CHEM 315 Study Guide - Quiz Guide: Certified Reference Materials, Standard Deviation, Reagent
18 Jun 2018
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Analyte Concentration in sample
1. major: > 1%
2. minor: 0.1 – 1%
3. trace: < 0.1%
SRM: standard reference material
Least square method
used for calibration curve
fit best line through data point
Assumptions: error y>x, same standard deviation for all data,
square the value to minimize the magnitude
Constructing calibration curve
1. Prepare blank solution and standard solution of analyte
2. Subtract average blank absorbance value from each standard solution absorbance value
3. make graph with corrected absorbance value and amount of protein
Quality Assurance (QA): what can you do to verify the analytical result in terms of
accuracy and precision?
1. Objectives: states purpose for which results will be used, which kind of data you collect,
which way collect the data.
What information do we need?
How accurate, precise do results need to be?
Speed and cost
Balance between speed, cost, accuracy and precision
2. Specification: how good the number must be, precautions in procedure
Sampling requirements
how should the samples be taken?
how many are needed?
special precautions? (prevent volatilization/ degradation)
chain of custody (document signed when samples changes hand)
Accuracy and Precision
use SRM?
reagent purity
tolerances for apparatus, which model?
Rate of false results
false positive: Exceeds legal limit when it is below limit
false negative: Below limit when it exceeds legal limit
better to have more false negative than positive
Selectivity
able to distinguish analyte from other species?
Sensitivity
detection limit must be lower than expected concentration
Acceptable blank values
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Document Summary
Analyte concentration in sample: major: > 1, minor: 0. 1 1% Least square method used for calibration curve fit best line through data point. Assumptions: error y>x, same standard deviation for all data, square the value to minimize the magnitude. Constructing calibration curve: prepare blank solution and standard solution of analyte, subtract average blank absorbance value from each standard solution absorbance value, make graph with corrected absorbance value and amount of protein. Balance between speed, cost, accuracy and precision: specification: how good the number must be, precautions in procedure. Chain of custody (document signed when samples changes hand) False positive: exceeds legal limit when it is below limit. False negative: below limit when it exceeds legal limit. Better to have more false negative than positive. Detection limit must be lower than expected concentration. Method blank: contains all components except analyte. Field blank: exposure to the site of sampling. Spike recovery: analyte can be decreased by something in sample (matrix)
