Answer: Perform a 1:10 dilution that makes at least 20 μL (e.g.Rearrange: Solute Volume = 300 μL / 100 = 3 μL.Plug values in: (300 μL) / Solute Volume = 100.Formula for 1:100 Dilution: Final Volume / Solute Volume = DF.Rearrange: Solute Volume = 20 μL / 10 = 2 μL.Plug values in: (20 μL) / Solute Volume = 10.Formula for 1:10 Dilution: Final Volume / Solute Volume = DF.Choose step DFs: With a total dilution factor of 1000, you can do a 1:10 followed by a 1:100 (10 * 100 = 1000).Example: Make only 300 μL of a 1:1000 dilution, assuming the smallest volume you can pipette is 2 μL.Use the formula: Final DF = DF1 * DF2 * DF3 etc., to choose your step dilutions such that their product is the final dilution. If the dilution factor is larger than the final volume needed, or the amount of stock is too small to be pipetted, one or more intermediary dilutions may be required. Answer: Place 1.2 μL of the stock solution into 300 μL – 1.2 μL = 298.8 μL diluent.Rearrange: Solute Volume = 300 μL / 250 = 1.2 μL.Plug values in: (300 μL) / Solute Volume = 250.Formula: Final Volume / Solute Volume = DF.Example: Make 300 μL of a 1:250 dilution.Dilution factors are related to dilution ratios in that the DF equals the parts of the solvent + 1 part. This is different than a “dilution ratio,” which typically refers to a ratio of the parts of solute to the parts of the solvent, for example, a 1:9 using the previous example. ![]() The dilution factor (DF) can be used alone or as the denominator of the fraction, for example, a DF of 10 means a 1:10 dilution, or 1 part solute + 9 parts diluent, for a total of 10 parts. This way of expressing a dilution as a ratio of the parts of solute to the total number of parts is common in biology. (Final Volume / Solute Volume) = Dilution Factor (can also be used with mass) To make a dilute solution without calculating concentrations, you can rely on a derivation of the above formula:
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