A new series of methyltrialkylammonium salts with an alkyl chain length (n) longer than the conventional methyltridodecylammonium (MTDDA, n = 12) has been developed, and these materials were examined for use as the ion-sensing component (ligand) in anion-selective electrodes (ISEs). Syntheses of the higher ammoniums with n = 16, 18, and 20 were carried out. In combination with an alcoholic plasticizer, the ammoniums with n = 12, 16, and 18 led to ISEs with fundamental characteristics, such as slope sensitivity, impedance, and time response, that were sufficient for practical applications. Compared with the conventional MTDDA, the ISEs based on the ligands of n = 16 and 18 showed marked improvement in chloride selectivity over both lipophilic and hydrophilic anions, deviating from the Hofmeister regime in some cases. Taking perchlorate as an example, the magnitude of the improvement was a factor of 20 for n = 16 and 15 for n = 18. When the new ISEs were applied to chloride analysis in blood serum, they improved the accuracy by a factor of 2-6. Therefore, the methyltrialkylammonium salts with alkyl chain lengths of 16 and 18 offer definite advantages over the conventional alternative and are strong candidates to become the standard compounds for use in future chloride ISEs.

Electrocatalysis of the reduction of 02 molecules was observed with pyrolytic graphite electrodes coated with an intermolecular complex of poly(xylylviologen)-poly(sulfonate). The half-wave potential of 02 reduction was independent of pH and its value was -0.40 V vs. a sodium chloride saturated calomel reference electrode. The reduction potential of 02 at the polymer-coated electrode was more positive than that obtained at a bare electrode by 350 mV (maximum). Analysis of the current-potential curves observed at the rotating disks coated with viologen films made possible the determination of the rate constants of the electron cross-reaction between the viologen monocation radical within the coating membrane and 02.Currently there is considerable interest in chemically modified electrodes, especially polymer-coated electrodes.Heinsohn.5b PXV was obtained as a yellow powder. The average molecular weight of PXV (meta derivative), determined viscometrically, was 8 X 103. Since o-PXV is insoluble in water, only m-PXV was used as poly(viologen) throughout the experiments.

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Compared with PPC, PBF proved to be a more conservative scoring method and captured an additional five patients who scored less-well on the Medi-Cog. Future studies are needed to explore the value of using pillbox assessments as well as cognitive screening prior to recommending pillbox use.

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