17十八章QAandQC

1环境监测过程中的质量控制QualityControl2QualityControlvs.QualityAssurance(质量控制与质量保证)Qualitycontrolisaseriesofmeasurementsusedtoassessthequalityoftheanalyticaldata–质量控制是一系列测量,以评价分析数据的质量–Howwellisthetestfulfillingrequirements?•试验满足要求的程度如何?3QualityControl（QC)vs.QualityAssurance(QA)(质量控制与质量保证)Qualityassuranceisamanagementplantoensuretheintegrityofdata(asystem)–质量保证是一种管理计划,以确保数据的完整性(一种体系)–Providesconfidencethatrequirementswillbefulfilled•为要求是否得到满足提供信心4QualitiesofAnalyticalMethods分析方法的质量Accuracy(准确度)Precision(精密度)Selectivity(选择性)Sensitivity(灵敏度)Linearity(线性)Range(范围)Robustness/Ruggedness(稳健性/稳度)5Accuracy(准确度)Degreeofagreementbetweenthe“true”valueandthemeasuredvalue(真值与测量值之间的一致程度)6Accuracy(准确度)Whatisthe“true”value?(什么是真值)•Theoretical(理论值)•Consensus(公议值)•Accepted/Assigned(可接受/赋值)7Accuracy(准确度)Expressedas(表示为)–theratiobetweentheassayedvalueandthe“true”value(%recovery)•分析值与真值间的比(%回收率)–thedifferencebetweentheassayandtheacceptedtruevalue(%Error)•分析与可接受真值间的差(%误差)8Precision(精密度)Closenessofagreementbetweenmeasurements(测量间的一致程度)–Repeatability(r)–sameconditions,shorttimeinterval(samerun)–shorttermprecision•重复性(r)-相同条件下\短时间间隔-短期内精密度–Intermediateprecision–samelabdifferentday,analyst,instrument•中间精密度-同一实验室不同日期,分析人员,仪器–Reproducibility(R)–agreementbetweenbatchesorbetweenlabs•复现性®-批间或实验室间的一致性9Precision(精密度)ExpressedasStandardDeviation,RelativeStandardDeviationorRelativePercentDifference–表示为标准偏差、相对标准偏差、相对百分差10Sensitivity（灵敏度）Degreeofresponsetoachangeinanalyteconcentration–resolution–被分析物浓度变化的响应变化程度-分辨率Lowestconcentrationthatcanbedistinguishedfrombackgroundnoise–detectionlimit–能从背景噪音识别出的最低浓度-检测限11Sensitivity（灵敏度）Limitofdetectionvs.Limitofquantification（检测限与定量限）–Limitofdetection(LOD)isthelevelthatwecansaywhetherananalyteispresentornot•检测限是我们判断被分析物是否存在的含量水平–Limitofquantitation(LOQ)isthelevelthatwecanquantifytheanalytewithaspecifiedaccuracy(20%)•定量限是我们按规定准确度（20%）能对被分析物量化的含量水平12Selectivity（选择性）Abilitytodetecttheanalyteinacomplexmatrix–检测复杂基体中被析物的能力Abilitytoexcludenon-analytespeciesfromsignal–通过信号排除非被分析物的能力Usuallyinverselyrelatedtosensitivity–通常与灵敏度成反比13Linearity（线性）Abilitytoproducearesponsethatisdirectlyproportionaltotheconcentrationoftheanalyte–所产生的反应与被分析物浓度成正比的能力Onlyholdstruewithinagivenrange–只在给定范围内是真实的14Linearity（线性）Expressedascorrelationcoefficient(r)orcoefficientofdetermination(r2)–表示为相关系数(r)或测定系数(r2)r2=ssxy2/ssxxssyy15Range（范围）Theintervalbetweenthehighestandlowestconcentrationforwhichthemethodhasshowntohavesuitablelevelsofaccuracy,precisionandlinearity.