1. INTRODUCTION:

Lisinopril[(2S)-1-[(2S)-6-amino-2-[[(1S)-1-carboxy-3-phenylpropyl]amino]hexanoyl]pyrrole-2-carboxylic acid].⁽¹⁾ It is an Angiotensin-Converting Enzyme (ACE) inhibitor used for treatment of hypertension and heart failure, prophylactically after myocardial infarction and in diabetic nephropathy. ⁽²⁾

It is an official drug and the British pharmacopeia described a titrimetric method for its assay as follow: dissolve 0.350 g in 50 ml of distilled water. Titrate with 0.1 M sodium hydroxide, determining the end-point potentiometrically.⁽¹⁾

Various analytical techniques have been employed for the determination of Lisinopril in pure and dosage forms including HPLC^(3-16), Gas chromatography^(17,18), capillary electrophoresis^(19,20), anodic stripping voltammetry⁽²¹⁾, polarography^(22,23), Spectrophotometry^{(10,11,22,24-31)}, derivative spectrophotometry^(14,32-34), spectrofluorimetry^(11,31,35), fluoroimmunoassay^(36,37) and Radio-immunoassay⁽³⁸⁾.

Cefixime[(6R,7R)-7-[[(Z)-2-(2-aminothiazol-4-yl)-2-[ (carboxymethoxy)imino]acetyl]amino]-3-ethenyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid trihydrate].⁽¹⁾

It is a bactericidal antibiotic and stable to hydrolysis by many beta-lactamases. It has a mode of action and spectrum of activity similar to the third generation cephalosporin cefotaxime, but some Enterobacteriaceae are less susceptible to cefixime. Haemophilus influenzae, Moraxella catarrhalis and Neisseria gonorrhoeae are sensitive, including penicillinase-producing strains. Of the Gram-positive bacteria, streptococci are sensitive to cefixime but staphylococci, enterococci and listeria spp. are not.⁽²⁾

British pharmacopeia described a chromatographic method for assay of cefixime it is conducted by using a mobile phase consisting of 25% acetonitrile and 75% tetrabutylammonium hydroxide over a 4 mm internal diameter column packed with octadecylsilyl silica gel for chromatography and monitoring chromatogram after 6 minutes at 254 nm.⁽¹⁾

Various analytical techniques have been reported for the determination of Cefixime in pure and dosage forms including HPLC^(39-48), HPTLC⁽⁴⁹⁾, capillary zone electrophoresis^(50,51), voltammetry^(52,53), selective membrane electrode⁽⁵⁴⁾, Spectrophotometry^(39,55-59) and spectrofluorimetry^{( 57,60)}.

In present work, two accurate methods for estimation of Lisinopril and Cefixime in pure and pharmaceutical dosage forms have been developed. The proposed methods can be used in laboratories where modern and expensive apparatus, such as that required for GC or HPLC are not available.

2. EXPERIMENTAL:

2.1. Apparatus

All of the spectrophotometric measurements were carried out using a Shimadzu UV-1800 with matched 1 cm quartz cells. A Lutron digital pH-meter was used for pH adjustment.

2.2. Materials and reagents

All solvents and reagents were of analytical grade and double distilled water was used throughout the work.

Lisinopril (Sigma Pharmaceuticals, Kwesna, Egypt) working solution 10 µg.ml^-1, and for molar ratio 1x10^-3M solution were prepared by dissolving in least amount of methanol then completing to volume with distilled water.

Cefixime (Sigma Pharmaceuticals, Kwesna, Egypt) working solution 10 µg.ml^-1, and for molar ratio 5X10^-3M solution were prepared by dissolving in distilled water.

Acetate and borate buffer solutions of pH values 3.5 – 10 were prepared as in recommended methods⁽⁶⁰⁾.

Congo red ((Fluka, Switzerland) 0.1 gm dissolved in least amount of methanol and completed to 250 ml with distilled water as working solution and 1X10^-3M and 5X10^-3M solutions for molar ratio determination.

Nickel sulfate(El-Nasr Chemicals) 1% aqueous solution and 1X10^-3M solution for mole ratio.

