Aromatic Nitration Enhances Absorption of Biomass Burning Brown Carbon in an Oxidizing Urban Environment.

Brown carbon (BrC) from biomass burning constitutes a significant portion of light-absorbing components in the atmosphere. Although the aging of BrC surrogates from biomass burning has been studied in many laboratory settings, BrC aging behavior in real-world urban environments is not well understood. In this study, through a combination of online dynamic monitoring and offline molecular characterization, the ambient optical aging of BrC was linked to its dynamic changes in molecular composition.

New Insights into the Brown Carbon Chromophores and Formation Pathways for Aqueous Reactions of α-Dicarbonyls with Amines and Ammonium.

Aqueous-phase reactions of αdicarbonyls with ammonium or amines have been identified as important sources of secondary brown carbon (BrC). However, the identities of most chromophores in these reactions and the effects of pH remain largely unknown. In this study, the chemical structures, formation pathways, and optical properties of individual BrC chromophores formed through aqueous reactions of αdicarbonyls (glyoxal and methylglyoxal) with ammonium, amino acids, or methylamine at different pH's were characterized in detail by liquid chromatography-photodiode array-high resolution tandem mass spectrometry.

Occurrence, spatial distribution, and partitioning behavior of marine lipophilic phycotoxins in the Pearl River Estuary, South China.

The occurrence, spatial distribution, and partitioning behavior of 17 marine lipophilic phycotoxins (MLPs) in surface and bottom seawater, particulate organic matter (POM), and surface sediment from the Pearl River Estuary (PRE) were investigated to understand current contamination and the potential risks to marine ecosystems in this region. Nine MLPs were detected, including azaspiracid1-3, gymnodimine, okadaic acid, dinophysistoxin 1-2, pectenotoxin2 (PTX2), and homoyessotoxin, with ΣMLP concentrations ranging 545-12,600 pg L and 619-8,800 pg L in surface and bottom seawater, respectively; 0-294 ng g and 0.307-300 ng g dry weight (dw) in surface and bottom POM, respectively; and 3.

Direct determination of nosiheptide residue in animal tissues by liquid chromatography-tandem mass spectrometry.

Because only very weak signals of fragment ions of nosiheptide can be obtained, nosiheptide is usually detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS) via the determination of its hydrolyzed degradation product named HMIA in previous studies. The indirect method suffers from several problems, such as complicated samplepreparation, unavailable commercial HMIA, and the risk of the false-positive result by HMIA. However, we found that nosiheptide could produce several significant fragment ions under high collision energy (CE).

Water-Insoluble Organics Dominate Brown Carbon in Wintertime Urban Aerosol of China: Chemical Characteristics and Optical Properties.

The chromophores responsible for light absorption in atmospheric brown carbon (BrC) are not well characterized, which hinders our understanding of BrC chemistry, the links with optical properties, and accurate model representations of BrC to global climate and atmospheric oxidative capacity. In this study, the light absorption properties and chromophore composition of three BrC fractions of different polarities were characterized for urban aerosol collected in Xi'an and Beijing in winter 2013-2014. These three BrC fractions show large differences in light absorption and chromophore composition, but the chromophores responsible for light absorption are similar in Xi'an and Beijing.

Uptake and Depuration Kinetics of Pacific Ciguatoxins in Orange-Spotted Grouper ().

Ciguatoxins (CTXs), produced by toxic benthic dinoflagellates, can bioaccumulate in marine organisms at higher trophic levels. The current study evaluated the uptake and depuration kinetics of some of the most potent CTXs, Pacific CTX-1, -2, and -3 (P-CTX-1, -2, and -3), in orange-spotted grouper () exposed to 1 ng P-CTXs g fish daily. Over a 30 d exposure, P-CTX-1, -2, and -3 were consistently detected in various tissues of exposed fish, and the concentrations of the total P-CTXs in tissues generally ranked following the order of liver, intestine, gill, skin, brain, and muscle.

Ultra-Performance Liquid Chromatography Hyphenated with Quadrupole-Orbitrap Mass Spectrometry for Simultaneous Determination of Necine-Core-Structure Pyrrolizidine Alkaloids in Crotalaria sessiliflora L. without all Corresponding Standards.

Introduction: Crotalaria sessiliflora L. is a Chinese traditional herb for treatment of cutaneum carcinoma and cervical carcinoma. In addition to monocrotaline, coexisting pyrrolizidine alkaloids (PAs) also require further quantification for quality control and pharmaceutical uses of the herb.

Composition, distribution and risk of total fluorine, extractable organofluorine and perfluorinated compounds in Chinese teas.

To explore the residual characteristics of fluorine and perfluorinated compounds (PFCs) in tea, the total fluorine (TF), extractable organofluorine (EOF) and PFCs in 19 Chinese commercial teas of five categories were measured using cyclic neutron activation analysis combined with HPLC-MS/MS. The results showed that fluorine mainly existed as inorganic fluorine in teas, and identified fluorine (∑PFCs quantified as F) only accounted for 0.023-0.

