On March 1997, the author started the doctoral program in Gadjah Mada University (Department of Chemistry) collaborated with Utrecht University. Netherlands, under a program namely Sandwich Program. At that time, there was an issue that doctoral candidates must find new compounds or new preparation procedures of chemical compounds. That issue was heard by the author's promoter, Prof.Dr. J.F. Arens. The promoter responded that author didn't have to listen to the issue. "You will never find any new compounds without doing experiments in laboratory. The desired new compounds will never be investigated without hard working. So you have to work hard," he said. Then the author kept those words and forwarded them when he also became a promoter.

After approximately 1 year doing research in laboratory, unpredictably author found a procedure to analyze the presence of acetone using vanillin NaOH reactor. which vanillin NaOH reactor with the addition of acetone would form red colour. A bachelor degree student who was doing thesis research in the same laboratory with author suggested to name that reaction "Aren-Hardjono Test" after the mechanism of reaction that was written by author being approved by Prof. Arens.

The collaboration between author and Prof. Arens meant if Prof. Aren went to Netherlands, author would follow. Otherwise, if Prof. Arens went to Indonesia. author would go back to Yogyakarta, too. The doctoral program must be finished in 4 years.