Flow injection determination of iodide ion in a photographic developing solution using iodide ion-selective electrode detector.
A potentiometric flow injection determination method for iodide ion in a photographic developing solution was proposed by utilizing a flow-through type iodide ion-selective electrode detector. The sensing membrane of the electrode was Ag(2)S-AgI membrane. The response of the electrode detector as a peak-shape signal was obtained for injected iodide ion in a photographic developing solution. A linear relationship in the subnernstian zone was found to exist between peak height and the concentration of the iodide ion in a photographic developing solution in a concentration range from 0 to 6.0x10(-5) mol l(-1). The relative standard deviation for ten injections of 2x10(-5) mol l(-1) iodide ion in a photographic developing solution was 0.96% and the sampling rate was approximately 12-13 samples h(-1). The iodide ion could be determined under coexisting of an organic reducing reagent and inorganic electrolytes of high concentration in a photographic developing solution sample solution by the present method.
Subsecond adsorption and desorption of dopamine at carbon-fiber microelectrodes.
High-repetition fast-scan cyclic voltammetry and chronoamperometry were used to quantify and characterize the kinetics of dopamine and dopamine-o-quinone adsorption and desorption at carbon-fiber microelectrodes. A flow injection analysis system was used for the precise introduction and removal of a bolus of electroactive substance on a sub-second time scale to the disk-shaped surface of a microelectrode that was fabricated from a single carbon fiber (Thornel type T650 or P55). Pretreatment of the electrode surfaces consisted of soaking them in purified isopropyl alcohol for a minimum of 10 min, which resulted in S/N increasing by 200-400% for dopamine above that for those that were soaked in reagent grade solvent. Because of adsorption, high scan rates (2,000 V/s) are shown to exhibit equivalent S/N ratios as compared to slower, more traditional scan rates. In addition, the steady-state response to a concentration bolus is shown to occur more rapidly when cyclic voltammetric scans are repeated at short intervals (4 ms). The new methodologies allow for more accurate determinations of the kinetics of neurotransmitter release events (10-500 ms) in biological systems. Brain slice and in vivo experiments using T650 cylinder microelectrodes show that voltammetrically measured uptake kinetics in the caudate are faster using 2,000 V/s and 240 Hz measurements, as compared to 300 V/s and 10 Hz.
A calcium-sensitive microelectrode suitable for intracellular measurement of calcium(II) activity
Abstract A calcium-selective microelectrode with a l-μm diameter tip suitable for impaling single neurons has been developed. The electroactive material is di[ p -(1,1,3,3-tetramethyl-butyl) phenyl] phosphoric acid (t-HDOPP). The selectivity coefficients are about 5 · 10 -7 for k Ca,K , 1–4·10 -7 for k Ca,Na , and 10 -3 for k Ca,Mg . Values reported previously for other calcium-selective electrodes based on long-chain phenylphosphoric acids are given for comparison. The calcium-selective microelectrodes have a linear response in 0.2 M KCl solutions over the range 10 -2 –10 -XXX M CaCl 2 ; 10 -7 and 10 -8 M CaCl 2 solutions containing 0.2 M KCl can be detected but the response is not linear.