Acyl-CoAs are highly unstable in alkaline and strongly acidic solutions . It is important to check the stability of acyl-CoA in the injection solvents to check for degradation rate and analysis time window. As mentioned previously in literature, methanol was considered to have good stability for acyl-CoA for 24 hours . For this experiment, the four representative acyl-CoA standards (C2:0-CoA, C8:0-CoA, C16:0-CoA and C18:1-CoA) were reconstituted in 5 different solutions, MeOH:Water (1:5,v/v), MeOH:Water:IPA (1:1:1,v/v), MeOH:50 mM ammonium acetate (1:1,v/v), MeOH:Water (1:1,v/v) and methanol (100%). The presence of water in the injection solvents is necessary for the solubility of acyl-CoA especially for the short-chain species. The four acyl-CoA standard samples were dissolved in solvents, placed in the autosampler, and analyzed with the HILIC-MS method at three different time points: 0 hours, 6 hours, and 24 hours (Figure ).