Cleaning Liquid Residue on Pipet Walls

Q. We are doing some experiments to quantify the amount of liquid residue on pipet walls before/ after cleaning. In practice, this would relate the accuracy of the pipet to its cleanliness. Could you inform us if the use of Alconox affects the amount of beading (of distilled water) on the walls of a brush cleaned and rinsed pipet, compared with the use of common dishwashing liquid?

A. Proper cleaning of a pipet will result in the designed amount of fluid being measured in a pipet, and the designed amount of beading resulting from the correct clean surface energy of the pipet and the surface tension of the fluid being measured. Typically pipets are calibrated for water, but you can get specialty pipets designed for other fluids – like milk.

Alconox® Powdered Precision Cleaner is free rinsing, which means it does not contain any fragrances, dyes, cationic surfactants, fluorescent whitening agents, corrosion inhibitors, skin emollients or other ingredients that are designed to leave deposits on the substrate being cleaned.  If you rinse thoroughly, you will not have any Alconox detergent residues to cause a change in surface energy of the pipet. 

A common dishwashing liquid might have a risk of depositing one of these non-free-rinsing ingredients that would typically be hydrophobic and would alter the surface energy of the glass/solution interface and change the accuracy of the pipet.  It is expected that the smaller the pipet the more you might be able to detect these effects. 

For more information about any one of our Alconox Cleaners, consult the specific technical bulletin for each product HERE. Or click here to access each of our detergent’s Safety Data Sheets.

You can also request a free sample of this or any Alconox Inc. detergents by completing the questionnaire at Get Sample.