Chapter 5 Flashcards
What we do to get the right answer
Quality assurance
Known solutions of analyte that don’t involve the unknown solution
External standards
Measurements
Raw data
Concentrations derived from raw data by use of calibration methods
Treated data
Quantities reported after statistical analysis of treated data
Results
States purpose for which results will be used
Use objective
Include sampling requirements, accuracy and precision, rate of false results, selectivity, sensitivity, acceptable blank values, recovery of fortification, calibration checks, and quality control samples
Specifications
Says that the concentration exceeds the legal limit when, in fact, the concentration is below the limit
False positive
Says that the concentration is below the limit when it is actually above the limit
False negative
Being able to distinguish analyte from other species in the sample (avoiding interference)
Selectivity (specificity)
The capability of responding reliably and measurably to changes in analyte concentration
Sensitivity
A sample containing all components except analyte, and it is taken through all steps of the analytical procedure
Method blank
Similar to method blank, but it has not been subjected to all sample preparation procedures
Reagent blank
Similar to method blank, but it has been exposed to the site of sampling
Field blank
Refers to everything in the sample other than the analyte
Matrix
A known quantity of analyte added to a sample to test whether the response to the spike is the same as that expected from a calibration curve
Spike (fortification)
Analyte solutions with known concentrations of analyte
Calibration check
A quality control measure to help eliminate bias introduced by an analyst who knows the concentration of the calibration check sample
Performance test samples (quality control samples or blind samples)
States what steps will be taken and how they will be carried out
Standard operating procedures
The process of (1) collecting data to show that analytical procedures are operating within specified limits and (2) verifying that final results meet use objectives
Assessment
The process of proving that an analytical method is acceptable for its intended purpose
Method validation
Measures how well a calibration curve follows a straight line, showing that response is proportional to the quantity of analyte
Linearity
Nearness to the truth
Accuracy
How well replicate measurements agree with one another
Precision
Describes how well one person can obtain the same results when analyzing the same sample by the same procedure with the same equipment in the same laboratory
Repeatability
Describes how well different people in different laboratories with different equipment can get the same results when analyzing similar samples by the same procedure
Reproducibility
Concentration range over which calibration curve is linear
Linear range
Concentration range over which there is measurable response
Dynamic range
Concentration range over which linearity, accuracy, and precision meet specifications for analytical method
Range
The concentration of analyte that gives a signal to three times the standard deviation of signal from a blank
Detection limit
The concentration below which regulations say that a given analyte is reported as “not detected”, which doesn’t mean that analyte is not observed
Reporting limit
The ability of an analytical method to be unaffected by small, deliberate changes in operating parameters
Robustness
A change in the analytical signal caused by anything in the sample other than analyte
Matrix effect
Standard deviation of the mean
Standard uncertainty
Added standard is the same substance as analyte
Standard addition
Added standard is different from analyte
Internal standard
Solutions with known concentrations of analyte are used to prepare a calibration curve
External standard
