How to Clean Lab Glassware

Cleaning volumetric lab glassware such as burets, pipettes, flasks, and graduated cylinders can be a daunting task for two reasons:  laboratory glassware is susceptible to breakage and associated replacement costs, and complex configurations make thorough cleaning difficult.   But all lab personnel know this.

The task is made easier with an ultrasonic cleaner – equipment widely used in labs for a variety of reasons.  One of these is being an excellent means to thoroughly remove tenacious contaminants from delicate laboratory glass.  The secret to effective sonic cleaning lab glassware is selecting the right cleaner, cleaning solution formulation and establishing a consistent cleaning procedure.

Cleaning is accomplished by cavitation action, the implosion of millions of minute air bubbles created by generator powered transducers bonded to the bottom of the cleaning tank and vibrating at ultrasonic frequencies such as 37,000 cycles per second (37 kHz).  The imploding bubbles safely and effectively remove contaminants from all glass surfaces immersed in the cleaning solution.

In general cleaning procedures are fairly straightforward.  But equipment and cleaning solution formulas depend heavily on the scope of your cleaning requirements and contaminants being removed.  We present here a representative operation for cleaning lab glassware but invite you, as suggested below, to contact us for more specific details related to your lab’s operations.

Selecting the Chemistry Glassware Ultrasonic Cleaner

If you do not have a sonic cleaner in your lab we recommend considering the Elmasonic E Plus series available from Tovatech in 8 models from 1.75 to 28 litres (0.5 to 7.5 gallons).  When considering capacity the important figures are internal tank dimensions, which will be slightly larger than the dimensions of the basket holding the glass.   Also to be considered is the working depth of the unit, which is the distance between the bottom of the cleaning basket and the surface of the solution.

The E Plus series is equipped with a permanent Sweep function that provides uniform distribution of cavitation action throughout the bath, thereby assuring optimized cleaning.    Units have an on-off switch, an activate ultrasound switch, and time and temperature dials.   Note that the cleaning process can be started manually or automatically when the set temperature is reached.

Selecting and Preparing the Lab-Ware Cleaning Solution

There are a variety of formulations available.  We’ll use as our example biodegradable elma lab clean A20sf, a surfactant-free concentrate with ammonia formulated for calibrated lab-ware.

Add water to the tank fill line.  While tap water can be used for cleaning, deionized water is suggested for cleaning and recommended for rinsing in order to avoid water and mineral spotting.

Add 1% by volume A20sf cleaning concentrate.  Turn on the unit, set the temperature to 60⁰C and activate the ultrasound.   Allow the equipment to run for approximately 10-15 minutes to both mix the solution and drive off trapped air in a process called degassing.  These steps must be taken each time a new solution is prepared.

4 Steps to Cleaning Glass Lab Ware

  1. Arrange glassware in the cleaning basket in such a way that the solution will fill interior spaces.
  2. Turn on the ultrasonic cleaner, set the temperature to 60⁰C and the timer to 10 minutes.  Actual time and temperature will depend on what you are cleaning and the nature of the contaminants.
  3. Lower the basket in the solution.  The ultrasound will start when the temperature is reached or you can manually start the cleaning procedure.
  4. At the end of the cycle remove the glassware, inspect, rinse in DI water and dry.  If you clean large amounts of lab glassware consider a rinsing tank and electric dryer.

With repetitive use the ultrasonic cleaning solution will begin to lose its effectiveness and should be replaced.  Dispose of it according to local regulations, clean the tank following user manual instructions and fill it with fresh solution.

Equipment for Large-Scale Lab Glassware Cleaning Requirements

If your lab cleans large quantities of chemistry glassware you should consider an ultrasonic cleaning system that can provide enhanced features such as mechanical agitation, and paired with a rinsing tank and electric dryer.

Contact the scientists at Tovatech for unbiased recommendations on ultrasonic equipment and procedures tailored to your laboratory size and requirements.

About Rachel Kohn

So how did an MIT Ph.D. end up selling refrigerators? When I figured out that a lot more scientists buy lab refrigerators than innovative leading-edge instruments. I hope that my many years of lab experience will help you find the right equipment for your work. Before co-founding Tovatech I worked in business development and project management at Smiths Detection, Photon-X, Cardinal Health, and Hoechst Celanese. And before that I spent 12 years as an R&D chemist at Hoechst Celanese and Aventis working on advanced drug delivery systems, polymer films and membranes, optical disks, and polysaccharides. Some day, eventually, I’ll make enough money to develop an innovative technology that will change the world. Read More