Jorge O. Oña-Ruales

Identification and quantification of six-ring C26H16 cata-condensed polycyclic aromatic hydrocarbons in a complex mixture of polycyclic aromatic hydrocarbons from coal tar

AbstractWe applied a combination of normal-phase liquid chromatography (NPLC) with ultraviolet–visible spectroscopy and gas chromatography with mass spectrometry (GC/MS) for the fractionation, identification, and quantification of six ring C26H16cata-condensed polycyclic aromatic hydrocarbons, PAHs, in the Standard Reference Material 1597a, Complex Mixture of PAHs from Coal Tar. For the characterization analysis, we calculated the GC retention indices of 17 C26H16 PAH authentic reference standards using the Rxi-PAH and DB-5 GC columns. Then, we used NPLC with ultraviolet–visible spectroscopy to isolate the fractions containing the C26H16 PAHs, and subsequently, we used GC/MS to establish the identity and quantity of the C26H16 PAHs using authentic reference standards. Following this procedure, 12 C26H16cata-condensed PAHs benzo[c]pentaphene, dibenzo[f,k]tetraphene, benzo[h]pentaphene, dibenzo[a,l]tetracene, dibenzo[c,k]tetraphene, naphtho[2,3-c]tetraphene, dibenzo[a,c]tetracene, benzo[b]picene, dibenzo[a,j]tetracene, naphtho[2,1-a]tetracene, dibenzo[c,p]chrysene, and dibenzo[a,f]tetraphene were identified and quantified for the first time, and benzo[c]picene was quantified for the first time in an environmental combustion sample. Graphical AbstractIdentification and quantification of C26H16cata-condensed PAHs in a complex mixture of coal tar

Identification and quantification of seven fused aromatic rings C26H14 peri-condensed benzenoid polycyclic aromatic hydrocarbons in a complex mixture of polycyclic aromatic hydrocarbons from coal tar.

A methodology for the characterization of groups of polycyclic aromatic hydrocarbons (PAHs) using a combination of normal phase liquid chromatography with ultraviolet-visible spectroscopy (NPLC/UV-vis) and gas chromatography with mass spectrometry (GC/MS) was used for the identification and quantification of seven fused aromatic rings C26H14 peri-condensed benzenoid polycyclic aromatic hydrocarbons, PAHs, in standard reference material (SRM) 1597a, complex mixture of PAHs from coal tar. The NPLC/UV-vis isolated the fractions based on the number of aromatic carbons and the GC/MS allowed the identification and quantification of five of the nine C26H14 PAH isomers; naphtho[1,2,3,4-ghi]perylene, dibenzo[b,ghi]perylene, dibenzo[b,pqr]perylene, naphtho[8,1,2-bcd]perylene, and dibenzo[cd,lm]perylene using a retention time comparison with authentic reference standards. For the other four benzenoid isomers with no available reference standards the following two approaches were used. First, the annellation theory was used to achieve the potential identification of benzo[qr]naphtho[3,2,1,8-defg]chrysene, and second, the elution distribution in the GC fractions was used to support the potential identification of benzo[qr]naphtho[3,2,1,8-defg]chrysene and to reach the tentative identifications of dibenzo[a,ghi]perylene, naphtho[7,8,1,2,3-pqrst]pentaphene, and anthra[2,1,9,8-opqra]naphthacene. It is the first time that naphtho[1,2,3,4-ghi]perylene, dibenzo[b,ghi]perylene, dibenzo[b,pqr]perylene, naphtho[8,1,2-bcd]perylene, and dibenzo[cd,lm]perylene are quantified, and the first time that benzo[qr]naphtho[3,2,1,8-defg]chrysene is potentially identified, in any sample, in any context.

Retention behavior of isomeric polycyclic aromatic sulfur heterocycles in gas chromatography on stationary phases of different selectivity

Retention indices for 48 polycyclic aromatic sulfur heterocycles (PASHs) were determined using gas chromatography with three different stationary phases: a 50% phenyl phase, a 50% liquid crystalline dimethylpolysiloxane (LC-DMPS) phase, and an ionic liquid (IL) phase. Correlations between the retention behavior on the three stationary phases and PASH geometry (L/B and T, i.e., length-to-breadth ratio and thickness, respectively) were investigated for the following four isomer sets: (1) 4 three-ring molecular mass (MM) 184Da PASHs, (2) 13 four-ring MM 234Da PASHs, (3) 10 five-ring MM 258Da PASHs, and (4) 20 five-ring MM 284Da PASHs. Correlation coefficients for retention on the 50% LC-DMPS vs L/B ranged from r=0.50 (MM 284Da) to r=0.77 (MM 234Da). Correlation coefficients for retention on the IL phase vs L/B ranged from r=0.31 (MM 234Da) to r=0.54 (MM 284Da). Correlation coefficients for retention on the 50% phenyl vs L/B ranged from r=0.14 (MM 258Da) to r=0.59 (MM 284Da). Several correlation trends are discussed in detail for the retention behavior of PASH on the three stationary phases.

