Sulfur fluorescence intensities

Naik et al (11) extracted hydralazine hydrochloride from tablets with 50 percent aqueous methanol and mixed a portion of the extract with 99 volumes of concentrated sulfuric acid to obtain fluorescence at 353 nm with excitation at 320 nm. The fluorescence intensity varied linearly with concentration in the range 2 to 8 ig hydralazine hydrochloride per ml. Injections were analyzed similarly. 

The addition of halide ions to 0.1M sulfuric acid solutions of triprolidine hydrochloride has a quenching effect on the fluorescent intensity. The degree of quenching is I > Br >C1 > F. A concentration of 10 M Cl has little effect on the fluorescent intensity, while 0.1M Cl reduces the intensity by approximately 75% of the chloride-free sulfuric acid solution. 

The Dp and Dq are the diffusion coefficients of probe and quencher, respectively, N is the number molecules per millimole, andp is a factor that is related to the probability of each collision causing quenching and to the radius of interaction of probe and quencher. A more detailed treatment of fluorescence quenching including multiexponential intensity decays and static quenching is given elsewhere/635 There are many known collisional quenchers (analytes) which alter the fluorescence intensity and decay time. These include O2/19 2( 29 64 66) halides,(67 69) chlorinated hydrocarbons/705 iodide/715 bromate/725 xenon/735 acrylamide/745 succinimide/755 sulfur dioxide/765 and halothane/775 to name a few. 

One AHH fluorescence unit equals the fluorescence intensity of a 3 ug/ml quinine sulfate 2H20 in 0.1 N sulfuric acid solution (excitation A 425 nm, emission a 555 nm). 7-Ethoxyresorufin deethylase activity was assayed essentially as described by Burke and Mayer (13) at a 7-ethoxyresorufin concentration of 2 yM, a final pH of 7.8, and an incubation temperature of 30° (14). 

The relation between fluorescence intensity and structure was studied by Goldzieher et al. [113]. For this work, 0.2 mL of an ethanolic steroid solution was added to 1 mL of 90% (v/v) sulfuric acid, the mixture heated at 80°C for 10 minutes, and finally diluted with 4.0 mL of 65% (v/v) sulfuric acid. The resultant solution contained 25-250 pg/ml, and was measured at an excitation wavelength of 436 nm. No correction was made for self-absorption of the solutions. 

When A -3-ketosteroids or A -3-ketosteroids are treated with zinc dust in 40% sulfuric acid, a fluorescent product is produced. This product can be extracted by butyl ether and measured quantitatively [115]. The relative order of fluorescence intensities was prednisolone (100), triamcinolone (95), triamcinolone acetonide (60), cortisone (3.7), hydrocortisone (3.5), and progesterone (5.2). 

Ueno et al. also prepared the b i s (2 - n ap h t h y I s u I fe n y 1) - y - CD series in which the naphthyl moieties are very limited in their movement because the linker between naphthalene and CD is only sulfur [37], All isomers of 12(AB), 13(AC), 14(AD), and 15(AE) exhibit only monomer fluorescence due to the rigid linker. It means that the two naphthalene moieties cannot take face-to-face orientation because of the limited flexibility. Although the excimer cannot be used for sensing molecules, Ueno et al. found that the monomer fluorescence intensity increases with increasing guest concentration. Thus, this modified CD series can be used as chemosensors of a different type. 

The standard solutions were diluted with hexane or methanol to prepare solutions that contained 2 yg/ml pesticide for the initial fluorescence measurements. Excitation and emission band widths on the spectrofluorometer were adjusted to 4 nm. A solution of quinine sulfate, 1 yg/ml in 0.1 N sulfuric acid, was used as a reference in determining the relative fluorescence intensity of the pesticides. The wavelengths for excitation and emission that would give the maximum fluorescence intensity in both hexane and methanol were obtained next by using 1 cm quartz fluorometer cells. Finally the excitation monochromator was set at 254 nm, and the fluorescence intensity was again measured at wavelength of maximum emission in both hexane and methanol. 

Concentration Profiles. The relative fluorescence intensity profiles for OH, S2, SH, SO, and SO2 were converted to absolute number densities according to the method already outlined. Resulting concentration profiles for a rich, sulfur bearing flame are exhibited in Figure 17. H-atom densities were calculated from the measured OH concentrations and H2 and H2O equilibrium values for each flame according to Equation 6. Similar balanced radical reactions were used to calculate H2S and S concentrations 6). Although sulfur was added as H2S to this hydrogen rich flame, the dominant sulfur product at early times in the post flame gas is S02 ... 

Guilbault (177), Moore notes, reported that maximum fluorescence intensity of quinine occurred in 0.1 N sulfate-sulfuric acid solutions and was quenched by the presence of halide ions. Moore noted a similar quenching of the photosensitizing ability of quinine. 

