I have two questions regarding dopamine and DA metabolites extraction from mouse striatum. I use the following protocol:

Weighed striatum tissue samples were homogenized on ice in 1 ml homogenization buffer (0.1M perchloric acid, 0.02% EDTA and 1% ETOH; prepared in HPLC water) using Polytron homogenizer. The homogenates were sonicated for 5 minutes in sonic bath and then centrifuged at 14,000 RPM at 4oC for 15min. The supernatants were transferred into fresh tubes and stored at -800C until HPLC analysis.

My questions are:

1. Whether 5 min-sonication is too long.

2. My Dopamine yield in naive mice is ~1000ng/100mg tissue (striatum). Does this yield sound reasonable?

Please suggest any additional protocols for dopamine extraction.