Definitions Flashcards
What is absolute error
AE= measured value-true value
What is relative error and the equation
Compares absolute error to the accepted value
RE=AE/true valuex100%
What is an analyze
The substance that needs to be detected/identified or quantified during analysis
What is a bias and what does it affect, and sometimes referred to
The difference between the mean test result and an accepted value
Affects accuracy
Sometimes referred to total systematic error and either positive or negative
What is a blank and where does it come from
Accounts for traces of analyte or another compound that interferes with your analyte
Can come from field, storage and analysis
What are the two types of blanks (3 for each)
Non laboratory
- trip
- field
- equipment
Laboratory
-reagent
-instrumental
-method
What’s a trip blank
Contamination from shipping to and from the lab
Originates from laboratory
What is a field blank
Cross contamination during sampling
Analyzed in lab as a real smple
What’s an equipment blank
Cross contamination during sampling by assessing the effectiveness of decontamination procedures
Analyzed as a real sample
What’s a reagent blank
Contamination of samples by reagents used to process them
What’s a method blank
Sample containing all components except analyzed of interest
What’s a calibration curve
A chemical or physical signal that is proportionate to the amount of analyte in the sample
Shows how the analyte signal changes with the concentration of the analyte
Usually a linear relationship
What’s certified reference material
Material that has had a specific analyte content assigned to it
Assigned concentration is usually the mean value determined from the analyses by many laboratories
What is the detection limit
Detection limit of an analytical procedure is the smallest amount of analyte in a sample that can be detected with confidence\
What is the limit of detection (LOD) and equation
The amount of analyte that is required to produce a signal greater than a prescribed quantity of noise
LOD= Sblank+3x noise
Noise/standard deviation of noise
What is the limit of quantitation (LOQ) and equation
Smallest amount of analyte in a sample that can be quantativley determined with suitable precision and accuracy
LOQ= Sblank +10 x standard deviation of noise
Instrumental detection limit and the equation (ADL)
How to detect it
Smallest amount of analyte that an instrument can detect
Aka. Analytical detection limit
Use analytical standards of analyte and determine how much analyte you can detect with a reasonable degree of certainty
Three types of errors and what they effect
Systematic- affects accuracy, determinate
Random- affects precision, indeterminate
Gross- affects precision and accuracy
What is a systematic error, what is it referred to, can it be identified
Can be identified
A reoccurring error that always has the same sign and magnitude for a given measurement
Referred to as a bias. Constantly misses the true value in the same direction
What’s a random error, can it be identified
Cannot be readily identified
Accounts for variability of individual measurements
Fluctuates in sign and magnitude
Measures of dispersion around central mean value and represented by standard deviation of repeated measurements
What is a gross error
Lab blunders
Recording, calibration errors and contamination
Outliers in data may be an symptom of mistake
Invalidate a good set of data
Linearity
Ability of an analytical procedure to obtain signals that are directly proportional to the amount of analyte in a sample
Method
Application of a technique for a specific analyte in a specific matrix
Interference and what does it cause
A chemical that contributes to the measured signal of the analyte
Causes systematic error in analytical results
