1. You are provided with Stock Tube A of antibiotic that has a concentration of
ID: 258871 • Letter: 1
Question
1. You are provided with Stock Tube A of antibiotic that has a concentration of 1000 ?g/?l. For lab, it is necessary to make the following dilutions:
a. Tube B: 15?L of the 1000 ?g/?l antibiotic stock in Tube A + 385?L of buffer. The dilution in Tube B is _____________ and the concentration is ______________.
b. Tube C: 20?L from Tube B + 30?L of buffer. Tube C represents a ____________dilution of the stock in Tube A. The concentration in Tube C is ______________.
Please give detailed explanations! Thanks!
Explanation / Answer
1. You are provided with Stock Tube A of antibiotic that has a concentration of 1000 ?g/?l. For lab, it is necessary to make the following dilutions:
a. Tube B: 15?L of the 1000 ?g/?l antibiotic stock in Tube A + 385?L of buffer. The dilution in Tube B is 26.6 and the concentration is 37.5ug/uL.
Dilution factor= (aliquot volume + diluent volume)/aliquot volume
Dilution factor= (15uL + 385uL)/15uL=26.6
Concentration
Stock conc=1000ug/uL
Stock Vol=15uL
Final vol=385+15=400uL
Final conc=?
C1V1= C2V2
(stock) (required)
C2=C1V1/V2 =(1000 x 15)/400=37.5ug/uL
Concentration on tube B=37.5ug/uL
b. Tube C: 20?L from Tube B + 30?L of the buffer. Tube C represents a 66.5 dilution of the stock in Tube A. The concentration in Tube C is 15ug/uL.
DF=(20+30)/20=2.5
Final DF= 2.5 x 26.66=66.5
Concentration on tube c=37.5/2.5=15ug/uL
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