INTRODUCTION:
Azelastine hydrochloride is a selective histamine antagonist and is used in a treatment of allergic rhinitis. Its trade name is optivar. It is orally administered azelastine and not affected by age, gender or hepatic impairment1. Azelastine nasal spray is used for treating symptoms of seasonal allergic rhinitis2 twice daily and rhinorrhea and sneezing. It is used to treat vasomotor rhinitis. The dosage of Azelastine eye drops is one drop twice daily or it may be increased to four times. Considering medicinal applications it was thought interesting to determined values of stability constants by using pH-metric technique. Formation of complex was confirmed by knowing stability constants so pH-metric technique has broad applications in sciences. Nitrogen, sulphur and oxygen containing organic molecules are pioneer member of medicinal chemistry3-4.
Determination of 
, 
, pK and log K of different chelating agents in
different solvents and their systems at different molar concentrations and
temperatures were reported5-11. So we have to decided to determined , , pK and log K of
azelastine hydrochloride with Cu(II), Co
(II) and Fe(II) metal ions by pH-metry.
MATERIALS AND METHOD:
Nitrate salts of Cu(II), Co(II) and Fe(II) were taken. Azelastine hydrochloride is denoted as AH. Water is used as a solvent for preparation of stock solutions. Irving and Rossotti method was used during this work. Pyrex glass beaker having capacity of 100ml was used for pH-metric titrations and titrations were carried out at 320C temperature by bubbling nitrogen gas by making use of magnetic stirrer. pH-Meteric readings were only taken when magnetic stirring stopped. During titration it was observed that first reading decreases and then increases, the point from which reading increases was treated as the end point of titration, this titration was further carried out to get minimum 10 readings. For completion of titration near about one hour was required.
During study titrations of 0.1 N NaOH were carried out with (i) free acid (0.01 M), (ii) free acid (0.01 M) and ligand (20 x 10-4M) and (iii) free acid (0.01 M), ligand (20 x 10-4) and metal ion (4 x 10-4M) respectively. In all titrations readings were recorded after addition of 0.2 ml solution. Graph of volume of alkali added against pH were plotted.
RESULTS AND DISCUSSION:
and values were
determined by using following expressions.
where,
V0 is the initial volume of the solution. E0 and TL0
are initial concentrations of mineral acid and ligand respectively. V1
and V2 are volumes of alkali of normality N during acid and ligand
titration at given pH. ‘γ’ is replaceable proton from ligand. Values were
determined at 32 (±1) °C in E0=1x10-2
M, TL0 = 20 x 10-4 M, V0 = 50 ml, N
= 0.2 N respective ratios of solutions. Plots
between volume of NaOH and pH of solution were used to determine proton-ligand
stability constant. Horizontal difference (V2-V1) was
measured accurately between titration curves of free acid and acid+ligand. It
was used to calculate formation number at various pH values and fixed ionic strength μ
= 0.2 M using equation 2. Where, notations have same meaning as given in
earlier equation. Horizontal difference (V3-V2) between
metal complex (A+M+L) and reagent (A+L) curve were used for determination of values. and values obtained
during study are given in Table-1
