Metabolism of 1-fluoropyrene and pyrene in marine flatfish and terrestrial isopods

Monofluorinated polycyclic aromatic hydrocarbons (F-PAHs) are useful reference compounds for a broad spectrum of PAH studies. The pyrene metabolite 1-hydroxypyrene is often used as a biomarker of PAH exposure. Two species, isopod (Porcellio scaber) and flatfish (Platichthys flesus), that produce 1-hydroxypyrene as the major intermediary metabolite and have distinct phase-II conjugates, were selected to investigate the cytochrome P450 catalyzed metabolism of 1-fluoropyrene. The fluorine atom blocks one of the four most favored carbon atoms, yielding different metabolite patterns and the results obtained in the selected species were compared with metabolite profiles obtained for unsubstituted pyrene. Charge densities in 1-fluoropyrene measured with (13)C-NMR were used to predict possible positions of hydroxylation, which were confirmed by (19)F-NMR. Additionally, the retention behaviour of conjugated 1-fluoropyrene metabolite isomers in reversed-phase liquid chromatography on a polymeric alkyl-bonded phase was interpreted based on the slot model. Whereas three phase-I metabolites were found in isopod hepatopancreas, only two were observed in flatfish bile. Phase-II metabolism appeared unaffected by the fluorine substituent. It was concluded that the phase-I enzyme cytochrome P450 is non-regioselective in the isopod: the activation is mostly influenced by the electron density distribution. In contrast, the enzymatic oxidation in the flounder is more selective. These differences will affect to what extent pyrene metabolite measurements can be used to assess the impact of PAHs to different species.

Quenched phosphorescence detection in cyclodextrin-based electrokinetic chromatography

Quenched phosphorescence detection is a sensitive detection method recently introduced in capillary zone electrophoresis. It is based on the dynamic quenching interaction of the analytes (quenchers) with a phosphorophore, 1-bromo-4-naphthalenesulfonate (BrNS), present in the separation buffer. In this study, it is shown that this detection method can also be used in cyclodextrin-based electrokinetic chromatography (CD-EKC) despite the presence in the buffer solution of cyclodextrins, which are known to reduce the luminescence quenching rate constants. Experiments indicate that BrNS mainly resides in the aqueous phase, while the analytes are distributed between both phases. In principle, the observed quenching might arise from the interaction of BrNS with uncomplexed as well as complexed analytes. However, from the dependence of the fractional quenching on the capacity factor (the normalized fractional quenching was found to be equal to the fraction of analyte in the aqueous phase), it was concluded that only aqueous-phase quenching contributes significantly to the observed quenching. Nevertheless, separation and detection can be regarded as fully compatible, because the capacity factors encountered in CD-EKC are generally low (in this study they ranged from about 0.1 to 2.5). Indeed, with nitroaromatic compounds as the target analytes, limits of detection in the 10(-8) M range were achieved.

Detection of nonderivatized peptides in capillary electrophoresis using quenched phosphorescence

A capillary electrophoresis detection technique for (small) peptides is presented, i.e. quenched phosphorescence, a method that is generally applicable and does not require chemical derivatization. For this purpose, a novel phosphorophore, 1-bromo-4-naphthalenesulfonic acid (BrNS), was synthesized. BrNS has sufficient water solubility and provides strong phosphorescence at room temperature over a wide pH range. The detection is based on the dynamic quenching of the BrNS phosphorescence background signal by electron transfer from the amino group of the peptides at pH 9.5-10. For the di- and tripeptides Val-Tyr-Val, Val-Gly-Gly, Ala-Ser, Gly-Asn, Gly-Ala, and Gly-Tyr, detection limits in the range of 5-20 microg/L were obtained. The novel technique is even a good alternative for the (limited) group of peptides containing tyrosine and, thus, exhibiting native fluorescence as well as strong UV absorption: using Gly-Tyr, Val-Tyr-Val, methionine enkephalin, and human angiotensin II as test compounds, quenched phosphorescence detection was found to compare favorably with absorption detection at 190- and 266-nm laser-induced fluorescence detection, as performed with a recently developed, small-size, quadrupled Nd:YAG laser.

