Lipophilic Toxins in Wild Bivalves from the Southern Gulf of California, Mexico

Most of the shellfish fisheries of Mexico occur in the Gulf of California. In this region, known for its high primary productivity, blooms of diatoms and dinoflagellates are common, occurring mainly during upwelling events. Dinoflagellates that produce lipophilic toxins are present, where some outbreaks related to okadaic acid and dinophisystoxins have been recorded. From January 2015 to November 2017 samples of three species of wild bivalve mollusks were collected monthly in five sites in the southern region of Bahía de La Paz. Pooled tissue extracts were analyzed using LC-MS/MS to detect lipophilic toxins. Eighteen analogs of seven toxin groups, including cyclic imines were identified, fortunately individual toxins did not exceed regulatory levels and also the total toxin concentration for each bivalve species was lower than the maximum permitted level for human consumption. Interspecific differences in toxin number and concentration were observed in three species of bivalves even when the samples were collected at the same site. Okadaic acid was detected in low concentrations, while yessotoxins and gymnodimines had the highest concentrations in bivalve tissues. Although in low quantities, the presence of cyclic imines and other lipophilic toxins in bivalves from the southern Gulf of California was constant.

Levels of PAHs, PCBs, and toxic metals in Ruditapes philippinarum and Donax trunculus in Marmara Sea, Turkey

BACKGROUND

The manila clam Ruditapes philippinarum and the wedge clam Donax trunculus are economic bivalve species which constitute an important part of the natural bivalve beds in the Marmara Sea, Turkey. Toxic chemicals such as, dioxins, dioxin-like polychlorinated biphenyls (PCBs), polycyclic hydrocarbons (PAHs), and toxic metals are recognized as important health risk factors that threaten public health via food or directly in the environment. In the present study, we aimed to determine and monitor levels of these toxic chemicals in both clam species, R. philippinarum and D. trunculus, between 2013 and 2017.

RESULTS

According to the results, maximum levels of dioxins, PAHs, and toxic metals (lead, cadmium, mercury) during the period were determined as 0.18 pg g^-1 , 2.43 mg kg^-1 , and 0.44-0.53-0.1 mg kg^-1 , respectively. The level of contaminants in both clam species were determined to be below the threshold or tolerable daily intake values established by the European Commission, European Food Safety Authority (EFSA), and Food and Agriculture Organization/World Health Organization (FAO/WHO). Seasonal fluctuations were observed to be similar in both species and also in seasons, but elevated levels of PCBs and PAHs were detected in warmer months during the period.

CONCLUSION

As a consequence, toxic chemicals in both clam species were found at low concentrations in this study from the point of view of public health concerns; however, the contaminants should be closely monitored in the future due to their elevated levels in samples. © 2020 Society of Chemical Industry.

Distribution Characteristics and Environmental Control Factors of Lipophilic Marine Algal Toxins in Changjiang Estuary and the Adjacent East China Sea

Marine algal toxins, highly toxic secondary metabolites, have significant influences on coastal ecosystem health and mariculture safety. The occurrence and environmental control factors of lipophilic marine algal toxins (LMATs) in the surface seawater of the Changjiang estuary (CJE) and the adjacent East China Sea (ECS) were investigated. Pectenotoxin-2 (PTX2), okadaic acid (OA), dinophysistoxin-1(DTX1), and gymnodimine (GYM) were detected in the CJE surface seawater in summer, with concentration ranges of not detected (ND)-105.54 ng/L, ND-13.24 ng/L, ND-5.48 ng/L, and ND-12.95 ng/L, respectively. DTX1 (ND-316.15 ng/L), OA (ND-16.13 ng/L), and PTX2 (ND-4.97 ng/L) were detected in the ECS during spring. LMATs formed a unique low-concentration band in the Changjiang diluted water (CJDW) coverage area in the typical large river estuary. PTX2, OA, and DTX1 in seawater were mainly derived from Dinophysis caudate and Dinophysis rotundata, while GYM was suspected to be from Karenia selliformis. Correlation analyses showed that LMAT levels in seawater were positively correlated with dissolved oxygen and salinity, but negatively correlated with temperature and nutrients, indicating that the hydrological condition and nutritional status of seawater and climatic factors exert significant effects on the distribution of LMATs.

Contamination status of lipophilic marine toxins in shellfish samples from the Bohai Sea, China

Lipophilic marine toxins in shellfish pose significant threats to the health of seafood consumers. To assess the contamination status of shellfish by lipophilic marine toxins in the Bohai Sea, nine species of shellfish periodically collected from five representative aquaculture zones throughout a year were analyzed with a method of liquid chromatography-tandem mass spectrometry (LC-MS/MS). Lipophilic marine toxins, including okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-2 (PTX2), yessotoxin (YTX), homo-yessotoxin (homo-YTX), azaspiracids (AZA2 and AZA3), gymnodimine (GYM), and 13-desmethyl spirolide C (13-DesMe-C), were detected in more than 95 percent of the shellfish samples. Toxins PTX2, YTX, 13-DesMe-C and GYM were predominant components detected in shellfish samples. Scallops, clams and mussels accumulated much higher level of lipophilic marine toxins compared to oysters. Toxin content in shellfish samples collected from different sampling locations showed site-specific seasonal variation patterns. High level of toxins was found during the stages from December to February and June to July in Hangu, while from March to April and August to September in Laishan. Some toxic algae, including Dinophysis acuminata, D. fortii, Prorocentrum lima, Gonyaulax spinifera and Lingulodinium polyedrum, were identified as potential origins of lipophilic marine toxins in the Bohai Sea. The results will offer a sound basis for monitoring marine toxins and protecting the health of seafood consumers.

