Industries Company (EIPICo) 10th of Ramadan City, Egypt. Rose bengal was supplied from (Aldrich), sodium acetate and methylene chloride were supplied from (Egyptian, Adewic).

Tablets containing the drugs were obtained from the local market. The pharmaceutical preparations of desloratadine pharmaceutical preparations were delarex tablets 5 mg/tab produced by (global napi Pharm. Cairo–Egypt). The chlorpheniramine maleate pharmaceutical preparations were anallerge tablets 4 mg/tab (Kahira Pharm. Cairo–Egypt). Diphenhydramine hydrochloride is sultan tablets, 50 mg/tab produced by Pharaonia pharmaceuticals. The fexofenadine hydrochloride pharmaceutical preparations were allerfen tablets 60 mg/tab produced by (Amoun Pharm. Cairo–Egypt).

Desloratadine (DSL) Chlorpheniramine maleate (CPM)
Diphenhydramine hydrochloride (DPH) Fexofenadine hydrochloride (FXO)

Fig. 1: Chemical structures of the studied drugs

Reagents and solutions

All chemicals and reagents used were of analytical-reagent grade and distilled water was used throughout the investigation.

Pure drugs

An accurately weighed quantity of the investigated drugs (20 mg) was dissolved in distilled water in a 100 ml measuring flask. Aliquots of the above prepared stock solution were further diluted to obtain 100 µg/ml working standard solutions.

Buffer solution

Citrate–phosphate buffer was prepared by adding 0.20 M disodium hydrogen phosphate (Fisher Scientific Co., Pittsburgh, PA) to 50 ml 0.1 M citric acid (Sigma Chemical Co., St. Louis, MO) to adjust the pH to 2–7 and the volumes were diluted to 100 ml with distilled water.

Dye stuff

A stock solution of 1×10-3M rose bengal {4,5,6,7-Tetrachloro-3',6'-dihydroxy-2',4',5',7'-tetraiodo-3H-spiro[isobenzofuran-1,9'-xanthen]-3-one}, was prepared by dissolving 97.367 mg from dye (99% purity) in distilled water and diluting to 100 ml in a measuring flask with distilled water.

Procedure for calibration curves

Into a series of separating funnels, accurately measured aliquots DSL, CPM, DPH or FXO in the concentration range shown in (table 1) were pitted out and then 2.0 ml of 1×10-3M of RB dye was added. The solution was diluted to 10 ml with distilled water after the addition of 2.0 ml of acetate buffer of pH 6 for CPM, DPH or FXO but buffer of pH 6.8 for DSL was added. The ion-pairs were extracted with 10 ml of dichloromethane by shaking for 2.0 min and then, the combined dichloromethane extracts were dried over anhydrous sodium sulphate. The absorbance of colored ion-pair complexes were measured within 5.0 min of extraction against the reagent blank prepared in the same manner except addition of drugs.

Procedure for tablets

Ten tablets of each commercial pharmaceutical formulation were crushed, powdered, weighed out and the average weight of one tablet was determined. An accurate weight equivalent to 20 mg each drug and then active component was transferred into a 100 ml measuring flask. About 25 ml of distilled water was added and the mixture was shaken thoroughly for about 5 min. Then, it was diluted up to the mark with distilled water, mixed well and filtered using filter paper. An aliquot of this solution was diluted appropriately to obtain the working concentrations and analyzed as described under the standard procedure.


Absorption spectra

The absorption spectra of the ion-pair complexes were measured in the range 525-630 nm against dichloromethane (blank). Antihistamine cations were found to react with anions of rose bengal dye in acidic buffer and gave an intense color with a maximum absorption at 550 nm as shown in fig. 2. Therefore, all the following measurements are carried out at 550 nm against blank where the investigated drugs, dyes, buffer and dichloromethane have no absorption in this region. The optimum conditions were established by varying one variable and observing its effect on the absorbance of the colored product.

Fig. 2: Absorption spectra of 6 µg/ml DSL with RB dye at pH = 6.8

Effect of pH

The influence of pH on the ion-pair complex formations of DSL, CPM, DPH and FXO with RB dye has been studied using different types of buffers of different media. The optimum buffer associated with the maximum color intensity is disodium hydrogen phosphate-citric acid of pH=6 in case of DPH, CPA or FXO but pH=6.8 in case of DSL (fig. 3). Buffer volume was determined by applying the same experiment and variation the volume regularly (0.5-4.0 ml). The higher absorbance value obtained at using 2.0 ml.

