Benzo pyrene, fluorescence

Colpa et al. (1963) calculated p/ (S )-values for a series of aromatic hydrocarbons, but could not detect fluorescence changes in the regions of acidity indicated by the Forster cycle, although fluorescence spectra attributed to proton complexes of 3,4-benzo-pyrene and 1,2-benzanthracene were observed in some solutions containing only the neutral molecule in the ground state. Flurry and co-workers (1963, 1966, 1967) have carried out theoretical and Forster cycle calculation on the excited state basicities of poly-methylbenzenes and Kuz min et al. (1967) have also calculated p/sT(S1)- and p7 (T )-values for polycyclic aromatic hydrocarbons increases in base strength of from 7 to 30 powers of ten were derived for Sj. 

Measurement of the influence of different micellar environments on proton transfer from excited states of 3-hydroxyflavone allows estimates to be made of micelle concentrations from measurement of the tautomer emission yield. Proton transfer reactions of benzimidazole excited singlet states have also been studied in ionic micelles. Magnetic fields are found to affect the behaviour of radicals generated by the photodissociation of benzil in micellar media. The starburst dendrites which are formed by anionic macromolecules in interaction with both anionic and cationic surfactants have been examined by pyrene fluorescence. Benzo[k]fluoranthrene fluorescence has served as a probe of the effects of metal salts on bile salt aggregation. The incorporation and distribution of benzoquinone into liposomes containing amphilic Zn(II) porphyrin has been followed by its effect on the quenching of the excited state °. A comparison of the photochromism of spirobenzpyran derivatives in unilamellar surfactant vesicles and solvent cast surfactant films has also been reported. ... 

Liquid paraffin benzo(a)pyrene 35-fold spray solution, 67% in n-hexane the fluorescence is stable for more than 10 h [245]... 

Indeed, great emphasis was placed on the presentation of compounds in crystalline form for many years, early chromatographic procedures for the separation of natural substances were criticized because the products were not crystalline. None the less, the invention by Tswett (3) of chromatographic separation by continuous adsorption/desorption on open columns as applied to plant extracts was taken up by a number of natural product researchers in the 1930s, notably by Karrer (4) and by Swab and lockers (5). An early example (6) of hyphenation was the use of fluorescence spectroscopy to identify benzo[a]pyrene separated from shale oil by adsorption chromatography on alumina. 

Figure 1. (a) Room-temperature fluorescence spectra of benzo(a)pyrene on 80% a-Room-temperature fluorescence spectrum of 500 ng of benzo(a)pyrene on 80% a-<7clodextrin—NaCl. = 300 nm. 

Figure 3. Three-dimensional plot of the room-temperature fluorescence of a mixture of 500 ng each of benzo(a)pyrene and benzo(e)pyrene on 80% q-cyclodextrin-NaCl. Numbers along dashed lines show the approximate wavelengths (nm) represented by these lines. The excitation wavelength was varied from 250 nm (front spectrum) to 370 nm (back spectrum) at 2-nm increments. Benzo(a)pyrene emitted from approximately 380 nm to 540 nm, and benzo(e)pyrene emitted from 365 nm to 505 nm.

We find that the fluorescence yield of freshly prepared covalent (+)-anti-BaPDE-DNA adducts in oxygen-free solutions is 66+2 lower than the yield of the tetraol 7,8,9,10-tetrahydroxytetrahydro-benzo(a)pyrene (BaPT) in the absence of DNA. Since the fluorescence lifetime of BaPT under these conditions is 200ns, the mean fluorescence lifetime of the adducts (see reference T7) can be estimated to have a lower limit of 3ns, which is close to the mean value of 0.52x1.6 + 0.42x4.0 = 2.7 ns estimated from the two short fluorescence components of Undeman et al (10). 

Schwarz, F.P., Wasik, S.P. (1976) Fluorescence measurements of benzene, naphthalene, anthracene, pyrene, fluoranthene, and benzo[a]pyrene in water. Anal. Chem. 48, 524—528. 

Dunn and Stich [78] and Dunn [79] have described a monitoring procedure for polyaromatic hydrocarbons, particularly benzo[a]pyrene in marine sediments. The procedures involve extraction and purification of hydrocarbon fractions from the sediments and determination of compounds by thin layer chromatography and fluorometry, or gas chromatography. In this procedure, the sediment was refluxed with ethanolic potassium hydroxide, then filtered and the filtrate extracted with isooctane. The isooctane extract was cleaned up on a florisil column, then the polyaromatic hydrocarbons were extracted from the isoactive extract with pure dimethyl sulphoxide. The latter phase was contacted with water, then extracted with isooctane to recover polyaromatic hydrocarbons. The overall recovery of polyaromatic hydrocarbons in this extract by fluorescence spectroscopy was 50-70%. 

