Keywords
spectrophotometric determination
pharmaceuticals formulations
ammonium
molybdate
How to Cite
Abstract
A new, simple, precise, rapid and low-cost spectrophotometric method for methyldopadetermination in pharmaceutical preparations is described. This method is based on the complexation
reaction of methyldopa with molybdate. Absorbance of the resulting yellow coloured product is measured
at 410 nm. Beer’s Law is obeyed in a concentration range of 50 – 200 μg ml -1 methyldopa with an
excellent correlation coefficient (r = 0.9999). No interference was observed from common excipients in
formulations. The results show a simple, accurate, fast and readily applied method to the determination of
methyldopa in pharmaceutical products. The analytical results obtained for these products by the proposed
method are in agreement with those of the Brazilian Pharmacopoeia procedure at 95% confidence level.
References
B. B. Hoffman, R. J. Lefkowitz, in: A.G. Gilman, J.G.
Hardman, L.E. Limbird, P.B. Molinoff, R.W. Ruddon (Eds),
The Pharmacological Basis of Therapeutics, MacGraw-Hill,
New York, 9th edn., 1996, chap. 12.
The United States Pharmacopoeial Convention, Rockville,
MD, The United States Pharmacopoeia 24th edn., The Na-
tional Formulary 19, 2000.
D. Amin, Analyst 111 (2) (1986) 255.
M. I. Walash, A. AbouOuf, F. B. Salem, J. Assoc. Off. Anal.
Chem. 65 (6) (1982) 1445.
W. I. Mohamed, F. B. Salem, Anal. Lett. 17 (B3) (1984) 191.
F. B. Salem, Talanta 34 (9) (1987) 810.
F. B. Salem, Anal. Lett. 26 (9) (1993) 1959.
F. B. Salem, Anal. Lett. 26 (2) (1993) 281.
C. Martinez-Lozano, T. Pérez-Ruiz, V. Tomas, O. Val,
Analyst 116 (8) (1991) 857.
M.E. Garrido, J.L.F.C. Lima, C. Delerue-Mattos, J.
Pharm. Biom. Anal. 15 (6) (1997) 845.
C. Sharma, S. Mohanty, S. Kumar, N. J. Rao, Analyst
(12) (1996) 1963.
H.B. Lee, R.L. Hong-You, P. J. A. Fowlie, J. Assoc. Off.
Anal. Chem. 72 (6) (1989) 979.
H. Tsuchiya, M. Sato, H. Kato, T. Okubo, L. R. Juneja,
M. Kim, J. Chromatogr. B 703 (1-2) (1997) 253.
L. R. Parsons, T. M. Kerr, F. Weiss, J. Chromatogr. B
(1) (1998) 35.
O. Nozaki, T. Iwaeda, Y. Kato, J. Biolumin. Chemilumin.
(6) (1996) 309.
O. Nozaki, T. Iwaeda, H. Moriyama, Y. Kato, Lumines-
cence 14 (3) (1999) 123.
K. D. Kozminski, D. A. Gutman, V. Davila, D. Sulzer, A.
G. Ewing, Anal. Chem. 70 (15) (1998) 3123.
A. G. Davidson, J. Pharm. Sci. 73 (11) (1984) 1582.
F. B. Salem, Anal. Lett. 18 (B9) (1985) 1063.
N. A. El-Rabbat, N. M. Omar , J. Pharm. Sci. 67 (6)
(1978) 779.
L. Zivanovic, S. Vasiljevic, D. Radulovic, Boll. Chim.
Farm. 130 (5) (1991) 162.
P. Nagaraja, R. A. Vasantha, K. C. S. Murthy, K. S.
Rangappa, Chemia Analityczna 46 (4) (2001) 569.
P. B. Issopoulos, Frenesius J. Anal. Chem. 336 (2) (1990)
T. Aman, I. U. Khan, N. Aslam, I. Ahmed, Anal. Lett. 31
(6) (1998) 1007.
J.J.B. Nevado, J.M.L. Gallego, P.B. Laguna, Frenesius
J. Anal. Chem. 353 (2) (1995) 21.
P. Nagaraja, K.C.S. Murthy, K. S. Rangappa, N. M. M.
Gowda, Talanta 46 (1) (1998) 39.
I. C. Vieira, O. Fatibello-Filho, Talanta 46 (4) (1998)
P. B. Issopoulos, P. T. Economou , Farmaco 48 (1)
(1993) 127.
M. I. Walash, A. AbouOuf, F. B. Salem, J. Assoc. Off.
Anal. Chem. 68 (1) (1985) 91.
P. Nagaraja, R. A. Vasantha, K. R. Sunitha, Talanta 55 (6)
(2001) 1039.
P. B. Issopoulos, Pharm. Acta Helv. 64 (3) (1989) 82.
G.P. Haight and V. Paragamian, Anal. Chem., 32(6)
(1960) 642.
K. Kustin and S.T. Liu, J. Am. Chem. Soc., 95 (1973)
Farmacopéia Brasileira, Atheneu Editora São Paulo, São
Paulo, 4th edn., 1996, 47–47.2.
A. G. Tininis, A. Leandro, H. R. Pezza, C. B. Melios, L.
Pezza, Anal. Lett. 33 (14) (2000) 2901.
J. C. Miller, J. N. Miller, Estadística para Química Analítica,
Addison-Wesley Iberoamericana, Delaware, 2nd edn., 1993,
chap. 3.
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