With glass labware, prolonged immersion times in alkaline media above 70 °C should be avoided. Such treatment, particularly with volumetric instruments, might cause volume changes through glass corrosion, and destruction of graduations.
Plastic items generally have smooth, non-wetting surfaces and can usually be cleaned effortlessly under low alkalinity conditions. Polystyrene or polycarbonate labware, e.g., centrifuge tubes, must only be cleaned manually with neutral detergents. Prolonged exposure even to low alkaline detergents will impair their strength. The chemical resistance of these plastics should be verified in each case.
Cleaning in trace analysis
To minimize metal traces, immerse labware in 1N hydrochloric acid. For extreme demands, boil glass labware in 1N nitric acid for approximately 1 hour as a second step. Plastic labware should not be boiled but may be immersed in nitric acid at room temperature. The maximum immersion time should not exceed 6 hours.
- Nitric acid is a strong oxidation agent and can
cause brittleness in many plastics.
Finally, rinse thoroughly with distilled water. To minimize organic traces, clean labware with alkalis or solvents (e.g., alcohol). Subsequently, immerse in 1N hydrochloric acid, then rinse thoroughly with distilled water.