[Residue Characteristics of Perfluorinated Compounds in the Atmosphere of Shenzhen].

In order to explore the residual characteristics of perfluorinated compounds (PFCs) in the atmosphere of Shenzhen, passive air samplers consisting of polyurethane foam (PUF) disks impregnated with XAD-4 power were deployed at 12 sites in Shenzhen from November 2014 to February 2015. Seven volatile and fifteen ionic PFCs were analyzed. The results indicated that ΣPFCs concentration ranged from 23.

Determination of four paraben-type preservatives and three benzophenone-type ultraviolet light filters in seafoods by LC-QqLIT-MS/MS.

For the first time, an efficient and sensitive analytical method based on liquid chromatography-quadrupole linear ion trap-tandem mass spectrometry (LC-QqLIT-MS/MS) was developed for the simultaneous determination of four paraben-type preservatives and three benzophenone-type ultraviolet light filters in both plant (Sargassum fusiforme, porphyra, kelp) and animal (hairtail, yellow croaker, shrimp) seafood. The samples were extracted in methanol by pressurized liquid extraction (PLE), and the extracts were then cleaned up by mixed-mode cationic exchange (MCX) solid-phase extraction cartridges. Both isotope-labeled internal standards and matrix-matched calibration standards were used to alleviate and correct for the matrix effects, and the limits of quantification (LOQs) were 10.

[Pollution fingerprints and sources of perfluorinated compounds in surface soil of different functional areas].

In order to explore the effect of regional functions on the pollution fingerprints and levels of perfluorinated compounds (PFCs), principal components analysis was combined with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and solid phase extraction enrichment in this research to analyze the levels of 14 PFCs species in 76 surface soil samples, which were collected from 4 functional regions, namely parks, communities, crossroads and surroundings of factories, as well as the urban background of Shenzhen. The results showed that regional functions had significant effect on total PFCs (sigma PFCs), which ranked as the following: surroundings of factories (P < 0.001) >> crossroads (P < 0.

[Distribution of perfluorinated compounds in surface water of Shenzhen reservoir groups].

In order to study the concentrations of 14 perfluorinated compounds (PFCs) in 25 surface water samples collected from 12 Shenzhen reservoirs in November of 2012 and January of 2013, high performance liquid chromatography-tandem mass spectrometry was combined with solid phase extraction enrichment in this research. The results indicated that perfluorohexane sulfonate and long-chain (C > or = 11) PFCs were below the detection limit in all samples and perfluorooctane acid was the primary species. No significant difference in concentration was found between samples from the center of the reservoir and the outlet.

[Influence of tap water treatment on perfluorinated compounds residue in the dissolved phase].

To study the perfluorinated compounds (PFCs) residues through water treatments including flocculation, sedimentation, sand filtration, ozonation with activated carbon and chlorination, as well as the seasonal variation of PFCs in the raw water of waterworks, 13 PFCs species in the dissolved phase of raw water, finished water, as well as the water samples after flocculation, sedimentation, sand filtration, and ozonation with activated carbon filtration were measured by the high performance liquid chromatography-tandem mass spectrometry combined with solid phase extraction. Results indicated that sigma PFCs residue in water was higher in spring and summer than that in fall and winter. The vast majority of PFCs in samples were of short and medium chains (C < or = 10), and perfluorooctane sulfonate was the most typical residue species.

[Residue of organic fluorine pollutants in hair and nails collected from Tianjin].

In order to explore the residue and distributions of organic fluorine pollutants in hair and nails, the residue levels of total fluorine (TF), extractable organic fluorine (EOF) and perfluorinated chemicals (PFCs) in hair and nails collected from Tianjin adults were measured by the cyclic neutron activation analysis (CNAA) combined with the high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that inorganic fluorine (mean: 2.0 mg.

[Determination of three estrogens in animal liver and kidney tissues by liquid chromatography-tandem mass spectrometry].

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of estrone, 17beta-estradiol, estriol in animal liver and kidney tissues. The sample was extracted by tert-butyl methyl ether, and the extract was evaporated by nitrogen at 45 degrees C. The residue was redissolved in hexane-dichloromethane (6:4, v/v), then purified on a silica solid-phase extraction column.

[Residue characteristics and distributions of perfluorinated compounds in surface seawater along Shenzhen coastline].

In order to explore the residue characteristics and distributions of 15 perfluorinated compounds (PFCs) in 18 surface seawater samples along Shenzhen coastline, high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) combined with solid phase extraction enrichment was applied in this research. The results indicated that residue level of PFCs in coastal surface seawater samples was significantly affected by human activities. Sigma PFCs residue levels in surface seawater from Shenzhen west coast, which locates below the estuary of Pearl River and Donghao River, are much higher than those from the east coast, which has low development and sparse population (P<0.

