I am trying to prepare Working solution of 200 mg/L (Cefotaxime) as per literature available. My silly questions were -
1. In literature they are using 200 mg per liter, But I need to use only 50 ml so what is the working concentration I have to use now?
2. If it is 10 mg ( For Example) How to prepare working solution from stock solution which contains 1mg/ 4ml water ( as suggested by company).
3. If I dissolve 1g in 1ml or 10 ml, Is stock solution contains 1000 mg in both 1 and 10 ml.
Thank You
200 mg per litre means: 0.2 mg/ml
for 50 ml stock solution, dissolve 10 mg Cefotaxime in 50 ml water
in 4 ml the compound will be 0.8 mg/4 ml
Respected Dr. Ahmad Sir
Thank You for your kind reply. But when we don't know the molecular weight how we can say or justify 4 ml contains 0.8 mg. Why because we are dissolving total Avagadro number in 4 ml. I am not sure about the answer as I am not good in basics.
Thank You
Dear Anil
If I understood your question: you want to to prepare a working solution 0.2 mg/mL from a stock solution containing 1mg Cefotaxime / 4mL water (i.e 0.25 mg/mL).
As your final volume is 50 mL, the initial volume is 50*0.2/0.25=40mL
Then take 40 mL of your stock solution in a 50 mL volumetric flask and complete the volume to 50 mL.
In the case I misunderstood the question please explain it clearly.
Regards!
NOBOSSE
Respected Nobosse
Thank You for Your Answer. But I need to prepare 200 mg / L antibiotic concentration. I have my stock solution is 1g/ 4ml. How should I prepare my working solution.
Thank You
Is it 1g/4ml or 1mg/4 ml?
If it is 1 mg/4 ml then add 1 ml water, the concentration will be 200 mg /litre
1 g/ L means 1000 mg/1000 ml or 1mg/ml
If you want 50 ml having 0.2 mg/ml concentration;
then take 10 ml [from 1 g/L stock solution] and add 40 ml water to make 50 ml total volume
Hey dear,
I understand your difficulty because of lack of mol wt. you could potentially work as per Ahmad's suggestion, go to the following link, makes your life much easier!..
http://www.physiologyweb.com/calculators/dilution_calculator_mass_per_volume.html
Just forgot to mention, scroll down to the link page and key in your requirements, click on changing the units as per your needs, and click on calculate, here we go............
Ahmad is correct
Since you need to make 50ml (V2) of 0.2mg/ml (200mg/L) C2 from 1mg/ml (1gm/L) (C1). from this simple formular C1V1=C2V2
where V1(the volume of the stock you need from C1)=C2V2/C1=(50ml X 0.2mg/ml)/1mg/ml=10ml
to get 50ml (200mg/L)measure out 10ml of the stock into a 50ml volumetric flask and make it up to 50ml with you diluent (or deionized water)
How do I calculate my c2 from a 1 mg/ml stock after measuring out a 100 microliter of the antibiotics into a 100 microliter of MHB as diluent
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