On the accuracy of acid-base determinations from potentiometric titrations using only a few points from the titration curve

There are several procedures which use only a few points on the titration curve for the calculation of equivalence volumes in acid-base titrations. The accuracy of such determinations will depend on the positions of the points on the titration curve. The effects of errors in the stability constants and in the pH measurements on the accuracy of the analysis have been considered, and the results are used to establish the conditions under which these errors are minimized.     

Thermodynamics of 1,10-phenanthrolinium ion and ferrous-1,10 phenanthroline complex in dioxane—water and ethanol—water at 25°c

Enthalpies of formation of 1,10-phenanthrolinium ion and ferrous-1,10-phenanthroline (tris) complex in dioxane—water and ethanol—water media at 25°C have been determined by calorimetry. Results are discussed in the light of ion—solvent and solvent—solvent interactions.     

Reaction of sulphate radical anion (SO<Superscript>.</Superscript><Subscript>4</Subscript><Superscript>-</Superscript>) with hydroxy-and methyl-substituted pyrimidines: a pulse radiolysis study

Reactions of sulphate radical anion (SO·₄ ^-) with 4,6-dihydroxy-2-methyl pyrimidine (DHMP), 2,4-dimethyl-6-hydroxy pyrimidine (DMHP), 6-methyl uracil (MU) and 5,6-dimethyl uracil (DMU) have been studied by pulse radiolysis at pH 3 and at pH 10. The transient intermediate spectra were compared with those from the reaction of hydroxyl radical (·OH). It is proposed that SO·₄ ^- produces radical cations of these pyrimidines in the initial stage. These radical cations are short-lived except in the case of DMHP where a relatively longer lived radical cation is proposed to be formed. When there is a hydrogen atom attached to the N(1) or N(3) position, a deprotonation from these sites is highly favored. When there is no hydrogen attached to these sites, deprotonation from a substituted methyl group is favored. At acidic pH, deprotonation from nitrogen is observed for DHMP, MU and DMU. At basic pH, the radical cation reacts with OH^- leading to the formation of OH adducts.     

Isolation of Some Soluble and Dispersed Materials of Oregano Water

Recent results obtained on determining the extraction efficiency and composition of organic volatiles in Oregano Water obtained from Origanum onites L. are described. Oregano Water was subjected to liquid-liquid extraction with a range of solvents with different polarities and each extract was analyzed by GC/MS.     

Comparison of glass fragments by neutron activation analysis

A method of comparing glass fragments of potential application to forensic sicence has been developed and evaluated. A representative sample of window glass from England and Wales has been collected and analysed for about 25 elements. An automated radiochemical separation followed by gamma-spectroscopy was used in order to determine the concentration of the maximum number of elements. Frequency distributions of the elemental concentration are shown and used to assess the discrimination of the technique and compare it with the measurement of refractive index. A few simulated cases have been included to demonstrate the possible application to forensic science problems.     

Über die synthese von in position 5 halogenierten,im aromatischen Kern substituierten Valerophenonen

The preparation of 5-chloro-2-methoxy-valerophenone and 5-iodo-2-methoxy-valerophenone proceeding from the -lactone of the corresponding 2-(o-methoxybenzoyl)-5-hydroxy-valeric acid is described.     

Octahedral cobalt(III) complexes of the chloropentammine type. XXVII. Effects of Methyl Substituents on reactivities of the cis-chloro-n-propylaminebis(ethylenediamine)-cobalt(III) cation

Salts of one isomeric form of the chloro-n-butylamine-, chloro-iso-butyl-amine- and chloro-sec-butylamine-bis(ethylenediamine)cobalt(III) cations have been prepared and characterised to have a cis-configuration (IR and VIS spectroscopy). Rate constants for their spontaneous aquation, mercury(II)-induced aquation and base hydrolysis have been determined and the activation parameters calculated. The results are compared with data obtained for the n-propylamine complex with a view to investigate the effects of methyl (α, β, γ) substituents on reactivities. The rate-determining dissociation of the outgoing group (Cl^? or HgCl⁺) takes place via either a square-pyramidal or a trigonal-bipyramidal intermediate, depending on whether the activation entropy is negative or positive.     

Isotope dilution analysis in the micro and submicro range by double-labelling and precipitation on paper

A new variation of isotope dilution analysis based on double labelling and carried out on filter paper is described. The determination of microgram and submicrogram amounts of silver (labelled with (110m)Ag) by precipitation with iodide (labelled with (131)I) and of calcium (labelled with (45)Ca) by precipitation with phosphate (labelled with (32)P) are given as examples. In the first example the two radio-elements ((110m)Ag and (131)I) are measured by gamma-spectrometry, in the second one ((45)Ca and(32)P) by a beta-absorption method. A number of results show the usefulness of the method.     

Parallel and multiplexed bead-based assays and encoding strategies

Advances in high throughput screening (HTS), together with the rapid progress in combinatorial chemistry, genomic and proteomic sciences have dramatically stimulated the development of a variety tools to enable the drug discovery process to become more efficient. Major future challenges in HTS include obtaining high density and good quality data based on assays that are rapid, reliable, inexpensive, sensitive, simple and miniaturised. This paper reviews the development and role of bead-based assays for HTS including DNA and single nucleotide polymorphism (SNP) assays, particularly from a multiplex perspective and evaluating the recent advances in bead-based arrays. The encoding strategies that are commonly used in bead-based assays are highlighted, while the importance of magnetic beads in genomic and proteomic purifications is discussed. In conclusion, bead-based assays offer a powerful promising approach for many aspects of drug discovery.