跑[HPLC]的專有名詞:[檢出限量]和[偵測極限]的定義?

Question

因為最近在以[HPLC]儀器分析油脂中的某種色素A,有二個專有名詞,我一直搞不清楚!!!1.何謂色素A的[檢出限量]?2.何謂色素A的[偵測極限]?3.色素A的[檢出限量]和[偵測極限]兩者之間的意思有何不同?麻煩請儀器分析化學的達人們幫我說明一下,謝謝!!!

Yy大師: 文字敘述仍然有點艱深難懂,有沒有計算題的範例可以讓我比較好了解?謝謝!!!

Answer 1

偵測極限Limit of DetectionThe limit of detection (LOD) is defined as the lowest concentration of an analyte in a sample that can be detected, not quantitated. 偵測極限:定義為分析物在樣品中可被偵測的最低濃度(不是定量)It is expressed as a concentration at a specified signal-to-noise ratio, usually three-to-one.通常以濃度為便單位 最低可檢出濃度訊號起碼為基線雜訊noise的3倍表達之 LOD是一種限度檢驗效能指標，它既反映方法與儀器的靈敏度和噪音的大小，也表明樣品經 處理後空白(基底)值的高低檢出限量Limit of QuantitationThe Limit of Quantitation (LOQ) is defined as the lowest concentration of an analyte in a sample that can be determined with acceptable precision and accuracy under the stated operational conditions of the method. 檢出極限定義為分析物在樣品中可被定量而且是準確性可被接受的最低濃度Sometimes a signal-to-noise ratio of ten-to-one is used to determine LOQ. 通常是以signal-to-noise ratio訊號對雜訊比 10倍的濃度表達之This signal-to-noise ratio is a good rule of thumb, but it should be remembered that the determination of LOQ is a compromise between the concentration and the required precision and accuracy. That is, as the LOQ concentration level decreases, the precision increases. If better precision is required, a higher concentration must be reported for LOQ.  http://www.nlfd.gov.tw/uploadfile/doc/AOACLETTER/3224/2005-11.pdf兩者之間差別要點是可靠準確性 如果雜訊少 則訊號對雜訊比為3倍的濃度訊號也可作為檢出極限 但是這是很難得到的 此外如果未檢出XX 如檢出限較高，應設法降低最低檢出限。在最低檢出限條件下，對照品能檢出時的最小進樣量的供試液量，進樣， 如沒檢出，可認為製劑或樣品在此檢出限下未檢出

2006-08-11 11:13:32 補充：
請參考:
http://www.lcgceurope.com/lcgceurope/article/articleDetail.jsp?id=284453&pageID=1
一些hplc data處理軟件內建S/N自動計算 人手算的請參考上述網頁 簡單說 以標準樣品最低可檢測濃度注射後 把層析圖準樣品訊號出現位置放大 樣品訊號從雜訊中間高度至尖峰高度為S 基線雜訊高度為N

2006-08-11 11:19:58 補充：
假設S=4cm N=1cm S/N14/1=4 則此標準樣品濃度仍沒達偵測極限最低濃度 標準樣品需稀釋再注射 至S=3cm N=1cm S/N=3 才是偵測極限 但如果要求檢出限量則標準樣品濃度需比以上的更濃 才得S/N=10