Cryogenic oven-trapping gas chromatography for analysis of volatile organic compounds in body fluids

Cryogenic oven-trapping (COT) with capillary GC has been successfully applied to analysis of chloroform, dichloromethane, trichloroethylene, diethyl ether, the components of solvent thinner (ethyl acetate, benzene, n-butanol, toluene, and others), xylene isomers, cyanide, ethanol, hexanes, general anesthetics, and styrene in human body fluids. This COT-GC technique was compared with headspace solid-phase microextraction (SPME) coupled with GC for some volatile organic compounds (VOC); for all compounds compared the sensitivity achieved using COT-GC was more than ten times higher than for headspace SPME-GC. The COT-GC method is recommended for widespread use in forensic and environmental toxicology, because it is simple, requires no special GC operations, and yet enables high sensitivity and high resolution.     

In situ control of cellular growth and migration on substrates using microelectrodes

We describe an electrochemical method to direct the growth and migration of mammalian cells on a substrate during cultivation in situ. Exposing the albumin-coated substrate to an oxidizing agent, hypobromous acid, electrochemically generated at the tip of the scanning microelectrode, locally switched the substrate from cytophobic to cell-adhesive. This transformation generated the formation of cellular micropatterns. Since the concentration of the oxidizing agent required for the surface processing did not cause significant damage to the cell cultures, we were able to direct in situ cellular proliferation and migration by drawing adhesive micropatterns over the preexisting cellular pattern.