CHMB16H3 Chapter Notes - Chapter 5: Standard Operating Procedure, Titration, Electropherogram
Chapter 5: Quality Assurance and Calibration Methods
Basics of Quality Assurance
•Quality Assurance: what we do to get the right answer for our purpose.
•Raw Data: individual values of a measured quantity.
•Treated Data: concentrations/amounts derived from raw data by use of
calibration method.
•Results: quantities reported after statistical analysis of treated data.
•Use Objectives: states purpose for which results will be used (drinking water is
usually disinfected with chlorine which kills microorganisms).
•Specifications: stating how good the numbers need to be and what
precautions are required in the analytical procedure.
oSampling Requirements: must collect representative samples and
analyte must be preserved after sample is collected.
oAccuracy and Precision
oRate of False Results
False Positive: says that the result is over but it is actually
under.
False Negative: says the result is below but it is actually above
the limit.
oSelectivity: being able to distinguish analyte from other species in the
sample.
oSensitivity: the capability of responding reliably and measurably to
changes in analyte concentration (sensitivity = slope of calibration
curve = change in signal / change in analyte concentration).
oAcceptable Blank Values: account for interference by other species in
the sample.
Method Blank: a sample containing all components except
analyte and it is taken through all steps of the analytical
procedure.
Reagent Blanks: similar to a method blank, but it has not been
subjected to all sample preparation procedures.
Field Blank: similar to method blank but it has been exposed to
the site of sampling.
oRecovery of Fortification or Spike: a known quantity of analyte added
to a sample to test whether response to a sample is the same as that
expected from a calibration curve (% recovery = Cspiked sample –
Cunspiked sample / Cadded x 100).
oCalibration Checks: we analyze solutions formulated to contain known
concentrations of analyte.
oQuality Control Samples: help eliminate bias introduced by an analyst
who known the concentration of the calibration check sample.
•Standard Operating Procedures: stating what steps will be taken and how they
will be carried out are the bulwark of quality assurance.
•To gauge accuracy, calibration checks, fortification recoveries, quality control
samples and blanks are used.
•To gauge precision, replicate samples and replicate portions of same sample
are used.
•Chain of Custody: the trail followed by a sample from the time it is collected to
the time it is analyzed and archived.
•Assessment: the process of collecting data to show that analytical procedures
are operating within specified limits and verifying that final results meet use
objectives.
Document Summary
Basics of quality assurance: quality assurance: what we do to get the right answer for our purpose, raw data: individual values of a measured quantity. False positive: says that the result is over but it is actually under. Method blank: a sample containing all components except analyte and it is taken through all steps of the analytical procedure. Reagent blanks: similar to a method blank, but it has not been subjected to all sample preparation procedures. Cunspiked sample / cadded x 100): calibration checks: we analyze solutions formulated to contain known, quality control samples: help eliminate bias introduced by an analyst concentrations of analyte. who known the concentration of the calibration check sample. Standard operating procedures: stating what steps will be taken and how they will be carried out are the bulwark of quality assurance. To gauge accuracy, calibration checks, fortification recoveries, quality control samples and blanks are used.