The analysis of aqueous solutions with ethanol-soluble reagents in a flow injection system

A spectrophotometric method for the determination of uranium is adapted to flow injection analysis. The reagent, 2(5-bromo-2-pyridylazo)-5-diethylaminophenol, forms a complex with uranyl ions, with an absorbance maximum at 578 nm. The detection limit of the procedure is 0.15 mg l^?1 uranium and 60 samples can be analyzed per hour. Iron, calcium, ammonium, sulphate and fluoridedo not interfere; phosphate interferes even at moderate levels and carbonate interferes at high concentrations. Difficulties encountered in mixing the aqueous stream carrying the sample with the ethanol reagent stream initiated an investigation of different kinds of mixers in flow systems. A tight coil of teflon tubing proved to be the most efficient mixer, i.e., the one yielding the least baseline noise without excessive dispersion.     

An improved metal extraction procedure for the determination of trace metals in sea water by atomic absorption spectrometry with electrothermal atomization

A rapid carbamate extraction method with pyrrolidinedithiocarbamate and diethyldithiocarbamate is described for the simultaneous determination of Cd, Co, Cu, Fe, Ni, Pb and Zn in sea water by atomic absorption spectrometry with a graphite atomizer. The metal—carbamate complexes are extracted from 500 ml of sea water into Freon TF and back-extracted into 10 ml of 0.3 M nitric acid. The method has considerable advantages over previously recommended extraction procedures. The metals are transferred to a solution in which their concentrations do not change with time, and which can be easily stored for transportation. The sensitivity is high enough for analysis of open ocean waters.     

Potentiometric stripping analysis for lead in urine

Potentiometric stripping analysis is based on the preconcentration of analytes by means of potentiostatic reduction and amalgamation at a thin-film mercury electrode. After preconcentration, the potentiostatic circuitry is disconnected and the amalgamated metals are oxidized either by mercury(II) ions or by dissolved oxygen. Lead can be determined in acidified urine samples by potentiometric stripping analysis after the addition of Triton X-100. In deaerated samples the detection limit is 1 μg l^?1, and in non-deaerated samples 12 μg l^t-1, the preconcentration time being 16 min.     

Selective reagents for solvent extraction of metals—III. Picolinic acids

Alkyl-substituted pyridine-2-carboxylic acids have been found to be efficient reagents for the extraction of Cu²⁺, Fe³⁺, Co²⁺ and Ni²⁺ from aqueous sulfate solutions at pH 1.7. The effects of the position and the nature of the substituent are discussed.     

Minimal blocking sets of size 2p – 2 and 2p – 3 in PG(2, p), p prime and p > 5

A general construction of minimal blocking sets of size 2p – 3, where p is a prime and p ≡ 1 (mod 4), p > 5, and of size 2p – 2, where p is a prime and p ≡ 3 (mod 4), p > 5 in PG(2, p) is presented. These blocking sets are all of Rédei type.      

A potential diquark in the proton

A non-relativistic, QCD-based, potential quark model for the proton and the neutron inevitably predicts a spin-0 diquark structure with an rms radius of the order of 0.35 fm or smaller. We prove this by solving the (S wave}) hamiltonian by De Rüjula et al. with variational methods. It is essential to include all quark interactions and to use realistic test wave–functions. The protondelta mass difference, the magnetic moments and the nucleon charge radii can be reproduced only with wave functions that contain a mixture of quark–diquark and three–quark states. Approaches with just a quark–diquark component give incorrect magnetic moments, while those without diquarks lead to a too low proton–delta mass difference.     

Statistical choice of standard samples and precision of analysis in emission spectroscopy

An approach utilizing mathematical statistics to aid the choice of standard concentrations in emission spectroscopy is presented. The method is applied to the analysis of isoformed samples by the tape method. Some other possible applications (eg. X-ray, fluorescence, absorption photometry) are briefly discussed.