The predictive power of the annellation theory: the case of the C32H16 benzenoid polycyclic aromatic hydrocarbons.

The positions of maximum absorbance for the p and β bands of the UV-vis spectra of the benzenoid polycyclic aromatic hydrocarbons, PAHs, with molecular formula C32H16 have been predicted by means of the annellation theory. In the C32H16 PAH group there are 46 isomers, 39 of which have not been synthesized so far, thus their characterization and possible presence in the environment remains unknown. The methodology has been validated using literature information for 7 isomers in this PAH group. The results have been satisfactorily substantiated by means of semi-empirical calculations using the ZINDO/S approach. It has been concluded that the annellation theory is a powerful tool for the prediction of the positions of maximum absorbance of aromatic compounds with unknown UV-vis spectra. It is the first time that the UV-vis spectral information on these 39 benzenoid C32H16 PAHs has been predicted.

Extended Y-Rule Method for the Characterization of the Aromatic Sextets in Cata-Condensed Polycyclic Aromatic Hydrocarbons

The location, number, and migrating behavior of the sextets in the cata-condensed benzenoid polycyclic aromatic hydrocarbons with available bay regions have been determined by a new proposed topological methodology called the extended Y-rule. The precursor of this rule is the well-known Y-rule method for determining sextets in peri-condensed polycyclic aromatic hydrocarbons. The new methodology has been successfully validated by means of literature information and by theoretical nucleus independent chemical shift (NICS) calculations. Even though the families of polycyclic aromatic hydrocarbons analyzed here comprise the C14H10, C18H12, C22H14, and C26H16 isomers, the procedure can practically be extended to the families C(10+4x)H(8+2x), where x = 1, ..., ∞. It is the first time that a straightforward procedure, easy to apply, has been proposed to obtain the sextets arrangement and behavior in the group of cata-condensed benzenoid polycyclic aromatic hydrocarbons.

Retention behavior of alkyl-substituted polycyclic aromatic sulfur heterocycle isomers in gas chromatography on stationary phases of different selectivity.

Retention indices for 10 sets of alkyl-substituted polycyclic aromatic sulfur heterocycles (PASHs) isomers (total of 80 PASHs) were determined using gas chromatography with three different stationary phases: a 50% phenyl phase, a 50% liquid crystalline dimethylpolysiloxane (LC-DMPS) phase, and an ionic liquid (IL) phase. Correlations between the retention behavior on the three stationary phases and PASH geometry [length-to-breadth (L/B) and thickness (T)] were investigated for the following PASHs: 4 methyl-substituted dibenzothiophenes (DBTs), 3 ethyl-substituted DBTs, 15 dimethyl-substituted DBTs, 8 trimethyl-substituted DBTs, 15 methyl-substituted naphthothiophenes, 30 methyl-substituted benzonaphthothiophenes, and 5 methyl-substituted tetrapheno[1,12-bcd]thiophene. Correlation coefficients for retention on the 50% phenyl phase vs L/B ranged from r=-0.28 (MeBbN23Ts) to r=0.92 (EtDBTs). Correlation coefficients for retention on the IL phase vs L/B ranged from r=0.13 (MeN12Ts) to r=0.83 (EtDBTs). Correlation coefficients for retention on the 50% LC-DMPS phase vs L/B ranged from r=0.22 (MeDBTs) to r=0.84 (TriMeDBTs).