Aliphatic and aromatic biomarkers for fingerprinting of weathered chemically dispersed oil

This study evaluated the applicability of eight types of biomarkers namely, adamantanes, diamantanes, sesquiterpanes, steranes, terpanes, TA-steranes, MA-steranes, and alkylated PAHs, to characterize chemically dispersed oil (CDO) after the 60-day weathering. The stability of diagnostic ratios of the selected biomarkers was evaluated and summarized. The results indicated that the concentrations of biomarkers with low molecular weight, such as adamantanes, diamantanes, and sesquiterpanes, in CDO were markedly affected by weathering and the associated diagnostic ratios were changed extensively. Most of the alkylated PAHs were degraded during weathering as well. These biomarkers thus were not recommended for characterizing CDO. The majority of the terpanes, steranes, TA-steranes, and MA-steranes could be used for weathered CDO fingerprinting due to the relatively stable diagnostic ratios. The findings could help to identify applicable biomarkers for fingerprinting of weathered dispersed oil.

5-Hydroxy-2-methylpyridine Isolated from Cigarette Smoke Condensate Aggravates Collagen-Induced Arthritis in Mice

The risk of rheumatoid arthritis (RA) is linked to environmental and genetic factors. Cigarette smoking is an established environmental risk factor for the disease that contributes to its development and severity. Previously, we found that cigarette smoke condensate (CSC), both mainstream and sidestream, aggravates collagen type II-induced arthritis (CIA), which was observed following either intraperitoneal inoculation or nasal exposure. In the present study, we aimed to identify the compound in CSC, which aggravates CIA. By sequential fractionation and analysis, extraction with water/ether in different pH values, silica gel column chromatography, TLC, octadecyl silica (ODS) HPLC, GC/MS, and NMR, the active compound was identified as 5-hydroxy-2-methylpyridine (5H2MP). Its isomer 2-hydroxy-3-methylpyridine, but not 3-hydroxy-2-methylpyridine, was also active. 5H2MP was not mutagenic, and did not exhibit aryl hydrocarbon receptor-dependent activity. Our data help clarify the mechanism underlying the pathogenic effects of cigarette smoking on RA.

Lipophilic marine toxins discovered in the Bohai Sea using high performance liquid chromatography coupled with tandem mass spectrometry

Some dinoflagellates can produce lipophilic marine toxins, which pose potent threats to seafood consumers. In the Bohai Sea, an important semi-closed inland sea with intensive mariculture industry in China, there is little knowledge concerning lipophilic marine toxins and their potential threats. In this study, net-concentrated phytoplankton samples were periodically collected from 5 typical mariculture zones around the Bohai Sea, including Laishan (LS), Laizhou (LZ), Hangu (HG), Qinhuangdao (QHD) and Huludao (HLD) in 2013 and 2014, and a method using high performance liquid chromatography (HPLC) coupled with a Q-Trap mass spectrometer was applied to analyze seven representative lipophilic marine toxins, including okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-2 (PTX2), yessotoxin (YTX), azaspiracid-1 (AZA1), gymnodimine (GYM), and 13-desmethyl spirolide C (desMeC). The method had high sensitivity and repeatability, and exhibited satisfactory recoveries for most of the lipophilic marine toxins (92.1-108%) except for AZA1 (65.8-68.9%). Nearly all the lipophilic marine toxins could be detected in phytoplankton samples from the Bohai Sea. OA, DTX1 and PTX2 were predominant components and present in most of the phytoplankton samples. The maximum content of lipophilic marine toxin in phytoplankton samples concentrated from seawater (OA 464 pg L^-1; DTX1 783 pg L^-1; YTX 86.6 pg L^-1; desMeC 15.6 pg L^-1; PTX2 1.11 × 10³ pg L^-1) appeared in June 2014. Based on toxins present in phytoplankton samples, it is implied that seafood in the Bohai Sea is more likely to be contaminated by OA group and PTX group toxins, and spring is the high-risk season for toxin contamination.

Occurrence of marine algal toxins in oyster and phytoplankton samples in Daya Bay, South China Sea

