Boiling cycler nightmare

Tim Spahlinger txs at po.cwru.edu
Wed Aug 16 11:29:27 EST 2000


I agree with most of Dr. Clark's response.  However, you should typically
calibrate your thermocouple over a range of temperatures that surround the
temperature of interest (i.e., 95 degrees and 100 degrees).  So, boiling
water would work on the high end, and an ice water bath would work on the
low end of the temperature range.  From a safety point of view, I would not
recommend trying liquid nitrogen.  I also suspect that the machine that you
have your thermocouple connected to would not be able to read that low a
temperature.

I know that Perkin-Elmer had previously sold a thermocouple kit to check the
calibration of their model 9600 thermocyclers (utilizes small, capped tubes
for PCR).  Not having their latest literature immediately in-hand, perhaps
you should check to see if they could accommodate your need for a
thermocouple kit to check a 96-well plate thermocycler, especially since
they sell machines like their model 7700 which, I believe, utilizes a plate
format.  I'd be interested in knowing the identity of the manufacturer of
the machine in question!

"Dr. Duncan Clark" wrote:

> In article <160820001549122963%jpcd100 at mole.bio.cam.ac.uk>, John Dixon
> <jpcd100 at mole.bio.cam.ac.uk> writes
> >So far the only accurate temperatures we can think of to test our
> >thermocouple with are:
> >
> >37C using waterbath with medical thermometer
> >100C boiling water bath
> >
> >Anyone got any cunning ideas of any other defined temperatures to check
> >our thermocouples accuracy?
>
> You will need a very fine thermocouple else the wire actually pulls heat
> from the 50ul of liquid you have in your microtube so it measures wrong.
> You will need a mineral oil overlay as well to stop evaporation. It's
> also not so much (I think) the accuracy of the thermocouple as the
> accuracy of the meter it is attached to. If I remember rightly the
> thermocouple's voltage is constant due to the dissimilar metals and the
> change in voltage per degree and voltage at a set temperature should be
> identical for every manufacturer's thermocouple's.
>
> I would test the thermocouple meter calibration in boiling water, ice
> water and how about liquid nitrogen?
>
> How come the orange dye is getting across the wells? That would suggest
> (apart from possible boiling) that the well seal is leaking? Can you
> eliminate the problem being poor plastics?
>
> On machines we run 9700's and 2400's and touch wood, haven't had
> problems.
>
> Good luck
>
> Duncan
> --
> The problem with being on the cutting edge is that you occasionally get
> sliced from time to time....
>
> Duncan Clark
> DNAmp Ltd.
> Tel: +44(0)1252376288
> FAX: +44(0)8701640382
> http://www.dnamp.com
> http://www.genesys.demon.co.uk






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