QUALITY ASSURANCE IN THE ANALYTICAL CHEMISTRY LABORATORY Flashcards
is Defined as the degree to which a set
of inherent characteristics fulfill requirements.
Quality
describes the overall measures that a
laboratory uses to ensure the quality of its operations.
Quality Assurance
QA includes
A quality systems
Suitable laboratory environment
Educated, Trained and skilled staff
Equipment suitably maintained and calibrated
Documented and validated methods.
Traceability and measurement uncertainty
Proficiency testing
Requirements for reagents, standards, reference
materials
Three of the most important components of laboratory
QA are:
QC
method validation
equipment maintenance
is an integrated system of management and
technical activities within an organization that ensures
overall activities meet the defined standard or quality
QA
The QA program is defined in a documented
laboratory quality system which consists of:
- QA Manual
- QC processes
- written management and technical
procedures - work instructions
- records
to ensure quality of
analytical data produced by the laboratory
and to demonstrate the competence of
the lab
QC processes
Contains the quality policies and
objectives
QA Manual
The most widely recognized and used QA
protocols and standards in chemical testing:
ISO/ IEC 17025:2005 (International
organization for standardization/ International
Electrotechnical Commission)
ISO 9001:2000
OECD Principles of Good Lab Practice
(organization for economic cooperation and
development)
Standard which addresses the technical
competence of laboratories to carry out
specific tests and calibrations and is used by
lab accreditation bodies worldwide
ISO/ IEC 17025:2005 (International
organization for standardization/ International
Electrotechnical Commission)
The standards which relates primarily to
quality management, for facilities carrying out
production, or providing services, including
chemical analysis
ISO 9001:2000
International standard that contains all the
requirements that testing and calibration
laboratories have to meet if they wish to
operate a quality system
ISO/ IEC 17025:2005 (International
organization for standardization/ International
Electrotechnical Commission)
Guidelines concerned with the organizational
processes and conditions under which
laboratory studies related to certain regulatory
work are carried out
OECD Principles of Good Lab Practice
ISO/ IEC 17025 : 2005 MANAGEMENT
Requirements:
- Organization
- Management system
- Document control
- review of requests, tenders and contracts
- Sub-contracting of tests and calibrations
- Purchasing services and supplies
- Service to the customer
- Complaints
- Control of non-conforming tests
- Improvement
- Corrective action
- Preventive Action
- Control of Records
- Internal audits
- Managements reviews
ISO/ IEC 17025 : 2005 TECHNICAL
Requirements:
- General
2. Personnel
3. Accommodation and environmental
condition
4. Test and calibration method validation
5. Equipment
6. Measurement traceability
7. Sampling
8. Handling of test and calibration items
9. Assuring the quality of test and calibration
results
10. Reporting of results
set of practice in the
chemical laboratory that controls the
laboratory activities and conditions that affect
the accuracy of analytical data
GLP ( limited sense)
set of
requirements covering the organization of test
facilities and conditions to ensure the
generation of high quality and reliable test data
for specific objectives
GLP principles ( expanded sense)
Component of GLP
QA Program
Laboratory Conditions
Test samples
Test measurements
Record management
Component of GLP that ensures consistent quality of data
QA Program
To preserve the identity and integrity of the
samples
Test samples
To ensure that an acceptable test method
will produce the expected performance
Test measurements
To ensure that laboratory conditions are
optimized to obtain the desired
performance of the test method
Laboratory Conditions
To enable retrieval of undistorted
information whenever required
Record management
GLP includes:
- implementing standard operating
procedures - Proper maintenance and calibration of
equipment - Correct practices of laboratory personnel in
performing analytical work - Efficient management of laboratory records
Ensures that the defined characteristics of
the method as required are met. The defined method
characteristics are also known as data quality objectives (DQOs)
Method of QA
are critical goals for accuracy, precision, sensitivity,
and selectivity of analytical data to be satisfied so as to
achieved analysis goals.
data quality objectives (DQOs)
Minimum requirements for Method of QA
Accuracy
Precision
Sensitivity
Selectivity
degree of agreement of measurements
with an acceptable reference value or degree of
acceptable method bias. Bias ( sometimes called
recovery) is the systematic error of the measuring
system
Accuracy
degree of spread of results ( degree of
differences in individual test results, expressed as
standard deviation, relative standard deviation or RSD).
Precision
is defined by detection limits:
Sensitivity
the measured concentration at which there is a stated probability ( 95% or 99%) that an analyte is present. MDL is defined as 3x standard deviation (of method blank runs).
Method detection limit (MDL)-
the lowest concentration level that can be determined to be statistically different from the blank; the lowest analyte concentration required to be present to ensure an analytical response that will exceed the MDL.
Reliable detection limit (RDL)
the level above
which quantitative results maybe obtained with
a specified degree of confidence. Confidence in
the apparent analyte concentration increases as
the analyte signal increases above the MDL.
