Proton-bound complex mediating retro-Michael-type fragmentation of protonated 3-substituted oxindoles in the Orbitrap high-energy collisional dissociation cell.

RATIONALE: Oxindole derivatives are valuable building blocks for indole chemistry. Systematically exploring the fragmentation behavior of the protonated 3-pyrazole-substituted oxindoles by kinetic methods combined with density functional theory (DFT) calculations is useful for further understanding their basic properties, and might provide some insights into their reactivity trends in synthesis and metabolism. METHODS: All high-resolution high-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) experiments were carried out using electrospray ionization hybrid Quadrupole-Orbitrap mass spectrometry in positive ion mode. Theoretical calculations were carried out by the DFT method at the B3LYP level with the 6-311G (d, p) basis set in the Gaussian 03 package of programs. RESULTS: In the fragmentation of protonated 3-pyrazole-substituted oxindoles, the characterized protonated 3-(3-methyl-5-oxo-1H-pyrazol-4(5H)-ylidene)indolin-2-one derivatives and the protonated 5-methylpyrazolone were observed, which were proposed from the cleavage of the C(ß)-C(γ) bond in a retro-Michael reaction. With the kinetic plot, a linear correlation was established between the intensities of this two competitive product ions and the difference in proton affinities of the corresponding neutral molecules, which demonstrated that the retro-Michael reaction was mediated by a proton-bound complex. CONCLUSIONS: Using the kinetic method combined with theoretical calculations, a proton-bound complex mediating retro-Michael reaction was proposed for the fragmentation of protonated 3-pyrazole-substituted oxindoles in the high-energy collisional dissociation tandem mass spectrometry for the first time, which provided potential evidence to further understand their intrinsic bioactivities.

[Rapid determination of benzidine, picric acid, carbaryl, atrazine, and deltamethrin in surface water by ultra-performance liquid chromatography-tandem mass spectrometry].

A method requiring no pre-treatment steps other than filtration, using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), has been developed and applied for the rapid determination of benzidine, picric acid, carbaryl, atrazine, and deltamethrin residues in surface water. Water samples were filtered with a 0.2-µ m syringe filter for particle removal and injected directly into the UPLC instrument. The separation was performed on a Waters Acquity UPLC HSS T3 column utilizing a gradient elution program of methanol (containing 2 mmol/L ammonium acetate) and water (containing 2 mmol/L ammonium acetate) as the mobile phases at a flow rate of 0.4 mL/min. The detection was accomplished by multiple-reaction monitoring scanning in positive/negative ion-switching electrospray ionization mode. Good linearity was observed in the range 0.10-10.0 µ g/L or 1.00-100 µ g/L for different targets with correlation coefficients of 0.996-0.999. The limits of detection (LODs) were 0.01-0.22 µ g/L. The recoveries ranged between 81.4% and 113% at three spiked levels with relative standard deviations (n=6) between 0.84% and 14.0%. The developed method was applied to the analysis of surface waters (river water and reservoir water) from Hangzhou; atrazine and deltamethrin were detected in part of the analyzed samples. This proposed method was characterized by high sensitivity and precision, extensive analytical range, and a high analytical rate, and showed suitability for the analysis of the five named pollutants in surface water.

[Pollution Characteristics and Health Risk Assessment of Volatile Organic Compounds (VOCs) and Semi-volatile Organic Compounds (SVOCs) in Qiantang River's Hangzhou Section During a Water Odor Pollution Event].

