Chromatograms ultraviolet

Specifications, Analysis, and Toxicity. Dicyandiamide is identified quaHtatively by paper chromatography and quantitatively by ultraviolet spectrometry of the chromatogram. More commonly, total nitrogen analysis is used as a purity control or the dicyandiamide is converted by hydrolysis to guanylurea, which is determined gravimetrically as the nickel salt (50). Methods based on the precipitation of silver dicyandiamide picrate are sometimes used (51). Dicyandiamide can also be titrated with tetrabutylammonium hydroxide ia pyridine solution. Table 4 gives a typical analysis of a commercial sample. Dicyandiamide is essentially nontoxic. It may, however, cause dermatitis. 

The product may be analyzed by gas chromatography on an 8 mm. x21S cm. column heated to 220-240° and packed with Dow-Corning Silicone Fluid No. 550 suspended on 50-80 mesh ground firebrick. The chromatogram obtained with this column exhibits a single major peak. The ultraviolet spectrum of an ethanol solution of the product has a maxium at 250 m>i (s = 17,200). 

Paper chromatography (benzene-chloroform 1 1—formamide system) of representative chromatogram fractions indicates the presence of a small quantity of a more polar ultraviolet absorbing component that gives a negative blue tetrazolium test and a very polar component (no ultraviolet negative tetrazolium test). These materials have not been characterized. 

Carry out prewashing of the plate with a mixture of 1 volume of concentrated ammonia R, 40 volumes of methanol R and 60 volumes of chloroform R. Allow the plate to dry in air. Apply separately to the plate 5 pL of each solution. Develop over a bath of 15 cm using the mixture of solvents prescribed for prewashing. Allow the plate to dry in air and examine in ultraviolet light at 254 nm. The principal spot in the chromatogram obtained with the test solution is similar in position and size to the principal spot in the chromatogram obtained with the reference solution. 

There is no change in the thin layer chromatogram (single spot) or in the fluorescence or ultraviolet spectra after irradiation in methanol with a xenon lamp for 20 hours. It is therefore concluded that there is no significant photodegradation of griseofulvin under reasonable conditions of light exposure (7). 

The ultraviolet (UV) absorption HPLC detector is basically a UV spectrophotometer that measures a flowing solution rather than a static solution. It has a light source, a wavelength selector, and a phototube like an ordinary spectrophotometer. The cuvette is a flow cell, through which the column effluent flows. As the mobile phase elutes, the chromatogram traces a line at zero absorbance, but when a mixture... 

The inclusion of a fluorescent dye into thin-layer plates can be used to detect substances that quench its fluorescence and so result in dark zones when the chromatogram is examined under ultraviolet radiation. Autoradiography can also be used in thin-layer chromatography and electrophoresis when samples are radio-labelled. 

Figure 6 shows the gas chromatogram of the reaction products obtained by the ultraviolet irradiation to phenylazide dissolved in 3-methyl-1-butene. It has four peaks from a to d. Peaks a and c agree with those of aniline and aziridine in their retention times, respectively. In this case, the peak due to azobenzene did... 

By a method similar to that described in the last section phenylazide in cyclohexene was irradiated with ultraviolet radiation and unreacted cyclohexene was distilled off with evaporation. The residue was extracted with n-hexane. The extract was separated into several products by gas and liquid chromatography. The gas chromatogram and the liquid chromatogram are shown in Figures 7 and 8, which give five peaks from A to E, and four peaks from A to D, respectively in addition to the peak due to the solvent. Peaks A and A were determined to be aniline by their retention times. Peaks B and C are due to 3,3 -bicyclohexenyl. Peaks C and D are those of aziridine[9] and the product which was formed by the insertion of phenylnitrene to C-H bond of cyclohexene. ... 

Infrared spectra were recorded on a Perkin Elmer Model 567 Spectrophotometer. Ultraviolet spectra were obtained on a Cary 1756 Spectrophotometer. Gas chromatograms were recorded on a Tracor Model 220 with electron capture detector. High pressure liquid chromatography studies were conducted with a Waters Model ALC-200 with ultraviolet and refractive index detectors. 

Chromatography and Electrophoresis of Antigens. Cotton dust (20-30 mg) was dissolved in water and passed through a small column (30 x 1.5 cm id) packed with 3 g of Sephadex G-75 that had been preswelled in water. Chromatograms were obtained with an LKB Uvicord ultraviolet monitor and a chopper bar recorder. Volumes of 5 ml each were collected in test tubes with an automatic fraction collector. Two components were detected at 250 nm. Samples of 10 mg were analyzed by disc gel electrophoresis according to procedures described by Davis (36), and Zacharius (37). 

The separation of a mixture of aromatic compounds (benzene, naphthalene, anthracene, chrysenes, and benz(a)pyrene) at 31 bar is shown in Figure 3. This chromatogram was obtained with a Perkin Elmer Model 250 ultraviolet detector with the high-pressure cell placed after the cooling heat exchanger and before the flow control valve. A similar chromatogram is obtained with an Isco Model UAA with a 10 mm micro cell placed after the flow control valve. 

Fig. 29.8.1 Chromatograms of a blank kidney sample (A), a kidney sample (B) fortified with 4 ppm of oxytetracycline (—), and 250 ppb of each tetracycline (—), and ultraviolet spectra (C) of the corresponding tetracyclines. Peaks OTC, oxytetracycline TC, tetracycline DMTC, demethylchlortetracycline CTC, chlortetracycline MC, methacycline DC, doxycycline. (From Ref. 296.). 

Analytes are detected at the outlet by their ability to absorb ultraviolet radiation from the lamp in Figure 0-4a. The graph of detector response versus time in Figure 0-5 is called a chromatogram. Theobromine and caffeine are the major peaks in the chromatogram. Small peaks arise from other substances extracted from the chocolate. 

Figure 22-20 Chromatograms of herbicides (designated 1-6) spiked into river water at a level near 1 ppb demonstrate increased signal-to-noise ratio in selected ion monitoring, (o) Ultraviolet detection at 240 nm (b) Electrospray reconstructed total ion chromatogram, (c) Electrospray selected ion monitoring at m/z 312. [From A. Lagana. G. Fago, and A. Marino, "Simultaneous Determination of imidazoiinone Herbicides from Soil and Natural Waters."Anal. Chem. 1998, 70.121.]...

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