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# Serial Dilutions Essay

1168 words - 5 pages

According to the Environmental Data Standards Council, a serial dilution is a numerical factor representing the number of equal volumes of diluent added to a sample (EDSC, 1). The process involving serial dilution is used to set up a series of different sample concentrations for an experiment. To accomplish this, a high concentration of sample is used as a starting point. A measured amount of sample is transferred to another well and mixed with dilution solvent, creating a lower concentration. For example, if 10 micro liters of sample is mixed with 90 micro liters of solvent, the resulting liquid will be 10% as concentrated. This is called a 1:10 dilution. Frequently in lab you may need ...view middle of the document...

The diluted material must then be thoroughly mixed to achieve the true dilution. For example, a 1:5 dilution (verbalize as "1 to 5" dilution) entails combining 1 unit volume of diluent (the material to be diluted) + 4 unit volumes of the solvent medium (hence, 1 + 4 = 5 = dilution factor). Example: Frozen orange juice concentrate is usually diluted in 4 additional cans of cold water (the dilution solvent) giving a dilution factor of 5, i.e., the orange concentrate represents one unit volume to which you have added 4 more cans (same unit volumes) of water. So the orange concentrate is now distributed through 5 unit volumes. This would be called a 1:5 dilution, and the OJ is now 1/5 as concentrated as it was originally. So, in a simple dilution, add one less unit volume of solvent than the desired dilution factor value (Abedon, 2-3).Serial Dilutions are a way for us to make solutions of varying concentrations very easily in succession. This method is desirable because it eliminates a lot of the uncertainty and vagueness involved in making very small concentrations relative to the stock solution. This method is based on the fact that there are two ways to achieve a 1 to 100 dilution. It can be done in one step adding 1 part solution to 99 parts water or by making a 1 to 10 dilution twice in a row, using the first made solution as the "stock" for the second dilution. Serial dilution is simply a series of simple dilutions which amplifies the dilution factor quickly beginning with a small initial quantity of material (i.e., bacterial culture, a chemical, orange juice, etc.). The source of dilution material for each step comes from the diluted material of the previous. In a serial dilution the total dilution factor at any point is the product of the individual dilution factors in each step up to it. An example of a three step 1:100 serial dilution of a bacterial culture (see figure below). The initial step combines 1 unit volume culture (10 ul) with 99 unit volumes of broth (990 ul) = 1:100 dilution. In the next step, one unit volume of the 1:100 dilution is combined with 99 unit volumes of broth now yielding a total dilution of 1:100x100 = 1:10,000 dilution. Repeated again (the third step) the total dilution would be 1:100x10,000 = 1:1,000,000 total dilution. The concentration of bacteria is now one million times less than in the original sample (4).Since serial dilutions are correlated...

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