Textbook Notes (369,067)
Canada (162,366)
Chemistry (275)
CHMB16H3 (16)
Chapter 5

CHMB16H3 Chapter 5 Notes.pdf

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Kagan Kerman

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Chapter 5 Quality Assurance ⇒ Quality Assurance: procedures to follow in order to obtain the correct answer for our purpose; the answer should have sufficient accuracy and precision ⇒ Raw Data: individual values of a measured quantity, i.e. volumes from a burette ⇒ Treated Data: concentrations or amounts found by applying a calibration procedure to the raw data ⇒ Results: quantities that are reported, i.e. mean or standard deviation, after applying statistics to treated data ⇒ Use Objectives: states the purpose for which the results will be used ⇒ Specifications: sampling requirements, accuracy and precision, rate of false results, selectivity, sensitivity, acceptable blank values, recovery of fortification (spiking), calibration checks, and quality control samples ⇒ Must collect representative samples and analyte must be preserved after the sample has been collected ⇒ Accuracy: calibration checks, fortification recoveries, quality control samples, blanks ⇒ Precision: replicate samples and replicate portions of same sample ⇒ False Positive: conclude that the results “YES” when in fact it is no ⇒ False Negative: conclude that the results “NO” when in fact it is yes ⇒ Selectivity: specificity: being able to distinguish analyte from other species in the sample (matrix); avoiding interference ⇒ Sensitivity: the capability of responding reliably and measurably to changes in analyte concentration; must have a detection limit lower than the concentrations to be measured; choose a method that can detect the analyte at the concentrations expected • Detection Limit: the smallest quantity of analyte that is significantly different from the blank • Reporting Limit: the concentration below which regulatory rules say that a given analyte is reported as not detected ⇒ Blanks: account for interference by other species in the sample and for traces of analyte found in reagents use for sample preservation; used to test a method’s selectivity ⇒ Method Blank: a sample containing all component except analyte and is taken through all steps of the procedures; Real Sample – Method Blank ⇒ Reagent Blank: containing all components except analyte but it not subjected to all sample preparation procedures; change one reagent at a time ⇒ Field Blank: containing all components except analyte and has been exposed to the site of sampling; detect any contamination from transport to and from the field ⇒ Spike Recovery: Spike: a known quantity of analyte added to a sample to test whether the response to sample is the same as that expected from a calibration curve ⇒ Matrix: everything else in the sample other than analyte ⇒ Matrix Effect: a change in the analytical signal caused by anything other than the analyte ⇒ Calibration Check: analyze solutions formulated to contain known concentrations of analyte = standard solutions; preparing solutions based on literature range; replicate Chapter 5 Quality Assurance each standard solution at least 3 times and take their average response; prevent errors over time if calibrate after a number of samples run ⇒ Performance Test Samples: quality control sample or blind sample: helps to eliminate bias introduced by the analyst knowing the concentration of the calibration check sample; samples of known compositions are provided to the analyst as unknowns and results are compared with the known values ⇒ Standard Operating Procedures: states what steps will be taken and how they will be carried out, how instruments should be maintained and calibrated to minimize human error • Good Laboratory Practice: how laboratory studies are planned, performed, monitored, recorded, reported, and archived ⇒ Assessment: collecting data to show that analytical procedures are operating with specified limits, verifying that final results meet use objectives ⇒ Method Validation: the process of proving that an analytical method is acceptable for its intended purpose ⇒ Method Specificity: the ability of an analytical method to distinguish the analyte from everything else ⇒ Method Linearity: measures how well a calibration curve follows a stra
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