Gold ultra-microelectrode arrays: application to the steady-state voltammetry of hydroxide ion in aqueous solution.

Gold ultra-microelectrode arrays are used to explore the electrochemical oxidation of hydroxide ions and are shown to be analytical useful. Two types of ultra-microelectrode arrays are used; the first consist of 256 individual electrodes of 5 microm in radius, 170 of which are electrochemically active in a cubic arrangement which are separated from their nearest neighbour by a distance of 100 microm. The second array compromises 2597 electrodes of 2.5 microm in radius and of which 1550 of which are electrochemically active in a hexagonal arrangement separated by the nearest neighbour by 55 microm. Well defined voltammetric waves are found with peak currents proportional to the concentration of hydroxide ions in the range 50 microM to 1 mM. Detection limits of 20 microM using the 170 ultra-microelectrode and 10 microM with the 1550 ultra-microelectrode array are shown to be possible but with a higher sensitivity of 4 mA M(-1) observed using the 1550 ultra-microelectrode array compared to 1.2 mA M(-1) with the 170 ultra-microelectrode array.     

THE RELATIONSHIP OF ACCESSORY PIGMENTS TO CHLOROPHYLL a CONTENT IN CHLOROPHYLL-DEFICIENT PEANUT AND SOYBEAN VARIETIES

Abstract— A relationship between Chl a and each of its accessory pigments, neoxanthin, violaxanthin, lutein, Chl b and carotene, is demonstrated in soybean and peanut genotypes. These genotypes include normal and Chl-deficient types. Plots of Chl a content against accessory pigment content generate straight-line relationships that are extrapolated to intersect the Chl a axis. The points of intersection correctly predict the order of origin of certain accessory pigments (lutein, carotene and Chl b ), but incorrectly predict that neoxanthin and violaxanthin arise after the introduction of Chl a .     

4-carboxy-1,2-cyclohexanedionedioxime complexes of nickel(ii) in alkaline media

The reactions of 4-carboxy-1,2-cyclohexanedionedioxime and nickel(II) were studied in alkaline media. Spectrophotometric studies indicate the presence of a 1:1 complex ion, NiD^-. Magnetic susceptibility measurements on a series of solutions of varying ratios of vic-dioxime and nickel(II) showed that the 1:1 complex ion was diamagnetic and that two paramagnetic complexes, probably NiD₂^4- and NiD₃^7-, are present in solution. The stability constants for the three complexes were calculated from spectrophotometric and magnetic susceptibility data. The log K values were found to be log K₁ = 28.74 ± 0.60, log K₂ = 0.76 ± 0.15, and log K₃ = 3.67 ± 0.73, respectively.     

Reversible dimethylamine addition as a protecting reaction for α,β-unsaturated methylene groups of γ-lactones and its regeneration by basic elimination of quaternary ammonium salts: A convenient synthesis of dehydrosaussurea lactone

The blocking and deblocking sequence pertaining to the α,β-unsaturated methylene γ-lactone unit of costunolide is described. Utilizing this approach a simple and practical synthesis of dehydrosaussurea lactone is reported.     

Iron-57 Mössbauer effect study of the distribution of divalent and trivalent ions in potassium transition metal fluorides having the tetragonal bronze structure

Mössbauer studies are reported for compounds of the type KM^IIM^IIIF₆ (M = first-row transition metal ion, Zn, or Mg) which have the tetragonal bronze structure. The results of this investigation provide evidence that the trivalent ions are located on the 8(j) sites of the bronze structure and that the divalent ions are distributed over both the 8(j) and 2(c) sites.     

Disposable highly ordered pyrolytic graphite-like electrodes: Tailoring the electrochemical reactivity of screen printed electrodes

We demonstrate that the electron transfer properties of disposable screen printed electrodes can be readily tailored via the introduction of a polymeric formulation into the ink used to fabricate these electrochemical platforms. This approach allows the role of the binder on the underpinning electrochemical properties to be explored and allows the electrochemical reactivity of the screen printed electrodes to be tailored from that of edge plane to basal plane of highly ordered pyrolytic graphite.