The procedure involved mixing 2.5 lL of sample with 100 lL of OPA mixture (2.5 mL of sodium tetraborate, 1 mL of 5% (w/v) SDS, 100 lL of 40 mg/mL OPA in methanol, 10 lL of 2-mercaptoethanol, and 1.39 mL of water).
The procedure involved mixing 2.5 lLof sample with 100 lL of OPA mixture (2.5 mL of sodium tetraborate,1 mL of 5% (w/v) SDS, 100 lL of 40 mg/mL OPA in methanol,10 lL of 2-mercaptoethanol, and 1.39 mL of water).