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QCM Systems 
Introduction to QCM - a New Device for an Evolving Technology
Direct measurement, real-time analysis, high sensitivity, high
specificity, wide dynamic range, hyphenated methods, broad range of
applications, and cost effectiveness are all desirable characteristics in high
performance analytical systems. Unfortunately, in most cases only some of the
above capabilities are available for the scientists in a single instrument to
optimise their needs. Acoustic devices offer a unique opportunity &
challenges, where all of the above characteristics can be combined.
Acoustics waves cover very broad range of frequencies form below
1Hz to well beyond GHz. From practical point of view, based on current state of
technology, cost, and availability, we shall focus on thickness-shear-mode (TSM)
resonators, which are also known as quartz-crystal-microbalances or QCMs. The
heart of a QCM device is the coated quartz crystal designed for an appropriate
frequency range and application. Most measurements have been conducted from 5MHz
to 20MHz, providing nanogram or in some cases better sensitivities.
What are the applications of QCM based devices?
Initially QCM was used for mass sensing & thickness
monitoring of adsorption processes in vacuum and air. With the advancement of
electronics QCM was made operable in liquids and a new category of applications
evolved in the areas analytical and physical chemistries, including:
- Biomolecular adsorption
- Molecular interactions
- Antibody-antigen interactions
- Immunoassays
- Testing the presence of antigens in blood
- Polymer science
- Toxic gas sensing
- Adsorption and hybridization of oligonucleotides
- Characterization of adsorbed proteins
- Biofilm formation
- Kinetic of cell spreading
- Electrochemical applications
- Studying solid state phase transition
- Measurement of trace quantities of volatile compounds in water
- Monitoring air pollution
- Measurment of film thickness
- Measurement of dissolution
- Clean room applications
What are some the unique advantages of QCM over other methods?
QCM, by its inherent nature, can be used to study
- Immunochemical & immuno-biological characteristics in neat mode
without the enzyme labels used in ELISA based tests
- Cell adhesion characteristics in neat mode
- QCM-PCR integration
- Viscoelastic kinetics in the evaluation of coagulation &
anticoagulation processes
- Real-time monitoring & rapid analysis of contaminants.
What are some the main challenges QCM faces?
- The development of high-throughput capability
- The assurance of quality in the raw data & test results
- The development of a functional system that can be used in a flexible
& reliable manner to integrate the various capabilities
Our intention is to develop a QCM knowledge base to assist the
advancement of this new evolving technology and to provide a platform via OVAL
(OPULUS Virtual Application Laboratory) for future collaborative studies.
OVAL has been developed recently for Web-based proficiency
testing. The first application has been added for LAL methodologies; see LALPT.
With the inclusion of QCM, we hope to catalyse the evolutionary process both in
the development of suitable analytical systems and in the standardization of the
measurement protocols.
DQ-IQ-OQ-PQ and 21 CFR part 11
Regulatory compliance in the pharmaceutical, biotechnology, and
medical device, industries is the foundation of good business practices.
DQ-IQ-OQ-PQ documents for QCM Systems provide significant support to reduce the
risk of non-compliance.
DQ (Design Qualification) - is the foundation of good science & good
compliance practices. You cannot get more out of a system that has been
built into it. DQ is the tool & methodology to make the evaluation of
suitability for specific requirements, including worst-case-scenario. DQ
also provides the baseline for meaningful Performance Qualification (PQ)
monitoring; without DQ, PQ flounders, it does not exist. 21 CFR Part 11
compliance is a major functionality relative to Design Qualification.
In the first part let us consider what may be the most important questions to ask relative to 21
CFR Part 11 DQ. 
DQ supports the functional
& quality specifications designed into QCM Systems. Documentary proof of DQ
compliance includes:
- Software Validation Plan,
- Software Validation Summary,
- 21 CFR Part 11 Validation Summary,
- Measurement Performance Design Summary, and
- Measurement Compliance Summary
IQ (Installation Qualification) - IQ supports the
requirement for proper installation and acceptance qualification for
QCM Systems. Documentary proof of IQ compliance includes:
- Receipt & acceptance checklist,
- Physical & electrical compliance checklist,
- Environmental compliance checklist,
- Training compliance checklist, and
- Final IQ Summary
OQ (Operational Qualification) - OQ supports the
specification compliant functioning of the system. Documentary proof of OQ
compliance includes:
- 21 CFR Part 11 operational specification checklist,
- Software operational specification checklist,
- Instrument interface operational specification checklist,
- Instrument operational specification checklist, and
- Final OQ Summary
PQ (Performance Qualification) - PQ supports quality
evaluation & quality compliance management of the system. PQ compliance
models include:
- 21 CFR Part 11 compliance models,
- SQC models for instrument qualification review,
- SQC models for method qualification review,
- SQC models for vendor qualification review, and
- SQC models for OOS investigations
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