title: Operation of a multichannel microcalorimetry system in the micro-submicrowatt region: some methodological aspects.
abstract: Monitoring heat flux values below approx. 4 microW requires in microcalorimetry non-standard experimental procedures in order to achieve high accuracy and reproducibility. With 5 ml ampoules, stable baselines are reached in 70 min if a three-level pre-thermostating procedure is used and if the gas phase above the liquid is reduced to 0.5 ml or less. A pairwise procedure of reference/measuring ampoules is used. Autoclaved sealing material of teflon, sterilized stainless steel ampoules in contact with a standard cell medium and culture plates of polystyrene do not contribute to measured heat flux. Further, we found that a standard cell culture medium develops a significant thermal heat flux, 0.10 microW.ml-1, probably reflecting an oxidation process in the medium itself.
authors.affiliation: Institute of Hygiene, University of Copenhagen, Denmark.
authors.forename: S A
authors.initials: SA
authors.lastname: Thorén
authors.forename: J
authors.initials: J
authors.lastname: Suurkuusk
authors.forename: B
authors.initials: B
authors.lastname: Holma
mesh_terms: D002151:Calorimetry / Q000295:instrumentation / Q000379:methods*; D003470:Culture Media; D008832:Microchemistry
chemical_list: D003470:Culture Media