For surface water samples collected from the Hangzhou section of Qiantang River (before, during, or after the occurrence of a water odor pollution event), 125 kinds of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs)were quantitatively determined via purge&trap-gas chromatography-mass spectrometry and liquid-liquid extraction-gas chromatography-triple quadrupole mass spectrometry. Then, the pollution characteristics of the VOCs and SVOCs were analyzed, and the health risk of these compounds was assessed. The results showed that 17 VOCs and SVOCs in the surface water samples of 4 monitoring sections were detected, in a concentration range of 0.01-1.21 µg·L-1, which is a low pollution level. The concentration of dichloromethane was the highest of 17 VOCs and SVOCs, accounting for 36.3%, and it was thus clear that dichloromethane was the main contributing factor. During the water odor pollution event, the concentrations of VOCs and SVOCs were significantly higher than they were in the three months before or after the occurrence of the event, by 2.1-4.6 times, reflecting the strong external source input. In addition, human health risk assessment of ingestion through drinking water and absorption through skin contact was performed using US EPA recommended methods. It indicated that the total non-carcinogenic and total carcinogenic risks (∑HI and ∑R) caused by VOCs and SVOCs are 2.4×10-3-3.6×10-2 and 1.9×10-7-1.0×10-6, respectively, both of which belong to the acceptable risk level. Therefore, although ∑HI and ∑R during the occurrence of the odor event were significantly higher than those in the three months before or after the event, the VOCs and SVOCs detected will not cause obvious non-carcinogenic nor carcinogenic health effects on humans.

[Simultaneous determination of nine perfluorinated compound precursors in atmospheric precipitation by solid phase extraction and ultra performance liquid chromatography with tandem mass spectrometry].

A high-throughput detection method has been developed for the determination of nine perfluorinated compound precursors (PFCPs) in atmospheric precipitation by solid phase extraction-ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (SPE-UPLC-ESI-MS/MS). The atmospheric precipitation samples were concentrated and purified with HLB solid phase extraction cartridges. The UPLC separation was performed on an HSS T3 column (100 mm×2.1 mm, 1.7 µm) utilizing a gradient elution program of methanol and water as the mobile phases at a flow rate of 0.2 mL/min. The MS/MS detection was performed under negative electrospray ionization (ESI-) in multiple reaction monitoring (MRM) mode. Good linearity was observed in the range of 0.05-5.00 µg/L, 0.50-50.0 µg/L or 5.00-500 µg/L with correlation coefficients from 0.9921 to 0.9995. The limits of detection (LODs) for the nine perfluorinated compound precursors were in the ranges of 0.05-7.9 ng/L. The recoveries ranged from 76.0% to 106% with the relative standard deviations between 0.72% and 13.7%. This method is characterized by high sensitivity and precision, extensive analytical range and quick analytical rate, and can be applied for the analysis of perfluorinated compound precursors in atmospheric precipitation.

[Perfluorinated Compounds in Snow from Downtown Hangzhou, China].

Snow samples were collected from the snow event on January 20-22, 2016 from 11 sites in downtown Hangzhou to explore the occurrence of sixteen perfluorinated compounds (PFCs) in the atmosphere. All samples were prepared by solid-phase extraction with Oasis WAX cartridges and analyzed using ultra performance liquid chromatography interfaced with tandem mass spectrometry (UPLC-MS/MS). The results showed that seven medium- and short-chain PFCs including C4 and C8 perfluorinated sulfonates (PFSAs) and C4-C6, C8, and C9 perfluorinated carboxylic acids (PFCAs) were detected in the snow samples. Total PFC concentrations ranged from 2.85 to 35.1 ng·L-1, whereas perfluorooctanoic acid (PFOA) dominated, with ranges of 2.15-23.0 ng·L-1, and perfluorooctane sulfonate (PFOS) was detected at lower levels, ranging from 0 to 0.46 ng·L-1. As compared to the results from other studies, the PFOA concentrations of the study region were at mid-level and the PFOS concentrations were relatively low. The spatial distribution of PFCs varied, and the pollutant concentrations of the snow samples from the sampling sites located in the urban areas were higher than those in the rural areas. The greatest total PFC concentrations were detected in Fuyang, whereas the lowest concentrations were detected in Jiande and Chun'an. In this study, the high concentrations of PFCs dominated by PFOA that were measured in the Hangzhou snow samples emphasize the importance of atmospheric wet deposition as one of the sources of PFC contamination in this ecological system and should be addressed. The occurrence of PFCs in the air, indicated by their presence in the snow, suggests that the atmospheric environment may be an important contributor in human and ecological exposure to PFCs by local residents.

