Dilutions. Instructor: Cecile Sanders, M.Ed., MT(ASCP), CLS (NCA). Dilutions for the Clinical Laboratory. Dilution = making weaker solutions from stronger ones Example: Making orange juice from frozen concentrate. You mix one can of frozen orange juice with three (3) cans of water.
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Cecile Sanders, M.Ed., MT(ASCP),
Example: Making orange juice from frozen concentrate. You mix one can of frozen orange juice with three (3) cans of water.
In the orange juice example on the previous slide, the dilution would be expressed as 1/4, for one can of O.J. to a TOTAL of four cans of diluted O.J. When saying the dilution, you would say, in the O.J. example: “one in four”.
If you dilute 1 ml of serum with 9 ml of saline, the dilution would be written 1/10 or said “one in ten”, because you express the volume of the solution being diluted (1 ml of serum) per the TOTAL final volume of the dilution (10 ml total).
One (1) part of concentrated acid is diluted with 100 parts of water. The total solution volume is 101 parts (1 part acid + 100 parts water). The dilution is written as 1/101 or said “one in one hundred and one”.
Example: 1/10 or “one in ten”
Two (2) parts of dye are diluted with eight (8) parts of diluent (the term often used for the diluting solution). The total solution volume is 10 parts (2 parts dye + 8 parts diluent). The dilution is initially expressed as 2/10, but the original substance must be expressed as one (1). To get the original volume to one (1), use a ratio and proportion equation, remembering that dilutions are stated in terms of 1 to something:
______2 parts dye = ___1.0___
10 parts total volume x
2 x = 10
x = 5
The dilution is expressed as 1/5.
The dilution does not always end up in whole numbers.
Two parts (2) parts of whole blood are diluted with five (5) parts of saline. The total solution volume is seven (7) parts (2 parts of whole blood + 5 parts saline). The dilution would be 2/7, or, more correctly, 1/3.5. Again, this is calculated by using the ratio and proportion equation, remembering that dilutions are stated in terms of 1 to something:
__2 parts blood_____ = ___1.0___
7 parts total volume x
2 x = 7
x = 3.5
The dilution is expressed as 1/3.5
Example: A technician performed a laboratory analysis of patient’s serum for a serum glucose (blood sugar) determination. The patient’s serum glucose was too high to read on the glucose instrument. The technician diluted the patient’s serum 1/2 and reran the diluted specimen, obtaining a result of 210 g/dl. To correct for the dilution, it is necessary to multiply the result by the dilution factor (in this case x 2). The final result is 210 g/dl x 2 = 420 g/dl.
Example: A 100 mg/dl solution of substrate is needed for a laboratory procedure. All that is available is a 500 mg/dl solution of substrate. A dilution of the stronger solution of substrate is needed.
V1 x C1 = V2 x C2
Example: To make 100 ml of the 100 mg/dl solution from the 500 mg/dl solution needed in the previous example:
V1 = 100 ml V2 = V2 (unknown)
C1 = 100 mg/dl C2 = 500 mg/dl
100 ml x 100 mg/dl = V2 x 500 mg/dl
V2 = 20 ml
Dilute 20 ml of 500 mg/dl solution up to 100 ml with water to obtain 100 ml of 100 mg/dl substrate solution
A technician makes a serial dilution using patient serum:
Tube #1 = 1/10
Tube #2 = 1/100
Tube #3 = 1/1000
Tube #4 = 1/10,000
Tube #5 = 1/100,000
Reactions occur in tubes 1 through 3, but NOT in tubes 4 or 5. The titer = 1000.