Peak fidelity

An alternative definition of peak distortion is peak fidelity or the ratio of the output peak height to the input peak height. Peak fidelity (f) can be approximated by ... 

For a peak fidelity of 98%, a o/t ratio of 4.92 or greater Is required. In other words, the standard deviation of the peak mxist be greater than 4.92 V For sharp, narrow peaks, the detector time constant can oe reduced by reducing the effective detector volume. Increasing the make-up gas flow rate, or both. However, Increasing the make-up gas flow rate decreases the detector responses, and results In a loss In detectivity If the noise remains constant. 

The stationary phase should be a thin film (0.1pm) and the column must operate with a steep programmed temperature gradient (e.g. 100 °C/min), now possible with modern GC instruments. Detector-response time also plays a significant role in achieving the best peak fidelity. 

Inside, on the back of your door, is the colorful FBI seal and motto Fidelity, Bravery, Integrity. The peaked beveled edge circumscribing the seal symbolizes the severe challenges confronting the FBI and the ruggedness of the organization. 

Fig. 8.3. A Acquired high SNR data and simulated noisy spectra (peak-to-peak noise = 0.001, 0.01, 0.1, and 0.4 a.u.), showing the degradation in data quality. Spectra are offset for clarity. B Spectra after noise reduction demonstrate the dramatic gains possible by chemometric methods. C Noise reduction was implemented to classify breast tissue and application of noise rejection allowed the same quality of classification (accuracy) to be recovered at higher noise levels. D In another example, image fidelity (here the nitrile stretching vibrational mode at 2227 cm-1) is much enhanced as a result of spectral noise rejection A and C are reproduced from Reddy and Bhargava, Submitted [165], D is reproduced from [43]...

Figure 3 A single GCxGC peak enlarged by bilinear interpolation (left) and nearest-neighbor interpolation (right). Bilinear interpolation yields a truer (i.e, higher fidelity), more pleasing spot but nearest-neighbor interpolation more clearly shows the individual data points.

The method of detection is the last factor. Fidelity of the concentration profile provided by the detector is a function of a number of parameters including mixing in the detector volume, mass or heat transfer (if a thermal device is used) to the detector, and slow response characteristics of the associated electronics. The situation of immobilized enzyme reactors is analogous [24] to the quantitative treatments of these parameters presented by several authors for chromatographic peaks [363, 364]. 

It is not easy to determine which factors play the greatest role in obtaining good accuracy and precision. One must consider the assumptions inherent in the theory as well as the chemical, mechanical, and instrumental parameters. In general, gas chromatographic methods agree within 1-5% with other physicochemical methods. For example, Hussam and Carr (22) showed that in the measurement of vapor/liquid equilibria via headspace GC, complex thermodynamic and analytical correction factors were needed. These often came from other experimental measurements that were not necessarily accurately known. Another source of significant error can be in determination of the mass of stationary phase contained within the column (59). Other sources of error include measurement of holdup time (60), flowrate, sample mass, response factors, peak area, or baseline fidelity. 

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