Spectrophotometric determination of manganese utilizing metal ion substitution in the cadmium-α,β,-γ,δ -tetrakis(4-carboxyphenyl)porphine complex

Manganese(II) reacts quickly with α, β, γ, δ-tetrakis(4-carboxyphenyl)porphine [T(4-CP)P] at room temperature by metal substitution with a cadmium—T(4-CP)P complex in weakly alkaline medium containing imidazole. Oxidation by dissolved oxygen gives a manganese(III) complex having the Soret band at 469 nm. This forms the basis of a spectrophotometric method for the determination of manganese in the range 25–560 μg l^-1. The sensitivity (0.001 absorbance) is 0.56 ng cm^-2. Interferences of 17 cations and 8 anions were examined; only Cu²⁺, Co²⁺, Cr³⁺ and Pb²⁺ interfered markedly. The method was successfully applied to the determination of manganese in tea leaves.     

A novel route to 2-imidazolin-5-one derivatives via oxidative cyclization of aryl-substituted (Z)-N-acetyl-α-dehydroalanines having a dialkylamino group

It was found that the reaction of the title compounds [(Z)-1] with oxygen in methanol proceeds according to the first-order kinetics to give (Z)-2-imidazolin-5-one derivatives and hydrogen peroxide in quantitative yields. Analysis of substituent and solvent effects on the rate constant for this oxidative cyclization led us to propose that electron transfer from the dialkylamino nitrogen in (Z)-1 to oxygen, amide-proton abstraction by superoxide and the subsequent intramolecular electron transfer are all rate-determining steps. The synthetic utility of the novel cyclization reaction of aryl-substituted (Z)-N-acetyl-α-dehydroalanine derivatives was discussed.     

Second-order necessary and sufficient optimality conditions for minimizing a sup-type function

In this paper, we give second-order necessary and sufficient optimality conditions for a minimization problem of a sup-type functionS(x)=sup{f(x,t);t T}, whereT is a compact set in a metric space and f is a function defined on ⁿ ×T. Our conditions are stated in terms of the first and second derivatives of f(x, t) with respect tox, and involve an extra term besides the second derivative of the ordinary Lagrange function. The extra term is essential when {f(x,t)} _t forms an envelope. We study the relationship between our results, Wetterling [14], and Hettich and Jongen [6].     

Supercritical fluid chromatography with a slurry-packed capillary column

A versatile system with a slurry-packed capillary column was developed for supercritical fluid chromatography, which is capable of programming both inlet and outlet pressure independently, as well as using a restrictor to apply back pressure. This system revealed the relationships between pressure drop, flow rate, and linear velocity in pressure-programmed supercritical fluid chromatography. In the restrictor system, both the pressure drop and the flow rate increased almost linearly with inlet pressure, while under conditions of constant pressure drop characteristic behavior was observed which depended on the density-viscosity relationships of supercritical fluid. Resolution in the separation of polysiloxane oligomers was found to be increased by increasing the ratio of pressure drop to pressure-programming rate, although the sensitivity decreased due to the increase in peak volume. The system controlling both inlet and outlet pressure has distinct advantages over the restrictor system controlling both inlet and outlet pressure has distinct advantages over the restrictor system in practical in practical operations.