Mother liquor contains DMF solvent and DCC,HOBT as by products.
Industry recycles solvent via distillation. Try using a rotovap. You may need to include a scavenger for amine breakdown products.
DMF can be removed by washing several times with cold water, as it is water-soluble.
Recovery of N,N-dimethylformamide (DMF) from mother liquor in peptide synthesis is achievable by various methodological approaches of varying efficiencies. Pre-eminent among them is vacuum distillation, performed under reduced pressure (10-20 mmHg) with temperature regulation in the range of 60-80°C, making separation on the basis of differential vapor pressure properties of DMF (b.p. 153°C under normal pressure). Alternatively, liquid-liquid extraction involving a highly ionic strength water phase (NaCl saturated solution) allows phase separation such that DMF can be partitioned into an organic solvent such as ethyl acetate or dichloromethane. Additional purification may employ 4Å molecular sieves to desorb water or calcium hydride treatment to purge remaining water and decomposition by-products. Spectroscopic techniques (FTIR, NMR) and chromatographic techniques (GC-MS, HPLC) are recommended to assess the purity of recycled DMF prior to reuse since contamination with leftover peptide fragments, coupling reagents, or dimethylamine (a hydrolysis product) might disrupt forthcoming synthetic applications.