Cryogenic trapping of carbonyl sulfide without using expendable cryogens

We report on a cryogenic trapping procedure that functions without the use of liquid cryogens at a trapping temperature of -150 degrees C. A heat-transfer device was designed that links a commercially available closed-cycle refrigerator to a cryotrap made of a glass-coated steel tube filled with Chromosorb W adsorbent material. This forms part of an analytical system incorporating GC separation with subsequent FPD detection, used for the analysis of carbonyl sulfide. The recovery is greater than 95% for trapping times up to 30 min. The analytical performance is excellent with both accuracy and precision better than 2%. Equipped with the new cryogenic trapping device, the measurement system is capable of continuous operation over a period of several weeks.