As a suspected carcinogenic agent and toxic pollutant, Cr(VI) poses a threat when present even at trace levels. Several electrochemical methods have been reported for the successful determination and quantification of Cr(VI),1-9 and these methods are of great interest due to the fact that they provide high sensitivity, portability, and the ability to distinguish Cr(VI) from Cr(III). An attractive method for analytical sensing is the use of sol-gel materials in conjunction with electrochemistry.10 We recently reported a method for the determination of Cr(VI) in solution using a pyridinium-functionalized sol-gel electrode.11 Unlike many sol-gel electrode films that are formed through either spin-coating or dip-coating processes, we have formed our sol-gel thin films using an electrodeposition process similar to that reported by Deepa and coworkers.12 In this process, a negative potential is applied at the electrode surface to generate hydroxide ions. When a sol solution is present, the OH-base catalyzes the hydrolysis and condensation of the sol at the electrode surface and produces a thin film. By incorporating precursors of varying functionality in the starting sol solution, films selective for a variety of analytes can be formed. In this research, we have used pyridinium-functionalized sol-gels for applications in Cr(VI) sensing, as previous studies have demonstrated the ability of pyridinium derivatives to form strong and stable complexes with Cr(VI) species.7,11,13

Researchers describe research design and equipment for electrochemical analysis of Martian soil. The Wet Chemistry Laboratory (WCL) was designed for the Mars Surveyor 2001 Lander by the Mars Environmental Compatibility Assessment (MECA) team. The WCL consists of four beakers, each containing an integral array of electrochemical sensors. In addition to describing WCL design, the article discusses WCL sensor selection and design, analytical goals of the MECA experiments, expected composition of the Martian regolith, survival and performance testing, and reference electrode selection. The description of the research design describes experiment initiation, warm-up, leaching solution, calibration, sampling, analysis, reagent addition, and data analysis.