Fig. 3: Effect of pH on the formation of ion-pair complex between RB and the studied drugs at 550 nm

Choice of organic solvent

A number of organic solvents such as dichloromethane, chloroform, carbon tetrachloride, benzene and toluene were examined for extraction of the ion-pair complexes in order to provide an applicable extraction procedure. Dichloromethane was found to be the most suitable solvent for extraction of colored complex yielding maximum absorbance intensity and it was also, observed that only one extraction was adequate to achieve a quantitative recovery of the complex and very low absorbance of the reagent blank and shortest time to reach the equilibrium between both phases.

Effect of RB dye concentration

Keeping other conditions unaltered, the influence of 1×10-3M RB dye concentration on absorbance was investigated. The results showed that the maximum absorbance was at using 3.0 ml from RB dye for DSL, CPM, DPH and FXO. After this volume, the absorbance remains constant by increasing the volume of RB dye. So any excess of reagents has no effect on the determination of the drugs.

Effect of shaking time

Shaking time of 1.0-4.0 min provided a constant absorbance and hence, 2.0 min was used as an optimum shaking time throughout the experiment. The ion-pair complexes were quantitatively recovered in one extraction only and were, also stable for at least 24 h without any change in color intensity.

Sequence of addition

The sequence of addition of drugs, buffer, and dye were studied via the formation of the colored complexes. The optimum sequence of addition was similar in all cases by starting with drug, then dye and at last buffer. Other sequences gave lower absorbance values under the same experimental conditions.

Effect of temperature and stability time

The effect of temperature on colored complexes was studied over the range 20-35 °C. It was found that the absorbance of the ion pair complex was constant up to 30 °C. At higher temperatures, the drug concentration was found to increase due to volatile nature of the dichloromethane. Therefore, the temperature chosen was 30 °C as the best temperature for micro-determination of the drugs under study in pure and pharmaceutical formulations. The stability time of the four extracted ion-pair complexes was more than 120 min.

Stoichiometric ratio

In order to establish the molar ratio between DSL, CPM, DPH, FXO drugs on one side and RB reagent used on the other, Job’s method of continuous variation was applied [62]. In this method, 5×10-3 M solutions of drug and reagent were mixed in varying volume ratios in such a way that the total volume of each mixture was the same. The absorbance of each solution was measured and plotted against the mole fraction of the drug. This procedure showed that a (1: 1) complex was formed through the electrostatic attraction between the positively charged drug, D+ions and negatively charged reagent, R-, ions. The extraction equilibrium can be represented as follows:

Daq+ + RaqD+RaqD+Rorg

Where D+and R-represent the protonated drug and the anion of the reagent, respectively and the subscripts “aq” and “org” refer to the aqueous and organic phases, respectively.


Under the optimum conditions described above, the calibration graphs for the investigated drugs were constructed by plotting absorbance versus concentration in μg/ml. (fig. 4). Conformity with Beer's law was evident in the concentration ranges cited in table 1. Regression equations, intercepts, slopes and correlation coefficients for the calibration data were presented in table 1.

The high molar absorptivities of the resulting colored complexes indicated high sensitivity of the method (2.35×104–6.28×104). The small values of Sandell's sensitivity indicate the high sensitivity of the proposed method in the determination of the drugs under investigation. The limit of detection (LOD) and limit of quantitation (LOQ) are calculated according to ICH guidelines [63] and the results are tabulated in (table 1).

Fig. 4: Calibration curves for determination of: DSL (1–6 µg/ml), CPM (4–18 µg/ml), DPH (6–16 µg/ml) and FXO (2–22 µg/ml) under optimum conditions

Accuracy and precision

In order to determine the accuracy and precision of the recommended procedure five replicate determinations at three different concentrations of the studied drugs were carried out. Precision and accuracy were based on the calculated relative standard deviation (RSD, %) and relative error (RE, %) of the found concentration compared to the theoretical one, respectively and indicate that the proposed method is highly accurate and reproducible (table 2).

Table 1: Analytical parameters and optical characteristics with RB dye







ƛmax (nm)










Beer’s law limit, µg/ml





Molar absorptivity, l mol-1 cm-1





Sandell’s sensitivity, ng/cm2





Correlation coefficient (r)





Linear regression equation*










Intercept (a)





Slope (b)





S. D. of slope (Sb)





S. D. of intercept (Sa)





LOD, µg/ml





LOQ, µg/ml





*A= a+bC, where A is the absorbance and C is the concentration of drug in µg/ml.

