. . . . "Niesnerov\u00E1, Irena" . . . . . "http://link.springer.com/article/10.2478%2Fs11532-013-0304-6" . "9"^^ . "93596" . . "Oligomers-Model Building in Protonation Equilibria of Sitagliptin" . "1895-1066" . "Mixed protonation constants of sitagliptin phosphate at various ionic strengths I (mol kg(-1)) in range 0.01 and 0.50 and at 298.15 K are determined using FBSTAC4 and HYPERQUAD nonlinear regression analyses of the potentiometric titration curve. At a low concentration c(L) = 1.1 mmol kg(-1) the monomers L, LH, LH2, LH3 and LH4 dominate, while for a concentration range from c(L) = 13.7 to 24.7 mmol kg(-1) dimers L2H2, L2H3, L2H4 and L2H are mainly present. The regression programme has almost no influence on the precision of the protonation constants. The accuracy of the protonation constants log beta(qr) depends on the accuracy of the group parameters. As two group parameters c(L,0), c(H,T) are ill-conditioned in a model, their determination is therefore uncertain: both can significantly cause a systematic error in the estimated common parameters log(10)beta(qr). Fitness tests using regression diagnostics have proven the reliability of the parameter estimates." . "Meloun, Milan" . "[9BDC22642C7F]" . "Oligomers-Model Building in Protonation Equilibria of Sitagliptin"@en . "Oligomers-Model Building in Protonation Equilibria of Sitagliptin" . . . . "RIV/00216275:25310/13:39896226!RIV14-MSM-25310___" . "PL - Polsk\u00E1 republika" . "Mixed protonation constants of sitagliptin phosphate at various ionic strengths I (mol kg(-1)) in range 0.01 and 0.50 and at 298.15 K are determined using FBSTAC4 and HYPERQUAD nonlinear regression analyses of the potentiometric titration curve. At a low concentration c(L) = 1.1 mmol kg(-1) the monomers L, LH, LH2, LH3 and LH4 dominate, while for a concentration range from c(L) = 13.7 to 24.7 mmol kg(-1) dimers L2H2, L2H3, L2H4 and L2H are mainly present. The regression programme has almost no influence on the precision of the protonation constants. The accuracy of the protonation constants log beta(qr) depends on the accuracy of the group parameters. As two group parameters c(L,0), c(H,T) are ill-conditioned in a model, their determination is therefore uncertain: both can significantly cause a systematic error in the estimated common parameters log(10)beta(qr). Fitness tests using regression diagnostics have proven the reliability of the parameter estimates."@en . . "protonation constant; sitagliptin phosphate; dimer; curve fitting; pH-titration; regression analysis"@en . . "Feren\u010D\u00EDkov\u00E1, Zuzana" . "Central European Journal of Chemistry" . "Pek\u00E1rek, Tom\u00E1\u0161" . . "RIV/00216275:25310/13:39896226" . "11" . "I, S" . "000324816000010" . . "4"^^ . . . "11" . . . "Oligomers-Model Building in Protonation Equilibria of Sitagliptin"@en . "10.2478/s11532-013-0304-6" . "25310" . . "3"^^ .