Dilute your sample 1mg/ml, 2mg/ml.....n

C1V1=C2V2

C1 = Mother drug concentration in ug/ml

v1 = volume .?

C2 = desire concentrarion 1mg/ml, 2mg/ml,..........n

v2 = total sample volume

12,000 X V1 = 1000ug x 1000 ul ( 1mg = 1000ul, 1ml = 1000ul)

V1 = 1000 ug x 1000ul / 12,000 ug

V1 = 83.33 ul

IF your sample volume is 1mg/ml than = 1000 - 83.33 = 916. 67ul solvent

for 1mg/ml sample solution volume add ( 83.33 + 916.67) total it become 1mg/ ml solution

Using the derivatization methods and the amount of essential oil or absolute extract obtained could be diluted and changed the specified concentrations. It should be noted that the solvent ratio with respect to the target analyte must be known in advance. Meanwhile, There are a series of the calculation relationships on the online sources that you can to search it, easily.

Regards