Derivative spectrometry with a vidicon detector

Design and evaluation of a vidicon based derivative spectrometer

“…The first derivative spectra for aqueous solutions of sodium excited in an air-acetylene flame were used as an early test of the viability of the concept. These spectra were generated with a 200-ms integration period followed by a 100-ms scan time without dark current correction, and were similar to those reported earlier (12). Regression analysis of sodium concentrations computed from peak-to-peak derivative signals vs. added amounts in the range from 0.01 to 1.0 mg/L yielded a slope of 1.02 ± 0.04, an intercept of -0.026 ± 0.018 and a correlation coefficient of 0.999.…”

“…When signal averaging was to be performed, the dark current signal was inverted and averaged for a period of time equal to the averaging time to be used for the signal; then points in each spectral scan were added algebraically to corresponding points in the dark current "spectrum" so that the time required for dark current correction was minimized. RESULTS AND DISCUSSION An earlier report included preliminary data to show that the vidicon based system is a viable approach to derivative spectroscopy and illustrated that derivative signals are linear with intensity over at least two orders of magnitude (12). In our continuing work with this system, we concluded that some problems we encountered were related to the fact that our custom designed system utilized a magnetic deflection tube, and our study was expanded to include an electrostatic deflection tube.…”

“…An early report from this laboratory described derivative spectra computed from the output of a silicon target vidicon based spectrometer (7). A subsequent report gave a brief description of a vidicon based derivative spectrometer in which first derivative spectra were generated directly by the spectrometer used in conjunction with a phase sensitive lock-in amplifier (12). In this latter system, wavelength modulation is accomplished by incorporating the modulation into the electronic deflection of the interrogating electron beam in the vidicon along the wavelength axis.…”

Fluorescence spectrometry with optoelectronic image detectors

“…Differentiation of raw spectral data has the equivalent effect of high-pass filtering, with the bandwidth of the filter decreasing with the order of differentiation. When applied to various spectrometric systems (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33), differentiation generally leads to two basic advantages: secondary, weak spectral features, e.g., slopes and peak shoulders are emphasized and thus become more easily identified and interpreted; and systematic errors, such as low-frequency noise, drift in light source, continuum background and stray light, are removed. However, the second advantage is achieved at the expense of enhancing random noise, e.g., white and other multiplicative noise sources (23 The effect of differentiation on SNR and peak distortion depends on the width of DS (AX), but in a manner fundamentally different from that in which smoothing is affected by the modulation depth (MD).…”

Determination of anions in boiler blow-down water with ion chromatography

“…We have work under way to determine if this technique offers any significant advantage for chromatographic processes. The vidicon detector offers a convenient approach for derivative spectroscopy (15,16) and there may be useful applications of derivative spectra for liquid chromatography. Finally, although this paper has emphasized the absorption process, vidicon detectors can also be used as fluorescence detectors (17), and multiwavelength fluorescence detection should offer real advantages in liquid chromatography.We conclude from this work that the silicon target vidicon is a viable multiwavelength detector for liquid chromatog-raphy, that it offers several potential advantages over single wavelength detectors, and that there still are several aspects of the concept which merit attention.…”