Recycling Solvents in Histology Department of Hospitals
Industrial rotary evaporator: eco-friendly and cost-saving
Solvents (ethanol, xylene and water) are used in histology for dewatering and destaining during the preparation of tissue sections.
Here we show how these solvents are recycled in an automated process using an industrial rotary evaporator.
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Histological findings, such as the unambiguous identification of a tumor, are provided on the basis of the appearance of tissue sections. The most common method of tissue preparation is the paraffin-embedding after formaldehyde-fixation.
The formaldehyde-fixation stops life processes in cells and tissues and prevents structural alterations in samples. The paraffin-embedding is used for further stabilization of the sample. Thereby, water in the sample is replaced by paraffin.
Since paraffin and water are not miscible, the tissue sample is immersed successively in an alcohol series – ethanol in increasing concentration. As it is equally miscible in both, ethanol and paraffin, xylene serves as intermediate solvent. Hot, liquefied paraffin is then poured over the tissue sample. After solidification, the sample has the necessary consistencyto be prepared with the microtome into very thin sections (below 10 µm). Those thin sections are then fitted on a glass slide.
The microsections are specifically stained before being examined in the light microscope. Most staining solutions (e.g., hematoxylin, eosin) are aqueous. The paraffin needs thus to be removed from the tissue section in the reversed order (xylene, ethanol, water).
After staining, the sample is dewatered again (alcohol series and xylene) and covered on the glass slide with a coverslip and the help of a synthetic mounting medium. The used solvents are collected separately. Their recycling for reuse is described below.