Limit of quantitation (LOQ)
Formula for LOQ
LOQ = 3.33 x MDL = 10 x s ( 99% CL)
susceptibility of the method to
interferences. This maybe determined by
recovery of spiked samples
Selectivity
A method QA program will:
Start with → DQOs
Involve → Method selection , documentation and validation
End with → Evaluation
Continue with → QC monitoring and instrument
maintenance Re-validation/ re-evaluation Improvement
Method of QA program covers:
Method Selection
Method Validation
Sampling
Equipment
Quality Control
Traceability
Measurement Uncertainty
Proficiency Testing
Factors to consider when selecting a method:
- Limit of detection
- precision
- Bias/Recovery
- Accuracy
- Selectivity
- Equipment required
- Sample size
- Time
- Cost
- Safety
Checks need to be carried out to ensure that the
performance characteristics of a method are understood and to demonstrate that the method is scientifically sound under the conditions in which it is to be applied.
These checks are collectively known as
Validation
Analytical procedures must be well documented before validation is performed. Documentation includes:
- Title of test method
- Scope and application
- Sample matrices
- Method detection level
- Interferences
- Safety considerations
- Sample collection, preservation, transport,
storage - Apparatus, equipment, and supplies
- Reagents, standards, reference materials
- actual test procedure:
- Calibration
- Standardization
- Sample preparation
- Calculations - Specific QC practices
- Acceptance criteria
- Tables, flowcharts, validation data
- Estimation of measurement uncertainty
- References
The inclusion of particular validation parameters
in a validation protocol depends on the
application, the test samples, the goal of the
method, and domestic or international guidelines
and regulations, as applicable. These include:
- Selectivity and specificity ( description of
the measurand) - Measurement range
- Calibration and traceability
- Bias
- Linearity
- Limit of detection/ LOQ
- Precision
- Ruggedness
Ways of performing validation of an analytical
method:
- Collaborative Validation
- Internal Validation
a method is validated in a laboratory before
use to prove that the method performs
adequately
Internal Validation
Requires participation of a number
of lab.
Requires the use of a common sample
of known concentration of the analyte.
Results are evaluated for the
collaborative mean value of the analyte. Assessment of the accuracy, precision,
ruggedness and detection limits of the
method
Collaborative Validation
Components of internal validation of methods:
Characterization of instrument calibration and
working range
Determination of sensitivity ( detection limits)
Determination of bias ( systematic error)
Determination of precision ( random error)
Assessment of ruggedness ( for lab-developed
methods and non-standard methods)
is incorporated in
the routine analysis to maintain the
performance of the method. It is also an evaluation program incorporated
into routine and lab activities that assesses the
accuracy and precision of measurements.
Quality Control
What are the three Quality Control Samples?
- Laboratory instrument QC Samples
- Laboratory method QC Samples
- Field QC Samples
to measure and control the instrument calibrations
or instrument performance.
Laboratory instrument QC Samples
solutions with certified concentration of analytes
used to verify the accuracy of the calibration
curve.
Lab Instrument Control Standard
one of the standard
solutions used in making the calibration curve
that verifies the stability of a calibration curve
over time
Verification Standard
solution to check for
instrument contamination and background levels.
Instrument Blank
assesses the precision of the
test procedure
Lab sample replicate
The three Laboratory instrument QC Samples
Lab Instrument Control Standard
Verification Standard
Instrument Blank
Three Lab method QC Samples
Method blank
Lab sample replicate
Method analyte spike
What are the Method analyte spike
Blank spike
Matrix spike
Sample spike
measures the recovery of a
method
. Method analyte spike
measures method contamination
background
Method blank
analyte spiked on clean
matrix to assess losses or contribution due
to the matrix
Matrix spike
analyte spiked on samples
to assess the losses or contribution due to
other components or characteristics of the
sample
Sample spike
analyte spiked on a
method blank
Blank spike
Naturally- occurring materials or synthetic materials with known concentrations of analytes (obtained through collaborative studies) certified by recognized certifying bodies (such as NIST, IAEA) used to assess the bias of the method; comes with Certificate of Analysis.
Certified Reference Materials
Three field QC samples
Field Blank
Field Analyte spike
Field Replicate Samples
measures recovery between
time of sampling and time of analysis
Field Analyte spike
measures contamination from
sampling activities
Field Blank
Corrective action on failed QC includes:
- investigation when QC failure
- correction of the cause of failure
- institution of preventive measures to preclude the recurrence of failure
- Investigation of QC failure can be started by identification
of the trend in the QC chart.
The ______ and ______ of analytical
measurement is the formal procedure of laboratory quality control. But _______ is the final stage of a management system of quality assurance
control of bias, random error
quality control
susceptibility of the method to
interferences. This maybe determined by
recovery of spiked samples
Selectivity
