Transcript Dilution

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.
Dilutions for the Clinical Laboratory
(cont’d)
 Dilutions are expressed as the volume of
the solution being diluted per the total
final volume of the dilution
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”.
Dilutions for the Clinical Laboratory
(cont’d)
 Another example:
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).
Dilutions for the Clinical Laboratory
(cont’d)
 Another example:
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”.
Dilutions for the Clinical Laboratory
(cont’d)
 Notice that dilutions do NOT have units
(cans, ml, or parts) but are expressed as
one number to another number
Example: 1/10 or “one in ten”
Dilutions for the Clinical Laboratory
(cont’d)
 Dilutions are always expressed with the
original substance diluted as one (1). If
more than one part of original substance
is initially used, it is necessary to
convert the original substance part to
one (1) when the dilution is expressed.
Dilutions for the Clinical Laboratory
(cont’d)
Example:
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
2x
=
10
x
=
5
The dilution is expressed as 1/5.
Dilutions for the Clinical Laboratory
(cont’d)
The dilution does not always end up in whole numbers.
Example:
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
2x
=
7
x
=
3.5
The dilution is expressed as 1/3.5
Dilutions for the Clinical Laboratory
(cont’d)
 Dilution Factor – used to correct for
having used a diluted sample in a lab test
rather than the undiluted sample. The
result (answer) using the diluted sample
must be multiplied by the RECIPROCAL
of the dilution made.
 The RECIPROCAL of a 1/5 dilution is 5.
Dilutions for the Clinical Laboratory
(cont’d)
 Correction for using a diluted sample
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.
Dilutions for the Clinical Laboratory
(cont’d)
 Sometimes it is necessary to make a
dilution of an existing solution to make it
weaker.
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.
Dilutions for the Clinical Laboratory
(cont’d)
 To make a weaker solution from a stronger one, use this
formula:
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
Serial Dilutions
 Dilutions can be made singly (as shown
previously) or in series, in which case the
original dilution is diluted further. A
general rule for calculating the dilution
of solutions obtained by diluting in a
series is to MULTIPLY the original
dilution by subsequent dilutions.
Serial Dilutions (cont’d)
 Example of a serial dilution:
Serial Dilutions (cont’d)
 In the serial dilution on the previous
slide, 1 ml of stock solution is mixed with
9 ml of diluent, for a 1/10 dilution. Then
1 ml of the 1/10 dilution is mixed with
another 9 ml of diluent. The second
tube also has a 1/10 dilution, but the
concentration of stock in the second
tube is 1/10 x 1/10 for a 1/100 dilution.
Serial Dilutions (cont’d)
 Continuing with the serial dilution, in the third
tube, you mix 1 ml of the 1/100 dilution from
the second tube with 9 ml of diluent in the
third tube. Again you have a 1/10 dilution in
the third tube, but the concentration of stock
in the third tube is 1/10 x 1/10 x 1/10 for a
1/1000 dilution.
 This dilution could be carried out over many
subsequent tubes.
Serial Dilutions (cont’d)
 Serial dilutions are most often used in
serological procedures, where
technicians need to make dilutions of
patient’s serum to determine the
weakest concentration that still exhibits
a reaction of some type. The
RECIPROCAL of the weakest
concentration exhibiting a reaction is
called a “titer”.
Serial Dilutions (cont’d)
 Example of determining a titer:
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.
References
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http://tinyurl.com/yrzv5n
http://tinyurl.com/yrblev
http://tinyurl.com/27kald
http://tinyurl.com/2hpsp8