Actually, for Idebenone, the HPLC or LCMS is more effective. The scientist are using HPLC or LCMS. Please have a look on the following link for solve your problem:
Article Development of UV Spectrophotometric method of Idebenone in ...
Article Determination of idebenone in plasma by HPLC/MS
Dear Gabriel. Mauro Winkler thank you for your interesting technical question. I fully agree with M. D.H. Prodhan in that LC-MS / HPLC-MS is more useful in this case. Please also have a look at the following useful articles:
Monitoring of idebenone treatment in patients with Friedreich’s ataxia by high-pressure liquid chromatography with electrochemical detection
Article Monitoring of idebenone treatment in patients with Friedreic...
and
Stability-Indicating HPLC Assay for Determination of Idebenone in Pharmaceutical Forms
Article Stability-Indicating HPLC Assay for Determination of Idebeno...
Both articles are freely available as public full texts on ResearchGate.