[Determination of 41 hormones in cereal feeds by liquid chromatography-tandem mass spectrometry].

A method was developed for the determination of 10 androgens, 11 progesterones, 10 glucocorticoids, 5 estrogens and 5 resorcylic acid lactones in cereal feeds by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Ethyl acetate was used to extract the sample, and the mixed QuEChERS sorbents were dispersed for purification. The extract was separated by a C18 column and detected in positive or negative multiple reaction monitoring (MRM) mode.

Investigation of zinc binding metallothioneins' polymerization in tris(hydroxymethyl)-aminomethane buffer by coupling of size exclusion chromatography with electrospray ionization mass spectrometry.

Polymerization of metallothioneins (MTs) is one of the commonly encountered puzzles in researching the structure and function of metallothioneins. In this work, a method involving SEC coupled with negative ion electrospray ionization mass spectrometry (ESI-MS) detection has been developed for the study of zinc binding MTs' polymerization in tris(hydroxymethyl)-aminomethane (TRIS) acetate buffer at physiological pH. This hyphenated technique allows separating the different polymeric states of MTs by SEC, followed by on-line identification of the individual MT subisoforms in each polymeric peak by ESI-MS detection.

Quantification of acetylcholine in microdialysate of subcutaneous tissue by hydrophilic interaction chromatography/tandem mass spectrometry.

It has recently been suggested that acetylcholine plays an important role in the modulation of tissue inflammation. In order to further understand the newly discovered cholinergic anti-inflammatory pathway, tracking the concentration changes of acetylcholine in tissue is required. This paper describes the development of a method coupling hydrophilic interaction chromatography with electrospray ionization tandem mass spectrometry (HILIC/ESI-MS/MS) for the separation and quantification of acetylcholine in microdialysis samples of normal rats and of rats with local inflammation.

[Analysis of three metabolite residues of dipyrone in bovine muscle and pork muscle using high performance liquid chromatography].

A method for the determination of metabolite residues of dipyrone, 4-formylaminoantipyrine (FAA), 4-aminoantipyrine (AA) and 4-methylaminoantipyrine (MAA) in bovine muscle and pork muscle has been developed. Homogenized muscle sample was extracted with Na2SO4-Na2SO3 solution. After filtration, the extract was cleaned-up by a C18 solid phase extraction cartridge.

[Determination of mercury in Chinese medicinal material and biological samples using pyrolysis atomic absorption spectrometry].

In this paper a rapid and simple method using pyrolysis coupled with atomic absorption spectrometry for the analysis of total mercury in Chinese medicinal material and biological samples is presented. No sample digestion was needed and this greatly simplifies the analytical procedure and minimizes potential sources of contamination. Under optimum conditions, the reproducibility of the method was 2.

[Study on Hg2+ distribution and speciation in different tissues of rats].

Mercury is one of the important pollutants that threaten people health greatly in environment. The purpose of this paper was to determine mercury distribution and mercury binding proteins in different tissues of rat fed orally with mercuric chloride by ICP-MS and SEC-UV-ICP-MS. The result showed that liver and kidney induced large amount of metallothioneins that was found to bind to mercury, copper and zinc after mercury intake in stomach and intestines.

[Determination of andrographolide and dehydroandrographolide in Andrographis paniculata nees materials and related patent medicines by reversed-phase high performance liquid chromatography].

A simple and accurate method for the determination of andrographolide and dehydroandrographolide in andrographis paniculata Nees materials and patent medicines with high performance liquid chromatography (HPLC) has been developed. The two components were extracted from powdered samples by shaking with methanol. The resultant extracts were separated within 15 min on a BECKMAN C18 column (4.

[Separation and identification of metallothionein isoforms and sub-isoforms by liquid chromatography].

A method has been established for the separation and identification of metallothionein (MT) isoforms and sub-isoforms by liquid chromatography. A mixture of rabbit liver MT was separated on a DEAE A-25 weak anion-exchange chromatographic (AEC) column. Inductively coupled plasma-mass spectrometer (ICP-MS) was used for off-line detection of Zn in each fraction.

[Characterization of Hg-binding metallothioneins in tissues of rat after oral intake of mercury chloride by size-exclusion chromatography coupled with inductively coupled plasma-mass spectrometry].

Hg concentrations, total metallothioneins (MTs) and metal-binding MTs in tissues of the rat after oral intake of HgCl2 were determined by the inductively coupled plasma-mass spectrometry (ICP-MS), a modifield mecurry saturarion assay and the size-exclusion chormatography (SEC) coupled with ICP-MS, respectively. The results indicated that Hg accumulation in all of the rat tissues, including kidney, liver, testicle, brain, heart, serum and blood plasma, in HgCl2 group significantly increased compared with that in the control group, especiallyin kidney,liver and testicle. A large amount of MTs was inducted in these exposed rat tissues, especially in their kidneys and livers.