On-line identification method in column liquid chromatography: UV resonance Raman spectroscopy

Ultraviolet resonance Raman spectroscopy (RRS) is presented as a novel identification tool for conventional-size column liquid chromatography (LC). The on-line coupling was made using a standard Z-shaped flow cell. A continuous-wave frequency-doubled argon ion laser operating at a wavelength of 244 nm was used for excitation. "On-the-fly" resonance Raman spectra of four model compounds, fluorene, phenanthrene, fluoranthene, and pyrene, were recorded after a standard acetonitrile/water reversed-phase LC separation. When applying a large-volume-injection procedure (32 mL), detection limits were at the nanogram per milliliter level. The results indicate that UV-RRS gives detailed spectral information at an appropriate sensitivity level so that coupling with LC becomes feasible.

Determination of isoflavone glucoside malonates in Trifolium pratense L. (red clover) extracts: quantification and stability studies

Isoflavones, their glucosides and their glucoside malonates were determined in red clover leaf extracts using reversed-phase LC coupled to atmospheric pressure chemical ionisation mass spectrometry (APCI-MS), UV and fluorescence detectors and the stability of the malonates was investigated. Extracts can be stored at least 1-2 weeks at -20 degrees C without loss of malonates. In LC-separated fractions the malonates are most stable when stored at low temperature after evaporation to dryness. The concentrations of eight major isoflavones ranged from 0.04 to 5 mg/g leaves.

UV-B absorbance and UV-B absorbing compounds (para-coumaric acid) in pollen and sporopollenin: the perspective to track historic UV-B levels

UV-B absorbance and UV-B absorbing compounds (UACs) of the pollen of Vicia faba, Betula pendula, Helleborus foetidus and Pinus sylvestris were studied. Sequential extraction demonstrated considerable UV-B absorbance both in the soluble (acid methanol) and insoluble sporopollenin (acetolysis resistant residue) fractions of UACs, while the wall-bound fraction of UACs was small. The UV-B absorbance of the soluble and sporopollenin fraction of pollen of Vicia faba plants exposed to enhanced UV-B (10 kJ m(-2) day(-1) UV-B(BE)) was higher than that of plants that received 0 kJ m(-2) day(-1) UV-B(BB). Pyrolysis gas chromatography-mass spectrometry (py-GC-MS) analysis of pollen demonstrated that p-coumaric acid and ferulic acid formed part of the sporopollenin fraction of the pollen. The amount of these aromatic monomers in the sporopollenin of Vicia faba appeared to increase in response to enhanced UV-B (10 kJ m(-2) day(-1) UV-B(BE)). The detection limit of pyGC-MS was sufficiently low to quantify these phenolic acids in ten pollen grains of Betula and Pinus. The experimental data presented provide evidence for the possibility that polyphenolic compounds in pollen of plants are indicators of solar UV-B and may be applied as a new proxy for the reconstruction of historic variation in solar UV-B levels.

Organic contaminants and trace metals in flounder liver and sediment from the Amsterdam and Rotterdam harbours and off the Dutch coast

Organic contaminants [polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenylethers (PBDEs), nonylphenols], organotin compounds and trace metals (cadmium, chromium, mercury and zinc) were determined in flounder (Platichthys flesus) liver and sediment from the Amsterdam harbour (North Sea Canal) and Rotterdam harbour (Euromonding) and off the Dutch coast between the Amsterdam and Rotterdam harbour mouths in order to assess the level of contamination in these harbours and to study contamination gradients.

