The role of chloroform in phase separation during RNA extraction from animal tissues and key safety considerations

Why chloroform is used in RNA extraction from animal tissues

In animal experiments and molecular biology research, researchers often need to extract RNA from animal tissues such as liver, kidney, muscle, and brain. Chloroform is an important organic solvent in the classic acid phenol-chloroform method. It does not directly dissolve RNA itself; rather, it works together with phenol so that after centrifugation the sample forms clear layers: the upper aqueous phase mainly contains RNA, while the lower organic phase and the interphase enrich proteins, lipids, and some DNA. In this way, RNA can be separated from impurities relatively conveniently.

This process can be simply understood as "using chloroform to help layering." The mixture after cell lysis has complex components, and chloroform changes the partitioning of each component between the organic phase and the aqueous phase, causing RNA to remain in the aqueous phase, where it is easier to recover. A common addition ratio is generally about 0.2 volume of chloroform per 1 volume of lysate, but the specific amount should follow the kit instructions or the laboratory standard operating procedures and should not be adjusted arbitrarily.

Key points and common misconceptions in operation

Many beginners easily mistake chloroform for a "disinfectant" or a "universal solvent," which is not accurate. In RNA extraction, the main role of chloroform is phase separation and protein removal, not direct cell lysis. If the amount added is insufficient, unclear layering may occur; if it is not mixed thoroughly after addition, or if the centrifugation speed and time are insufficient, the aqueous phase may also become turbid and recovery efficiency may decrease.

In addition, chloroform is volatile and has a distinctive odor, so operations should be carried out in a fume hood. When handling it, nitrile gloves, goggles, and a lab coat should be worn to avoid direct contact with skin and eyes. When pipetting the upper aqueous phase after centrifugation, movements should be gentle and steady, and the pipette tip should not touch the interphase or the lower organic phase, so as to avoid carrying impurities back into the RNA sample.

Safe use and waste liquid disposal cannot be ignored

When animal experiment platforms use chloroform, in addition to focusing on experimental results, they must also pay attention to personnel safety and environmental protection. Chloroform may have adverse effects on the human liver, kidneys, and central nervous system, and long-term or high-concentration exposure poses health risks. Therefore, laboratories generally require chloroform to be stored in well-sealed bottles and kept away from heat sources and open flames.

Waste liquid containing chloroform must not be poured directly into the sewer. It should be collected in dedicated waste liquid containers and handed over to qualified units for disposal. Waste liquid mixed with animal tissues must also meet the dual requirements of biosafety and chemical management. For general readers, understanding these regulations helps explain why researchers always emphasize protection and procedures when using chloroform.