Once a protein of interest has been separated by gel electrophoresis, the gel can be stained using Coomassie Blue stain. Following the staining procedure, the gel is typically destained by soaking it in a 20 percent methanol/10 percent acetic acid solution.

If the protein has not been radiolabeled, it is possible to regenerate and reuse the destaining solution, thereby reducing the total volume of listed hazardous waste generated in the laboratory.

Applicable Regulations
40 CFR Parts 260-268.

State of Michigan Act 451 Part 111.

Overview of Procedure
Following the destaining procedure, the destaining solution (methanol/acetic acid) is adulterated with Coomassie blue dye and is not suitable for reuse. However, by pouring the destaining solution through a charcoal filter, the blue dye binds to the charcoal, resulting in a purified destaining solution suitable for reuse.

Waste Minimization Procedure
Fill a large filter paper lined funnel with 5 - 10 grams of activated charcoal powder (Norit). Pour the destaining solution into the funnel and allow it to flow through by gravity into an 8-liter container fitted with an outflow valve (see diagram below). The charcoal will typically have a service life greater than 50 cycles per 10 grams. Once the charcoal is no longer effective, it can be collected into suitable containers for proper disposal.

Known Limitations
The destaining solution cannot be reused once it has been in contact with a radioactive gel.

Safety & Health Precautions/Personal Protective Equipment
Follow all applicable safety and health protocols and regulations as established by your institution.

Regenerating and reusing the destaining solution results in a decrease in the amount of methanol/acetic acid that must be disposed of as a listed hazardous waste. This leads to a cost savings on both the purchase and disposal of these laboratory chemicals.

None known.

Project Related Costs
The amount of money saved on purchase and disposal costs for methanol and acetic acid will depend upon the number of times the staining procedure is performed in the laboratory. Typically, the researcher will use 100 mL of destaining solution per gel. The charcoal has proven effective in removing the stain from the destaining solution for more than 50 cycles. This represents a savings in the generation of at least 5 liters of methanol/acetic acid waste.

Because the purchase price of laboratory reagents fluctuates, it is advisable to consult the U-M stores catalogue or your institution's purchasing department for current purchasing costs of methanol and acetic acid. Norit charcoal is available from the Sigma Chemical Company.

Disposal costs would be approximately $4.50 per liter for this type of waste, based upon current U-M costs. This represents a disposal cost savings of $22.50 ($4.50 per liter x 5 liters) for 50 cycles when the destaining solution is regenerated and reused.