Dear Sir. Concerning your issue about the two solvents of ACN:DMF refluxing temperature. I think the following below links may help you in your analysis:

http://www.sciencedirect.com/science/article/pii/S187853521400327X

https://ac.els-cdn.com/S187853521400327X/1-s2.0-S187853521400327X-main.pdf?_tid=21647f68-e6e5-11e7-be8d-00000aab0f02&acdnat=1513925924_9557f48d52601ef27f6ed2c8b8613ac2

http://waset.org/publications/10000430/recovery-of-acetonitrile-from-aqueous-solutions-by-extractive-distillation-effect-of-entrainer

Thanks