Determination of tromethamine in an eye-care pharmaceutical by capillary electrophoresis

Tromethamine [tris(hydroxymethyl)aminomethane] is used as an emulsifying agent, alkaliser and buffering agent in pharmaceutical preparations such as eye-care solutions. A new method for the determination of this compound in an eye-care preparation was developed using capillary zone electrophoresis with indirect UV detection. The method displayed linearity between 2.5 and 25 mg l-1 with a correlation coefficient of 0.9992. The limit of detection was 2.5 mg l-1. Precision and accuracy were determined as relative standard deviation and % deviation, and were found to be 0.42% and 1.62%, respectively. Recovery studies of tromethamine in the pharmaceutical preparation gave a 102.98% recovery.     

The detection of potassium sulfate in excess of potassium pyrosulfate

X-Ray diffraction, infrared, and raman spectroscopic methods were investigated for the detection of K₂SO₄ in excess of K₂S₂O₇ in solid solutions.The X-ray diffraction lines of K₂SO₄ were found to be overlapped by the diffraction pattern of K₂S₂O₇ and infrared studies indicated that K₂SO₄ absorption bands corresponded to regions of strong absorption in K₂S₂O₇. The detection of sulfate could not be carried out by the X-ray diffraction and infrared methods. However, the raman method indicated that a strong and narrow K₂SO₄ band at 981 cm^?1 could unambiguously be used for the detection of sulfate in solid solutions of K₂SO₄ in K₂S₂O₇, as pyrosulfate showed no absorption around this band.     

Formation of hydrogen peroxide upon oxidation of oxalic acid in presence and absence of oxygen-II Oxygen as oxidant

Hydrogen peroxide, m a mixture that is 0.1M in manganese(II) sulphate and sulphuric add and exposed to light from a tungsten lamp, decomposes slowly at room temperature in a nitrogen atmosphere. At 75 degrees the reaction is fairly rapid in the dark (about 20-25% in 4 hr) and about 60% faster in light. Presence of oxalic add has little effect on the rate of disappearance of peroxide, the overall reaction corresponding to H(2)C(2)O(4) + H(2)O(2) --> 2CO(2) + 2H(2)O. In the presence of oxygen [and manganese(II)] this reaction does not take place; instead, hydrogen peroxide is formed and oxalic add disappears in equimolar amounts. The extent of all reactions greatly increases with increasing concentration of manganese. Acrylonitrilc acts as a retarder. Conditions m the presence of mangancse(II) are described, under which oxalic add can be oxidized quantitatively by oxygen to carbon dioxide with formation of an amount of hydrogen peroxide equimolar to the oxalic add oxidized. Reaction mechanisms are proposed to account for the fact that in the absence of oxygen 1 mole of peroxide disappears and in the presence of oxygen 1 mote of peroxide is formed for each mole of oxalic add reacted.     

PHOTOREACTIVITY OF 5-GERANOXYPSORALEN AND LACK OF PHOTOREACTION WITH DNA

5-Geranoxypsoralen, commonly called bergamottin, a major furocoumarin contained in bergamot oil, is reported in vitro as a highly photoreactive psoralen. In ethanol, it exhibits quite a high triplet state quantum yield (approximately 0.37). The triplet state is involved in subsequent photochemistry which depends on the initial concentration and on the presence of oxygen. In contrast to most psoralens, absorption and fluorescence data suggest that 5-geranoxypsoralen does not interact with DNA in the dark. No UVA-induced interstrand cross-links in DNA were shown.     

Crystallization and Preliminary Crystallographic Analysis of β- Trichosanthin, an Isoform of Trichosanthin from the Root Tuber of Trichosanthe kirilowii

β-Trichosanthin,a type 1 ribosome-inactivating protein (RIP) isolated from the root tuber of Trichosanthe kirilowii Maxim,is an isoform of trichosanthin. Here we report its crystal-lization in two crystal forms using the hanging-drop vapor-diffusion method. The form A and form B crystals belong to the orthorhombic space group P212121 and monoclinic space group P21,respectively. X-ray data have been collected to 1.6 and 1.2 resolution for form A and form B crystals,respectively,using a synchrotron source.     

Transition and post-transition metal ion chemistry of dibenzo-substituted,mixed-donor macrocycles incorporating five donor atoms

The transition and post-transition metal ion chemistry of a wide range of potentially pentadentate dibenzo-substituted macrocyclic ligands incorporating nitrogen, oxygen and/or sulfur donors is reviewed and shown to result in a diverse range of structural types. Aspects of metal ion recognition, bulk membrane transport, systems incorporating appended chromophores, a sulfate binding system, induced Cu(I)/Cu(II) redox switching, coordination polymers, and unsymmetric macrocyclic ligand systems are all discussed.     

MULTIDIMENSIONAL UPWIND RESIDUAL DISTRIBUTION SCHEMES FOR THE CONVECTION–DIFFUSION EQUATION

Multidimensional residual distribution schemes for the convection–diffusion equation are described. Compact upwind cell vertex schemes are used for the discretization of the convective term. For the diffusive term, two approaches are compared: the classical finite element Galerkin formulation, which preserves the compactness of the stencil used for the convective part, and various residual-based approaches in which the diffusive term, evaluated after a reconstruction step, is upwinded along with the convective term.     

Differential non-destructive image current detection in a fourier transform quadrupole ion trap

Dual-detector differential non-destructive Fourier transform detection in a quadrupole ion trap is shown to improve signal intensity and reduce noise compared with spectra recorded using a single detector. A larger area detector in each end-cap electrode is machined to fit its hyperbolic shape and so minimize field imperfections on the z-axis. Argon, acetophenone and bromobenzene spectra were recorded to allow a comparison between single- and dual-detector (differential) modes of detection and to demonstrate the improvement achieved with differential detection. Copyright 1999 John Wiley & Sons, Ltd.     

Voltammetric,potentiometric and amperometric studies with a rotated aluminum wire electrode : Amperometric titration of fluoride with aluminum

The rotated aluminum electrode is a suitable indicator electrode in the amperometric titration of fluoride, Fluoride in concentrations varying between 1.10^-4 and 2.10^-3M was titrated with a standard aluminum nitrate solution in aqueous buffer solutions (pH between 3.6 and 46) Equilibrium was established within 15 mim. The fluoride-aluminum ratio at the (true) end-point was found to increase from 2 2 in 10^-4M fluoride to 28 in. 2.10^-3M fluoride. The titration calculated from the stability constants of the various aluminum-fluoride complexes were found to be in excellent agreement with the experimental curves.From a practical point of view titration in an acetate buffer in 50% alcohol in the presence of 0 5 M potassium or sodium nitrate is recommended. The fluoride-aluminum ratio at the end-point was found to be 5 9 ± 0 1 and independent of the fluoride concentration.