the acid-base equilibrium of lorazepam was studied by means of potentiometry andmultiwavelengths spectrophotometry. the stoichiometric equilibrium constants were determinedat 25 °c and constant ionic strength 0.1 mol l-1 (nacl). the acidity constants pk1=1.58±0.05and pk2=11.67±0.07 were found by potentiometry, and pk1=1.54±0.02 and pk2=11.61±0.03 bymulti-wavelengths spectrophotometry. potentiom...

Early workers in the field of potentiometry faced a serious problem. The type of cell commonly used in potentiometric studies could supply only a tiny current and often had a high internal electrical resistance. If the electromotive force (emf) of such a cell is to be measured accurately, the apparatus must draw essentially no current from the cell. One obvious approach is to oppose this emf wi...

A polyoxapolyaza heteroditopic macrobicyclic compound (btpN(4)O(3)) was synthesized. The acid-base behaviour of the compound as well as its binding ability for zwitterionic amino acids were studied by potentiometry at 298.2 ± 0.1 K in H(2)O-MeOH (50:50 v/v) and at I = 0.10 ± 0.01 M in NMe(4)TsO. The H(n)btpN(4)O(3)(n+) showed preference for amino acids containing tetrahedral anionic groups.

Introduction Careful temperature control is essential for a wide variety of chemical measurements. High-precision potentiometry, for instance, requires thermostatting, since the slope of the straight line E vs log a is highly temperature dependent (E is the measured emf, log a is the logarithm of the activity of species i). The equation describing the relationship between the measured quantity ...

1. The midpoint potentials of the various iron-sulphur centres in Site I were determined at different pH values by the technique of redox potentiometry. An interesting feature is the pH-dependence of Centre N-2, the highest potential component of the NADH dehydrogenase segment of the respiratory chain. 2. The apparent midpoint potentials of Centre N-2 (NADH dehydrogenase) and S-1 (succinate deh...

Oxidation-reduction midpoint potentials have been determined for the flavin, cytochrome b557 and Mo-pterin prosthetic groups of spinach (Spinacia oleracea L.) assimilatory nitrate reductase using visible, c.d. and room-temperature e.p.r. potentiometric titrations. At pH 7 and 25 degrees C, the midpoint potential for the FAD/FADH2 couple was determined by c.d. potentiometry to be -280 +/- 10 mV ...

The development of a variety of selective ion-sensitive electrodes focuses attention on numerical scales for the activity of individual ionic species, for these electrodes measure the activity of the selected ion only relative to that of the same species in a reference solution of known or assigned ion activity. Nevertheless, scales of ion activity must be based on a convention from outside the...

Fig. 1. Regression analysis (regression line – continuous – and 95% prediction interval – dashed lines) to evaluate commutability of IRMM BCR-304 (triangle) and NIST SRM 956c (black circles) between direct potentiometry and colorimetry assays for serum lithium. Gray circles identify native serum samples. Commutability of two JCTLM-listed secondary reference materials for two commercial lithium ...