# DILUTIONS AND STANDARDS Notes

Many of the laboratory procedures involve the use of dilutions. It is important to understand the concept of dilutions, since they are a hand tool used throughout all areas of the clinical laboratory. These dilutions have to be considered as they make a quantitative difference in what is going on. First, there are several terms used in expressing dilution:

1. "Dilution: - Dilutions are expressed as the ratio of the quantity of a desired solute (serum, urine, chemical solution, etc.) contained in a solvent (diluent). A 1:10 dilution of serum was made by adding one part serum to nine parts diluent to make a total of ten parts. If 1.0 milliliter of serum is added to 9.0 milliliters of H20, a total volume of 10.0 milliliters is obtained. Therefore, the dilution is expressed according to the following equation.

volume of serum/volume of solution = [1.0 mL serum ]/[1.0 ml serum + 9.0 mL H20]

1.0 mL serum/10 mL solution = 1:10 total

This means that each milliliter of solution contains 1/10 as much serum as each milliliter of the original serum. Another way to say this a serum sample was diluted 1:10 with H20. One precaution: Some people write ratio meaning the amount of solute in proportion to the amount of solute. If you are unsure of someone's intent, ask to clarify.

2. "Diluted to" - This is essentially the same as "dilution." If 1 milliliter is diluted to 10 milliliters, enough diluent is added to the original volume to yield a final, total volume of 10 milliliters. For example, if a 1 milliliter of serum is diluted to 10 milliliters of solution, 9 milliliters of H20 is added to the original serum sample. Using this information, one can see why "diluted to" is the same as "dilution" using the following equation:

volume of serum/total volume of solution = 1 mL/10mL = 1:10 One milliliter of serum was diluted to 10 milliliters.

3. "Added to" - This expression is usually a hang-up since it is not the same as "diluted...

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