Copper sulfate(El-Nasr Chemicals) 0.1% aqueous solution and 1X10^-3M solution for mole ratio.

Trimethyl ammonium bromide (C1), Sodium lauryl sulfate(A1)(El-Nasr Chemicals) and tween 80(N1) (El-Nasr Chemicals) 1% w/v, 1% w/v, 1% w/v and 1% v/v, respectively, aqueous solutions were prepared.

2.2.1. Pharmaceutical preparations

The following available pharmaceutical preparations were analyzed

Ximacef® Capsules labeled to contain 400 mg cefixime per capsule. Batch No.90640 (Sigma Pharmaceuticals, Kwesna, Egypt).

Zestril® tablets labeled to contain 20 mg lisinopril per tablet. Batch No.90133 (AstraZeneca Pharmaceutical Company, Egypt)

2.3. Procedure

2.3.1. General spectrophotometric procedure for determination of Lisinopril.

2.3.1.1.Congo red method

2.3.1.1.1. In presence of Nickel.

In 10 ml measuring flask add 2 ml dye, 1ml borate buffer pH 7.5 followed by 1 ml nickel, add lisinopril (20-80µg/ml), complete to mark with distilled water, heat for 15 minutes in water bath at 80ºC., cool to 25ºC. measure absorbance at 499 nm against reagent blank similarly prepared.

2.3.1.1.1. In presence of Copper.

In 10 ml measuring flask add 2 ml Congo Red, 1ml borate buffer pH 7.5 followed by 0.5 ml copper, add lisinopril(10-50 µg/ml), complete to mark with distilled water, heat for 10 minutes in boiling water bath, cool to 25ºC. measure absorbance at 497 nm against reagent blank similarly prepared.

2.3.2. General spectrophotometric procedure for determination of Cefixime.

In 10 ml measuring flask add 2 ml dye, add 1ml borate buffer pH 7.5 followed by cefixime( 20-65 µg/ml), complete to mark with distilled water, measure absorbance at 595 nm against reagent blank similarly prepared.

2.3.3. Procedure for pharmaceutical preparations

For Zestril® tablets 20 tablets were were crushed and a weight equivalent to 200 mg was taken, extracted three successive times with 20 ml methanol, filtered into 100 ml measuring flask and then completed to volume with distilled water. Then follow the same procedures described for determination as in raw sample.

For Ximacef® capsules contents of 10 capsules were obtained and weight equivalent to 500 µg was taken, extracted three successive times with 20 ml methanol, filtered into 100 ml measuring flask and then completed to volume with distilled water. Then follow the same procedures described for determination as in raw sample.

2.3.4. Procedure for determination of molar ratio

Job’s method: Lisinopril, Congo red, Nickel and Copper solutions of equimolar concentrations (1x10^-3) were prepared. Aliquots of Lisinopril and Congo red solutions were added in different ratios to a series of 10 ml measuring flasks, so that the total volume of both was 2 ml and metal concentration was kept constant (2X10^-3M), in presence of recommended buffer, according to the recommended addition sequence and volume was completed with distilled water. Absorbance was measured against reagent blank at the appropriate wave length. Same procedures were repeated while drug concentration was kept constant (2X10^-3M) and Congo red and Lisinopril solutions were added in different ratios. Also the same procedure were repeated keeping constant concentration of congo red (2X10^-3M) and adding different ratios of both lisinopril and metal.

Cefixime and Congo red solutions of equimolar concentrations (5X10^-3) were prepared. Aliquots of both solutions were added in different ratios to a series of 10 ml measuring flasks, so that the total volume of both was 2 ml in presence of recommended buffer, according to the recommended addition sequence and volume was completed with distilled water. Absorbance was measured against reagent blank at the appropriate wave length.

3. RESULT AND DISCUSSION:

3.1. Absorption spectrum

Absorption spectra of the Lisinopril with Congo red in presence of either copper or nickel were studied over range of 200-800 nm. Lisinopril reacts with Congo red in presence of nickel after heating for 15 minutes at 80ºC water path to yield a dark red complex that exhibit maximum absorption at 499 nm Fig.(1). This ternary complex is freely soluble in water and after removal from water path absorbance decreases gradually then it remains stable after reaching to room temperature. So, absorption can be measured directly against reagent blank without extractive procedure.