Dose- and time-dependent formation of biliary benzo[a]pyrene metabolites in the marine flatfish dab (Limanda limanda)

Polycyclic aromatic hydrocarbons (PAHs) are abundant pollutants, and many PAHs are carcinogenic, but only after metabolic activation. Benzo[a]pyrene (BaP) is among the most carcinogenic PAHs. The dose and time response of two enzymes involved in BaP metabolism and the amounts of BaP metabolites excreted into the bile were evaluated in an experiment with dab (Limanda limanda). Ninety dab were exposed orally to one of five doses of BaP (0, 0.08, 0.4, 2, or 10 mg/kg) and sampled at 3, 6, or 12 d after exposure. None of the doses studied caused significant induction of either microsomal ethoxyresorufin-O-deethylase (EROD). which reflects cytochrome P450 1A (CYP1A) activity, or cytosolic glutathione-S-transferase activity (GST). Concentrations of biliary BaP metabolites significantly increased with dose and significantly decreased with time after exposure. It is concluded that biliary BaP metabolites provide a much more sensitive method than EROD (CYP1A) or GST activity to monitor recent exposure to PAHs in dab.

Applicability of surface-enhanced resonance Raman scattering for the direct discrimination of ballpoint pen inks

In situ surface-enhanced resonance Raman spectroscopy (SERRS) with excitation at 685 nm is suitable for the direct discrimination of blue and black ballpoint pen inks on paper. For black inks, shorter excitation wavelengths can also be used. For blue inks, SERRS at 514.5 and 457.9 nm does not provide adequate discriminative power. At these excitation wavelengths, the SERRS signals of the Methyl Violet derivatives present in inks easily dominate the overall spectrum because of resonance enhancement and preferential interaction with silver sol particles. At 685 nm, this problem is not encountered as the Methyl Violet derivatives do not show resonance enhancement, while other components may still exhibit resonance. Thirteen blue and thirteen black ink lines were examined. For the blue and black inks, on the basis of the 685 nm SERR spectra, eight and six groups of spectra, respectively, could be distinguished. This discrimination largely agrees with information from thin layer chromatography (TLC) experiments, although some differences in group compositions are found. The in situ SERR spectra show good repeatability with regard to the Raman frequencies, band shapes and relative intensities of the spectral bands. However, absolute intensities cannot be used for discrimination purposes.

Natural and synthetic organic compounds in the environment-a symposium report

In March 2000, an international two-day symposium was organized in Noordwijkerhout, The Netherlands, on 'Natural and synthetic organic compounds in the environment'. The emphasis of the symposium was on the following classes of compounds: polycyclic aromatic hydrocarbons, xeno-estrogens, phyto-estrogens, and veterinary drugs. Sources, environmental distribution, uptake, biotransformation and toxic effects from the molecular to the population level were discussed. Other important aspects were the development of biomarkers, analytical methods, bioassays, molecular modelling and other research tools. Finally, the implications of the findings for government policies were discussed. In this paper, a summary is given of the most important facts and views presented at the symposium.

Liquid-core waveguide technology for coupling column liquid chromatography and Raman spectroscopy

The on-line coupling of liquid chromatography (LC) and Raman spectroscopy (RS) via an entirely plastic liquid-core waveguide (LCW) was optimized in terms of excitation wavelength of the laser, especially in relation to the fluorescence background, and the length of the LCW. Excitation at 632.8 nm (He-Ne laser) was found to be a good compromise between a wavelength long enough to strongly reduce the fluorescence background and, on the other hand, short enough to avoid (re)-absorption of laser light and Raman signals by H2O in LCWs of considerable length. This conclusion is supported by a theoretical discussion on the optimization of LCW lengths as function of the excitation wavelength for H2O and 2H2O. When using the He-Ne laser the optimum length is approximately 50 cm for H2O; this corresponds to a detection cell volume of 19 microl for an LCW of 220 microm I.D., which is fully compatible with conventional-size LC. The influence of an organic modifier, usually necessary for reversed-phase LC, on the free spectral window was evaluated. The potential applicability of LC-LCW-RS was shown for a mixture of adenosine 5'-monophosphate (AMP), guanosine 5'-monophosphate (GMP) and uridine 5'-monophosphate (UMP), utilizing an aqueous eluent without the addition of a modifier. Improved detectability was achieved by using the stopped-flow mode and applying a large-volume-injection procedure (injection volume: 200 microl). Under these conditions, the limit of identification for AMP, GMP and UMP was in the 0.1-0.5-mg/ml range.

