User guide Cleaning and inspection of pipettes Modern quality management in the laboratory calls for regular cleaning and inspection of dispensing systems. How often a pipette needs to be cleaned and inspected depends on how it is used, for example: frequency of use, the number of people who use the pipette, the type of aggressiveness of the liquids being dispensed and, last but not least, the acceptable maximum permissible error specified by the user. Sources of contamination and its prevention There are three sources of contamination  from pipette to the sample  from sample to the pipette  from sample to sample (also known as “carry over“) Pipette to sample contamination results from using a contaminated pipette or non-certified pipette tips. The contamination of samples can be prevented by using sterile pipette tips and by cleaning or autoclaving the pipette. Sample to pipette contamination occurs if the sample or its aerosols enter the pipette. To avoid this, hold the pipette vertically when aspirating the liquid. Furthermore, it is recommended to immediately eject the pipette tip after use to prevent vapors from entering the pipette, and to store the pipette suspended in a pipette stand. In addition, the control button should generally be moved slowly upwards during aspiration. Filter tips offer the most effective way to prevent contamination. They prevent aerosols from entering the pipette and, thus, contamination of the pipette. Using positive displacement pipettes with tips featuring a piston with integrated sealing lip is also a way to prevent contamination of the pipette (Fig. 1). Sample to sample contamination occurs if a part of sample A adheres in droplet form to the inside of the pipette tip during sample dispensing. This part of sample A is then mixed with sample B resulting in false test results (Fig. 2). To avoid this source of contamination the pipette tip should be replaced after each dispensing of a sample. Air-cushion pipette with filter tip Air-cushion pipette with standard tip Positive-displacment pipette with integrated piston in the tip Sample to sample contamination Protected area Filter Unprotected area Risk of contamination via aerosols Aerosol barrier No risk of contamination via aerosols Fig. 1: Preventing contamination with piston-stroke pipettes Remains of Sample A in the pipette tip Fig. 2: Sample to sample contamination (“carry over”) PRODUCT DATA SHEET | CLEANING & INSPECTION OF PIPETTES

Decontamination and cleaning External contamination can be removed using soap solution or isopropanol. Afterwards, the components should be rinsed with distilled water and dried. Do not allow any liquid that has been aspirated to become dry; the piston must be cleaned and afterwards treated with a touch of silicone grease (table 1). Decontamination and Cleaning Substance classification Handling, special features Aqueous solutions and buffers The pipette is calibrated with distilled water and, thus, provides very high levels of accuracy. Open the pipette, rinse contaminated parts with distilled...

Regular inspection of the pipette’s condition Piston-stroke pipettes used today can either be fully autoclaved or just the parts that got contaminated due to improper use. This helps to dissipate any doubts the user may have regarding sterility, thus opening new fields of application for these devices. Air-cushion pipettes as well as pipette tips are normally autoclaved at 121 °C with a positive pressure of 1 bar (100 kPa) over a period of 20 mins. Precise and correct dispensing of samples and reagents is of key importance for both research and diagnostics applications. To ensure reliable results,...