The occurrence and seasonal variations of marine algal toxins in phytoplankton and oyster samples in Daya Bay (DYB), South China Sea were investigated. Two Dinophysis species, namely, D. caudata and D. acuminata complex, were identified as Okadaic acid (OA)/pectenotoxin (PTX) related species. Liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis demonstrated that 2.04-14.47 pg PTX2 per cell was the predominant toxin in single-cell isolates of D. caudata. D. acuminata was not subjected to toxin analysis. The occurrence of OAs in phytoplankton concentrates of net-haul sample coincided with the presence of D. accuminata complex, suggesting that this species is most likely an OA producer in this sea area. OA, dinophysistoxins-1 (DTX1), PTX2, PTX2sa, gymnodimine (GYM), homoyessotoxin (homoYTX), and domoic acid (DA) demonstrated positive results in net haul samples. To our best knowledge, this paper is the first to report the detection of GYM, DA, and homoYTX in phytoplankton samples in Chinese coastal waters. Among the algal toxins, GYM demonstrated the highest frequency of positive detections in phytoplankton concentrates (13/17). Five compounds of algal toxins, including OA, DTX1, PTX2, PTX2sa, and GYM, were detected in oyster samples. DA and homoYTX were not detected in oysters despite of positive detections for both in the phytoplankton concentrates. However, neither the presence nor absence of DA in oysters can be determined because extraction conditions with 100% methanol used to isolate toxins from oysters (recommended by the EU-Harmonised Standard Operating Procedure, 2015) would likely be unsuitable for this water-soluble toxin. In addition, transformation of DA during the digestion process of oysters may also be involved in the negative detections of this toxin. GYM exhibited the highest frequency of positive results in oysters (14/17). OAs were only detected in the hydrolyzed oyster samples. The detection rates of PTX and PTX2sa in oysters were lower than those in the net haul samples.

Distribution of Marine Lipophilic Toxins in Shellfish Products Collected from the Chinese Market

To investigate the prevalence of lipophilic marine biotoxins in shellfish from the Chinese market, we used hydrophilic interaction liquid chromatography-tandem mass spectrometry (LC-MS/MS) to measure levels of okadaic acid (OA), azaspiracid (AZA1), pectenotoxin (PTX2), gymnodimine (GYM), and spirolide (SPX1). We collected and analyzed 291 shellfish samples from main production sites along a wide latitudinal transect along the Chinese coastline from December 2008 to December 2009. Results revealed a patchy distribution of the five toxins and highlighted the specific geographical distribution and seasonal and species variation of the putative toxigenic organisms. All five lipophilic marine biotoxins were found in shellfish samples. The highest concentrations of OA, AZA1, PTX2, GYM, and SPX1 were 37.3, 5.90, 16.4, 14.4, and 8.97 μg/kg, respectively. These values were much lower than the legislation limits for lipophilic shellfish toxins. However, the value might be significantly underestimated for the limited detection toxins. Also, these toxins were found in most coastal areas of China and were present in almost all seasons of the year. Thus, these five toxins represent a potential threat to human health. Consequently, studies should be conducted and measures should be taken to ensure the safety of the harvested product.

Lipophilic shellfish toxins in Dinophysis caudata picked cells and in shellfish from the East China Sea

We reported previously that okadaic acid (OA) and dinophysistoxin-1 (DTX1) were responsible for diarrhetic shellfish poisoning (DSP) incidents due to consuming cultivated mussels (Mytilus galloprovincialis) in coastal cities near the East China Sea in May 2011. Pectenotoxin-2 (PTX2) and its seco acids were also present in these mussels. Causative species of microalgae were not identified because detailed information on the location of the contaminated shellfish was not recorded. In order to explore potential causes for these poisoning events, the lipophilic toxin profiles in picked cells of Dinophysis and in shellfish samples collected from two mariculture zones in the East China Sea were analyzed in the present study. Single-cell isolates (100 cells total for each location) of Dinophysis were collected from the aquaculture zones of Gouqi Island (Ningbo City, Zhejiang Province) and Qingchuan Bay (Ningde City, Fujian Province) in July and September 2013, respectively, for lipophilic toxin profiling. Shellfish samples collected over the course of a year from the Gouqi Island aquaculture zone and mussels (M. galloprovincialis) collected four times from the Qingchuan Bay aquaculture zone were tested for lipophilic toxins by LC-MS/MS. The Dinophysis cells isolated from both sampling sites were identified under the light microscope as Dinophysis caudata. Average quota of PTX2, the predominant toxin in D. caudata isolated from the coastal waters of Gouqi Island and Qingchuan Bay, was 0.58 and 2.8 pg/cell, respectively. Only trace amounts of OA and DTX1 were detected in D. caudata. PTX2, PTX2sa, 7-epi-PTX2sa, OA, and/or DTX1 were found in samples of mussels (M. galloprovincialis and Mytilus coruscus) collected in the Gouqi Island aquaculture zone from the end of May to the beginning of July 2013. PTX2, PTX2sa, and 7-epi-PTX2sa were also detected in oyster (Crassostrea gigas) during that period, but almost no OA and DTX1 were present. Gymnodimine (GYM) was detected in almost all mussel (M. coruscus) samples, with the highest levels occurring in winter. Trace amounts of pectenotoxins (PTXs) and OAs were also found in mussels (M. galloprovincialis) collected from Qingchuan Bay. D. caudata is suggested as an important source of PTXs in shellfish cultivated in the East China Sea. This is the first report of toxin profiles for single-cell isolates of Dinophysis in the East China Sea.

