The slides carry the sections, and both, sections and slides, go through all the steps of the histological technique. Before the attachment of the sections, the slides have to be as clean as possible. Otherwise, a weak adhesion may happen, which leads to losing the sections, or some artifacts may appear, such as background staining and precipitates caused by dust, dirty, or some organic debris that may be on the slide surface.
Just bought new slides do not usually need a special cleaning process. However, recycled slides have to be cleaned. There are different ways to clean slides, from simple protocols to more thorough treatments.
Procedure
a) Mild treatment
1) Dip the slides in ethanol, acetone, or a mix of ethanol-acetone for more than 15 minutes.
2) Leave the slides draining in a dry and free of dust place.
3) Once the slides are dried, they can be stored in a box protected from dust and moisture.
b) Medium treatment
1) Wash the slides with soap or dishwasher.
2) Rinse the slides in water until soap is completely removed.
3) Dip the slides in acetic acid for 15 minutes.
4) Rinse in distillate water, about ten times.
5) Check the pH. It should be near 6 or 7, otherwise more rinses are necessary. .
6) Dry the slides in the stove at 60 ºC overnight.
7) Store the slides in a box free of dust and moisture.
c) Strong treatmenmt (sulfochromic mixture)
1) Sufochromic mixture: potassium dichromate 10%, sulfuric acid 20%, and distilled water 70%.
2) Dip the slides in the sufochromic mixture for at least 24 hours.
3) Thoroughly rinse the slides in distilled water.
4) Let the slides to get completely dried, and after that store them in a box for dust and moisture protection.
Notes
The commercial slides are usually clean and degreased enough to be used directly from the slide pack. However, a mild cleaning can be done.
The sulfochromic mixture has to be prepared in a fume hood and, if it is possible, on a tray with ice, because the mixing reaction is exothermic. After each treatment, the sulfochromic mixture can be stored in a well-sealed crystal container and used many times.
The sulfochromic mixture can be used as long as it preserves a reddish color. It has to be replaced when the solution color turns greenish.
The non-useful sulfochromic mixture has to be recycled chemically. Do not flush it down the sink.
Products
a) Mild treatmen
Ethanol, acetone, ether
Distilled water
b) Medium treatment
Soap, dishwasher
Acetic acid
Distilled water
c) Strong treatment
Potassium dichromate
Sulfuric acid
Distilled water
Labware
Slides
Sealed glass container
Glass racks for slides
Glass staining dish
Stove at 60 ºC
Fume hood
Box to store processed slides