Fig.(1) Absorption spectrum of Lisinopril (70 µglml) with Congo red in presence of Nickel (A) and reagent blank(B).

Also, Lisinopril reacts with Congo red in presence of copper after heating for 10 minutes in boiling water bath to yield an orange red complex that exhibit maximum absorption at 495 nm Fig.(2). That complex also is freely soluble in water and its absorption decreses gradually after removal from water path but it remains stable after reaching room temperature and so absorption can be measured directly without extraction.

Fig.(2) Absorption spectrum of Lisinopril (60 µglml) with Congo red in presence of Copper (A) and reagent blank (B).

Cefixime reacts with Congo red directly in presence of 7.5 buffer to produce a dark red complex that exhibit absorption maximum at 595 nm Fig.(3)

Fig.(3)Absorption spectrum of Cefixime (40 µg/ml) with Congo red.

3.2. Effect of pH

Variation in pH from 3.0 to 10.0 was investigated on the reaction of Congo red with Cefixime and Lisinopril in presence of Nickel or Copper and results obtained showed that the reaction is pH sensitive and showed absorption peaks at pH 7-10 but maximum absorption at pH 7.5. No absorption peak was noticed in acidic pH values.

3.3. Effect of temperature

3.3.1. For Lisinopril

In presence of Ni Heating in water bath at 80ºC is required for maximum absorption of formed ternary complex however, complex is not formed by heating at temperature lower than 50ºC and heating at temperature above 90ºC resulted in decomposition of the formed complex Fig. (4)

Fig.(4) Effect of temp. on the ternary complex of Lisinopril with Congo red and Nickel.

For Lisinopril in presence of Cu formation of the complex requires heating in boiling water bath. Complex starts to be formed at 70ºC and maximum absorption is reached after boiling Fig.(5)

Fig(5) Effect of temp. on the ternary complex of Lisinopril with Congo red and Copper.

3.3.2. For Cefixime

Increase in temperature result in decomposition of complex and gradual decrease in absorption intensity. So, reaction was done at room temperature.

3.4. Effect of Heating Time and cooling

For Lisinopril in presence of Nickel absorbance increase with increase in heating time and maximum absorption is reached after 10 minutes and remains stable till 20 minutes of heating but further heating for more than 20 minutes result in decrease in absorption. Also, the absorption decrease with decrease in temperature after removal from water path but once it reaches room temperature it becomes stable for at least 1 hour. So, reaction is cooled to room temperature before measuring absorbance. Fig.(6)

For Lisinopril in presence of Copper absorbance increase with increase in heating time and maximum absorption is reached after 10 minutes and absorption remains nearly constant for heating up to 60 minutes. But, absorption decrease with decrease in temperature after stopping heating and remain stable for 2 hours once it reaches room temperature. So, cooling to room temperature is done once reaction is removed from water path. Fig.(6)

Fig. (6) Effect of heating time on ternary complex formed between Lisinopril and Congo Red in Presence of Nickel or Copper

3.5. Effect of Congo red volume

3.5.1. For Lisinopril

In presence of Nickel 2ml Congo Red were enough for maximum absorbance lower and higher concentrations resulted in decreased absorbance. Fig.(7)

In presence of Copper although, increase in Congo Red concentration above 1.5 ml resulted in increased absorbance but with distorted peaks. Fig.(7)

Fig. (7) Effect of Congo Red concentration on absorbance of ternary complex with lisinopril in presence of Nickel or Copper.

3.5.2. For Cefixime

Effect of reagent concentration on the intensity of absorption was studied by varying the reagent volume while other factors were held constant Fig.(8) and optimum reagent volumes were recorded in the general procedure.

Fig. (8) Effect of reagent concentrations with Cefixime.