Laser-induced fluorescence detection at 266 nm in capillary electrophoresis. Polycyclic aromatic hydrocarbon metabolites in biota

The separation of five phenolic polycyclic aromatic hydrocarbon metabolites (hydroxy-PAHs) has been performed by cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) using a 30 mM borate buffer (pH 9.0) containing 60 mM sodium dodecyl sulfate and varying concentrations of gamma-cyclodextrin (gamma-CD). A concentration of 12.5 mM gamma-CD was found to provide a baseline separation of the five hydroxy-PAHs. We applied conventional fluorescence and laser-induced fluorescence (LIF) detection, using a new, small-size, quadrupled Nd-YAG laser emitting at 266 nm. The best limits of detection, in the low ng/ml range, were achieved using LIF detection. For all analytes, linearity was observed up to ca. 100 ng/ml. As an application, conjugated pyrene metabolites in hepatopancreas samples from the terrestrial isopods Oniscus asellus and Porcellio scaber were separated and detected. Finally, flatfish bile samples from individuals exposed to polluted sediment or crude oil, which were part of an interlaboratory study, were analyzed by CD-MEKC with conventional fluorescence and LIF detection to determine the 1-hydroxypyrene concentrations.

Surface-enhanced resonance Raman spectroscopy as an identification tool in column liquid chromatography

The compatibility of ion-pair reversed-phase column liquid chromatography and surface-enhanced resonance Raman spectroscopy (SERRS) for separation and identification of anionic dyes has been investigated, with emphasis on the at-line coupling via a thin-layer chromatography (TLC) plate. SERR spectra using silver sols were recorded both for aqueous solutions and for samples deposited on aluminum oxide and silica TLC plates at 514.5- and 457.9-nm laser excitation. For some dyes, the shorter wavelength was needed to diminish the fluorescence background. For aqueous solutions and for samples deposited on aluminum oxide, clear SERR spectra were obtained upon addition of poly(L-lysine); for the silica plates, the addition of nitric acid was required. Upon drying the plates, the SERRS signals decreased in intensity; simply adding a drop of water could largely restore them. At-line coupling of LC and SERRS was successfully achieved when using silica, but not aluminum oxide, plates. The application of a gradient, a high water content, and the presence of ion-pair reagents needed for the separation did not adversely affect the deposition and the recording of SERR spectra. The identification limits were 10-20 ng of deposited material, depending on the dye selected, which corresponded to injected concentrations of 5-10 microg mL(-1).

Pyrene metabolites in the hepatopancreas and gut of the isopod porcellio scaber, a new biomarker for polycyclic aromatic hydrocarbon exposure in terrestrial ecosystems

The object of this study was to investigate the formation of pyrene metabolites by the isopod Porcellio scaber as a possible tool in the environmental risk assessment of polycyclic aromatic hydrocarbon (PAH) exposure in terrestrial ecosystems. The formation of pyrene metabolites was studied after either pulse exposure to a single high dose, or prolonged exposure (14 d) to a lower dosage. Exposure studies were carried out with unlabeled or radiolabeled pyrene, ion pair chromatography was used for analysis, and reference conjugates were synthesized. We also measured pyrene metabolites in field-exposed animals, to explore their use as biomarkers of PAH exposure. Analysis of the hepatopancreas and gut of single isopods revealed the formation of five products, one of which was 1-hydroxypyrene. Four of the remaining products were identified as phase II metabolites of 1- hydroxypyrene, with UV absorption and fluorescence characteristics similar to that of pyrene. One metabolite was identified as pyrene-1-glucoside, which is in accordance with high rates of glucosidation, reported for these isopods. Another conjugate was identified as pyrene-1-sulfate. None of the metabolites coeluted with a pyrene-1-glucuronide reference obtained from fish bile. A fifth metabolite detected by on-line scintillation detection did not exhibit any absorption at 340 nm, possibly because one of the aromatic rings of pyrene had lost its aromatic character. Although pyrene is not known for its toxicity, it usually co-occurs with other PAHs that are transformed into toxic products. Investigating the metabolism of pyrene can provide information with regard to the biotransformation capacity of invertebrate species and uptake and elimination kinetics. Because pyrene is one of the most predominant PAHs in the environment, analysis of its metabolites provides an extra tool for the environmental risk assessment of ecosystems with regard to PAH exposure, bioavailability, and biotransformation.