Signatures in vibrational and UV-visible absorption spectra for identifying cyclic hydrocarbons by graphene fragments

To promote possible applications of graphene in molecular identification based on stacking effects, in particular in recognizing aromatic amino acids and even sequencing nucleobases in life sciences, we comprehensively study the interaction between graphene segments and different cyclic organic hydrocarbons including benzene (C6H6), cyclohexane (C6H12), benzyne (C6H4), cyclohexene (C6H10), 1,3-cyclohexadiene (C6H8(1)) and 1,4-cyclohexadiene (C6H8(2)), using the density-functional tight-binding (DFTB) method. Interestingly, we find obviously different characteristics in Raman vibrational and ultraviolet visible absorption spectra of the small molecules adsorbed on the graphene sheet. Specifically, we find that both spectra involve clearly different characteristic peaks, belonging to the different small molecules upon adsorption, with the ones of ionized molecules being more substantial. Further analysis shows that the adsorptions are almost all due to the presence of dispersion energy in neutral cases and involve charge transfer from the graphene to the small molecules. In contrast, the main binding force in the ionic adsorption systems is the electronic interaction. The results present clear signatures that can be used to recognize different kinds of aromatic hydrocarbon rings on graphene sheets. We expect that our findings will be helpful for designing molecular recognition devices using graphene.

Discovery of gymnodimine fatty acid ester metabolites in shellfish using liquid chromatography/mass spectrometry

RATIONALE

Gymnodimines (GYMs) are fast-acting toxins that belong to the cyclic imine group, a subclass of lipophilic marine toxins. GYMs are considered to be emerging toxins but have not yet been linked to incidents of human poisoning, Limited knowledge on the metabolism of GYMs means that a proper risk assessment has not been possible and caution must be taken when establishing the relevance of GYMs in terms of food safety of marine products.

METHODS

A series of mass spectrometric experiments involving precursor and product ion scans, selected reaction monitoring (SRM), and high-resolution mass spectrometry (MS) were used to detect and confirm 10-O-acyl esters of gymnodimine-A (1).

RESULTS

We have detected for the first time the presence of a range of acyl ester derivatives of GYMs in shellfish samples from the Gulf of Gabes, Tunisia. The MS fragmentation pathways of 1 and its esters were also elucidated. Partial synthesis of a palmitic acid ester of 1 facilitated confirmation of identity and calibration of SRM analyses. Evidence of acyl ester metabolites of gymnodimine-B and -C was also obtained.

CONCLUSIONS

A semi-quantitative analysis indicated that the majority of GYMs present in the sample were in the acylated form (>90%), suggesting that these compounds must not be neglected when trying to understand the risks associated with GYMs. There is a clear need for toxicology studies on these esters and assessment of bio-availability to humans.

Development of a solid-phase receptor-based assay for the detection of cyclic imines using a microsphere-flow cytometry system

Biologically active macrocycles containing a cyclic imine were isolated for the first time from aquaculture sites in Nova Scotia, Canada, during the 1990s. These compounds display a "fast-acting" toxicity in the traditional mouse bioassay for lipophilic marine toxins. Our work aimed at developing a receptor-based detection method for spirolides using a microsphere/flow cytometry Luminex system. For the assay, two alternatives were considered as binding proteins, the Torpedo marmorata nicotinic acetylcholine receptor (nAChR) and the Lymnaea stagnalis acetylcholine binding protein (Ls-AChBP). A receptor-based inhibition assay was developed using the immobilization of nAChR or Ls-AChBP on the surface of carboxylated microspheres and the competition of cyclic imines with biotin-α-bungarotoxin (α-BTX) for binding to these proteins. The amount of biotin-α-BTX bound to the surface of the microspheres was quantified using phycoerythrin (PE)-labeled streptavidin, and the fluorescence was analyzed in a Luminex 200 system. AChBP and nAChR bound to 13-desmethyl spirolide C efficiently; however, the cross-reactivity profile of the nAChR for spirolides and gymnodimine more closely matched the relative toxic potencies reported for these toxins. The nAChR was selected for further assay development. A simple sample preparation protocol consisting of an extraction with acetone yielded a final extract with no matrix interference on the nAChR/microsphere-based assay for mussels, scallops, and clams. This cyclic imine detection method allowed the detection of 13-desmethyl spirolide C in the range of 10-6000 μg/kg of shellfish meat, displaying a higher sensitivity and wider dynamic range than other receptor-based assays previously published. This microsphere-based assay provides a rapid, sensitive, and easily performed screening method that could be multiplexed for the simultaneous detection of several marine toxins.

Cyclic volatile methylsiloxane bioaccumulation in flounder and ragworm in the Humber Estuary

Cyclic volatile methylsiloxanes are being subjected to regulatory scrutiny as possible PBT chemicals. The investigation of bioaccumulation has yielded apparently contradictory results, with high laboratory fish bioconcentration factors on the one hand and low field trophic magnification factors on the other. In this study, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) were studied along with polychlorinated biphenyls (PCBs) in sediments, ragworm, and flounder from six sites in the Humber Estuary. Bioaccumulation was evaluated using multimedia bioaccumulation factors (mmBAFs) which quantified the fraction of the contaminant present in the aquatic environment that is transferred to the biota. PCB 180, a known strongly bioaccumulative chemical, was used as a benchmark. The mean mmBAF of D5 was about twice that of PCB 180 in both polycheates and flounder, while for D4 it was 6 and 14 times higher, respectively. The mmBAF of D6 was a factor 5-10 lower than that of PCB180. The comparatively strong multimedia bioaccumulation of D4 and D5, even in the absence of biomagnification, was explained by both compounds having a >100 times stronger tendency to partition into lipid rather than into organic carbon, while PCB 180 partitions to a similar extent into both matrices.