3.6. Effect of addition sequence

3.6.1. For Lisinopril

Different addition sequences were tested and most appropriate addition sequence was Congo Red, buffer, drug then metal (Copper or Nickel) was added and volume was completed with distilled water.

3.6.2. For Cefixime

Addition sequences were tested. It was found that the most appropriate order was dye, buffer, drug then completed to volume with distilled water.

3.7. Effect of surfactants

The effect of different surfactants including anionic, cationic and nonionic surfactants was tested and no obvious effect was noticed on both the ternary complex of Lisinopril and Congo Red in presence of Copper or Nickel and ion pair of Congo Red with Cefixime.

3.8. Effect of organic solvents

Effect of different organic solvents including acetonitrile, DMSO, DMF, methanol and ethanol. They did not result in obvious changes.

3.9. Composition of the formed complexes

The nature of the ternary complex was determined using Job’s method of continuous variation. The result illustrated that the lisinopril : Ni ratio in presence of excess constant concentration of congo red was 1:1 (Fig. 9 B) and lisinopril : congo red ratio in presence of excess metal is 1 : 1 (Fig.9) and congo red : metal ratio in presence of excess lisinopril is 1:1 (Fig.9). So, the composition of that complex may be expressed as lisinopril-congo red-Ni (1:1:1)

In the same way it revealed a 1:1:1 ratio of lisinopril-congo red-cu complex. Fig (10)

Fig. (9) continuous variation plots of lisinopril: congo red (1X10^-3M) in presence of excess Ni(9A), continuous variation plots of lisinopril: Ni (1X10^-3M) in presence of excess congo red (9B) and continuous variation plots of congo red:Ni (1X10^-3M) in presence of excess drug.

Fig. (10) continuous variation plots of lisinopril: congo red (1X10^-3M) in presence of excess Cu (10 A), continuous variation plots of lisinopril: Cu (1X10^-3M) in presence of excess congo red (9B) and continuous variation plots of congo red:Ni (1X10^-3M) in presence of excess drug.

Also it revealed 1:1 ratio for Cefixime : Congo Red Fig.(11)

Fig. (13) Job’s method indicating 1:1 ratio for Congo Red to Cefixime

Table(1) Analytical parameters for the determination of Lisinopril and Cefixime using proposed methods.

Parameters	Lisinopril with Congo Red in presence of		Cefixime with Congo Red
Parameters	Nickel	Copper	Cefixime with Congo Red
Volume of reagent, ml	2	2	2
pH	7.5	7.5	7.5
λmax, nm	499	497	595
Beer's law limits µg/ml	20-80	10-50	20-65
Regression equation*	-0.1679	-0.1061	-0.33935
Intercept	-0.1679	-0.1061	-0.33935
Slope	0.00926	0.0289	0.02009
Correlation Coefficient	0.9983	0.9988	0.9985
Molar ratio	2:2:1	1:1:1	1:1

Scheme 1: Lisinopril – metal – congo red complex

M: either Cu or Ni

Table(2). Results of the analysis for determination of Lisinopril and Cefixime using proposed method.

Parameters	Lisinopril with Congo Red in presence of*						Cefixime with Congo Red*
	Nickel			Copper			Cefixime with Congo Red*
	Taken	Found	Recovery	Taken	Found	Recovery	Taken	Found	Recovery
	20.00	20.09	100.49	10.00	10.12	101.24	20.00	20.38	101.88
	30.00	29.81	99.39	20.00	19.98	99.88	25.00	24.56	98.23
	40.00	39.53	98.84	30.00	29.65	98.85	35.00	34.36	98.18
	50.00	50.33	100.67	40.00	39.99	99.97	40.00	39.54	98.85
	60.00	60.05	100.09	50.00	50.46	100.93	45.00	46.11	102.47
	80.00	79.60	99.50				50.00	50.94	101.88
							55.00	54.72	99.49
							60.00	59.85	99.75
							65.00	64.63	99.43
Mean	99.83			100.17			100.090
S D	0.71			0.95			1.739
RSD	0.71			0.95			1.738
SE	0.32			0.42			0.778
Variance	0.50			0.90			3.025
Slope	0.01			0.03			0.020
LOD	3.04			1.73			2.062
LOQ	10.14			5.78			6.873
S.S.	0.18			0.05			0.106
Molar absorbitivity L mol-1cm-1X103	2.619			8.64			4.359

* Average of three independent procedure.

