Study of protonation equilibrium of lorazepam by potentiometry and multiwavelengths spectrophotometry
محورهای موضوعی : Journal of the Iranian Chemical Research
Ateesa Yazdanipour
1
(Department of Chemistry, Faculty of Sciences, Islamic Azad University, Arak Branch, Arak, Iran)
کلید واژه: Spectrophotometry, Potentiometry, Lorazepam, Acidity constants,
چکیده مقاله :
The acid-base equilibrium of lorazepam was studied by means of potentiometry andmultiwavelengths spectrophotometry. The stoichiometric equilibrium constants were determinedat 25 °C and constant ionic strength 0.1 mol L-1 (NaCl). The acidity constants pK1=1.58±0.05and pK2=11.67±0.07 were found by potentiometry, and pK1=1.54±0.02 and pK2=11.61±0.03 bymulti-wavelengths spectrophotometry. Potentiometric determination of equilibrium constantswas performed by application of the formation function method. Data analysis program appliedfor multi-wavelengths spectrophotometric determination of acidity constants.
[1] D. Kara, M. Alkan, Spectrochim. Acta Part A 56 (2000) 2753-2761.
[2] S. Pichini, R. Pacifici, I. Altieri, A. Palmeri, M. Pellegrini, P. Zuccaro, J. Chromatog. B 732 (1999)
509-514.
[3] R.G. Lister, D.R. Abernethy, D.J. Greenblatt, S.E. File, J. Chromatog. B 277 (1983) 201-208.
[4] L.B. Pfendt, D.M. Sladic, T.J. Janjic, G.V. Popovic, Analyst 115 (1990) 383-387.
[5] I. Scarminio, M. Kubista, Anal. Chem. 65 (1993) 409-416.
[6] W.W. Han, G.J. Yakatan, D.D.J. Maness, J. Pharm. Sci. 66 (1977) 573-577.
[7] F.J.C. Rossotti, H. Rossotti, The Determination of Stability Constants, McGraw-Hill, New York,
1961.
[8] G. Popovic, L. Milovanovic, V. Kapetanovic, J. Pharm. Biomed. Anal. 18 (1998) 859-863.
[9] M. Kubista, R. Sjoback, J. Nygren, Anal. Chim. Acta 302 (1995) 121-125.
[10] J. Nygren, J.M. Andrade, M. Kubista, Anal. Chem. 68 (1996) 1706-1710.
[11] M. Kubista, J. Nygren, A. Elbergali, R. Sjoback, Crit. Rev. Anal. Chem. 29 (1999) 1-28.
[12] A. Niazi, A. Yazdanipour, J. Ghasemi, M. Kubista, Collect. Czech. Chem. Commun. 71 (2006) 1-14.
[13] A. Niazi, M. Ghalie, A. Yazdanipour, J. Ghasemi, Spectrochim. Acta Part A 64 (2006) 660-664.
[14] A. Niazi, A. Yazdanipour, J. Ghasemi, M. Kubista, Spectrochim. Acta Part A 65 (2006) 73-78.
[15] A. Niazi, A.A. Rezaei, F. Shahhosseini, Annali di Chimica 97 (2007) 199-211.
[16] J. Ghasemi, A. Niazi, M. Kubista, Spectrochim. Acta Part A 62 (2005) 649-656.
[17] A. Elbergali, J. Nygren, M. Kubista, Anal. Chim. Acta 379 (1999) 143-158.
