It is practically impossible to prepare such solution from the mentioned stocks. Although there are three alternative methods:

1. Use pure materials (not stock solutions)

2. Mix 1 ml of each stock solution (esterone and triclosan) and add 8 ml 1.5 ug/ml ACN solution to have a final concentration of both esterone and triclosan and 1.2 ug/ml ACN.

3. If possible, you can also add 8 ml of a higher concentration (about 1.85 ug/ml) of ACN solution to 1 ml of each stock solution. 

100 mg/l = 100000ug/l= 100 ug/ml which is 10 times of 10ug/ml.

so take 1 ml from the stock solution of 100 mg/l into 10 ml of volumetric flock and make up the volume. concentration of final solution will be 10ug/ml. for 1.5 ug/ml, take 1.5 ml from stock solution of 10ug/ml in 10 ml volumetric flask and make up the volume. using both stock solution you can prepare various dilutions

can we use simple V1S1=V2S2 formula here ? here V1 =vol. of stock sol we need to add S1= conc. of stock i.e,100mg/l or 100ug/ml V2=vol. of final sol. which is 1ml S2=conc. of final sol. that is 10ug/ml. if we calculate this by using v1s1=v2s2 we will get 100ul . this 100 ul should be added to the final solution from stock

How can i Prepare 100,50,10 ug/ml form a stock solution of 20mg/ml ?

I need an answer its urgent

Kovan Ismael well it depends how much final volume you need, lets say you are going to make solution with a 30ml final volume with a concentration of 100ug/ml from a concentration of 20mg/ml (Proteinase K most probably).

so.! first adjust all the units to be the same like for 100ul convert it to mg which is 0.1mg/ml.... Now.!

C1V1C2V2 where C1=20mg/ml, V1=?,, C2=0.1mg/ml and V2=30ml.

20x?=0.1x30,

3/20=0.15 or 150ul.

So, take 150 uL of your 20 mg/mL stock, and add it to final volume ( 30 mL for practical purposes) of your diluent.

Take 1ml of the stock solution (covert(100ug/ml) and add 9mls of water to produce a100ug/10ml solution. 1ml of this will give 10ug/ml.