Simultaneous Analysis of the Metabolome and Lipidome Using Polarity Partition Two-Dimensional Liquid Chromatography-Mass Spectrometry.

Comprehensive metabolic profiling is a considerable challenge for systems biology since the metabolites in biological samples have significant polarity differences. A heart-cutting two-dimensional liquid chromatography-mass spectrometry (2D-LC-MS) method-based polarity partition was established to analyze both the metabolome and lipidome in a single run. Based on the polarity partition strategy, metabolites with high polarity were retained and separated by one-dimensional hydrophilic chromatography, while low- and medium-polarity lipids were collected into a sample loop and injected into two-dimensional reversed-phase chromatography for separation. A simple online dilution strategy realized the online coupling of the 2D-LC-MS, which effectively solved band broadening and peak distortion caused by solvent incompatibility. Moreover, a dual gradient elution procedure was introduced to further broaden the coverage of low-polarity lipids. The metabolites' log P values, which this 2D-LC-MS method could analyze, ranged from -8.79 to 26.86. The feasibility of the 2D-LC-MS system was demonstrated by simultaneous analysis of the metabolome and lipidome in rat plasma related to depression. A total of 319 metabolites were determined within 40 min, including organic acids, nucleosides, carbohydrate derivatives, amino acids, lipids, and other organic compounds. Finally, 44 depression-related differential metabolites were screened. Compared with conventional LC-MS-based methods, the 2D-LC method covered over 99% of features obtained by two conventional methods. In addition, the selectivity and resolution of the hydrophilic metabolites were improved, and the matrix effects of the hydrophobic metabolites were reduced in the developed method. The results indicated that the established 2D-LC system is a powerful tool for comprehensive metabolomics studies.

Brominated flame retardants in black plastic kitchen utensils: Concentrations and human exposure implications.

Concerns exist that restricted brominated flame retardants (BFRs) present in waste polymers may have, as a result of recycling, inadvertently contaminated items not required to meet flame retardancy regulations (e.g. plastic kitchen utensils). To investigate the extent to which kitchen utensils are contaminated with BFRs and the potential for resultant human exposure, we collected 96 plastic kitchen utensils and screened for Br content using a hand-held X-ray fluorescence (XRF) spectrometer. Only 3 out of 27 utensils purchased after 2011 contained detectable concentrations of Br (≥3µg/g). In contrast, Br was detected in 31 out of the 69 utensils purchased before 2011. Eighteen utensils with Br content higher than 100µg/g, and 12 new utensils were selected for GC-MS analysis of BFRs. BFRs targeted were polybrominated diphenyl ethers (PBDEs) BDE-28, 47, 99, 100, 153, 154, 183 and 209, and novel BFRs (NBFRs) pentabromoethylbenzene (PBEB), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (BEH-TEBP) and decabromodiphenyl ethane (DBDPE). The ability of XRF to act as a surrogate metric of BFR concentration was indicated by a significant (Spearman coefficient=0.493; p=0.006) positive relationship between Br and ΣBFR concentration. Measurements of ΣBFRs were always exceeded by those of Br. This may be due partly to the presence of BFRs not targeted in our study and also to reduced extraction efficiency of BFRs from utensils. Of our target BFRs, BDE-209 was the most abundant one in most samples, but an extremely high concentration (1000µg/g) of BTBPE was found in one utensil. Simulated cooking experiments were conducted to investigate BFR transfer from selected utensils (n=10) to hot cooking oil, with considerable transfer (20% on average) observed. Estimated median exposure via cooking with BFR contaminated utensils was 60ng/day for total BFRs. In contrast, estimated exposure via dermal contact with BFR-containing kitchen utensils was minimal.

Vehicles as outdoor BFR sources: Evidence from an investigation of BFR occurrence in road dust.

