Lab Pipette Cleaning: Removing Wax

Q. What is the best way for removing wax from pipettes and other glassware in the laboratory?

A. The best way to clean lab pipettes with wax and petrolatum in them is to use very hot, emulsifying 1-3% solutions of cleaners such as Alconox® Powdered Precision Cleaner, or Liquinox® Critical Cleaning Liquid Detergent. By very hot, we mean above the melting point, or at least above the softening point of the wax. Typically this can be reached at 170 deg F (77 deg C). In practical terms this is a difficult temperature to reach. It would typically require heating a soak solution on a hot plate or other external source of heat.

Petrolatum can be successfully cleaned at as “low” a temperature as 140 deg F (60 deg C), although even this is often hotter than you can get out of a hot water tap.

Specifically for pipettes, soak the pipette in the hot or very hot solution of 1-3% Alconox or Liquinox detergent for at least 10 minutes. Then drain the pipette 3 times filling and emptying with the hot or very hot solution. Then move the pipette to a normal ambient temperature 1% Alconox or Liquinox soak solution to hold it until you are ready to clean in a siphon pipette washer with Alcotabs® Tablet Pipet Detergent. You could skip the ambient temperature soak and go directly to the siphon pipette washer with Alcotabs if you want to.

The idea is to not let the pipette dry out or be exposed to plain water where trace wax or petrolatum might plate out on the inside of the pipette. With any used pipette whether it has wax and petrolatum residues or any other residue, it is good practice to place the pipette in a 1% Alconox® or Liquinox® soak solution immediately after use to avoid any residues drying on to the pipette. If it is not practical to pre-soak in a very hot or even hot 1-3% solution of Alconox or Liquinox, you can often get satisfactory cleaning from just prompt pre-soaking in an ambient 1% Alconox or Liquinox in accordance with our recommendations for standard pipette handling.

Low melting saponifiable natural and synthetic ester waxes can often be adequately cleaned by this method. Higher melting waxes like bees wax, require at least a hot water (circa 140 deg F, 60 deg C) 1% Alconox or Liquinox  10 minute pre-soak. If this is absolutely not practical, it is possible to remove high melting natural and synthetic ester waxes using a 1% Solujet® Low-Foaming Phosphate-Free Liquid pre-soak which can saponify the waxes.

Note that Solujet is a potassium hydroxide based corrosive liquid that requires skin and eye protection for use. It is important to immerse the pipette completely in the Solujet solution to avoid etching the glass at the air/solution interface. In fact, it is good practice to always completely immerse pipettes or any glassware to minimize any concerns about etching no matter what soak solution you are using (even deionized water).

Normally, we do not recommend Solujet for manual cleaning operations unless it is absolutely necessary. Petrolatum in heavy quantities in the absence of emulsifiers that may be present in cream or lotion may not be adequately cleaned by the simple ambient temperature pre-soak. If the cream or lotion with the petrolatum contains emulsifiers that are effective on petrolatum already, even an ambient temperature pre-soak in 1% Alconox or Liquinox detergent soak can be quite effective.

Visit our website www.alconox.com for detergent-specific Technical Bulletins and MSDSs.

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