Quality Assurance & Quality Control

Question 1

Quality assurance

Answer 1

– steps designed to ensure adequate data
– 1. documentation 2. quality assessment 3. quality control
250 million analyses performed each day in North America
 10% (25M) poor and have to be repeated
 Cost $5 billion per year
Goal is to minimize errors through the implementation of data quality standards
That… Get the right data
Get the data right
Keep the data right
Why is this important….
Even well-executed procedures produce some false conclusions due to random
error. Quality Assurance helps reduce all other errors.

Question 2

Documentation

Answer 2

Documentation is critical. Standard protocols provide direction for what must be
documented and how documentation is to be done.

Question 3

Notebook

Answer 3

legal record of activities and results obtained during a procedure

Question 4

Standard Operating Procedure (SOP)

Answer 4

– written procedure that details all steps in
performing an analysis (assures quality results, developed in house)
- includes sampling, sample prep, standards, calibration, storage, reporting

Question 5

Regulatory Procedure

Answer 5

SOP written by regulatory bodies to ensure that analyses

performed in various labs are correct

Question 6

Method validation– process of proving that an analytical method is acceptable for
the intended purpose – four basic considerations

Answer 6

Accuracy – nearness to the correct answer
– compare with another (validated) method
– analyze a Standard Reference Material that has a certified analyte
– concentration and a matrix similar to your sample
Specificity – ability of method to distinguish analyte from everything in matrix
Linearity – analytical signal depends directly on analyte concentration over what
range of concentrations
Precision – reproducibility of a result
Instrument precision – same sample multiple times, 1 person, same day
Intra-assay precision – aliquots of sample, 1 person, same day
Intermediate precision (ruggedness)
– aliquots of same sample, different people, different days

Question 7

Quality Control

Answer 7

– active measures taken to ensure the accuracy and precision of
the required measurement

Question 8

Performance test sample (control sample, blind sample)

Answer 8

samples of know concentration submitted to analyst as an unknown
– QC manager (Dr. Kiema) compares to correct concentration

Question 9

Proficiency test sample

Answer 9

– samples of know concentration submitted to lab as an unknown
– this tests overall quality assurance procedures of lab
– out of range result can result in decertification of lab for that analysis
– not allowed to perform analysis, until investigation and corrective measures

Question 10

Blank

Answer 10

solution identical to sample except that it does not contain any analyte.
[Analyte] = 0 theoretically should see no signal
In practice may see signal due to:
contamination, non-specific response to matrix or reagents, etc.

Question 11

Spike (fortification)

Answer 11

known quantity of analyte added to a sample to test

whether the analyte response is the same in the presence of the matrix

Question 12

Matrix

Answer 12

components of the sample other than the analyte of interest.
In practice matrix may alter the analytical response (systematic error).
Examples: effect of sample ionic strength on fluoride electrode
- if matrix known, prepare standards to match sample
- if matrix unknown, do “standard addition”

Question 13

Quality Control Calibration Methods

Answer 13

External Standard
– most common method
– standards run separately and calibration
curve prepared
– samples run, signal collected,
concentrations are determined
– best results if unknown concentration
comes out in calibration standard range
Standard Addition
– Used when sample matrix affects response
(slope) of analytes
– Standard is added to sample, increasing
concentrations
– Concentration is determined by
extrapolation (= |X-intercept|)

Question 14

Horowitz Trumpet

Answer 14

Allows for understanding of variation
in interlaboratory precision
When setting an allowable limit (eg: 1 ppb)
must include interlaboratory variation
1 ppb + (0.45) = 1.45 ppb

Question 15

Quality Control Chart

Answer 15

Control charts used to monitor performance to see if results are stable over time
or to compare the work of different employees.
±2 = warning lines and ±3 = action lines

1 beyond action line, ≥2 between warning/action, ≥7 consecutive above or below mean
6 steady increasing or decreasing, 14 points alternating up/down
All Unlikely Events – method immediately shut down and investigated