The [H(+)]-catalyzed dissociation rate constants of several trivalent lanthanide (Ln) complexes of 1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (LnDO2A(+), Ln = La, Pr, Eu, Er and Lu) have been determined in two pH ranges: 3.73-5.11 and 1.75-2.65 at four different temperatures (19-41.0 °C) in aqueous media at a constant ionic strength of 0.1 mol dm(-3) (LiClO(4)). For the study in the highe...

In this study, the direct determination of cefixime as an anti-bacterial agent, in pharmaceutical formulations, urine and human blood plasma was conducted based on spectrophotometric measurements using parallel factor analysis (PARAFAC) and partial least squares (PLS). The calibration set was composed of fourteen solutions in the range of 0.50- 9.00 µg mL-1. PLS models were calculated at each p...

A voltammetric method has been developed for the determination of acid dissociation constant (pKa) (RfSO2)2CHR (Rf = perfluoroalkyl), which is a strongly acidic molecule that serves as an catalyst. In acetonitrile solution containing small quantity acid, reduction peak potential quinone caused by shifted to more positive side accompanied increase in acidity acid. This relationship was good agre...

The interactions of dipyridamole with alpha(1) acid glycoprotein of plasma and with human platelets are related to inhibition of adenosine uptake by platelets. Binding studies by equilibrium gel filtration suggested that 1 mol of dipyridamole binds per mol of alpha(1) acid glycoprotein with a dissociation constant of 1.6 muM. Platelets contain two populations of binding sites, one with high and...

Estimation of the dissociation constant, or pKa, of weak acids continues to be a central goal in theoretical chemistry. Here we show that ab initio Car-Parrinello molecular dynamics simulations in conjunction with metadynamics calculations of the free energy profile of the dissociation reaction can provide reasonable estimates of the successive pKa values of polyprotic acids. We use the distanc...