The distribution of brominated flame retardants (BFRs) including ∑8PBDEs, DBDPE, BTBPE, EH-TBB, BEH-TEBP and PBEB in road dust (RD) collected in Xinxiang, China was characterized. Analysis of RD samples indicated that the BFR abundance declined as traffic density decreased, with total mean levels of 292, 184, 163, 104 and 70 ng g-1 dust at sites from traffic intersections, main roads, collector streets, bypasses and parks, respectively. A possible explanation for this phenomenon is that the majority of BFRs may be emitted from the interior of vehicles via their ventilation systems. Of the 13 analyzed substances, BDE-209 and BEH-TEBP were the most abundant components in RD from Xinxiang. Similar amounts of ∑BDEs excluding BDE-209 were found at different types of sampling sites, and thus, atmospheric deposition is also a probable source of BFRs in RD which can be subject to air transportation. The main PBDE sources were traced to commercial products including DE-71, Bromkal 79-8DE, Saytex 201E and Bromkal 82 DE mixtures. Our results confirm that the use of deca-BDE commercial mixture is a major source of PBDE contamination in RD. Risk assessment indicated the concentrations of BFRs in RD in this study do not constitute a non-cancer or cancer risk to humans through ingestion. Annual emission fluxes of the commonly detected BFRs via RD in China were estimated to be up to 4980 kg year-1.

Ozonation of indomethacin: Kinetics, mechanisms and toxicity.

Ozonation of a commonly used non-steroidal anti-inflammatory drug indomethacin (IM) was studied. Kinetic constants of IM with ozone and hydroxyl radicals were measured at an order of magnitude of 105M-1s-1 and 109M-1s-1, respectively. IM was degraded within 7min under the lowest ozone dose, but TOC removal was only 50% even under the highest ozone dose used in the experiments. Ozone rather than hydroxyl radicals was found to be the main oxidant during reaction, with a contribution rate of 80% under pH 7. Six intermediates were identified by high resolution mass spectrometer. Nitrogen atom, CC double bond and benzene ring were found to be the main reaction sites. Electrophilic attack or Criegee cyclo-addition were proved to be the most probable pathways at the first step. The formation mechanism of one of the ozone products was first proposed during the experiment, then confirmed by the density functional theory (DFT) calculation. Acetic acid, formic acid and oxalic acid were detected as small molecule organic products. The toxicity change during ozonation was measured by luminescent bacterium with results showing that the toxicity can be reduced to zero when ozone dose was high enough.

Concentrations of "legacy" and novel brominated flame retardants in matched samples of UK kitchen and living room/bedroom dust.

Concentrations of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDDs) and 5 novel brominated flame retardants (NBFRs) were measured in paired samples of kitchen and living room/bedroom dust sampled in 2015 from 30 UK homes. BDE-209 was most abundant (22-170,000 ng/g), followed by γ-HBCDD (1.7-21,000 ng/g), α-HBCDD (5.2-4,900 ng/g), ß-HBCDD (2.3-1,600 ng/g), BDE-99 (2.6-1,440 ng/g), BDE-47 (0.4-940 ng/g), decabromodiphenyl ethane (DBDPE) (nd-680 ng/g) and bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (BEH-TEBP) (2.7-630 ng/g). The concentrations in kitchens and living rooms/bedrooms are moderate compared with previous studies. Concentrations of BDE-209 in living room/bedroom dust were significantly lower and those of DBDPE significantly higher (p < 0.05) compared to concentrations recorded in UK house dust in 2006 and 2007. This may reflect changes in UK usage of these BFRs. All target BFRs were present at higher concentrations in living rooms/bedrooms than kitchens. With the exception of BDE-28, pentabromoethylbenzene (PBEB) and DBDPE, these differences were significant (p < 0.05). No specific source was found that could account for the higher concentrations in living rooms/bedrooms.

Ozonation of trimethoprim in aqueous solution: identification of reaction products and their toxicity.

This work aimed to better understand the ozonation process of a typical antibiotic pharmaceutical, trimethoprim in aqueous solution. The parent compound was almost completely degraded with ozone dose up to 3.5 mg/L with no mineralization. Twenty one degradation products were identified using an electrospray quadrupole time-of-flight mass spectrometer. Several ozonation pathways were proposed including hydroxylation, demethylation, carbonylation, deamination and methylene group cleavage. Two species of luminescent bacteria Photobacterium phosphoreum and Vibrio qinghaiensis were selected to assess the toxicity of ozonation products. For P. phosphoreum, higher level of toxicity was observed compared to the parent compound, but a negligible toxicity change was observed for V. qinghaiensis, indicating different modes of action for the same water sample. This was further confirmed by quantitative structure-active relationship analysis. This work proves the dominant role of ozone rather than hydroxyl radicals in the reaction and the potential risk after ozonation.