Using Units of Measurement
Jeff Lawrence (Z31)
Concentrated solutions can be expressed in terms of fold-concentrated. If a standard, final concentration is termed 1X (1 fold concentrated), a solution concentrated ten-fold is termed 10X. A 1X solution can be made from a 10X solution be diluting the 10X solution ten-fold. Examples:
AmountFinal (1X)stockConc. StockFoldfor 1LHow?50 mg/ml50 mg/ml1000 X1 mL(50,000 mg/ml)/(50 mg/ml) = 100010 mg/ml50 mg/ml5000 X200 mL(50,000 mg/ml)/(10 mg/ml = 500020 mg/ml10 mg/ml500 X2 mL0.2%40%200 X5 mL(5 mL)*(200X) = (1000 mL)*(1X)0.4%40%100 X10 mL(10 mL)*(100X) = (1000 mL)*(1X)1%40%40 X25 mL50 mM1 M20 X50 mL20 mM1 M50 X20 mL20 mM0.4 M20 X50 mL0.4 M=400 mM; (400 mM)/(20 mM)=20X1. Make 20 mL of 5 M NaOH, molecular weight 40 g/mol:
1 M = 40 g/L1 M = 4g/(100 mL)1 M = 0.4g/(10 mL)1 M = 0.8g/(20 mL)5 M = 4.0 g/(20 mL)∴ Add 4 g NaOH to 20 mL water2. Make 100 mL of a 200X stock for ampicillin, used at a final concentration of 50 mg/ml:
1X = 50 mg/ml200X = 200*50 mg/ml = 10,000 mg/ml = 10 mg/ml(10 mg/ml)*(100 mL) = 1000 mg = 1 g∴ Add 1 g ampicillin to 100 mL water3. How much of this stock do I use to make plates with a concentration of 20 mg/ml ampicillin?
(10,000 mg/ml stock)/(20 mg/ml final) = 500X∴ Use 1 mL of this stock for every 500 mL plates; or 2 mL per liter.4. If 200X methionine is 0.9%, what is the final concentration in plates?
(0.9%)/200 = .0045%OR: 0.9% = 0.9g/(100 mL) = 0.009g/ml = 9 mg/ml = 9000 mg/ml&there4 conc. is (9000 mg/ml)/200 = 45 mg/ml5. How much 40% galactose is added to make 500 mL of MacConkey-Galactose?
MacConkey plates use 1% final concentration of galactose(40%)/(1%) = 40X∴ Use 1 mL per 40 mL plates(500 mL)/(40 mL) = 12.5∴ Use 12.5 mL of 40% galactose to make 500 mL of 1% galactoseLast Update: Thursday June 19 2014This page has been viewed Failed to execute CGI : Win32 Error Code = 2
times.Eric Kofoideckofoid at ucdavis.edu
