Which cleaning method is listed as best for plastic and glassware?

• A. Soaking in sulfuric acid-dichromate solution (best)
• B. Dilute bleach followed by oven drying
• C. 20% nitric acid for 12-24 hours
• D. Boiling water rinse

Answer: (A)

When cleaning plastic and glassware, you want an approach that thoroughly removes organic residues and provides a high level of decontamination. Soaking in sulfuric acid with potassium dichromate creates a very strong oxidizing environment that breaks down stubborn oils, proteins, and other films that simple rinses or milder cleaners can miss. This powerful cleaning action helps ensure surfaces are truly clean and ready for subsequent analytical work, which is why it’s often considered the best option for both glassware and compatible plastics in many lab cleaning protocols.

Dilute bleach can disinfect effectively, but it may not fully remove organic residues and can leave chlorine residues that require thorough rinsing. Boiling water rinse lacks the capability to break down and remove stubborn films, especially oils and proteins. Using a harsh acid like nitric acid is effective for certain tasks but can risk etching glass or degrading some plastics, making it less universally suitable.