Quality assurance 5 Flashcards
VAM principles of best analytical practice
Measurements should be made to satisfy an agreed requirement, and should be made using methods and equipment which have been tested to ensure they are fit for purpose
Staff should be qualified and competent
There should be a regular independent assessment
Organisations making analytical measurements should have well defined quality control and quality assurance procedures
Equipment qualification
Provides documented evidence that the instrument is fit for intended purpose, and kept in state of maintenance and calibration
Four stages of equipment qualification
Design qualification
Installation qualification
Operational qualification
Performance qualification
Design qualification
Usually performed by the manufacturer
Design of user requirement specification for intended application
Defines the functional and operational specification of the instrument
Installation qualification
Covers installation of the instrument up to and including initial turn on
Operational qualification
Initially follows installation qualification
Repeated: following relocation of instrument, following maintenance of instrument, periodically at defined intervals
Performance qualification
Undertaken regularly during routine use
Provides evidence that performance remains consistent and within required limits over time
General considerations
What is its intended use?
Instrument set up and control
Module compatibility/software
Data acquisition, processing and software
In built diagnostics
Sample introduction and throughput
Sample preparation, clean up or pre-treatment
Initial performance qualification
Holistic performance test to verify correct functioning and performance of entire system
Analyse test mix on a test column under defined operating conditions
Allows performance to be compared to other instruments and throughout life
Accuracy vs precision
Accuracy: how close measured value is to true value
Precision: how close the measured values are to each other
Injection volume precision
Important for accuracy and precision of results
Test by determining relative standard deviation in detector response (peak area/height) to repeated injections of same volume of standard solution
Should be <1% RSD
Shape of the peak should be reproducible
Injection volume linearity
Important where various volumes are injected
Test by determining detector response (peak area/height) to injections of different volumes of standard solution
Should be linear i.e. double volume = double response
Injection carry over
Important for accuracy and precision of results and reproducibility of peak area/height
Determined by measuring detector response to blank injection immediately following standard solution
Other injection considerations
Flow rate precision
Proportioning precision
Column oven thermostatting precision
Linearity of detector response
Important for accuracy of results
Determined by producing calibration curve of detector response (peak area/height) against standard solution concentration
Signal to noise ratio
Important for sensitivity and limit of detection
Determined by measuring detector response to blank injection compared to diluted standard solution
S:N ratio=height of dilute analyte peak/ height of largest baseline fluctuation
Method validation
Doing a thorough method validation can be tedious, but the consequences of not doing it right are wasted time, money and resources
Analysis in discovery, development and manufacture of pharmaceuticals
Screening of potential drug candidates Aid in development of drug synthesis Support formulation studies Monitor stability of bulk pharmaceuticals and formulated products Testing of final products
Prior to analysis
You need to establish minimum criteria and set minimum requirements
Agree a complete list of criteria between analyst and end users before method is developed so that expectations are clear
Precision and accuracy both important
Performance characteristics assessed in method validation include:
Specificity (how method is specific for the compound) Range (between LofD and LofQ) Linearity (calibration) Limit of detection (how low you get) Limit of quantitation (how high you get) Ruggedness (signal to noise ratio) Uncertainty (precision and bias)
Specificity
Ability to accurately measure analyte in the presence of al potential sample components
Compare the response to analyte alone with response to analyte in test mixtures containing analyte and all other components
Subject sample to extreme conditions to monitor degradation: heat, light, acid, base, oxidant and humidity
Linearity
Verify that sample solution is within concentration range where analyte response is linearly proportional to concentration
Test standard solutions at five different concentrations over a range of 50 to 150% of target analyte concentration
Precision
Scatter in results obtained from multiple analyses of homogenous sample
Instrument precision can be determined by repeatedly injecting the same sample
repeatability, or intra-assay precision, can be determined by repeatedly analysing aliquots of same sample in same lab on same day
Accuracy
Can be determined by:
Analysing sample of known concentration and compare measured value to true value
Determining the recovery of known amounts of analyte spiked into blank sample matrix
Comparing results from new method with results from existing alternative method known to be accurate
Range
Concentration range over which acceptable accuracy, linearity and precision obtained
Determined using data from linearity and accuracy studies
Precision calculated from replicate analyses of spiked samples in accuracy study
Limits of detection and quantitation
LOD: lowest analyte concentration that produces a response that is detectable above noise
LOQ: lowest level of analyte that can be accurately and precisely measured
Ruggedness
The degree of reproducibility of results obtained by the analysis of the same sample under a variety of normal test conditions
Different analysts, different laboratories etc.
Stability
Stability of product
Stability of reagents, mobile phases and standard solutions
Essential that solutions are stable enough to allow for delays
Uncertainty
Measurement depends on system, method, operator and environment
Repeat measurements performed under the same conditions should provide results with a small degree of error
Acceptable level of uncertainty depends on reason for analysis and application of reesults
Typical problems that can be avoided
Impurities co-elute with peak- need to know sample composition
Degradation of analyte of interest- information on stability and properties of analyte
QA audit of validation report finds no documentation on how method was performed- must keep comprehensive records of analysis
