From owner-diagnostics@net.bio.net Sun Mar 26 23:00:00 1995 Path: biosci!bcm!cs.utexas.edu!uunet!newsfeed.pitt.edu!quadra800.pathology.pitt.edu!user From: rapr@med.pitt.edu (Robert Preston) Newsgroups: bionet.diagnostics Subject: Re: low boiling point Date: Mon, 27 Mar 1995 12:41:12 -0500 Organization: U.Pittsburgh Sch. Med. Lines: 27 Message-ID: NNTP-Posting-Host: quadra800.pathology.pitt.edu forbes@cip.org.ec wrote: > >We would like to initiate some PCR based methods near Quito, > >Ecuador at an altitude of 3050 m above sea level. Water boils > >here at 89 C which will not allow us to bring the vials up above > >this temperature. Simple capping of the tubes (this is essential anyway, to prevent water loss by evaporation even in the absence of boiling) will be sufficient to prevent boiling at temperatures up to 95-100C or higher. If your reagents are pure, and your equipment is clean (and they have to be, if you intend to do successful PCR) the reactions would probably superheat above the boiling point even if the tubes had no caps at all. Capping will allow pressurization at high temp that will prevent both superheating and boiling. BUT, you have to keep those caps CLOSED despite the pressurization, so plan to add whatever weight you need to the tops of the tubes to prevent them from popping open. (which they tend to do even in a boiling water bath at sea level, due to the pressure of the heated air ABOVE the liquid phase!) Bring a small clothing iron to the lab, or pour a custom lead (Pb) cap-weight, or use screw-cap tubes (baad idea, unless you're only doing a few reactions at a time) or best of all, use a cycler that has a heated-cap/pressure plate assembly, in which case you would also eliminate the messy oil overlay. -- Robert Preston rapr@med.pitt.edu University of Pittsburgh Pittsburgh PA 15261 .