Fixation on Histology

GEN.41770 of the CAP checklist requires that CAP accredited labs have “written procedures for handling and cleaning glassware, including methods for testing for detergent removal”. To be in compliance with this checklist item, your lab needs to establish an SOP (standard operating procedure) that clearly lays out the process your lab goes through when washing glassware. This should include all steps to be followed, including any rinsing, bleach soaking, or use of a dishwasher.

The second part of this checklist item, the testing for detergent residue must also be documented. There are several methods to check for residue. A common method is using bromcresol purple (available as a pre-made solution sold by vendors). Pipette approximately 5 cm (2 inches) of distilled water into the glassware item you want to test. Add two to three drops of bromcresol solution. A purple color means there is residual detergent. A yellow color means it has been rinsed properly.

Another method of testing residue is by testing the pH of water added to the glass. Add water to the glassware you would like to test and swish the water around to extract any residue. Take the pH of the water. Compare this pH with the pH taken from water in a clean rinsed beaker (both should be using the same water source). If there is a significant difference between pHs, there is possible detergent residue; significant change here being 0.2 or more pH units on a pH meter measuring to 0.1 pH units of sensitivity. A result of less than 0.2-pH units change indicates properly rinsed glassware.

Testing should be done and recorded daily. If you are washing different types of glassware, test at least two different types.

References:

https://technotes.alconox.com/wp-content/uploads/2013/04/cap.pdf

https://www.nsh.org/communities/community-home/digestviewer/viewthread?GroupId=13&MessageKey=8845a6ba-24a5-4f3f-99c0-801d2865abf0&CommunityKey=007ca8ea-3c4f-4359-b441-44ef10bc9dad&tab=digestviewer&ReturnUrl=%2ftheblock%2fcommunities%2fcommunity-home%2fdigestviewer%3fcommunitykey%3d007ca8ea-3c4f-4359-b441-44ef10bc9dad%26tab%3ddigestviewer

http://lists.utsouthwestern.edu/pipermail/histonet/2016-February/075677.html