Table(3). Statistical analysis of results obtained by the proposed methods applied on Zestril® tablets compared with reference method

Parameters	Congo Red		Reference Method(23)
Parameters	In Presence of Ni	In Presence of Cu	Reference Method(23)
n	6	5	5
Mean Recovery	100.14	99.83	100.209
S D	1.43	1.75	3.512
RSD	1.43	1.748	3.505
SE	0.641	0.781	1.571
Variance	2.057	3.046	12.33
Student- t test⁽⁶¹⁾	0.038(2.57)a	0.123(2.57)a
F-test⁽⁶²⁾	0.1668(5.05)b	0.247(6.256)b

a and b are the Theoretical Student t-values and F-ratios at p_0.05.

Table(4). Statistical analysis of results obtained by the proposed methods applied on Ximacef® capsules compared with reference method

Parameters	Congo Red	Reference Method(55)
n	5	5
Mean Recovery	100.0017	99.65
S D	0.2879	3.308
RSD	0.288	3.319
SE	0.129	1.479
Variance	0.083	10.94
Student- t test⁽⁶¹⁾	0.158(2.57)a
F-test⁽⁶¹⁾	0.007576334(6.256)b

a and b are the Theoretical Student t-values and F-ratios at p_0.05.

4. CONCLUSION:

The proposed methods were successfully utilized for the determination of Lisinopril and Cefixime in pure form and in pharmaceutical formulations and the described method proved to be highly sensitive, simple, accurate, precise and less time consuming. Student t- and F-values gave lower values than the theoretical ones indicating no significant difference compared to the reference one. The formed ternary and ion pair complexes were readily soluble in water avoiding time and cost consuming extractive procedure.

5. REFERENCES:

1. British Pharmacopoeia, HM Stationery Office, London, UK, PA, 2007

2. Martindale: The Complete Drug Reference, Pharmaceutical Press;35 edition (2007)

3. Qin, W. W.; Zhang, Z. J.*; Tian, Y.; Xu, F. G.; Wang, N.; Chen, Y.; Biomedical Chromatography, 2007, 21 (4), 415-421.

4. Huang, J. C.; Xu, Y.*; Liu, F.; Gao, S.; Guo, Q. X.; Rapid Communications in Mass Spectrometry, 2005, 20 (2), 248-252

5. Kousoulos, C.; Tsatsou, G.; Dotsikas, Y.; Loukas, Y. L.; Analytica Chimica Acta, 2005, 551 (1-2), 177-183

6. Tashtoush, B. M.; Alali, F. Q.; Najib, N. M.; Die Pharmazie, 2004, 59 (1), 21-24

7. Tsakalof, A.; Bairachtari, K.; Georgarakis, M.; J.Chromatography B: Anal. Technol. Biomed. Life Sci., 2003, 783 (2), 425-432

8. Beasley, C. A.; Shaw, J.; Zhao, Z.; Reed, R. A.; J. Pharm. and Biomed. Anal, 2005, 37 (3), 559-567

9. Sagirli, O.; Ersoy, L.; J. Chromatography B: Anal. Technol. Biomed. Life Sci., 2004, 809 (1), 159-165

10. El-Emam, A. A.; Hansen, S. H.; Moustafa, M. A.; El-Ashry, S. M.; El-Sherbiny, D. T.; J. Pharm. and Biomed. Anal, 2004, 34 (1), 35-44

11. El-Gindy, A.; Ashour, A.; Abdel-Fattah, L.; Shabana, M. M.; J. Pharm. and Biomed. Anal, 2001, 25 (5-6), 913-922

12. Anzenbacherova, E.; Anzenbacher, P.; Macek, K.; Kvetina, J.; J. Pharm. and Biomed. Anal, 2001, 24 (5-6), 1151-1156

13. Erk, N.; Kartal, M.; Analytical Letters, 1999, 32 (6), 1131-1141

14. Bonazzi, D.; Gotti, R.; Andrisano, V.; Cavrini, V.; J. Pharm. and Biomed. Anal, 1997, 16 (3), 431-438

15. Sane, R. T.; Valiyare, G. R.; Deshmukh, U. M.; Singh, S. R.; Sodhi, R.; S. P. Mandali`s Ther; Indian Drugs, 1992, 29 (12), 558-560

