The voltammetric detn. of trace amts. of gold was studied using a chem. modified electrode. The role played by the host mol. attached to a glassy carbon electrode (GCE), i.e. 8,9,17,18-dibenzo-1,7-dioxa-10,13,16-triazacyclooctadecane (DDTC), was examd. by electrochem. and spectrochem. techniques. Cathodic stripping voltammetry (CSV) was applied to study the various parameters affecting the affinity of gold ions by a DDTC modified electrode as well as the interferences by other ions. Finally, the method was successfully applied to det. gold traces in a geol. sample. In addn., the formation of an AuCl4--DDTC complex was followed and its formation const. was detd. by spectrophotometry. [on SciFinder(R)]

The scanning electrochem. microscope was applied to drive the deposition of Ni(OH)2 structures. Nickel hydroxide was deposited from aq. solns. onto platinum surfaces as a result of changing the pH locally on the electrode surface. The increase in pH is driven by an oxidn.-redn. process, i.e., N,N'-dimethyl-4,4'-bipyridinium, MV2+, which is reduced at an ultramicroelectrode, diffuses to the surface where it is regenerated upon the redn. of protons, causing a local increase of pH and the deposition of Ni(OH)2. The different parameters that control the efficiency of the deposition, such as the pH and the concn. of the buffer, were examd. [on SciFinder(R)]

A glassy carbon electrode (GCE) coated with 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8.]hexacosane, Kryptofix-222, was used for the very sensitive and selective detn. of very low levels of mercury. A detection limit lower than 10-12 M (<0.2 ppt) was obtained applying anodic stripping voltammetry (ASV). The parameters that governed the sensitivity and possible interferences by other ions have been examd. in detail. The electrode has been successfully applied for detg. mercury in seawater, wastewater, and also in human saliva and amniotic fluid. The modified electrode exhibited high stability and, therefore, could be used repeatedly without mech. regeneration. [on SciFinder(R)]

Self-assembled monolayers of ω-mercaptocarboxylic acids, HS(CH2)nCO2H (n = 1, 2, 5, 10), on mercury film (MF) and gold electrodes have been used for the very sensitive and selective anal. of ultralow levels of cadmium(II). The authors find that shorter ω-mercaptocarboxylic acids provide superior sensitivity. Other parameters that govern the sensitivity and selectivity of this system have been examd. in detail. Optimizing these factors resulted in a detection limit of 4 × 10-12 M (0.45 ppt). The method has been verified by detg. cadmium in std. solns. and it has been successfully applied to the anal. of cadmium in seawater. [on SciFinder(R)]