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Methods of analysis .nilhhhhhhhhhhh
1. METHODS OF ANALYSIS For β CD
COMPLEX
Guided By:
Mrs. S.P. CHAUDHRI
Prepared By:
Mr. NILESH K. GAWARE
Marathwada Mitra Mandals’s College of Pharmacy, Pune-33
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2. METHODS OF ANALYSIS
There are 6 methods to analyse the β cd complex.
1.
2.
3.
4.
5.
6.
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Method of continuous variation
Spectroscopy method
Distribution method
pH titration methods
Solubility methods
General method
NILESH GAWARE
MM COLLEGE OF PHARMACY.
3. 1.
METHOD OF CONTINUOUS
VARIATION
In this we measured additive property.
JOB suggested the use of additive property such as
spectrophotometric extinction coefficient (dielectric
constant & square of R.I)
If the property for two species is different and when
they are mixed no interaction is occur
The value of the property is calculated by taking mean
of there individual species in mixture
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
4. If the additive property such as dielectric constant is plotted Vs
mole fraction from 0-1
If there is no complex formation then it will give linear
relationship.
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
5. If the solution of two species A & B are of equal molar
conc. are mix & if complex is form between them then
value of additive property will pass from maximum.
For a constant total conc. of A & B the complex is at
highest conc. at point where the species A & B are
combined in the ratio in which they occur in the
complex.
The line show a change in slope occurs at the mole
fraction corresponding to the complex .
The change in slope occur at a mole fraction indicate a
type of complex .
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
6. Spectrophotometric approach
In this method measure the absorbance of the solutions of
various mole fraction in which the complex is form.
Measure the absorbance of another same mole fraction of
solution in which the complex is not form.
Take the absorbance difference of this solutions and plot a graph
Vs mole fractions.
Extrapolate the intersect point on x axis gives the conk . of mole
fraction require to form stable complex of cd’s.
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
8. Another relation can be used that is absorbance is
proportional to the only conc. of the complex MAn,the
molar ratio of ligand A to metal M and stability constant
can be calculated as follows.
M + nA
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NILESH GAWARE
MAn
MM COLLEGE OF PHARMACY.
9. Log[Man]=log k + log [M]+nlog [A]
where,
Log[MAn]=conc. of complex
Log k = equm.constant
N= no. of ligand
Log[M]= conc. of uncomplex metal ion
In this the conc. of metal ion is kept constant while the conc. of
ligand varried & corrsponding to the formation of complex is
obtained from the spectrophotometric analysis.
If we plot the graph of log[MAn] Vs log[A] then slope of line
gives no. of ligand mole require to form complex & intercept
gives the stability constant.
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
10. pH titration methods
This is a method used in which the complexation is achieve by
change in pH.
Eg.chelation of cupric ion by glycine.
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
11. CONTINUE……
As the two proton are formed in the reaction of equation the
addition of glycine to a solution containing cupric ion should
result in a decrease in pH .
Titration curve can be obtained by adding a strong base to
solution of glycine & to another solution containing glycine &
cupric ion.
Plot the graph of pH Vs no. of ml strong base added.
The curve for glycine metal mix is well below that for the glycine
alone & decreased in pH show that complexation is occur is
throughout most of the neutralization range.
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
13. The results can be treated to obtain stability constant for the
complex.
The 2 successive equilibrium between the cu ion M, and glycine
or ligand A, so
M + A= MA
k1=[MA]/ [M].[A]
MA+A =MA2
k2=[MA2]/ [MA]. [A]
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MM COLLEGE OF PHARMACY.
14. M + 2A =MA2;β
β= K1.K2=[MA2]/ [M].[2A]
Where ,
k1 & k2=formation constant,
β = equilibrium constant
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MM COLLEGE OF PHARMACY.
15. The average number of ligand group bound per metal ion present
is given by
The denominator gives the total conc. of metal present in in all
form.
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MM COLLEGE OF PHARMACY.
16. [MA]+ 2[MA2] =[M] + [MA] +[MA2]
[M] =[MA2]
β=K1.K2=1/[A]2
P[A]= ½ log β n =1
P[a]=log k1 n=1/2
P[A]= log k2 n=3/2
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
17. If we know the value of n & β we can determine the individual
complex formation constant & stability constant.
