Signal detection limit

Several authors have developed highly sensitive CL detection coupled to CE for ion analysis. Huang et al. [96] used luminol as a component of the separation electrolyte that prevented loss of the light signal. Detection limits of 20 zmol, 2 amol, 80 amol, 740 amol, and 100 fmol for Co(II), Cu(II), Ni(II), Fe(III), and... 

Case I - Signal Detection (A - ignored), (y- ) gives an estimate of the net signal (Ax), and the signal detection limit is determined from as discussed in the first section of... 

Case II - Analyte Detection (A - assumed). Here, the analyte- rather than signal-detection limit is calculated, but the systematic error in A, applied in the estimation of x from Equation 2c imposes systematic error bounds which must be applied to the analyte detection limit. The limit is no longer purely probabilistic in nature ( ). 

Another common way to define detection limit is from the least-squares equation of a calibration curve signal detection limit = b + 3sv, where b is the y-intercept and. v, is given by Equation 4-20. 

Methods Tracers/labels Strategy Signal Detection limit References... 

For simple RSSF UV-visible spectroscopy, the SPD linear array is adequate for a wide variety of applications (see Section 2). The MCP-SPD linear array should extend the useful wavelength range and signal detection limits to make possible studies in the UV region between 200 and 300 nm, studies at higher scan rates and studies where the signal intensity is low. Gating on a nanosecond time scale also renders these detectors suitable for use in a variety of time-resolved spectroscopies. 

A procedure was used in which electric current in a detector is proportional to analyte concentration. From previous measurements of a low concentration of analyte, it was estimated that the signal detection limit was in the low nanoampere range. Signals from seven replicate samples with a concentration about three times... 

Signal arises from what we seek to measure and noise is random variation in the instrument response. At the signal detection limit (Equation 5-2), signal is 3 times greater than noise. At the lower limit of quantitation, the signal-to-noise ratio is 10, which we can measure with moderate precision. 

The explanation of the parameters of the curves a, b and c of Figures 9 (A-D) is in Table 3. Absorption measurement sensitivity of the spectrometer is limited by the ability of the instrument to discriminate between the two nearly equal signals. Detection limit for even the most favorable cases rarely exceeds 10 moles. But fluorometric instruments are hmited only by the intensity of exciting light and the ability to detect low light levels. Under the ideal conditions the concentrations of IO12 moles can be measured. 

The detection limit metric, as used here, is different from the sensitivity metric. Unlike sensitivity, which deals only with absolute signal, detection limits consider signal-to-noise ratio (S/N). Detection limits also consider the entire analytical method including sample extraction efficiencies and injection volumes in addition to the response characteristics and noise levels of the mass spectrometer signal. Detection limits are therefore analytically more relevant than sensitivity. Sensitivity measurements allow one to estimate the theoretical limits for the quantity of a compound that can be detected, whereas detection limits define what can actually be achieved in a practical setting to provide a meaningful result toward the solution of some application of mass spectrometry. 

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