Thoughts from Christmas Past

It was 1991, and I had arrived at Berridge Environmental Laboratories in Chelmsford, hot off the train from Edinburgh, where I had just completed a 5-year joint honours degree. As shared in previous Blogs, I was being mentored by Dennis, a semi-retired elderly gentleman with a shock of white hair and asbestos fingers from all his years of handling hot GC components.

It was my first Christmas at Berridge, and we were to be closed through Christmas and into the New Year. On the last afternoon before the holiday, Dennis was in the Lab to oversee the preparation of the GCs for hibernation over the holiday period. The following is a Christmas reminiscence that may or may not apply to the current GC instrumentation. Still, I already knew by this time that advice from Dennis was never without experience.

Dennis shared that he had found that problems would arise if standard GCs were wholly powered down. He went on to say that his theory was that power transformers and amplifiers, when left switched on for long periods, reach a constant operational temperature and, if allowed to cool to room temperature for any considerable time, would have a greater tendency to fail when switched back on. GC ovens were then set to 40°C with columns removed. Injectors and detectors with blocking nuts applied to inlets were set to 110°C, and a trickle of helium was left through the splits. This was toensure that water condensation would not occur. The only other gas left on was a small flow of nitrogen make-up through the ECDs to prevent any possible source oxidation. Dennis believed that having the GC ovens at 40°C and heated zones at 110°C would ensure that a reasonable temperature would be maintained throughout the body of the instruments and gas line connections would be less likely to develop leaks. My own personal experience has backed this up. On two occasions, power supplies failed immediately on power up after being instructed to power down instruments completely for the Christmas holiday period.