RESUMO
Electrodes constructed from single-crystal sections of rare earth fluorides respond to fluoride ion activity over more than five orders of magnitude and show a high selectivity for fluoride over other common anions. These electrodes can be used for either direct measuremnent of fluoride ion activity or detection of the end point in titration.
Assuntos
Técnicas de Química Analítica/instrumentação , Fluoretos/análiseRESUMO
A new potassium electrode, made from valinomycin, which uses commercially available electrode configurations, responds to potassium ion concentrations from 1 mole per liter to below 10(-6) mole per liter. It is highly selective for potassium ion over sodium ion and divalent ions and can be used for the direct determination of potassium ion in human serumn. No significant complexing of potassiium appears to occur in normal seruin.
Assuntos
Antibacterianos , Eletroquímica , Equipamentos e Provisões , Potássio/sangue , Eletrodos , Humanos , Sódio/sangueRESUMO
The Viking Landers were unable to detect evidence of life on Mars but, instead, found a chemically reactive soil capable of decomposing organic molecules. This reactivity was attributed to the presence of one or more as-yet-unidentified inorganic superoxides or peroxides in the martian soil. Using electron paramagnetic resonance spectroscopy, we show that superoxide radical ions (O2-) form directly on Mars-analog mineral surfaces exposed to ultraviolet radiation under a simulated martian atmosphere. These oxygen radicals can explain the reactive nature of the soil and the apparent absence of organic material at the martian surface.
Assuntos
Marte , Solo , Superóxidos , Silicatos de Alumínio/química , Espectroscopia de Ressonância de Spin Eletrônica , Exobiologia , Meio Ambiente Extraterreno , Íons , Oxigênio , Compostos de Potássio/química , Superóxidos/análise , Superóxidos/químicaRESUMO
NASA: 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.^ieng