Preparation, isolation, and characterization of Dibenzo[a,l]pyrene diol epoxide-deoxyribonucleoside monophosphate adducts by HPLC and fluorescence line-narrowing spectroscopy

Dibenzo[a,l]pyrene (DB[a,l]P) is the most potent carcinogenic polycyclic aromatic hydrocarbon that has been identified in the environment. Earlier studies in our laboratory indicated that more than 80% of the DB[a,l]P-DNA adducts formed in vitro were depurinating adducts and that most of the stable adducts were formed from diol epoxide intermediates. To complete the profile of both stable and depurinating adducts of DB[a,l]P, we have synthesized standard adducts by reacting 3'-dAMP or 3'-dGMP with either (+/-)-anti- or (+/-)-syn-dibenzo[a,l]pyrene 11,12-dihydrodiol 13, 14-epoxide (DB[a,l]PDE). The adducts were separated by HPLC with an ion-pair column and were identified by fluorescence line-narrowing spectroscopy (FLNS). A total of six pairs of stereoisomers along with another stable DB[a,l]PDE-DNA adduct were successfully isolated and identified. Pairs of (+/-)-trans and (+/-)-cis isomers were expected to be formed from the reaction of anti-DB[a,l]PDE with either dAMP or dGMP. While we were able to identify two pairs of stereoisomeric (+/-)-syn-DB[a,l]PDE-dAMP (cis and trans) and two pairs of stereoisomeric (+/-)-anti-DB[a,l]PDE-dAMP (cis and trans) adducts, identification of all the stereoisomers of dGMP adducts proved to be impossible. A pair of (+/-)-syn-trans-DB[a,l]PDE-dGMP adducts, a pair of (+/-)-anti-cis-DB[a,l]PDE-dGMP adducts, and one syn-cis-DB[a,l]PDE-dGMP adduct were conclusively identified by FLNS. These standard adducts will be used to identify the stable DNA adducts formed by DB[a,l]P and DB[a,l]PDE in vitro and in vivo.

A novel method for the isolation and identification of stable DNA adducts formed by Dibenzo[a,l]pyrene and Dibenzo[a,l]pyrene 11, 12-dihydrodiol 13,14-epoxides in vitro

