Why are samples centrifuged at 4°C after the addition of chloroform when using RNeasy Lipid Tissue Kits?
FAQ ID -533

Phase separation by centrifugation at 4°C after adding chloroform to the samples when using RNeasy Lipid Tissue Kits ensures minimizing genomic DNA contamination. Subsequent centrifugation steps with the RNeasy Mini Spin Columns have to be carried out at room temperature to prevent buffer salt precipitation, guarantee optimum binding of RNA to the column and obtain highest RNA yields.