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Determination of dissociation constants of uniprotic acids with known spectrum of
acidic or basic component
Determination of dissociation constants of uniprotic acids with known spectrum of acidic or basic component
HA A- + H+
[HA] =
Ct [H+][H+] + Ka
[A-] =
Ct Ka
[H+] + Ka
D XHA XA= +
cHA
sHA
= cA
sA
+
R = D - XHA = D - cHAsHAT
Determination of dissociation constants of uniprotic acids with known spectrum of acidic or basic component
R = D - XHA = D - cHAsHAT
cHA =f (Ka)
sHAD
rafa_Ka.m
Determination of Pka value for an uniprotic acid with known spectrum of HA
species
Calling function rafa_Ka
?Investigate the effects of extent of spectral overlapping on the determined pKa value by RAFA
Di-protic Acids
[H]2 + Ka1 [H] + Ka1 Ka2
Ct [H]2
[H2A] =
[H]2 + Ka1 [H] + Ka1 Ka2
Ct Ka1 [H]2
[HA] =
[H]2 + Ka1 [H] + Ka1 Ka2
Ct Ka1 Ka2[A] =
R = D - XH2A = D - cH2AsH2AT
cH2A =f (Ka1, Ka2)
pKa1= 3.0 pKa2=4.0
pKa1= 3.0 pKa2=4.5
pKa1= 3.0 pKa2=5.0
pKa1= 3.0 pKa2=5.5
pKa1= 3.0 pKa2=6.0
pKa1= 3.0 pKa2=6.5
pKa1= 3.0 pKa2=7.0
Determination of amount and pKa values of an acid in a mixture with known spectrum of
its components
HA A- + H+
[HA] =
Ct [H+][H+] + Ka
[A-] =
Ct Ka
[H+] + Ka
XHA XAD = +
cHA
sHAcA
sA
= +
R = D - XHA - XA = D - cHAsHAT- cA sA
T
Determination of amount and pKa values of an acid in a mixture with known spectrum of its components
Interferences+
+ Interferences
pH-metric titration of a mixture containing an acid with known spectrum of components
D sHA sA
R = D - XHA -XA= D - cHAsHAT - cA sA
T
cHA =f (C0,Ka) cA =f (C0,Ka)
rafa_CKa.m
Determination of concentration and Pka
values for an uniprotic acid with known spectrum of
HA and A component
Calling function rafa_CKa
?Use RAFA_CKa and determine the amount and pKa values of a known acid in an unknown mixture
Rank Annihilation Factor Analysis for Spectrophotometric Study of Complex Formation Equilibria
Anal. Chim. Acta486, 109-123, 2003
M + nL MLnM + nL MLn
[M] [L][MLn]
Kf= n[M] [L][MLn]
Kf= n
CL = [L] + [ [MLn]
CM = [M] + [ [MLn]
Kf[L]n+1 + (nKfCM – KfCL) [L]n + [L] –CL = 0
[MLn] = Kf CM[L]n / (1+Kf[L]n)
[M] = CM / (1 + Kf[L]n)
One-step complex formation equilibria
XMLnD = XL +
cL
sLcMLn
sMLn
= +
R = D - XL = D - cLsLT
+ Interferences
cL= f(Kf,n)
Rank Annihilation Factor Analysis for Spectrophotometric Study of Complex Formation Equilibria
One step complex formation (n=2)
M + 2L MLM + ML2
[L] [M]
[ML2]
CL=0.001KL=106.
5
rafa_MLn.m
Determination of stoichiometry and
formation constant values for an MLn complex with known spectrum of ligand
n=1
n=2
n=3
n=4n=
5
?Create the data for ML3 system and use RAFA for determination of Kf and its stoichiometry.
MLn.m
Simulation of MLn complex formation system
Calling function MLn
[M] [L][ML]
K1=
[ML] [L][ML2]K2=
CL = [L] + [ML] + 2 [ML2]CM = [M] + [ML] + [ML2]
K1K2[L]3 + (K1(1+K2(2CM –CL)))[L]2 + (1+K1(CM –CL))[L]–CL = 0
ML + L ML2
M + L ML
Two successive step complex formation
A = AL + AML + AML2 + R
= L [L]T + ML [ML]T + ML2 [ML2]T + R
= E CT + R
Two successive step complex formation
R = D - XL = D - cLsLT
cL= f(K1 , K2)
Determination of dissociation constants of uni-protic acids without known spectrum
12
543
54
123
11
111
52
0.20.51
0.1 0.2 0.3 0.40.1 0.3 0.4 0.2
0.1 0.2 0.3 0.40.1 0.3 0.4 0.2
0.60.30.20.150.12
1.70.80.50.350.26
2.31.10.70.50.38
1.40.80.60.50.44
=
0.60.60.60.60.6
1.71.61.51.41.3
2.32.22.12.01.9
1.41.61.82.02.2
=
12
543./
12
543./
A simple mathematical rule
12
543
54
123
12
543./
11
111
52
0.20.51
00
000
3.260.26
-1.54-1.24-0.74
12
543
54
123
32
451./
0.331
1.250.83
1.662
0.250.43
-0.746 0.1980.538
-1.212-1.0621.538
-0.076 1.924-0.276 0.174
Mean centering
Mean centering
Rank = 2 Rank = 2 Rank = 1
Rank = 2 Rank = 2 Rank = 2
HA A- + H+
[HA] =
Ct [H+][H+] + Ka
[A-] =
Ct Ka
[H+] + Ka
D XHA XA= +
cHA
sHAcA
sA
= +
D’ = D ./ cHA
Determination of dissociation constants of uni-protic acids
Mean centering (D’)
cHA = f(Ka)
Titration of an uni-protic acid or a mixture containing an uni-protic acid
Rafa_mcKa.m
Determination of dissociation constants of
uni-protic acids
Calling function rafa_mcKa
?Use mean centering based method for determination of acidity constant of an uniprotic acid in a mixture
Determination of dissociation constants of di-protic acids without known spectrum
cHA =f (Ka1, Ka2)
Determination of dissociation constants of di-protic acids without known spectrum
D’ = D ./ cHA Mean centering (D’)
Rafa_mcH2A.m
Determination of dissociation constants of
di-protic acids
Calling function rafa_mcH2A
?Use mean centering based method for determination of acidity constant of an di-protic acid in a mixture