Quantitative determination of gymnodimine-A by high performance liquid chromatography in contaminated clams from Tunisia coastline

Quantitative determination by high performance liquid chromatography (HPLC) was performed for gymnodimine-A (GYM-A), a phycotoxin responsible for the contamination of Tunisian clams. This study demonstrates a rapid and reproducible HPLC-ultraviolet (UV) method for extraction, detection and quantification of GYM-A in toxic clams. The extraction of GYM-A from the digestive gland of clams in acetone, subsequent clean-up with diethyl ether and extraction with dichloromethane is the more valid protocol. Chromatography analyses were performed using a gradient of acetonitrile-water (10:90 to 90:10), containing trifluoroacetic acid (0.1%) for 20 min at 1 mL/min rate with a C18 column. Recovery rates exceeded 96%, and limits of detection and quantification were 5 ng/mL and 8 ng/g digestive gland, respectively. Repeatability and reproducibility were tested for various samples containing different levels of GYM-A. A significant correlation was observed between toxicity level of samples and the determined amount of GYM-A. Also, the persistence of GYM-A in contaminated clams from Boughrara lagoon was demonstrated. The kinetics discharge study of GYM-A in controlled medium, during 1 month, showed that the process of depuration was biphasic with an exponential discharge of 75% of the total amount of sequestered GYM-A during the first 12 days followed by a slow discharge (>10%) for the subsequent days up to the seventeenth day. This is the first time that a quantitative study of GYM-A in clams from Tunisian coasts is performed through the development of a new method for detection and quantify of this phycotoxin. We found HPLC-UV a reliable and suitable alternative to the mouse bioassay.

[Analysis of volatile oil in herb of pimpinella candolleana by SPME-GC-MS]

OBJECTIVE

To analyze components of volatile oil from the herb of Pimpinella candolleana.

METHOD

The components of volatile oil were investigated by SPME-GC-MS.

RESULT

Sixty-five compounds were identified which accounted for 92. 17% of total volatile oil.

CONCLUSION

The main constituents in the essential oil were alpha-zingiberene (24.82%), pregeijerene (16.27%), beta-bisabolene (4. 82%), 2-isopropyl-5-methyl-9-methylene-bicyclo [ 4. 4. 0] dec-l-ene (4.03%), beta-sesquiphellandrene (3.98%), trans-beta-farnesene (3.68%), ar-curcumene (3.54%).

Hydrocarbon uptake by roots of Vicia faba (Fabaceae)

Vicia faba was grown in crude oil polluted soil and its roots were extracted for the detection and estimation of hydrocarbons. Saturated and unsaturated Aliphatic Hydrocarbons (AHs) ranging from C(22) to C(36) were identified in AHs fraction. However, PAHs were not present in the same extract. This could be due to the fact that PAHs being toxic compounds are not accumulated in the plant root extracts of V. faba grown in crude oil polluted soil. Three phytoalexins were identified and estimated by mass spectrometric analysis in the root extracts of V. faba. These three compounds are 2-t-butyl-4-(dimethyl benzyl) phenol, 2, 4-bis (dimethyl benzyl) phenol and 2,4-bis (dimethyl benzyl)-6-butyl phenol. These phenolics in V. faba are being reported for the first time. These compounds are presumably elicited as a direct stress on crude oil hydrocarbons on the roots of this plant.

Toxin screening in phytoplankton: detection and quantitation using MALDI triple quadrupole mass spectrometry

The investigation of a MALDI triple quadrupole instrument for the analysis of spirolide toxins in phytoplankton samples is described in this study. A high-frequency (kHz) laser was employed for MALDI, generating a semicontinuous ion beam, thus taking advantage of the high duty cycle obtained in sensitive triple quadrupole MRM experiments. Initially, several experimental parameters such as type of organic matrix and concentration, solvent composition, and matrix-to-analyte ratio were optimized, and their impact on sensitivity and precision of the obtained ion currents for a reference spirolide, 13-desmethyl-C, was studied. In all quantitative experiments, excellent linearities in the concentration range between 0.01 and 1.75 microg/mL were obtained, with R2 values of 0.99 or higher. The average precision of the quantitative MALDI measurements was 7.4+/-2.4% RSD. No systematic errors were apparent with this method as shown by a direct comparison to an electrospray LC/MS/MS method. Most importantly, the MALDI technique was very fast; each sample spot was analyzed in less than 5 s as compared to several minutes with the electrospray assay. To demonstrate the potential of the MALDI triple quadrupole method, its application to quantitative analysis in several different phytoplankton samples was investigated, including crude extracts and samples from mass-triggered fractionation experiments. 13-Desmethyl spirolide C was successfully quantified in these complex samples at concentration levels from 0.05 to 90.4 microg/mL (prior to dilution to have samples fall within the dynamic range of the method) without extensive sample preparation steps. The versatility of the MALDI triple quadrupole method was also exhibited for the identification of unknown spirolide analogues. Through the use of dedicated linked scan functions such as precursor ion and neutral loss scans, several spirolide compounds were tentatively identified directly from the crude extract, without the usual time-consuming chromatographic preseparation steps. Moreover, high-quality CID spectra were obtained for low-abundant spirolides present in the phytoplankton samples.

Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry in the identification of organic compounds in atmospheric aerosols from coniferous forest

Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOF-MS) was applied in the identification of organic compounds in atmospheric aerosols from coniferous forest. The samples were collected at Hyytiälä, Finland, as part of the QUEST campaign, in Spring 2003. Manual and automated search procedures were compared in the identification. An automated procedure is preferable when a large number of data files need to be processed; but manual search was more accurate with the present samples, where the number of compounds was large and most of the compounds of interest were present at trace level. Altogether, about 50 compounds were identified on the basis of mass spectra and linear retention indices. The identified compounds included oxidised monoterpenes, acyclic alkanes, alkenes, ketones and aldehydes, as well as a few alcohols, acids, and aromatic compounds.

Multiresidue method for determination of algal toxins in shellfish: single-laboratory validation and interlaboratory study

A method that uses liquid chromatography with tandem mass spectrometry (LC/MS/MS) has been developed for the highly sensitive and specific determination of amnesic shellfish poisoning toxins, diarrhetic shellfish poisoning toxins, and other lipophilic algal toxins and metabolites in shellfish. The method was subjected to a full single-laboratory validation and a limited interlaboratory study. Tissue homogenates are blended with methanol-water (9 + 1), and the centrifuged extract is cleaned up with a hexane wash. LC/MS/MS (triple quadrupole) is used for quantitative analysis with reversed-phase gradient elution (acidic buffer), electrospray ionization (positive and negative ion switching), and multiple-reaction monitoring. Ester forms of dinophysis toxins are detected as the parent toxins after hydrolysis of the methanolic extract. The method is quantitative for 6 key toxins when reference standards are available: azaspiracid-1 (AZA1), domoic acid (DA), gymnodimine (GYM), okadaic acid (OA), pectenotoxin-2 (PTX2), and yessotoxin (YTX). Relative response factors are used to estimate the concentrations of other toxins: azaspiracid-2 and -3 (AZA2 and AZA3), dinophysis toxin-1 and -2 (DTX1 and DTX2), other pectenotoxins (PTX1, PTX6, and PTX11), pectenotoxin secoacid metabolites (PTX2-SA and PTX11-SA) and their 7-epimers, spirolides, and homoYTX and YTX metabolites (45-OHYTX and carboxyYTX). Validation data have been gathered for Greenshell mussel, Pacific oyster, cockle, and scallop roe via fortification and natural contamination. For the 6 key toxins at fortification levels of 0.05-0.20 mg/kg, recoveries were 71-99% and single laboratory reproducibilities, relative standard deviations (RSDs), were 10-24%. Limits of detection were <0.02 mg/kg. Extractability data were also obtained for several toxins by using successive extractions of naturally contaminated mussel samples. A preliminary interlaboratory study was conducted with a set of toxin standards and 4 mussel extracts. The data sets from 8 laboratories for the 6 key toxins plus DTX1 and DTX2 gave within-laboratories repeatability (RSD(R)) of 8-12%, except for PTX-2. Between-laboratories reproducibility (RSDR) values were compared with the Horwitz criterion and ranged from good to adequate for 7 key toxins (HorRat values of 0.8-2.0).

Quantitative 1H NMR with External Standards: Use in Preparation of Calibration Solutions for Algal Toxins and Other Natural Products

We examine the use of external standards for quantitative measurement by 1H NMR of solution concentrations of natural products and other low molecular weight, hydrogen-containing compounds and show that precision and accuracy ca. 1% is obtainable with a commercial 11.7 T spectrometer when standards and analytes are contained in separate but identical sealed precision glass NMR tubes. Numerous factors contributing to the intensity of the NMR signals are evaluated. Precise measurements of 360 degrees pulse lengths for each sample provide direct corrections for variations in probe Q-factor that enable samples in different solvents to be compared, provided single-coil excitation and detection is used throughout. Samples need not be prepared in deuterated solvents if the 1H spectra of the solvents are simple enough for peak suppression by presaturation. The approach is particularly suitable for hazardous materials kept in sealed tubes and for the preparation of certified calibration solution reference materials for use with LC-MS and other techniques where deuterated solvents should be avoided.

