Deck 6: Dilutions

Question 1

The initial volume of a sample is 100 μL.It is diluted with saline by a factor of 4.The final volume is 400 μL.Testing the diluted sample finds an analyte concentration of 25 μg/mL.Which of the following expressions can be used to calculate the initial analyte concentration of this sample?

A)
B)
C)
D)

Answer 1

Question 2

Which of the following must be done in order to create a standard curve from a single vial of a known concentration of glucose?

A) Additional known quantities of glucose must be added to the vial.
B) Other vials of known glucose concentrations must be obtained.
C) Serial dilutions must be made.
D) The vial must be tested daily for 10 days.

Answer 2

Serial dilutions must be made.

Question 3

Because the tube dilution is the same for all tubes in a serial dilution,the sample dilution for a given tube can be determined using which equation (in all cases N is the number of the tube in the sequence)?

A)
B)
C)
D)

Answer 3

Question 4

A laboratory technician is given a blood sample and asked to calculate the concentration of dopamine.The first test reveals that the concentration of dopamine falls outside the reliable range for the testing method.He adds 100 μL saline solution to 100 μL of the sample and retests the sample.How does the concentration of dopamine in the diluted sample compare to the concentration of dopamine in the original sample?

A) The concentration in the diluted sample is one-half that of the original sample.
B) The concentration in the diluted sample is one hundred times that of the original sample.
C) The concentration in the diluted sample is one-tenth that of the original sample.
D) The concentration in the diluted sample is twice that of the original sample.

Question 5

Which of the following expressions defines the dilution ratio of a sample?

A)
B)
C)
D)

Question 6

How is antibody titer determined?

A) Calculating the ratio of antibody to antigen in the highest possible sample dilution in which all antigen is bound
B) Measuring highest possible dilution where antibody is able to bind antigen
C) Measuring the minimum possible concentration of antibody necessary to bind all antigen present in a sample
D) Taking the reciprocal of the highest sample dilution ratio at which antibody is detectable

Question 7

What is a serial dilution?

A) A dilution of a series of samples
B) A dilution that must always be performed
C) A sample that requires more than one dilution
D) A series of small dilutions

Question 8

A laboratory technician performs an antibody titer.A reaction is detected in every dilution from 1:2 up to and including 1:64.What does this tell the technician about the amount of antibody present?

A) The amount of antibody in the original sample can be calculated by multiplying 64 by the total number of tubes used in the dilution.
B) The antibody is able to detectably bind all the antigen present in a sample when the concentration of antibody is at a 1:64 dilution.
C) There is enough antibody in the serum to react visibly with antigen when diluted 64-fold, but not at 128-fold or more.
D) All of the above

Question 9

A laboratory technician is asked to determine the concentration of LDL present in a blood sample.The initial test finds the concentration of LDL to be outside the reliable range for the testing method.Accordingly,she dilutes the blood sample in 100 μL distilled water (dH₂O).What is the diluent in this scenario?

A) The blood-dH₂O mixture
B) The blood sample
C) The dH₂O
D) The LDLs

Question 10

A technologist picks up a serum sample with a label indicating it is a 1:4 dilution.What does this tell the technologist about the sample?

A) The concentration of any substance within the sample is 0.01 times its real value.
B) The concentration of any substance within the sample is one-fourth its real value.
C) The concentration of any substance within the sample is 100 times its real value.
D) The concentration of any substance within the sample is four times its real value.

Question 11

A urine sample is diluted 1:3 before testing.The test results identify 50 μg phenylpyruvate.What is the dilution factor that the result must be multiplied by to determine the true concentration of phenylpyruvate in the urine?

A) 1
B) 3
C) 10
D) 50

Question 12

A 100 μL sample of blood is diluted with 200 μL saline solution.What is the dilution ratio of the sample after dilution?

A) 1:2
B) 1:3
C) 1:4
D) 1:10

Question 13

A urine sample is diluted 1:4 before testing.Testing indicates that the concentration of protein present is 10 μg.What is the true concentration of protein in the urine?

A) 2.5 μg
B) 10 μg
C) 20 μg
D) 40 μg

Question 14

When is it advisable to perform a serial dilution rather than a simple dilution?

A) When a sample must be divided into several tubes or vessels
B) When a very large dilution is required
C) When multiple samples require dilution
D) All of the above

Question 15

Which of the following equations defines the tube dilution in a serial dilution?

A)
B)
C)
D)

Question 16

Which of the following is a reason to make dilutions?

A) The concentration of a given analyte is higher than the upper limit of the method to be used.
B) The concentration of analyte falls below the normal expected range.
C) The sample does not contain the desired analyte to be measured.
D) The type of analyte is unable to be read using the desired method or equipment.

Question 17

What does the term "tube dilution" refer to?

A) The amount of diluent in a tube before sample is added
B) The dilution factor of each tube in a serial dilution
C) The number of tubes used in a serial dilution
D) The total volume of diluent used in a serial dilution

Question 18

A sample ready for analysis is a 1:2 dilution.Which of the following is true about this sample?

A) The volume of the sample is decreased by a factor of 2, and the concentration is decreased by 2.
B) The volume of the sample is decreased by a factor of 2, and the concentration is increased by 2.
C) The volume of the sample is increased by a factor of 2, and the concentration is decreased by 2.
D) The volume of the sample is increased by a factor of 2, and the concentration is increased by 2.

Question 19

What is an antibody titer?

A) The amount of antibody bound to a specific antigen in a sample
B) The amount of antibody present in a serum against a particular antigen
C) The concentration of all antibodies present in a sample
D) The volume of serum composed of antibodies

Question 20

A sample of turbid knee fluid arrives in your laboratory and needs to be analyzed for the presence of white blood cells (WBC).An initial test reveals that the WBC concentration is higher than the upper limit of the automated blood analyzer.Which of the following should be done in order to achieve an accurate reading?

A) Extrapolate the concentration from a standard curve.
B) Obtain another sample.
C) Order a more sensitive machine.
D) Perform a dilution of the sample.