Shinkichi Yamada

Relation of sorption behavior of agricultural chemicals in solid-phase extraction with their n-octanol/water partition coefficients evaluated by high-performance liquid chromatography (HPLC)

Abstract The HPLC method for the evaluation of the n -octanol/water partition coefficients ( P ow ) of agricultural chemicals was investigated, and the P ow values of 46 agricultural chemicals were determined by the proposed method. Then the sorption behavior of these chemicals in solid-phase extraction(SPE) was investigated using eight different types of Sep Pak Plus cartridges and five eluents in the relation to these P ow values. The chemicals with a logxa0 P ow below about 4.5 were completely retained onto the alkyl-modified silica and polystyrene cartridges, and easily eluted with any of the eluents except for n- hexane. The recovery of the chemicals with higher P ow values decreased with the increase of P ow values due to incomplete elution, but the extent of elution could be improved by adding methanol to the sample solution. Moreover, by back flush elution the chemicals with a logxa0 P ow below about 5.5 could be completely recovered without the addition of methanol. However, in order for the complete elution of the extremely hydrophobic chemicals the addition of methanol was required even with the back flush. The results suggest that the P ow values evaluated with the HPLC method can be used as the most useful key parameter for the selection of the key conditions in SPE. It is interesting that the cyanopropylated-silica cartridge can retain the more hydrophobic chemicals so that it could be used for selective reversed-phase SPE for the extremely hydrophobic chemicals.

Kinetic studies on thiolato-ligand substitution reactions with halide ions of square-planar palladium(II) complex with bis(2-(diphenylphosphino)ethyl)phenylphosphine

Abstract The square-planar thiolato palladium(II) complex with a terdentate phosphine bound ligand, [Pd(pt)(p3)](BF4) (p3=bis(2-(diphenylphosphino)ethyl)phenylphosphine, pt=1-propanethiolate) has been synthesized and characterized by 31P NMR spectroscopy. The solid state structure of [PdI(p3)]I was determined by an X-ray crystal structure analysis. The kinetic parameters for the thiolato-ligand substitution reactions with halide ions, [Pd(pt)(p3)]++X−→[PdX(p3)]++pt− (X−=Cl−, Br−, I−), in chloroform were obtained as follows: k298=7.22, 1.68 and 10.1×10−4 s−1, ΔH‡=67±2, 56±2 and 63±3 kJ mol−1 and ΔS‡=−80±7, −128±6 and −92±11 J mol−1 K−1, respectively. These kinetic results are compared with those for the corresponding reactions of the trigonal-bipyramidal complex with an analogous phosphine bound ligand, [Pd(pt)(pp3)](BF4) (pp3=tris(2-(diphenylphosphino)ethyl)phosphine).

Catalytic effect of some inorganic ligands on a ligand substitution reaction involving mercury(II) and its application as a differential kinetic method of analysis.

To design a sensitive and selective kinetic method for determining a catalyst, the kinetics of the ligand substitution reaction between the mercury(II)-4-(2-pyridylazo)resorcinol complex and 1,2-cyclohexanediamine-N,N,N,N-tetraacetic acid together with the catalytic effect of some inorganic ligands on this reaction were studied. The rate constant for a catalyzed reaction path was found to be linearly correlated with the electron donor constant of the catalyst. From this correlation, the difference in reactivity between sulfite or thiosulfate and sulfate was established. Under the selected conditions, sulfite up to 1.5 x 10(-6) M and thiosulfate up to 7 x 10(-7) M could be determined with detection limits of 3 x 10(-8) and 2 x 10(-8) M in the presence of 10 000 and 25 000-fold molar amounts of sulfate, respectively. The tolerance level in the determination of 1 x 10(-6) M of sulfite and 4 x 10(-7) M of thiosulfate was studied for 15 inorganic anions and 44 metal ions.