Laboratory Glassware Cleaning Practices

Use of clean laboratory glassware is critical for high accuracy and precision of your results. Cleanliness of glassware up to the required degree prior to start of analytical work is often underestimated and some analysts feel the job can be entrusted to laboratory support staff. A dedicated analyst on the other hand is never ashamed of washing laboratory glassware to his or her own satisfaction.

Breakages can be frustrating and lead to loss of valuable time. A few precautions taken can avoid such embarrassing situations

  • Prevent breakage by exercising care by avoiding hitting of burettes, pipettes or measuring cylinder tips to tap or washbasin walls
  • Measuring cylinders, Centrifuge tubes, flasks, etc should be dried on wooden or plastic pegs mouth downwards
  • Only soft brushes should be used if necessary. Never clean absorption cells with brushes as scratches will lead to wrong absorbance readings and result in optical mismatch of the cell pair
  • Volumetric flask should never be dried in the drying oven with temperatures exceeding 65°C. Always un stopper cover before placing in the oven

Cleaning Agents

Used laboratory glassware should be soaked in water even if immediate cleaning is not possible. Most commonly available detergents can be used for subsequent cleaning. An oxidizing agent such as Potassium dichromate in sulphuric acid is a good choice. The solution becomes green on continued use due to loss of its oxidizing power and should be discarded. A mixture of 3N HCL and 1 volume of methyl alcohol is useful for cleaning of stains in absorption cells. This mixture should not be shaken in closed vessels due to generation of heat.

Grease can be removed from the joints and stoppers by boiling in a weak solution of sodium bicarbonate and subsequently soaked in a solution of potassium dichromate or acetone prior to rinsing with distilled water.

New laboratory glassware is slightly alkaline. Soak in 1% HNO3 or HCl solution for about an hour and then wash with distilled water before drying.

Laboratory Glassware washing machines

Labware Washing Machines

Labware Washing Machines

Laboratory glassware washing machines provide superior cleaning and convenience. Valuable laboratory time is saved when bulk washing is necessary. Such machines can accommodate a wide range of glassware shapes and sizes with adjustable racks to accommodate wide mouth glassware (beakers, conical flasks, graduated cylinders, etc) as well as narrow mouth glassware (volumetric flasks). Cycle operations permit wash and dry operations between rinses. Built-in heating of wash water and forced air drying are common features provided by most suppliers. Some of the popular suppliers are

  1. Labconco
  2. Lancer
  3. Miele
  4. Cole Parmer
  5. Scientek

You will agree that the quality of results that you generate will depend largely  on the cleanliness of glassware used and to some extent on  the sophistication of the analytical technique adopted.

Please do leave your suggestions and share comments on the topic.

About Dr. Deepak Bhanot

Dr Deepak Bhanot is a seasoned professional having nearly 30 years expertise beginning from sales and product support of analytical instruments. After completing his graduation and post graduation from Delhi University and IIT Delhi he went on to Loughborough University of Technology, UK for doctorate research in analytical chemistry. His mission is to develop training programs on analytical techniques and share his experiences with broad spectrum of users ranging from professionals engaged in analytical development and research as well as young enthusiasts fresh from academics who wish to embark upon a career in analytical industry.

Comments

  1. Aliecia says:

    Good day. In my lab we use Conrad detergent for lab wares and we notice a lot of hardness soap deposits after left to dry. How can we get rid of them and how to prevent them since we used deionized water

    • Dr. Saurabh Arora says:

      Hi Aliecia, you need to make a standardised procedure including the conc. of the detergent and how to wash and rinse the glass ware. You can try it with different cons and them implement the same procedure. Deposits usually come if the water used for final rinse has high TDS, I suggest you take a look at that also.

  2. Cherry Lyn J. Sardovia says:

    Good Day!
    For glassware used in HPLC, what is the best way to wash it. Our sample are concentrated mixture of vitamins that sometimes stained in the glass. We are using methanol and propanol in the analysis.

    • I believe you are referring to volumetric glassware used in sample preparation.You can use ordinary detergent washing followed by deionized water and drying before reuse.It would be a good idea to use diluted solutions in analysis and as additional precaution you can remove detector flow cell and rinse with 10% nitric acid followed by deionized water in a sonication bath.This should solve the problem and give better results.

  3. Rakesh Kumar Sondhiya says:

    Dear Sir,
    Please post Mycotoxin use glasswares procedures.

    • After testing for mycotoxins immerse the glassware in detergent solutionfor around half an hour. Wash with ordinary water and rinse with distilled water. Further you can autoclave for about half an hour before reuse.

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