2 Quality Assurance vs. Quality Control An overallmanagement plan toguarantee theintegrity of data(The “system”)A series ofanalyticalmeasurements usedto assess thequality of theanalytical data(The “tools”)
3 True Value vs. Measured Value The known, accepted value of a quantifiable propertyMeasured ValueThe result of an individual’s measurement of a quantifiable property
4 Accuracy vs. Precision Accuracy How well a measurement agrees with an accepted valuePrecisionHow well a series of measurements agree with each other
6 Systematic vs. Random Errors Systematic ErrorAvoidable error due to controllable variables in a measurement.Random ErrorsUnavoidable errors that are always present in any measurement. Impossible to eliminate
7 Quality Control Measures Standards and CalibrationBlanksRecovery StudiesPrecision and Accuracy StudiesMethod Detection LimitsNJQLs
8 Standards and Calibration Prepared vs. Purchased StandardSignals: Peak Area, Beer’s LawCalibration CurvesContinuing Calibration ChecksInternal StandardsPerformance Testing.
9 The concentration of the analyte Calibration CurvesGraphical representation of the relationship between:The concentration of the analyteandThe analytical signal
11 Continuing Calibration Verification Many methods don’t require that daily calibration curves are preparedA “calibration verification” isanalyzed with each batch of samples
12 Sample Batch 10 - 20 samples (method defined) or less Same matrix Same sample prep and analysisContains a full set ofQC samples
13 Internal Standards A compound chemically similar to the analyte Not expected to be present in the sampleCannot interfere in the analysisAdded to the calibration standards and to the samples in identical amounts.
14 Internal Standards Refines the calibration process Analytical signals for calibration standards are compared to those for internal standardsEliminates differences in random and systematic errors between samples and standards
15 Performance Testing ? ? ? Blind samples submitted to laboratories Labs must periodically analyze with acceptable results in order to maintain accreditation
17 Laboratory Reagent Blanks Contains every reagent used in the analysisIs subjected to all analytical proceduresMust give signal below detection limitMost methods require one with every batch
18 Instrument BlankA clean sample (e.g., distilled water) processed through the instrumental steps of the measurement process; used to determine instrument contamination.
19 Field Reagent Blanks Prepared in the lab, taken to the field Opened at the sampling site, exposed to sampling equipment, returned to the lab.
20 Trip Blanks Prepared in the lab, taken to the field Not opened Returned to the labNot always required in EPA methods
21 Recovery StudiesMatrix SpikesLaboratory Control SamplesSurrogates .
22 Matrix Spikes Sample spiked with a known amount of analyte Subjected to all sample prep and analytical proceduresDetermines the effect of the matrix on analyte recoveryNormally one per batch
23 Laboratory Control Sample Analyte spiked into reagent waterSubjected to all sample prep andanalytical procedures
24 Laboratory Control Sample Also known as:Laboratory Fortified Blank (LFB)Quality Control Sample (QCS)
25 Surrogates Similar to an internal standard Added to all analytical samples, and to all QC samples to monitor method performance, usually during sample prepMethods often have specific surrogate recovery criteriaMost common in Organic methods
26 Quality Control Measures Standards and CalibrationBlanksRecovery StudiesPrecision and Accuracy StudiesMethod Detection LimitsNJQLs
27 Precision and Accuracy Required for initial certification and annually thereafterA series of four laboratory control samplesMust meet accuracy (recovery) and precision (standard deviation) requirements, often in method
28 Precision and Accuracy Required with a change in instrumentation or personnelSpecific to the analystOther names include:P&A, DOC, IDOC
29 Method Detection Limit “The minimum concentration of a substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero”N.J.A.C 7:
30 Method Detection Limit MDLs are determined according to 40 CFR, part 136, Appendix BSeven replicate laboratory control samples, analyzed for precisionMultiply standard deviation by 3.14 (Student’s t- value)
31 Method Detection Limit Must be performed initially for certificationMust meet criteria specified in methodMust be performed with change in instrumentation or test methodAnnually with ELCP
32 New Jersey Quantitation Limits (NJQLs) The minimum concentration of an analyte that can be quantified with statistical confidence5 x MDL, for the NJ Lab Certification Program