16. Wong, Y.-C.; Charles, B. G.; J. Chromatography, B: Biomedical Applications, 1995, 673 (2), 306-310

17. Leis, H. J.; Fauler, G.; Raspotnig, G.; Windischhofer, W.; Rapid Communications in Mass Spectrometry, 1998, 12 (21), 1591-1594

18. Avadhanulu, A. B.; Pantulu, A. R. R.;Indian Drugs, 1993, 30 (12), 646-649

19. Hillaert, S.; de Grauwe, K.; van den Bossche, W.; J. Chromatography, 2001, 924 (1-2), 439-449

20. Gotti, R.; Andrisano, V.; Cavrini, V.; Bertucci, C.; Fulanetto, S.; J. Pharm. and Biomed. Anal, 2000, 22 (3), 423-431

21. Razak, O. A.; Belal, S. F.; Bedair, M. M.; Haggag, R. S.; Talanta, 2003, 59 (5), 1061-1069

22. Razak, O. A.; Belal, S. F.; Bedair, M. M.; Barakat, N. S.; Haggag, R. S.; J. Pharm. and Biomed. Anal, 2003, 31 (4), 701-711

23. El-Enany, N.; Belal, F.; Al-Ghannam, S.; Mikrochimica Acta, 2003, 141 (1-2), 55-61

24. Rahman, N.; Siddiqui, M. R.; Azmi, S. M. H.; Chemia Analityczna (Warsaw, Poland), 2007, 52 (3), 465-480

25. Cetin, G.; Sungur, S.; Reviews in Analytical Chemistry, 2006, 25 (1), 1-10

26. Paraskevas, G.; Atta-Politou, J.; Koupparis, M.; J. Pharm. and Biomed. Anal, 2002, 29 (5), 865-872

27. Rajasekaran, A.; Udayavani, S.; J. Indian Chemical Society, 2001, 78 (9), 485-486

28. El-Gindy, A.; Ashour, A.; Abdel-Fattah, L.; Shabana, M. M.; J. Pharm. and Biomed. Anal, 2001, 25 (5-6), 923-931

29. Jain, H. K.; Agrawal, R. K.; Indian Drugs, 2000, 37 (4), 196-199

30. Panzade, P. D.; Mahadik, L. R.;Indian Drugs, 1999, 36 (5), 321-323

31. El-Yazbi, F. A.; Abdine, H. H.; Shaalan, R. A.; J. Pharm. and Biomed. Anal, 1999, 19 (6), 819-827

32. Ozer, D.; Senel, H.; J. Pharm. and Biomed. Anal, 1999, 21 (3), 691-695

33. Prasad, C. V. N.; Saha, R. N.; Parimoo, P.; Pharmacy and Pharmacology Communications, 1999, 5 (6), 383-388

34. Erk, N.; Spectroscopy Letters, 1998, 31 (3), 633-645

35. Zacharis, C. K.; Tzanavaras, P. D.; Themelis, D. G.; Theodoridis, G. A.; Economou, A.; Rigas, P. G.; Analytical and Bioanalytical Chemistry, 2004, 379 (5), 759-763

36. Yuan, A. S.; Gilbert, J. D.; J. Pharm. and Biomed. Anal, 1996, 14 (7), 773-781

37. Shepley, K.; Rocci, M. L., jun.; Patrick, H.; Mojaverian, P.; J. Pharm. and Biomed. Anal, 1988, 6 (3), 241-257

38. Worland, P. J.; Jarrott, B.; J. Pharmaceutical Sciences, 1986, 75 (5), 512-516

39. Shah, P. B.; Pundarikakshudu, K.; Journal of AOAC International, 2006, 89 (4), 987-994

40. Meng, F.; Chen, X. Y.; Zeng, Y. L.; Zhong, D. F.; J.Chromatography B: Anal. Technol. Biomed. Life Sci., 2005, 819 (2), 277-282

