A stock solution was prepared by dissolving 2% benzoyl chloride
in acetonitrile to enhance the reaction with amines. For derivatisation
of standard amine solutions, 100 lL were taken (4 mL for extracted
bacterial cultures) from each free base standard solution
(10 mg/mL). Sodium hydroxide (1 mL of 2 M) was added, followed
by 40 lL of benzoyl chloride and the solution mixed on a vortex
mixer for 1 min. The reaction mixture was left at room temperature
for 20 min. After that, the benzoylation was stopped by adding
2 mL of saturated sodium chloride solution and the solution extracted twice with 2 mL of diethyl ether. The upper organic layer
(4 mL) was transferred into a clean tube after mixing. Afterwards,
the organic layer was evaporated to dryness in a stream of nitrogen.
The residue was dissolved in 1 mL of acetonitrile and 10-lL
aliquots were injected into the HPLC (Ozogul, 2004).