Our laboratory previously reported the identification and quantification of depurinating DNA adducts of dibenzo[a,l]pyrene (DB[a,l]P) in vitro, which comprise about 84% of all the DNA adducts that are formed [Li, K.-M., et al. (1995) Biochemistry 34, 8043-8049]. To determine a complete adduct profile and identify both stable and depurinating DNA adducts, we have developed a relatively simple, nonradioactive method for the identification of stable DNA adducts by combining enzymatic digestion, HPLC, and fluorescence line-narrowing spectroscopy (FLNS) techniques. Calf thymus DNA, bound to either (+/-)-anti- or (+/-)-syn-DB[a,l]PDE or rat liver microsome-activated DB[a,l]P, was first digested to 3'-mononucleotides with micrococcal nuclease and spleen phosphodiesterase. The adducts were then separated by HPLC with an ion-pair column and identified by FLNS by using the spectra of standards for comparison. In reactions with (+/-)-anti-DB[a,l]PDE, three adducts, an anti-cis-DB[a,l]PDE-dGMP, an anti-trans-DB[a, l]PDE-dAMP, and an anti-cis-DB[a,l]PDE-dAMP, were identified by HPLC and FLNS. In reactions with (+/-)-syn-DB[a,l]PDE, a pair of syn-trans-DB[a,l]PDE-dGMP adducts as well as a syn-cis-DB[a, l]PDE-dGMP, a syn-cis-DB[a,l]PDE-dAMP, and a pair of syn-trans-DB[a, l]PDE-dAMP adducts were identified. From the digest of microsome-activated DB[a,l]P-bound DNA, a syn-trans-DB[a,l]PDE-dGMP, an anti-cis-DB[a,l]PDE-dGMP, a syn-trans-DB[a,l]PDE-dAMP, and a syn-cis-DB[a,l]PDE-dAMP adduct were identified. An anti-cis-DB[a, l]PDE-dAMP adduct was identified only by (32)P-postlabeling. A total of five of the stable adducts formed by DB[a,l]P and nine of the stable adducts formed by DB[a,l]PDE in vitro have been identified. These adducts were also correlated to adduct spots in the (32)P-postlabeling method by cochromatography with standards. Approximately 93% of the stable adducts formed in reactions with (+/-)-anti-DB[a,l]PDE, 90% of adducts with (+/-)-syn-DB[a,l]PDE, and 85% of adducts formed with microsome-activated DB[a,l]P have been identified as Gua or Ade adducts. Equal amounts of stable Gua and Ade adducts were observed in the microsome-catalyzed binding of DB[a, l]P to calf thymus DNA, while 1.4 times more Gua adducts than Ade adducts were obtained in reactions with (+/-)-anti- or (+/-)-syn-DB[a,l]PDE.

Stability and storage problems in organotin speciation in environmental samples

The stability of both tributyltin (TBT) and triphenyltin (TPT) in water, sediment, oysters and cockles was studied over a period of 18 months using several storage conditions. Butyltins were stable in unacidified sea-water stored in polycarbonate bottles in the dark at 4 degrees C for 7 months, but half of the TBT concentration was lost after 540 d. A comparable preservation time was achieved for butyltins stored on C18 cartridges at room temperature. However, phenyltins extracted from sea-water were stable for only 60 d stored on cartridges and even more pronounced losses (about 90% after 540 d) occurred when they were stored in either polycarbonate or Pyrex glass bottles. Losses of organotins were observed in sediments after air drying and pasteurization treatments using a freeze-dried sediment as a comparator, whereas both butyltin and phenyltin species remained stable in sediments stored at -20 degrees C for the 18 months tested, irrespective of the treatment used for stabilization. Air drying followed by pasteurization was shown to be superior to other treatments for the stabilization of organotin compounds in sediments stored at higher temperatures, but 30% of TBT was lost after 540 d at 25 degrees C. Finally, butyltins were stable in both frozen cockles and oysters in the dark over a 7 month period and in freeze-dried samples stored at 4 degrees C for 5 months, but TBT losses of about 70% were observed after 540 d.

Evaluation of the state-of-the-art of butyl- and phenyltin compound determinations in freshwater sediment prior to certification of a reference material

In order to control the quality of butyl- and phenyltin compound determinations in sediment, the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a project, the final aim of which is to certify a freshwater sediment for its contents of a range of organotin compounds (mono-, di- and tributyltin, and mono-, di- and triphenyltin). The first part of this project involved an interlaboratory study which aimed to test the feasibility of preparation of candidate freshwater sediment reference material and to detect and remove most of the pitfalls observed in organotin determinations. This paper presents the main results of this interlaboratory study carried out prior to the certification campaign. The agreement obtained among laboratories for the six compounds determined was considered to reflect the state-of-the-art and was encouraging enough to decide upon the organisation of a certification campaign, which will be concluded in June 1999.