Table 2: Evaluation of intra-day accuracy and precision of the proposed method

Drugs Drug taken μg/ml Drug founda μg/ml Recovery, % RSD, % REb, %
DSL 1.0 0.999 99.994 3.410 -0.100
3.0 2.999 99.996 2.104 -0.033
5.0 4.999 99.994 1.152 -0.020
CPM 4.0 3.999 99.996 4.255 -0.025
8.0 7.999 99.994 6.075 -0.012
14 13.999 99.996 2.542 -0.007
DPH 2.0 1.999 99.994 4.214 -0.050
6.0 5.999 99.994 1.401 -0.016
10 9.999 99.996 1.759 -0.010
FXO 2.0 1.999 99.996 3.871 -0.050
10 9.999 99.994 0.994 -0.010
18 17.999 99.996 3.759 -0.005

aMean value of five determinations, bRE: Relative error.

Analysis of dosage forms

To evaluate the validity and reproducibility of the method, known amounts of the DSL, CPM, DPH and FXO drugs were added to the previously analyzed pharmaceutical preparations and the mixtures were analyzed by the proposed method. The percent recoveries are given in table 3. Interference studies revealed that the common excipients and other additives such as lactose, starch, gelatin, talc and magnesium trisilicate, that are usually present in the tablet dosage forms did not interfere at their regularly added levels.

Table 3: Recovery of the studied drugs in pharmaceutical formulations using the proposed method

Drug formulations Drug taken μg/ml Drug founda μg/ml Recovery, % RSD, % REb, %

sultan tablets,

50 mg/tab

2 1.999 99.994 1.232 -0.050
6 5.999 99.994 1.761 -0.016
10 9.999 99.999 2.929 -0.010

anallerge tablets,

4 mg/tab

4 3.999 99.994 4.134 -0.025
8 7.999 99.996 2.910 -0.012
14 13.999 99,994 1.579 -0.007

allerfen tablets,

60 mg/tab

6 5.999 99.994 4.762 -0.016
14 13.999 99.996 2.936 -0.007
18 17.998 99.994 2.375 -0.011

delarex tablets,

5 mg/tab

2 1.999 99.994 4.377 -0.050
4 3.999 99.996 3.466 -0.025
5 4.999 99.996 3.811 -0.020

aMean value of five determinations, bRE: Relative error.


The proposed spectrophotometric method is simple, sensitive, and suitable for the determination of DSL, CPM, DPH and FXO drugs in bulk and pharmaceutical dosage forms. The proposed method offers the advantages of accuracy and time saving as well as simplicity of reagents and apparatus. The developed method may be recommended for routine and quality control analysis of the investigated drugs in pharmaceutical preparations.