Several properties of hepatic microsomal AHH activity were compared in control and DBA-pretreated male little skates as shown in Table I. Following treatment there was an approximately 35-fold increase in specific enzyme activity, as quantitated by fluorescence of the phenolic metabolites formed (3, 21). The pH optimum, which was fairly broad, and the concentration of benzo(a)-pyrene (0.06 mM) that had to be added to the incubation mixture to achieve maximum enzyme activity were the same for both control and induced skate hepatic microsomes. The shorter periods observed for linearity of product formation with microsomes from the induced skates is thought to be related to the much higher AHH activity present, and may be due to substrate depletion or the formation of products which are inhibitory (i.e., compete with the MFO system as they are substrates themselves). A similar explanation may be relevant for the loss of linear product formation at lower microsomal protein concentrations in the induced animals. 

PAHs also generally have well-structured emission spectra (see Figs. 10.6-10.10) and relatively large fluorescence quantum yields. For example, in degassed n-heptane at room temperature, the fluorescence quantum yields are as follows fluoranthene, 0.35 benz[ ]anthracene, 0.23 chrysene, 0.18 BaP, 0.60 BeP, 0.11 and benzo[g/zi]perylene, 0.29 (Heinrich and Giisten,1980). Cyclopenta[crf]pyrene, however, does not fluoresce. 

FIGURE 10.10 UV absorption and fluorescence spectra of benzo[a]pyrene in cyclohexane (adapted from Karcher et al., 1985). 

Benzo[e]pyrene was analyzed by using HPLC with fluorescence detection for the Shimadzu, the optimum wavelengths were 280 nm (excitation) and 394 nm (emission). 

Air analysis may be performed by U.S.EPA Method TO 13 (U.S.EPA 1988), which is quite similar to the above method. PAH-bound particles and vapors (many compounds may partially volatilize after collection) may be trapped on a filter and adsorbent (XAD-2, Tenax, or polyurethane foam), and then desorbed with a solvent. The solvent extract is then concentrated and analyzed by HPLC (UV/Fluorescence detection), GC-FID, or GC/MS (preferably in SIM mode). Because of very low level of detection required for many carcinogenic PAHs, including benzo(a)pyrene, the method suggests the sampling of a very high volume of air (more than 300,000 L). 

Morizane [182] has applied high performance liquid chromatography with fluorescence detection to the determination of benzo(a) pyrene in methylene dichloride extracts of potable waters in amounts down to 0.28pg. 

Das and Thomas [200] used fluorescence detection in high performance liquid chromatography to determine nine PAHs in occupational health samples including process waters. The nine compounds studied were benzo(a)anthracene, benzo(k)fhioranthene, benzo(a)pyrene/fhioranthene, chrysene, benzo(k)fluorene, perylene, benzo(e)pyrene, deibenz(ah)-anthracene and benz(ghi)perylene. 

Figure 3. Fluorescence spectrum of benzo(a)pyrene in solution and in the living...

Figure 1. Dye-laser-induced fluorescence spectra of SRC-1 in an n-heptane matrix at 15 K. In each case, a delay was imposed between the arrival of a laser pulse at the sample and measurement of the actual fluorescence note the difference between the 3-ns and 35-ns spectra at an excitation wavelength of 383.0 nm. Identified compounds BaP, benzo[a]pyrene Pe, perylene. U denotes a compound that cannot be identified because its spectrum is not included in our file of pure-compound...

Figure 2. Fluorescence spectrum in a nitrogen matrix at 15 K (excited by a 2.5-kW mercury-xenon lamp) of an adsorption chromatography fraction from a coking plant water sample. Compounds BbF, benzo[b]fluorene C, chrysene BeP, ben-zo[e]pyrene P, pyrene BkF, benzo[k]fluoranthene BaP, benzo[a]pyrene U, unknown ( ).

Figure 3. Fluorescence spectra excited by a dye laser at 389.2 nm in an r -heptane matrix at 15 K of an adsorption chromatography fraction from a coking plant water sample (left,) and of pure benzo[a]pyrene (right,). Note that the two spectra are virtually superimposable ( 1).

The siimples were analysed by fluorescence spectroscopy at the conditions for each specific PAH [5] previously determined with the model compounds. The PAH studied are those listed by the US Environmental Protection Agency as priority pollutants [6] Fluorene, Benzo(a)Pyrene, Pyrene, Chrysene, Anthracene, Acenaphthene, Bezo(a)Anthracene, Dibenzo(a,h)Anthracene, Coronene, Perylene and Benzo(k)fluoranthene. In addition, Coronene emissions were also reported due to their important role on PAH stabilization at extreme conditions [7]. These 16 PAH were analysed from all runs in each of the four samples. 

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