Sonochemical reaction of selected cyclic C6Hx hydrocarbons in organic solvents

The rates and products of the sonochemical reactions of benzene, 1,4-cyclohexadiene, 1,3-cyclohexadiene, cyclohexene, and cyclohexane in selected organic solvents have been investigated. The sonochemical reactions of these educts in the investigated organic solvents follow first-order kinetics. Generally, they are sonicated more rapidly in polar than in non-polar solvent; higher volatility of the solute results in faster sonolysis in the organic solvents. However, the sonication of cyclohexane in n-decane and the sonication of benzene in n-propanol are exceptional cases. Since cyclohexane exhibits a much higher lipophilicity and benzene a much higher hydrophilicity than other educts, it might be more difficult to transfer either educt from the bulk liquid into the cavitation bubbles. In tetrachloroethylene, the reactivity of the tested educts with in situ generated chlorine as well as chlorine-containing radical intermediates can accelerate the rate of sonochemical reactions under the employed conditions. In n-propanol and n-decane, the pyrolysis during the collapse of the cavitation bubbles is the only reaction pathway of sonolysis. In tetrachloroethylene, the pyrolysis during the collapse of the cavitation bubbles and the free radical reaction in the bulk liquid may occur simultaneously. Except for the products generated from sonolysis, products formed from chlorine transformations (substitution or addition reactions) are detected. Benzene is hardly decomposed in tetrachloroethylene. However, when FeCl3 is added into the reaction system, benzene is sonoconverted rapidly, and the product chlorobenzene was detected. In organic solvents, the sonoreaction rates and the sonoproducts are dependent on the physicochemical properties of the solvents used, as well as the volatility, the polarity and the reactivity of educts.

Evaluation of a biologically active cover for mitigation of landfill gas emissions

Landfills are the third largest source of anthropogenic CH4 in the United States, and there is potential for reduction in this source of greenhouse gases and other contaminants. The objective of this work was to contrast emissions of CH4 and non-methane organic compounds (NMOCs) from landfill cells covered with soil or a biologically active cover consisting of yard waste compost. On the basis of four field campaigns over 14 months, CH4 emissions from the biocover (BC) varied from -1.73 to 1.33 g m(-2) d(-1), with atmospheric uptake measured in 52% of tests. BC emissions did not increase when the gas collection system was turned off. Uptake of atmospheric CH4 was measured in 54% of tests on the soil cover (SC) when the gas collection was system active and 12% when the gas collection system was off. Many (26%) relatively high fluxes (>15 g m(-2) d(-1)) were measured from the SC as were some dramatic effects due to deactivation of the gas collection system. In tests with positive emissions, stable isotope measurements showed that the BC and SC were responsible for oxidation of 55% and 21% of the CH4 reaching the bottom of the respective cover. Seven of the highest 10 NMOC emissions were measured in the SC, and 17 of 21 fluxes for speciated organic compounds were higher in the SC. The relationship between CH4, NMOC, and individual organic compound emissions suggested a correlation between CH4 and trace organic oxidation. BCs can reduce landfill gas emissions in the absence of a gas collection system and can serve as a polishing step in the presence of an active system.

Modelling soot and SOF emissions from a diesel engine

Modelling of soot and SOF emissions from a typical European turbocharged diesel engine has been made. The model consists of a detailed kinetic mechanism with 472 reactions (120 chemical species) and data from the thermodynamic diagnostic procedure of the combustion process of the engine. The forward kinetic constants were obtained from literature and the background constants from a self-developed non-linear fitting routine based on the Marquardt algorithm. The dilution and mixing processes inside the engine are represented by a simple Wiebe function. The system of ordinary differential equations is solved with the Rosenbrock method for rigid systems and using the interpolating Lagrange polynomials to calculate the heat capacity of each species at the corresponding temperature. The kinetic model has been implemented in Digital Visual Fortran 6.0. The model has been executed for five different fuels and three mixtures of biodiesel and reference diesel operating under three diverse conditions from the European transient urban/extraurban Certification Cycle and the results of soot and SOF predicted are compared with experimental data.

Source diagnostic and weathering indicators of tar balls utilizing acyclic, polycyclic and S-heterocyclic components

This study represents a forensic chemical analysis to define the liability for the coastal bitumens polluting the beaches of the Mediterranean city of Alexandria. Six tar balls collected from several locations along the coast of the city were analyzed for their acyclic and polycyclic hydrocarbons as well as sulfur heterocycles using GC/FID, GC/AED and gas chromatography/mass spectrometry techniques. The analysis of one Egyptian crude oil is also included as a possible source oil. The tar ball samples were at early stages of weathering. Based on the GC traces and biomarker signatures, the tar balls could be genetically different. One sample collected from the Eastern Harbor region appears to be a Bunker C type fuel produced from Egyptian crudes. The refining process has removed the low molecular weight components. On the other hand, the wide n-alkane distribution together with the absence of an unresolved complex mixture suggests that crude oils probably from tank washings, ballast discharges or accident spills from tankers could have contributed significantly to the other tar ball samples. The distribution of source specific hopane and sterane markers revealed that the tar samples probably originate from different oil fields.

Atmospheric pressure chemical ionization studies of non-polar isomeric hydrocarbons using ion mobility spectrometry and mass spectrometry with different ionization techniques

The ionization pathways were determined for sets of isomeric non-polar hydrocarbons (structural isomers, cis/trans isomers) using ion mobility spectrometry and mass spectrometry with different techniques of atmospheric pressure chemical ionization to assess the influence of structural features on ion formation. Depending on the structural features, different ions were observed using mass spectrometry. Unsaturated hydrocarbons formed mostly [M - 1]+ and [(M - 1)2H]+ ions while mainly [M - 3]+ and [(M - 3)H2O]+ ions were found for saturated cis/trans isomers using photoionization and 63Ni ionization. These ionization methods and corona discharge ionization were used for ion mobility measurements of these compounds. Different ions were detected for compounds with different structural features. 63Ni ionization and photoionization provide comparable ions for every set of isomers. The product ions formed can be clearly attributed to the structures identified. However, differences in relative abundance of product ions were found. Although corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra detected are complex and differ from those obtained with 63Ni ionization and photoionization.