When graph is plotted of n Vs p[A] w.r.t to pHs
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
18. It is seen that value of n is reach up to certain value which
indicate that maximum no of glycine mole that can combine with
cu ion.
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
19. SOLUBILITY METHOD
Higuchi & Lach used this method for detection of complex.
Take a container with closure system. Add drug in to the
container along with the solution of complexing agent.
Make series of solution of different conc.of complexing agent
& the bottle's are agitated in a constant temperature bath.
Aliquid portion is removed & analyzed.
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
20. In this p-amino benzoic acid(PABA) is drug & caffeine is
complexing agent.
The results of above experiments is plotted as molar conc.of PABA
Vs. molar conc. of caffeine.
The point A at which the line crosses the vertical axis show the
solubility of drug in water.
Add caffeine then observed. There is increase in solubility of PABA
linearly owing to complexion.
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
22. At point B the solution is saturated w.r.t. the complex & to the
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drug itself.
The complex continue to form & precipitate from the saturated
system as more caffeine is added.
At point ‘C’ all excess solid PABA has passed into solution & has
converted to the complex.
Although the solid drug is exhausted and the solution is no
longer saturate some of the PABA remain uncomplexd in
solution.
It is further combine with caffeine to form higher complex as
shown in fig.
NILESH GAWARE
MM COLLEGE OF PHARMACY.
23. Distribution Methods
The method of distributing a solute, between two
immiscible solvent can be used to determine the stability
constant for certain compound.
The complexion of iodide by Potassium iodide may be used
as.
E.g. To explain this method equation
I2 + I-
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NILESH GAWARE
I3 ---
MM COLLEGE OF PHARMACY.
24. Higuchi investigate the complexing action of caffeine, glycols on
number of acidic drugs using this method.
According to Higuchi & Zuck the reaction between caffeine &
benzoic acid to form the B.A– caffeine complex
K= [B.A - caffeine]/ [B.A - caffeine]
K=37.5
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NILESH GAWARE
at 0
MM COLLEGE OF PHARMACY.
25. SPECTROSCOPY & CHARGE TRANSFER
COMPLEXATION
It is used for charge transfer complexation.
When iodine is analyzed in a noncomplexing solvent such as
CCL4 a curve is obtained with single peak at about 520nm
having violet color.
A solution of iodine in benzene exhibits a max. shift to
475nm & peak considerably intensity for the charge shifted
band appears at 300nm.
A solution of iodine in diethyl ether shows a still greater shift
to lower wavelength & the appearance of a new max.
solution is red to brown.
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MM COLLEGE OF PHARMACY.
26. In benzene & ether iodine is electrons accepter accepter & the
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organic solvent is donor in in ccl4;no complex is formed.
The shift towards the u.v. region becomes greater as the
electron donor solvents becomes a strong electron releasing
agents.
This spectra arise from the transfer of an electron from donor
to the accepter in close contact contact in the in the excited
state of the complex.
The more easily a donor release its electrons as measured by
its ionization potential, the stronger it is as a donor.
Ionization potential of a series of donor produce a straight line,
when plotted against the charge transfer energy for solution of
iodine in the donor solvent.
NILESH GAWARE
MM COLLEGE OF PHARMACY.
27. The complexation constant K can be obtained by use
of UV spectroscopy.
The association between the donor D & accepter A is
given as
K1
D + A
DA
K-1
Where,
k1/k-1 = equilibrium constants for complexation
k1& k-1 =interaction rate constant.
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
28. The Benesi-Hildebrand eq.given relation of k that is.
A0/A=1/€+1/K €*1/D0
A0
&
D0 = initial conc. in mole/lit.
€ = molar .absorptivity of the charge transfer complex.
K= stability constant L/mole
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
29. result in a straight line with
slope of 1/K € is observe
A plot of A0/A Vs 1/D0
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MM COLLEGE OF PHARMACY.
30. GENERAL METHODS
It include Nuclear magnetic resonance ,infra red
spectroscopy, polarography x-ray diffraction , kinetics etc &
many more.
NMR SPECTROSCOPY ;
EG.complexation of caffeine with tryptophan in aq.solution
was given by Nishijo et.al using H1 NMR
Caffeine interacts with L-tryptophan at a molar ratio of
1:1 by parallel stacking
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NILESH GAWARE
MM COLLEGE OF PHARMACY.
