Ultraviolet line separation

Ultraviolet resonance Raman Wide-line separation Wild type... 

Other reports deal with individual elements, such as Ni [1, 86, 87] or Fe [11,84]. The efficiency [71—73] of flame methods (AAS) has been compared with flameless techniques (NFAAS) (Table 6). Because of their significance there have been attempts to determine the elements P [38] and S [78] directly with AAS. This, however, requires a device which can measure ultraviolet lines (ca. 180 nm) with sufficient sensitivity. Good results can also be achieved by gas chromatographic separation and successive AAS determination [92] and simultaneous multielement analysis with a Vidicon-detector has been tried [68] because the speed with which the information is gained can be very important in practice. Some work [39, 53] reports on the problem of molecular bands which can appear when working with... 

NH2 was also observed by Ginns and Symons [12] in aqueous glasses containing sodium or potassium azide which were exposed to Co 7-rays or 254 nm ultraviolet light at 77°K. These authors also observed features in the ESR spectra which are characteristic of neutral nitrogen atoms, namely, three hyperfine lines separated by 5.0 G. However, fine structure expected for the 3/2 ground state of N was not observed. Further, it is unclear from reference [12] whether the... 

In liquid chromatography, in contrast to gas chromatography [see Section 9.2(2)], derivatives are almost invariably prepared to enhance the response of a particular detector to the substance of analytical interest. For example, with compounds lacking an ultraviolet chromophore in the 254 nm region but having a reactive functional group, derivatisation provides a means of introducing into the molecule a chromophore suitable for its detection. Derivative preparation can be carried out either prior to the separation (pre-column derivatisation) or afterwards (post-column derivatisation). The most commonly used techniques are pre-column off-line and post-column on-line derivatisation. 

When the solvent has moved to the top of the plate (10-20 cm) or, preferably, to a line that has been scored across the plate about 1 cm from the top edge (Figure 3.4) the plate is removed and dried quickly. The separated bands can be visualized by using a suitable reagent or by viewing under ultraviolet light and their positions marked. 

The besl isolation of radiant energy can he achieved with flame spectrometers that incorporate either a prism sir grating monochromator, those with prisms having variable gauged entrance and exii slits. Both these spectrometers provide a continuous selection of wavelengths with resolving power sufficient lo separate completely most of the easily excited emission lines, and afford freedom from scattered radiation sufficient lo minimize interferences. Fused silica or quartz optical components are necessary to permit measurements in Ihe ultraviolet portion of the spectrum below 350 nanometers Sec also Analysis (Chemical) Atomic Spectroscopy Photometers and Spectra Instruments. 

Ultraviolet-visible (UV-Vis) spectrophotometric detectors are used to monitor chromatographic separations. However, this type of detection offers very little specificity. Element specific detectors are much more useful and important. Atomic absorption spectrometry (AAS), inductively coupled plasma-atomic emission spectroscopy (ICPAES) and inductively coupled plasma-mass spectrometry (ICP-MS) are often used in current studies. The highest sensitivity is achieved by graphite furnace-AAS and ICP-MS. The former is used off-line while the latter is coupled to the chromatographic column and is used on-line . 

It is convenient for photochemical studies in the near ultraviolet to use the mercury resonance line at 3130 A. from a medium pressure mercury arc as a light source. This particular wavelength can be separated in high intensity from the remainder of the spectrum by suitable filters. 

The advantages of an on-line LC-MS approach are many. Both techniques show high separation power and their combination on-line is a powerful tool for identification purposes as well as quantitative studies. Many detectors are available for high-performance liquid chromatography (HPLC) ultraviolet (UV), conductivity, electrochemical, fluorescence, refractometer, and so forth. Unfortunately, most of them lack specificity, selectivity, and sensitivity. Hence, identification of unknown compounds is actually impossible. 

Problems are often found in many analytical methods due to the complex nature of the mixture and the lack of adequate detection means, thus leading to poor quantitation techniques. For the routine separation of a broad range of surfactants, high-performance liquid chromatography (HPLC) appears to be the most cost-effective [7-18]. Ultraviolet (UV) and fluorescence detectors are commonly used in HPLC analysis of surfactants because of their compatibility with separation techniques requiring gradient elution. However, these detectors have two inherent limitations (a) the detector response is dependent on molecular structure (i.e., degree of aromaticity and type of substitution) and (b) only species with a chromophore can be detected. To overcome those limitations, postcolumn reaction detectors, based on extraction of fluorescent ion pairs, were introduced for on-line detection of alkylsul-... 

A prism will separate the light emitted by hydrogen into four visible lines of specific frequencies (colors). Hydrogen also emits light in the non-visible ultraviolet and infrared parts of the spectrum. ... 

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