The influence of the aromatic character in the gas chromatography elution order: the case of polycyclic aromatic hydrocarbons

ABSTRACT A link between the aromatic character of polycyclic aromatic hydrocarbons (PAHs) and gas chromatography (GC) elution order in columns with a polysiloxane backbone in the stationary phase is reported for the first time. The aromatic character was calculated using a method that combines the π-Sextet Rule and the Pauling Ring Bond Orders to allow the establishment of the location and migration of aromatic sextets in PAH structures. One GC column with a polysiloxane-like backbone (Rxi-PAH) and three GC columns with a polysiloxane backbone (DB-5, SE-52 and LC-50) were used for the analysis. According to the results of this study, within an isomer group, PAHs that contain a lower number of rings affected by the aromatic sextets tend to elute earlier than PAHs that contain a higher number of rings affected by the aromatic sextets. The PAHs that follow the calculated elution order are 88% in the Rxi-PAH column, 88% in the DB-5 column, 93% in the SE-52 column and 85% in the LC-50 column. It is expected that future analyses with other aromatic compounds in GC columns with a polysiloxane backbone in the stationary phase will follow a GC elution order that agrees with the aromatic character of the molecules.

The Predictive Power of the Annellation Theory: The Case of the C26H16 Cata-Condensed Benzenoid Polycyclic Aromatic Hydrocarbons

The Annellation Theory was applied to establish the locations of maximum absorbance for the p and β bands in the UV-vis spectra of eight benzenoid cata-condensed polycyclic aromatic hydrocarbons (PAHs) with molecular formula C26H16 and no available syntheses procedures. In this group of eight isomers, there are seven compounds with potential carcinogenic properties due to geometrical constraints. In addition, crude oil and asphaltene absorption spectra exhibit similar properties, and the PAHs in heavier crude oils and asphaltenes are known to be the source of the color of heavy oils. Therefore, understanding the electronic bands of PAHs is becoming increasingly important. The methodology was validated using information for the remaining 29 isomers with available UV-vis spectra. The results satisfactorily agree with the results from semiempirical calculations made using the ZINDO/S approach. The locations of maximum absorbance for the p and β bands in the UV-vis spectra of the eight C26H16 cata-condensed isomers dibenzo[c,m]tetraphene, naphtho[1,2-c]chrysene, dibenzo[c,f]tetraphene, benzo[f]picene, naphtho[2,1-a]tetraphene, naphtho[2,1-c]tetraphene, dibenzo[c,l]chrysene, and naphtho[1,2-a]tetraphene were established for the first time.

An Efficient Synthesis of Dibenzo[a,l]tetracene and Dibenzo[a,j]tetracene and Their Identification in a Coal Tar Extract

ABSTRACT An efficient synthesis of potentially carcinogenic dibenzo[a,l]tetracene 1 and dibenzo[a,j]tetracene 2 has been developed and the synthetic standards were used to establish their environmental presence. The synthesis involves Diels–Alder reaction of in situ generated ortho-quinodimethane with phenanthrene-1,4-dione, followed by reductive aromatization as key steps. This synthetic strategy resulted in good overall yield and the mixture of 1 and 2 is easily separable by reversed-phase liquid chromatography (RP-LC). Compounds 1 and 2 were identified in a complex mixture of polycyclic aromatic hydrocarbons from coal tar (Standard Reference Material 1597a) and thus could be potential environmental hazards.

Prediction of the Ultraviolet-Visible Absorption Spectra of Polycyclic Aromatic Hydrocarbons (Dibenzo and Naphtho) Derivatives of Fluoranthene.

The annellation theory method has been used to predict the locations of maximum absorbance (LMA) of the ultraviolet–visible (UV-Vis) spectral bands in the group of polycyclic aromatic hydrocarbons (PAHs) C24H14 (dibenzo and naphtho) derivatives of fluoranthene (DBNFl). In this group of 21 PAHs, ten PAHs present a sextet migration pattern with four or more benzenoid rings that is potentially related to a high molecular reactivity and high mutagenic conduct. This is the first time that the locations of maximum absorbance in the UV-Vis spectra of naphth[1,2-a]aceanthrylene, dibenz[a,l]aceanthrylene, indeno[1,2,3-de]naphthacene, naphtho[1,2-j]fluoranthene, naphth[2,1-e]acephenanthrylene, naphth[2,1-a]aceanthrylene, dibenz[a,j]aceanthrylene, naphth[1,2-e]acephenanthrylene, and naphtho[2,1-j]fluoranthene have been predicted. Also, this represents the first report about the application of the annellation theory for the calculation of the locations of maximum absorbance in the UV-Vis spectra of PAHs with five-membered rings. Furthermore, this study constitutes the premier investigation beyond the pure benzenoid classical approach toward the establishment of a generalized annellation theory that will encompass not only homocyclic benzenoid and non-benzenoid PAHs, but also heterocyclic compounds.