The bench top analyzer was first calibrated using commercial gravimetrically based diesel standards. Two sets of commercial diesel standards and a set of in-house prepared standards were used to generate three different calibration curves for comparison. The first set of standards, made from No. 2 diesel (Vendor A), included sulfur concentration levels of 0 ppm (blank), 5 ppm, 10 ppm, 100 ppm, 500 ppm, 1000 ppm, and 3000 ppm. The second set, made from a synthetic diesel fuel matrix (Vendor B), included sulfur levels of close to 0 ppm (blank), 20 ppm, 50 ppm, 100 ppm, 200 ppm and 500 ppm. The in-house standards were made by mixing different ratios of decalin and n-butyldisulfide (CgHigS) gravimetrically with resulting sulfur concentration levels of close to 0 ppm (blank), 10 ppm, 48.6 ppm, 87.6 ppm, 320 ppm, and 946 ppm. The measured sulfur fluorescent X-ray intensity, in coimts, for each standard is listed in Table 1. 

The absorption of both the excitation beam and the characteristic sulfur X-rays of the sample is matrix dependent. In general, the matrix effect is minor and there is no need for correction. However, if the sample measured has a high oxygen content or very different hydrogen-to-carbon H7C ratio compared to the calibrant, a correction will be necessary. Due to the monochromatic excitation, the matrix correction is simple if the major composition of the matrix is known. The primary fluorescence intensity for an element in the matrix can be simply found from the first principle for monochromatic excitation [4] ... 

By reflecting and focusing the X-ray beam, a higher flux of excitation radiation is transmitted to the sample. This increases the sensitivity, and lower power X-ray (less than 50 W) tubes can be utilized. A spectrum with a sulfior in oil sample at a sulfur concentration of 100 mg/kg is displayed in Fig. 6. The peak-to-background ratio is improved to 5.5 1, and the intensity of the sulfur fluorescence line is increased by a factor of 2 in comparison to the example of polarization excitation and by a factor of 6 in comparison to the example of direct excitation fi om above. 

One common approach to fluorescence sensing is to rely on fluorophores which are collisionally quenched by the analyte. There are many known collisional quenchers (andytes) which alter the fluorescence intensity and decay time. These include O2 (27-31), chloride (32-33), chlorinated hydrocarbons (34), iodide (35), bromate (36), xenon (37), acrylamide (38), succinimide (39), sulfur dioxide (40), and halothane (41), to name a few. The quenching process obeys the Stem-Volmer equation ... 

Other classes of alkaloids, which exhibit fluorescence, include the quinoline and isoquinoline alkaloids. Quinoline is weakly fluorescent. The anti-malarial drug quinine includes a methoxy substituent on the 6 position of the quinoline moiety and fluoresces very intensely. Quinine, in sulfuric acid solution, is often used as a standard in fluorescence spectroscopy for determining a quantum yield. Its fluorescent properties are sensitive to pH. At pH 2 it has an excitation maximum of 347 nm with fluorescence at 448 nm. At pH 7 the peaks shift to absorb at 331 nm and emit at 382 nm. In hydrochloric acid solution, absorption is unaffected but fluorescence intensity is quenched greatly by the halide anions. 

There is also a great, number of oxygen-containing heterocyclic compounds that fluoresce. Coumarins and flavonoids are the two largest classes of oxygen heterocycles. Coumarins fluoresce more intensely under basic conditions where flavones fluoresce weakly. In 30% sulfuric acid solution, flavones fluoresce intensely and coumarins do not. 

Relative Fluorescence Intensities of Sterols with Acetic Anhydride-Sulfuric AcrD ... 

The ESR spectrum of the pyridazine radical anion, generated by the action of sodium or potassium, has been reported, and oxidation of 6-hydroxypyridazin-3(2//)-one with cerium(IV) sulfate in sulfuric acid results in an intense ESR spectrum (79TL2821). The self-diffusion coefficient and activation energy, the half-wave potential (-2.16 eV) magnetic susceptibility and room temperature fluorescence in-solution (Amax = 23 800cm life time 2.6 X 10 s) are reported. 

Note Sulfuric acid is a universal reagent, with which almost all classes of substance can be detected by charring at elevated temperatures (150—180°C). The production of colored or fluorescent chromatogram zones at lower temperature (< 120 C) and their intensities are very dependent on the duration of heating, thf... 

Note Like sulfuric acid (q.v.) ort/io-phosphoric add is a universal reagent, with which almost all classes of substance can be detected at high temperatures (150-180 °C) by charring e.g. high molecular weight hydrocarbons (mineral oils) [20]. The colors and fluorescences produced at lower temperatures (<120°C) and their intensities are very dependent on the temperature and period of heating. It is not possible to use meta- or pyrophosphoric acid in place of or/Ao-phosphoric add, since, for instance, amanita toxins react well with alcoholic phosphoric add only weakly with aqueous phosphoric add and not at all with meta- or pyrophosphoric acid [17]. 

P.R.90 is derived from the fluorescein structure (147). Fluorescein is a yellow dye with intensely green fluorescence which was discovered by A.v.Bayer in 1871. It is prepared by heating resorcin and phthalic anhydride with zinc chloride or concentrated sulfuric acid ... 

Sweat [114] studied the fluorescence of sulfuric acid reacted corticosteroids, and adopted the following procedure. To 1 mL of an ethanolic steroid solution, 1 mL of concentrated sulfuric acid was added rapidly. The solution was thoroughly mixed, and allowed to stand at room temperature for 20 minutes. The relative intensities of observed... 

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