Declared None


  1. Kleemann A, Engels J. “Encyclopedia of Pharmaceutical Substances,” 4th ed. Pdf; 2000.
  2. Graul A, Leeson PA, Castaner J. Sitaxsentan sodium. Endothelin ET(A) antagonist treatment of heart failure treatment of pulmonary hypertension. Drug Future 2000;25:339-46.
  3. Day JH, Briscoe MP, Clark RH,  Ellis AK, Gervais P. Onset of action and efficacy of terfenadine, astemizole, cetirizine, and loratadine for the relief of symptoms of allergic rhinitis. Ann Allergy Asthma Immunol 1997;79:163-72.
  4. Qi M, Wang P, Geng Y. Determination of desloratadine in drug substances and pharmaceutical preparations by liquid chromatography. J Pharm Biomed Anal 2005;38:355–9.
  5. El-Sherbiny DT, El-Enany N, Belal FF, Hansen SH. Simultaneous determination of loratadine and desloratadine in pharmaceutical preparations using liquid chromatography with microemulsion as eluent. J Pharm Biomed Anal 2007;43:1236–42.
  6. Shen JX, Xu Y, Tama CI, Merka EA, Clement RP. Simultaneous determination of desloratadine and pseudoephedrine in human plasma using micro-solid-phase extraction tips and aqueous normal-phase liquid chromatography/tandem mass spectrometry. Rapid Commun Mass Spectrom 2007;21:3145–55.
  7. Liu LL, Qi M, Wang P, Li H. High-performance liquid chromatographic method for the bioequivalence evaluation of desloratadine fumarate tablets in dogs. J Pharm Biomed Anal 2004;34:1013–9.
  8. El-Enany N, El-Sherbiny D, Belal F. Spectrophotometric, spectrofluorometric and HPLC determination of desloratadine in dosage forms and human plasma. Chem Pharm Bull 2007;55:1662–70.
  9. Walash MI, Belal F, El-Enany N, Eid M, El-Shaheny RN. Stability-indicating micelle-enhanced spectrofluorimetric method for the determination of loratadine and desloratadine in dosage forms. Luminescence 2011;26:670–9.
  10. Patel JM, Talele GS, Fursule RA. Spectrophotometric determination of desloratidine in bulk and tablets form. Asian J Chem 2004;16:1220-2.
  11. Patel JM, Talele GS, Furule RA, Surana SJ. Extractive spectrophotometric determination of desloratadine from its bulk and pharmaceutical dosage form. Indian Drugs 2006;43:507.
  12. Cağlar S, Oztunç A. Sensitive spectrophotometric method for the determination of desloratadine in tablets. J AOAC Int 2007;90:372-5.
  13. Howland R, Mycek M. Lippincott's Illustrated Reviews: Pharmacology. 4th Edition Lippincott Williams & Wilkins; 2009.
  14. Algaba C, Saldaña J, Camañas R, Sagrado S, Hernánde M. Analysis of pharmaceutical preparations containing antihistamine drugs by micellar liquid chromatography. J Pharm Biomed Anal 2006;40:312-21.
  15. Romero J, Broch S, Agustí M, Peiró M, Bose D. Micellar liquid chromatography for the determination of drug materials in pharmaceutical preparations and biological samples. TrAC Trends Anal Chem 2005;24:75-91.
  16. Zhao S, Li D, Qiu J, Wang M, Yang S, Chen D. Simultaneous determination of amantadine, rimantadine and chlorpheniramine in animal derived food by liquid chromatography-tandem mass spectrometry after fast sample preparation. Anal Methods 2014;6:7062–7.
  17. Heydari R. A new HPLC method for the simultaneous determination of acetaminophen, phenylephrine, dextromethorphan and chlorpheniramine in pharmaceutical formulations. Anal Lett 2008;41:965–76.
  18. Lou H, Yuan H, Ruan Z, Jiang B. Simultaneous determination of paracetamol, pseudoephedrine, dextrophan and chlorpheniramine in human plasma by liquid chromatography–tandem mass spectrometry. J Chromatogr B 2010;878:682–8.
  19. Vignaduzzo SE, Kaufman TS. Development and validation of a HPLC method for the simultaneous determination of bromhexine, chlorpheniramine, paracetamol, and pseudoephedrine in their combined cold medicine formulations. J Liq Chromatogr RT 2013;36:2829–43.
  20. Qi ML, Wang P, Leng YX, Gu JL, Fu RN. Simple HPLC method for simultaneous determination of acetaminophen, caffeine and chlorpheniramine maleate in tablet formulations. Chromatographia 2002;56:295-8.
  21. Al-Rimawi F. Normal-phase LC method for simultaneous analysis of pseudophedrine hydrochloride, dextromethorphan hydrobromide, chlorpheniramine maleate, and paracetamol in tablet formulations. Saudi Pharm J 2010;18:103-6.
  22. Gómez M, Avies M, Sagrado S, Camañ R, Hernández M. Characterization of antihistamine–human serum protein interactions by capillary electrophoresis. J Chromatogr A 2007;1147:261–9.
