Purifying glassware in a high temperature Carbolite oven has enabled Manchester, U.K.-based Elga LabWater to stop using chromic acid for the preparation of samples in its research and development laboratory.

Elga, which designs high-purity water systems, used to soak glassware in chromic acid to stop water samples from being contaminated by organic compounds on the glass. (Minimal total organic carbon levels, an indicator of overall organic purity, are a key requirement for users of pure water in laboratories.) However, chromic acid is both toxic and corrosive. To meet the recommendations in “Preparation and Testing of Reagent Water in the Clinical Laboratory” (CLSI 4th edition, 2006), the company now rinses sample bottles in ultra-pure water and then heats them to 842°F (450°C) for two hours in the Carbolite oven.

Tests have shown that any organic contamination present after this procedure is not detectable, according to Dr. Paul Whitehead, Elga’s R&D laboratory manager.

The oven has a maximum temperature of 932°F (500°C) and a 15.85-gal capacity stainless steel chamber. A PID controller ensures temperature stability, and fan-assisted air circulation gives temperature uniformity better than ±9°F (±5°C), as well as fast heatup and recovery times.

Carbolite, Watertown, Wis., manufactures high-temperature LHT ovens in three sizes, each with a choice of 752, 932 or 1,112°F (400, 500 or 600°C) maximum temperatures.