41. Pehourcq, F.; Jarry, C.; J. Chromatography, 1998, 812 (1-2), 159-178

42. Liu, S. Q.; Dai, Q.; Ma, W. X.; Lin, C.; Tang, X. Z.; Yaowu Fenxi Zazhi, 1998, 18 (1), 33-36

43. Liu, G. L.; Sha, R. G.; Gao, S.; Shen, Y. X.; Wang, S. X.; Yaoxue Xuebao, 1993, 28 (3), 216-221

44. Nahata, M. C.; Journal of Liquid Chromatography and Related Technologies, 1991, 14 (20), 3755-3759

45. McAteer, J. A.; Hiltke, M. F.; Silber, B. M.; Faulkner, R. D.; Clinical Chemistry (Washington D.C.) , 1987, 33 (10), 1788-1790

46. Tokuma, Y.; Shiozaki, Y.; Noguchi, H.; J. Chromatography: Biomedical Applications, 1984, 36 (2 (J. Chromatogr., 311)), 339-346

47. Manna, L.; Valvo, L.; Chromatographia , 2004, 60 (11-12), 645-649

48. Gonzalez-Hernandez, R.; Nuevas-Paz, L.; Soto-Mulet, L.; Lopez-Lopez, M.; Hoogmartens, J.; Journal of Liquid Chromatography and Related Technologies, 2001, 24 (15), 2315-2324

49. Eric-Jovanovic, S.; Agbaba, D.; Zivanov-Stakic, D.; Vladimirov, S.; J. Pharm. and Biomed. Anal, 1998, 18 (4-5), 893-898

50. Solangi, A. R.*; Memon, S. Q.; Khuhawar, M. Y.; Bhanger, M. I.; Acta Chromatographica, 2007 (19), 81-96

51. Honda, S.; Taga, A.; Kakehi, K.; Koda, S.; Okamoto, Y.; J. Chromatography, 1992, 590 (2), 364-368

52. Golcu, A.; Dogan, B.; Ozkan, S. A.; Talanta, 2005, 67 (4), 703-712

53. Reddy, T. M.; Sreedhar, M.; Reddy, S. J.; J. Pharm. and Biomed. Anal, 2003, 31 (4), 811-818

54. Ganjali, M. R.; Naji, L.; Poursaberi, T.; Shamsipur, M.; Haghgoo, S.; Analytica Chimica Acta, 2003, 475 (1-2), 59-66

55. Shankar, D. G.; Sushma, K.; Lakshmi, R. V.; Reddy, M. N.; Murthy, T. K.; Rao Srinivasa, Y.; Indian Drugs, 2001, 38 (12), 617-619

56. Al-Momani, I. F.; J. Pharm. and Biomed. Anal, 2001, 25 (5-6), 751-757

57. El Walily, A. F. M.; Gazy, A. A. K.; Belal, S. F.; Khamis, E. F.; Spectroscopy Letters, 2000, 33 (6), 931-948

58. El-Walily, A. F. M.; Gazy, A. A.; Belal, S. F.; Khamis, E. F.; J. Pharm. and Biomed. Anal, 2000, 22 (2), 385-392

59. Agbaba, D.; Eric, S.; Karljikovic-Rajic, K.; Vladimirov, S.; Zivanov-Stakic, D.; Spectroscopy Letters, 1997, 30 (2), 309-319

60. Bebawy, L. I.; El Kelani, K.; Abdel Fattah, L.; J. Pharm. and Biomed. Anal, 2003, 32 (6), 1219-1225

61. Vogel Qualitative analysis, fifth edition, 1992

62. Modern Analytical Chemistry, David Harvey, McGraw-Hill Companies, first edition, 2002

Received on 24.01.2012 Accepted on 10.07.2012

Asian J. Pharm. Ana. 2(3): July-Sept. 2012; Page 90-97