【正文】 Quantitation Levels 定性和定量水平 Limit of detection: LOD檢出限 Limit of quantitation: LOQ定量限 There are numerous definitions and approaches for estimating these levels有很多定義和方法評估這兩個量 LOD and LOQ are important parameters for residue methods在殘留分析中 LOD 和 LOQ 是重要參數(shù) 42 來自 中國最大的數(shù)據(jù)庫下載 LOD Determination: Example 1 例一： LOD測定 Common approach for residue analysis:農(nóng)殘分析常用方法 ? spike 5 portions of blank sample at the estimated LOD在估計的 LOD水平上測定 5個加標(biāo)樣品 ? Calculate the standard deviation, and multiply by 3 to get the ，乘以 3，得到 LOD Must be able to show that the peaks are identifiable at this calculated LOD (ie. Example chromatogram)必須能夠證明在計算出的 LOD 值水平上色譜峰能夠識別（例如氣象色譜圖） 43 來自 中國最大的數(shù)據(jù)庫下載 LOQ Determination: Example 1 例一： LOQ測定 The example given for LOD determination may also be used to calculate the LOQ ? LOD測定的例子也可用于 LOQ的計算 Multiply the standard deviation by 10 to get the LOQ 標(biāo)準(zhǔn)偏差乘以 10即 LOQ Must also be able to show that the precision is within a reasonable range (typically 20%)* at the LOQ LOQ水平的精密度應(yīng)在合理范圍內(nèi) (典型的 20%此值可能在參考方法中或由客戶規(guī)定） *(this value may be specified in the reference method or by the customer) 44 來自 中國最大的數(shù)據(jù)庫下載 LOD and LOQ: Example 2 例二： LOD 和 LOQ Signaltonoise ratio calculations信噪比計算 ? Not based on statistics非統(tǒng)計學(xué)原理 Example: Chromatography data如色譜數(shù)據(jù) ? The “Signal” refers to the magnitude of the analyte signal above the background”信號 ”是指大于背景的被測物信號值 ? “Noise” refers to the fluctuations in the baseline of the chromatogram at or near the retention time of the analyte”噪聲”是指被測物保留時間附近色譜基線的波動 45 來自 中國最大的數(shù)據(jù)庫下載 LOD and LOQ: Example 2 例二： LOD 和 LOQ The signaltonoise (S/N) ratio generally must be信噪比通常必須 : ? Greater than 3:1 at the LOD 在 LOD水平上大于 3:1 ? Greater than 10:1 at the LOQ 在 LOQ水平上大于 10:1 The ratios may differ depending on the method and application根據(jù)分析方法和應(yīng)用的差異該比值是不同的 46 來自 中國最大的數(shù)據(jù)庫下載 LOD and LOQ Determination LOD 和 LOQ 的測定 Choose the method of determination most appropriate for the application選擇最適宜的方法 Document the definition and approach used記錄定義和方法 If working under regulatory guidelines (eg. EPA, FDA), the approach prescribed for the program needs to be followed如果按照 EPA, FDA等法規(guī)指南定義進(jìn)行，須遵守其規(guī)定 47 來自 中國最大的數(shù)據(jù)庫下載 Precision and Accuracy 精密度和準(zhǔn)確度 May be determined by analysis of reference materials, if available 如果有 ,可以通過參考物質(zhì)的分析進(jìn)行測定 If reference materials not available若無參考物質(zhì) : ? Determine precision and accuracy using matrix blanks and fortified (spiked) matrix blanks通過基體空白和添加基體空白測定精密度和準(zhǔn)確度 48 來自 中國最大的數(shù)據(jù)庫下載 Preparation of Spikes 加標(biāo)樣品的制備 Add a known quantity of the analyte(s) to the matrix blank prior to sample preparation在樣品預(yù)處理前，將已知量的被測物加入的基體空白中 Treat exactly like a sample according to procedures in the method按照方法中的程序?qū)⑵湟暈楸粶y樣品進(jìn)行預(yù)處理和測定 49 來自 中國最大的數(shù)據(jù)庫下載 Critical Points Regarding Spikes 加標(biāo)的關(guān)鍵點 Spiking procedure must be very precise and accurate加標(biāo)過程必須準(zhǔn)確 Document steps and techniques used for spiking加標(biāo)步驟和技術(shù)形成文件 Spike at the right step: typically prior to any sample extraction steps按正確步驟加標(biāo)：應(yīng)在樣品萃取之前加標(biāo) ? Spiking may occur at a variety of steps during method development or validation study to aid in troubleshooting recovery problems 在方法開發(fā)或確認(rèn)研究時，加標(biāo)可在不同步驟中加入，來幫助解決回收率的問題 50 來自 中國最大的數(shù)據(jù)庫下載 Spike Recovery Data 加標(biāo)回收數(shù)據(jù) The assumption is made that the spiked sample is chemically and physically representative of the actual samples加標(biāo)樣品在理化性質(zhì)上假設(shè)與實際樣品相同 Spike recovery data do not necessarily reveal the true recovery of the analyte from the sample加標(biāo)回收數(shù)據(jù)不必反映樣品被測物的實際回收率 51 來自 中國最大的數(shù)據(jù)庫下載 Precision and Accuracy 精密度和準(zhǔn)確度 A minimum of 5 recovery determinations at each of 5 calibration levels must be 5個校準(zhǔn)水平下必須每個水平至少測定 5個加標(biāo)回收樣品 One set of recovery determinations must include a blank, and 5 or more nonzero spikes, including the LOQ as the low level.每組加標(biāo)樣品必須包括空白、 5個以上非零加標(biāo)，其中低值應(yīng)為 LOQ 52 來自 中國最大的數(shù)據(jù)庫下載 Precision and Accuracy 精密度和準(zhǔn)確度 The linear range of the method, as well as precision and accuracy are calculated from these 到方法線性范圍，以及精密度和準(zhǔn)