2Quality Assurance vs. Quality Control An overallmanagement plan toguarantee theintegrity of data(The “system”)A series ofanalyticalmeasurements usedto assess thequality of theanalytical data(The “tools”)
3True Value vs. Measured Value The known, accepted value of a quantifiable propertyMeasured ValueThe result of an individual’s measurement of a quantifiable property
4Accuracy vs. Precision Accuracy How well a measurement agrees with an accepted valuePrecisionHow well a series of measurements agree with each other
6Systematic 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
7Quality Control Measures Standards and CalibrationBlanksRecovery StudiesPrecision and Accuracy StudiesMethod Detection LimitsNJQLs
8Standards and Calibration Prepared vs. Purchased StandardSignals: Peak Area, Beer’s LawCalibration CurvesContinuing Calibration ChecksInternal StandardsPerformance Testing.
9The concentration of the analyte Calibration CurvesGraphical representation of the relationship between:The concentration of the analyteandThe analytical signal
11Continuing Calibration Verification Many methods don’t require that daily calibration curves are preparedA “calibration verification” isanalyzed with each batch of samples
12Sample Batch 10 - 20 samples (method defined) or less Same matrix Same sample prep and analysisContains a full set ofQC samples
13Internal 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.
14Internal 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
15Performance Testing ? ? ? Blind samples submitted to laboratories Labs must periodically analyze with acceptable results in order to maintain accreditation
17Laboratory 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
18Instrument BlankA clean sample (e.g., distilled water) processed through the instrumental steps of the measurement process; used to determine instrument contamination.
19Field Reagent Blanks Prepared in the lab, taken to the field Opened at the sampling site, exposed to sampling equipment, returned to the lab.
20Trip Blanks Prepared in the lab, taken to the field Not opened Returned to the labNot always required in EPA methods
21Recovery StudiesMatrix SpikesLaboratory Control SamplesSurrogates .
22Matrix 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
23Laboratory Control Sample Analyte spiked into reagent waterSubjected to all sample prep andanalytical procedures
24Laboratory Control Sample Also known as:Laboratory Fortified Blank (LFB)Quality Control Sample (QCS)
25Surrogates 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
26Quality Control Measures Standards and CalibrationBlanksRecovery StudiesPrecision and Accuracy StudiesMethod Detection LimitsNJQLs
27Precision 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
28Precision and Accuracy Required with a change in instrumentation or personnelSpecific to the analystOther names include:P&A, DOC, IDOC
29Method 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:
30Method 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)
31Method Detection Limit Must be performed initially for certificationMust meet criteria specified in methodMust be performed with change in instrumentation or test methodAnnually with ELCP
32New 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