  23. Al-Shaalan NH. Determination of phenylephrine hydrochloride and chlorpheniramine maleate in binary mixture using chemometric-assisted spectrophotometric and high-performance liquid chromatographic-UV methods. J Saudi Chem Soc 2010;14:15–21.
  24. Kazemipour M, Ansari M. Derivative spectrophotometry for simultaneous analysis of chlorpheniramine maleate, phenylephrine HCl and phenylpropanolamine HCl in ternary mixtures and pharmaceutical dosage forms. Iran J Pharm Res 2005;3:147-53.
  25. Erk N. Quantitative analysis of chlorpheniramine maleate and phenylephrine hydrochloride in nasal drops by differential-derivative spectrophotometric zero-crossing first derivative UV spectrophotometric and absorbance ratio methods. J Pharm Biomed Anal 2000;23:1023-31.
  26. Kaura AK, Gupta V, Kaura M, Roy GS, Bansal P. Spectrophotometric determination of chlorpheniramine maleate and phenylpropanolamine hydrochloride by “two wavelengths method. J Pharm Res 2013;7:404-8.
  27. Suliman F, Al-Hinai M, Al-Kindy S, Salama S. Chemiluminescence determination of chlorpheniramine using tris(1,10-phenanthroline)–ruthenium(II)peroxydisulphate system and sequential injection analysis. Luminescence 2009;24:2–9.
  28. Pojanagaroon T, Liawruangrath S, Liawruangrath B. A direct current polarographic method for the determination of chlorpheniramine maleate in pharmaceutical preparations. Chiang Mai J Sci 2007;34:135-42.
  29. Abu-Shawish H. Potentiometric response of modified carbon paste electrode based on mixed ion–exchangers. Electroanalysis 2008;20:491–7.
  30. El-Gindy A, Emaraa S, Mostafa A. Application and validation of chemometrics-assisted spectrophotometry and liquid chromatography for the simultaneous determination of six-component pharmaceuticals. J Pharm Biomed Anal 2006;41:421–30.
  31. Goicoechea HC, Olivieri AC. Chemometric assisted simultaneous spectrophotometric determination of four-component nasal solutions with a reduced number of calibration samples. Anal Chim Acta 2002;453:289-300.
  32. Basavaiah K, Charan VS. Titrimetric and spectrophotometric assay of some antihistamines through the determination of the chloride of their hydrochlorides. IL Farmaco 2002;57:9-17.
  33. Hassan WS, El-Henawee MM, Gouda AA. Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations. Spectrochim Acta A 2008;69:245-55.
  34. Ulu ST, Elmali FT. Spectrophotometric method for the determination, validation, spectroscopic and thermal analysis of diphenhydramine in pharmaceutical preparation. Spectrochim Acta A 2010;77:324-9.
  35. Tipparat P, Lapanantnoppakhum S, Jakmunee J, Grudpan K. Determination of diphenhydramine hydrochloride in some single tertiary alkylamine pharmaceutical preparations by flow injection spectrophotometry. J Pharm Biomed Anal 2002;30:105–12.
  36. Sumandeep R, Garg RK, Singla A. Rapid analysis of urinary opiates using fast gas chromatography–mass spectrometry and hydrogen as a carrier gas. Egypt J Forensic Sci 2014;4:100-7.
  37. El Ries MA, Khalil S. Indirect atomic absorption determination of atropine, diphenhydramine, tolazoline, and levamisole based on formation of ion-associates with potassium tetraiodometrcurate. J Pharm Biomed Anal 2001;25:3-7.
  38. Donmez OA, Ascı B, Bozdoǵan A, Sungur S. Simultaneous determination of potassium guaiacolsulfonate, guaifenesin, diphenhydramine HCl and carbetapentane citrate in syrups by using HPLC-DAD coupled with partial least squares multivariate calibration. Talanta 2011;83:1601–5.
  39. Wang C, Fan G, Lin M, Chen Y, Zhao W, Wu Y. Development and validation of a liquid chromatography/tandem mass spectrometry assay for the simultaneous determination of D-amphetamine and diphenhydramine in beagle dog plasma and its application to a pharmacokinetic study. J Chromatogr B-Anal Technol Biomed Life Sci 2007;854:48-56.
  40. Gomez MR, Sombra L, Olsina RA, Martínez LD, Silva MF. Development and validation of a capillary electrophoresis method for the determination of codeine, diphenhydramine, ephedrine and noscapine in pharmaceuticals. IL Farmaco 2005;60:85-90.
  41. Liu JF, Cao WD, Yang XR. Determination of diphenhydramine by capillary electrophoresis with tris(2,20-bipyridyl)ruthenium(II) electrochemiluminescence detection. Talanta 2003;59:453–9.