Analysis of linear and cyclic oligomers in polyamide-6 without sample preparation by liquid chromatography using the sandwich injection method. I. Injection procedure and column stability

We report a method for reliable routine polymer sample introduction with minimal bias, a separation method of the first six linear and cyclic oligomers by liquid chromatography, quantification using group equivalents and long term method performance. Injecting a polymer sample in a mobile phase containing an aqueous non-solvent often results in blocked systems as the polymer precipitates in the connecting capillaries. In this first part we focus on a new injection technique, in which the dissolved polyamide is placed between two zones of formic acid, preventing the polymer to precipitate before it reaches the column. Development of this sandwich injection method makes direct injection of the polymer into an aqueous acetonitrile gradient feasible. The oligomeric polyamide recovery of this technique, extraction, dissolution/precipitation and direct injection on a hexafluoro-isopropanol (HFIP) gradient were compared. With the sandwich injection method the polymer remains on the column, slowly changing the stationary phase. The influence of this on resolution and retention was studied. Column stability allows sixty injections before cleaning or replacing the column is necessary.

Validity of biomarkers in environmental health studies: the case of PAHs and benzene

Exposure biomarkers, which have long been restricted to the framework of occupational hygiene, currently arouse increasing interest in the field of environmental pollution. To assess their validity, we propose here a conceptual framework that is based on their intrinsic characteristics and on properties related to the procedures for their analysis. The most important criteria are specificity for the toxic substance under consideration and sensitivity, that is, the ability to distinguish contrasted levels of exposure. Their analytic sensitivity and specificity are also important. Fulfilling these criteria is especially important in the context of environmental pollution, because the levels of exposure, and thus the contrasts, are low. This framework is used to assess the validity of some biomarkers for polycyclic aromatic hydrocarbons (1-hydroxypyrene and DNA adducts) and for benzene (urinary and serum benzene, trans,trans muconic acid, and S-phenylmercapturic acid). This evaluation shows that the most relevant biomarkers for estimating individual exposure to environmental pollution are 1-hydroxypyrene for polycyclic aromatic hydrocarbons and urinary benzene and S-phenylmercapturic for benzene.

A survey of cyclopropenylidene (C3H2) in galactic sources

We report the results of an initial survey in a variety of Galactic sources for cyclopropenylidene (C3H2), the first interstellar hydrocarbon ring molecule. C3H2 is found to be very widespread throughout the Galaxy. This, together with its large dipole moment and many observable transitions, makes cyclopropenylidene a promising probe for physical conditions in the interstellar medium. The ortho 1(10)-1(01) transition at 18 GHz is detected in a variety of environments, including giant molecular clouds, diffuse clouds, cold dark clouds, the spiral arm clouds in the direction of distant continuum sources, and the envelope of the carbon star IRC + 10216. The 2(20)-2(11) para line at 21.6 GHz was surveyed in many sources having strong 1(10)-1(01) emission, and, when detected, it was always seen in absorption. A more limited survey of the ortho 2(12)-1(01) transition at 85.3 GHz has been conducted. In addition, the 2(11)-2(02) line of the para species at 46.8 GHz was detected in the dark clouds TMC-1 and L134N. Maps have been made of the clouds TMC-1, L134N, W51, and Orion, confirming that the C3H2 emission is extended in these objects. The data obtained thus far suggest that C3H2 is one of the more abundant organic constituents of the dense interstellar medium.

Collisional excitation of interstellar cyclopropenylidene

Theoretical rotational excitation rates were computed for C3H2 in collisions with He atoms at temperatures from 30 to 120 K. The intermolecular forces were obtained from accurate self-consistent field and perturbation theory calculations, and collision dynamics were treated within the infinite-order sudden approximation. The accuracy of the latter was examined by comparing with the more exact coupled states approximation.

Detections of 13C-substituted C3H2 in astronomical sources

We report observations of the 2(12)-1(01) rotational transition of the 13C isotopic species of cyclopropenylidene (C3H2) toward TMC-1, Sgr B2, and IRC +10216 using the laboratory rest frequencies which have recently become available. Our detections allow estimates to be made of the fractional abundance of the unsubstituted similar species in these sources. The fractional abundance relative to H2, f(C3H2), is 1-2 x 10(-8) in TMC-1, and this is similar to the abundance of HCN, one of the more abundant organic molecules in the interstellar medium. In IRC +10216 f(C3H2) is one order of magnitude greater than in TMC-1. The 12C species in Sgr B2 shows a self-absorbed profile and the relative abundance of C3H2 estimated to be about an order of magnitude less than in TMC-1.

The C3H2 2(20)-2(11) transition: absorption in cold dark clouds

The first observations of the 2(20)-2(11) transition of cyclopropenylidene (C3H2) at 21.6 GHz are described. In all cases where it has been detected, the line appears in absorption, showing that this transition is "refrigerated" (i.e., Tex < 2.7 K) in cold dust clouds. These results are compared with those for the 1(10)-1(01) transition of C3H2, and the consequences for the excitation of C3H2 qualitatively discussed.