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第13楼2010/12/22
ICH Q2关于检测限是这样描述的：
6. DETECTION LIMIT
Several approaches for determining the detection limit are possible, depending on whether the procedure is a non-instrumental or instrumental. Approaches other than those listed below may be acceptable.
6.1. Based on Visual Evaluation
Visual evaluation may be used for non-instrumental methods but may also be used with instrumental methods.
The detection limit is determined by the analysis of samples with known concentrations of analyte and by establishing the minimum level at which the analyte can be reliably detected.
6.2. Based on Signal-to-Noise
This approach can only be applied to analytical procedures which exhibit baseline noise.
Determination of the signal-to-noise ratio is performed by comparing measured signals from samples with known low concentrations of analyte with those of blank samples and establishing the minimum concentration at which the analyte can be reliably detected. A signal-to-noise ratio between 3 or 2:1 is generally considered acceptable for estimating the detection limit.
6.3 Based on the Standard Deviation of the Response and the Slope
The detection limit (DL) may be expressed as: DL = 3.3 σ/ S
where σ = the standard deviation of the response
S = the slope of the calibration curve
The slope S may be estimated from the calibration curve of the analyte. The estimate of σ may be carried out in a variety of ways, for example:
6.3.1 Based on the Standard Deviation of the Blank
Measurement of the magnitude of analytical background response is performed by analyzing an appropriate number of blank samples and calculating the standard deviation of these responses.
6.3.2 Based on the Calibration Curve
A specific calibration curve should be studied using samples containing an analyte in the range of DL. The residual standard deviation of a regression line or the standard deviation of y-intercepts of regression lines may be used as the standard deviation.
6.4 Recommended Data
The detection limit and the method used for determining the detection limit should be presented. If DL is determined based on visual evaluation or based on signal to noise ratio, the presentation of the relevant chromatograms is considered acceptable for justification.
In cases where an estimated value for the detection limit is obtained by calculation or extrapolation, this estimate may subsequently be validated by the independent analysis of a suitable number of samples known to be near or prepared at the detection limit.
6．检测限
根据分析方法是采用非仪器分析还是仪器分析可用几种方法来确定检测限度，除了下面所列的方法外其他的方法也可能被接受。
6．1 根据直观评价
直观评价可以用于非仪器分析方法，也可用于仪器分析方法。
检测限度的测定是通过对一系列已知浓度分析物的样品进行分析，并以能准确测得被分析物的最小量来建立。
6．2 根据信噪比
该方法仪适用于出现基线噪音的分析方法。
信噪比的测定是通过比较含已知低浓度被分析物的样品与空白样品的测试信号，确定被分析物可被确切地检测的最小浓度，当信噪比在3：1 或2：1 时的检测限度通常被接受。
6．3 根据响应值的标准差和斜率
检测限度（DL）表示为：DL=3.3δ/S
δ：响应值的标准差
S：校正曲线的斜率
斜率 S 可从被分析物的校正曲线来估算，δ的值可由多种途径估算。如：
6．3．1 根据空白的标准差
通过几份空白样品的分析，然后计算其响应值的标准差，测出分析背景响应值的大小。
6．3．2 根据校正曲线
通过对含有DL 范围内被分析物样品的分析来研究其标准曲线，回归线的剩余标难差或回归线的y 轴截距标准差都可作为标准差。
6．4 推荐数据
必须同时提供检测限度和测定检测限度的方法。如果见是根据直观评估或信噪比得来的，应提供相关的一些色谱图。
如通过计算或外推法得到检测限度的估算值，可对一系列接近或等于检测限度样品的逐个分析来论证这一估算值。