  42. Marchesini AF, Williner MR, Mantovani VE, Robles JC, Goicoechea HC. Simultaneous determination of naphazoline, diphenhydramine and phenylephrine in nasal solutions by capillary electrophoresis. J Pharm Biomed Anal 2003;31:39-46.
  43. The Merck Index, an encyclopedia of chemicals, drugs and biologicals. Merck & Co, Inc, Whitehouse Station, NJ; 2001.
  44. Simpson K, Jarvis B. Fexofenadine: a review of its use in the management of seasonal allergic rhinitis and chronic idiopathic urticaria. Drugs 2000;59:301–21.
  45. Breier AR, Paim SC, Menegola J, Steppe M, Schapoval EE. Development and validation of a liquid chromatographic method for fexofenadine hydrochloride in capsules. J AOAC Int 2004;87:1093–7.
  46. Maher HM, Sultan MA, Olah IV. Development of validated stability-indicating chromatographic method for the determination of fexofenadine hydrochloride and its related impurities in pharmaceutical tablets. Chem Cent J 2011;5:76.
  47. Arayne MS, Sultana N, Shehnaz H, Haider A. RP-HPLC method for the quantitative determination of fexofenadine hydrochloride in coated tablets and human serum. Med Chem Res 2011;20:55–61.
  48. Miura M, Uno T, Tateishi T, Suzuki T. Determination of fexofenadine enantiomers in human plasma with high performance liquid chromatography. J Pharm Biomed Anal 2007;43:741–5.
  49. Yamane N, Tozuka Z, Sugiyama Y, Tanimoto T, Yamazaki A, Kumagai Y. Microdose clinical trial: quantitative determination of fexofenadine in human plasma using liquid chromatography/electrospray ionization tandem mass spectrometry. J Chromatogr B Anal Technol Biomed Life Sci 2007;858:118–28.
  50. Arayne MS, Sultana N, Mirza AZ, Siddiqui FA. Simultaneous determination of gliquidone, fexofenadine, buclizine, and levocetirizine in dosage formulation and human serum by RP-HPLC. J Chromatogr Sci 2010;48:382–5.
  51. Arayne MS, Sultana N, Shehnaz H, Haider A. RP-HPLC method for the quantitative determination of fexofenadine hydrochloride in coated tablets and human serum. Med Chem Res 2011;20:55–61.
  52. Vekaria H, Limbasiya V, Patel P. Development and validation of RP-HPLC method for simultaneous estimation of montelukast sodium and fexofenadine hydrochloride in combined dosage form. J Pharm Res 2013;6:134–9.
  53. Mahgoub H, Gazy AA, El-Yazbi FA, El-Sayed MA, Youssef RM. Spectrophotometric determination of binary mixtures of pseudoephedrine with some histamine H1-receptor antagonists using derivative ratio spectrum method. J Pharm Biomed Anal 2003;31:801–9.
  54. Kumar KS, Ravichandran V, Raja MM, Thyagu R, Dharamsi A. Spectrophotometric determination of fexofenadine hydrochloride. Indian J Pharm Sci 2006;68:841–2.
  55. Maggio RM, Castellano PM, Vignaduzzo SE, Kaufman TS. Alternative and improved method for the simultaneous determination of fexofenadine and pseudoephedrine in their combined tablet formulation. J Pharm Biomed Anal 2007;45:804–10.
  56. Polawar PV, Shivhare UD, Bhusari KP, Mathur VB. Development and validation of spectrophotometric method of analysis for fexofenadine. Res J Pharm Technol 2008;1:539–41.
  57. Vekaria HJ, Muralikrishna KS, Patel GF. Development and validation of spectrophotometric method for estimation of fexofenadine hydrochloride and montelukast sodium in combined dosage form. Pharm Anal Qual Assur 2011;4:197–9.
  58. Ashour S, Khateeb M, Mahrouseh R. Extractive spectrophotometric and conductometric methods for determination of fexofenadine hydrochloride in pharmaceutical dosage forms. Pharm Anal Acta 2013;S2:1–6.
  59. Abd El-Hay SS, Colyer CL, Hassan WS, Shalaby A. Spectrofluorimetric determination of etodolac, moxepril HCl and fexofenadine HCl using europium sensitized fluorescence in bulk and pharmaceutical preparations. J Fluoresc 2012;22:247–52.
  60. Abbas MN, Fattah AA, Zahran E. A novel membrane sensor for histamine H1-receptor antagonist fexofenadine. Anal Sci 2004;20:1137–42.
  61. Breier AR, Garcia SS, Jablonski A, Steppe M, Schapoval EES. Capillary electrophoresis method for fexofenadine hydrochloride in capsules. J AOAC Int 2005;88:1059–63.
  62. Job P. Formation and stability of inorganic complexes in solution. Ann Chim 1928;9:113–23.
  63. Miller JN, Miller JC. Statistics and chemometrics for analytical chemistry. 5th ed. Prentice Hall, England; 2005.