–在方法具有适宜的准确度、精密度和线性的条件下，最高和最低浓度范围16Robustness（稳健性）Abilityofmethodtobeunaffectedbysmallchangesinmethod(internal)conditions（方法不因条件的较小变化（内部）而受影响的能力）–Temperature（温度）–pH–Compositionofmobilephase（流动相组成）Usefulwhenmethodmovesfromdevelopmenttoproduction（从方法开发到使用很有用）19QualityControlMeasures质量控制手段Calibrationstandards（校准标准）Blanks（空白）Recoverystudies（回收率研究）Precisionstudies（精密度研究）Sensitivitystudies（灵敏度研究）–DetectionLimit（检测限）–Quantitationlimit（定量限）20Calibration(校准)Directlyaffectsaccuracy(直接影响准确度)Preparationofstandards(标准制备)–Matrix(基体)–Stability(稳定性)Signaltype:peakarea,peakheight–信号类型:峰面积,峰高21Calibration(校准)Calibrationcurves(校准曲线)–1storder–straightline(一级-直线)–Quadratic–acceptablebutrequiresmorepoints(二次方程-可以接受,但需要更多点)Internalstandards(内标)–Refinescalibrationresponse(增强校准响应)–Addedtosamplesandstandards(加入样品和标准中)–Mustbehaveliketheanalyte(象被分析物一样表现)–Cannotbeinsamples–rareelements,deuteratedcompounds(样品中没有-稀有元素,含重氘的化合物)22Externalmethod外标法外标法也称为标准曲线法。特点及要求：外标法不使用校正因子，准确性较高;操作条件变化对结果准确性影响较大;对进样量的准确性控制要求较高，适用于大批量试样的快速分析。23Internalmethod内标法内标物要满足以下要求：（1）试样中不含有该物质；（2）与被测组分性质比较接近；（3）不与试样发生化学反应；（4）出峰位置应位于被测组分附近，且无组分峰影响。试样配制：准确称取一定量的试样W，加入一定量内标物mS计算式：SsiisiSsiisiAfAfmmAfAfmm'''';100100100%''''SsiisSsiisiiAfAfWmWAfAfmWmc24Calibration(校准)Calibrationverification(校准验证)–Repeatedcalibrationstandard•重复校准标准–Intervalmaybeevery20samples(ICPMS)oronceeveryrun(GC-FID)•间隔:20个样品(ICPMS)•每次(GC-FID)25Blanks(空白)Usedtomonitorcontamination(监测污染)–Reagentblanks(试剂空白)–Instrumentblanks(仪器空白)–Fieldblanks(场地空白)–Tripblanks(路途空白)–Procedural/methodblanks(程序/方法空白)–Matrixblanks(基体空白)–Others?(其它)26RecoveryStudies（回收率研究）Usedtomonitoraccuracy（监测准确度）–Matrixspikes（基体加标）–Fortifiedblanks（增加加标）–Surrogates（替代）–ReferenceMaterials（参考物质）27MatrixSpikes（基体加标）Knownamountofanalyteaddedtosample–在样品中加入已知量的被分析物Importantwithcomplexmatrix–对复杂基体很重要Generallyaddedpriortoextractionprocess（通常在提取前加入）Sometimesdifficulttoknowamounttospikeaheadoftime（有时很难提前知道加标量）28FortifiedBlanks（增强空白）Analytespikeintoreagentblank–在试剂空白中加入被分析物标样Carriedthroughsamplepreparationprocess–在样品准备过程中加入29Surrogate（替代）Compoundwithsimilarpropertiestotargetanalyte–与被分析物具有相近特性的化合物Addedtoallsamples(unknownsandQC)butnotstandards–在所有样品(未知的和QC)中加入，但标样中不加Usedtomonitormethodperformanceonasample(matrix)specificbasis–应基于特定样品（基体），用于监测方法表现30SampleSurrogatePretreatmentandclean-upInstrumentAnalysisInternalStandardSurrogatestandard:TomonitortheperformanceofthewholeanalyticalprocessInternalStandard:Forquantitativeinstrumentalanalysis31Isotopedilution(同位素稀释法）在待分析样品中加入已知量