[Residue Concentration and Distribution Characteristics of Perfluorinated Compounds in Surface Water from Qiantang River in Hangzhou Section].

This study studied the pollution characteristics of perfluorinated compounds (PFCs) in Qiantang River in Hangzhou section (QR). Surface water samples, collected in July 2014 and January 2015 from 14 sites in QR were analyzed for 16 PFCs. All samples were prepared by solid-phase extraction with Oasis WAX cartridges and analyzed using the ultra performance liquid chromatography interfaced to tandem mass spectrometry ( UPLC-MS/MS). The results showed that 8 medium-and short-chain PFCs including C4 and C8 perfluorinated sulfonates (PFSAs) and C4-C9 perfluorinated carboxylic acids (PFCAs) were detected in the surface waters. The total concentrations of PFCs ranged from 0.98 to 609 ng · L⁻¹, while perfluorooctanoic acid (PFOA) dominated, with range of 0.59-538 ng L⁻¹, and perfluorooctane sulfonate (PFOS) was detected at lower levels, ranging from 0 to 2.48 ng · L⁻¹. The spatial distribution of PFCs varied, and the pollutant concentrations at the sampling sites located in upstream of the river such as Lanjiangkou and Jiangjunyan were relatively high, PFCs concentration showed a decreasing trend from the upstream to the downstream. According to the ratio of feature components, PFCs in surface water of QR originated largely from the input of direct sewage emissions. Taken together, the PFCs pollution was highly correlated with the upstream of Qiantang River valley's industry distribution, and most of the mass load in the investigated river was attributed to upstream running water with a minor influence from the wastewater discharges along the river basin. Overall, the results presented here indicated that greater attention should be given to the contamination of PFCs, especially for PFOA in water body of QR.

[Simultaneous determination of sixteen perfluorinated organic compounds in surface water by solid phase extraction and ultra performance liquid chromatography with electrospray ionization tandem mass spectrometry].

A high-throughput detection method has been developed for the determination of sixteen perfluorinated organic compounds (PFCs) in surface water by solid phase extraction-ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (SPE-UPLC-ESI-MS/MS). The water samples were concentrated and purified through WAX solid phase extraction cartridges. The UPLC separation was performed on an ACQUITY UPLC BEH C18 column utilizing a gradient elution program of methanol (containing 2 mmol/L ammonium acetate) and water (containing 2 mmol/L ammonium acetate) as the mobile phases at a flow rate of 0.4 mL/min. The MS/MS detection was performed under negative electrospray ionization ( ESI ) in multiple reaction monitoring (MRM) mode. Good linearities were observed in the range of 0.5-100 gg/L or 1.0 - 100 microg/L with correlation coefficients from 0.998 7 to 0.999 9. The limits of detection (LODs) for the sixteen perfluorinated organic compounds were in the range of 0.06-0.46 ng/L. The recoveries ranged from 67.6% to 103% with the relative standard deviations between 2.94% and 12.0%. This method was characterized by high sensitivity and precision, extensive range and high speed, and can be applied for the analysis of PFC contaminants in surface water.

[Pollution characteristics and health risk assessment of organochlorine pesticides (OCPs) in the water of Lake Qiandao and its major input rivers].

Organochlorine pesticides (OCPs) were quantitatively determined by GC in several surface water samples collected in July 2011 and November 2011 from Lake Qiandao (Xin'an River Reservoir) and its major input rivers. Then the component characteristics and source apportionment of HCHs and DDTs were confirmed, and the health risk assessment was evaluated. The results showed that 8 OCPs were found to be in trace amount, and p,p'-DDT, a-HCH and p,p'-DDE were the highest frequently detected OCPs. The concentrations of total OCPs in surface water of the studied Lake ranged from 1.9 to 7.6 ng-L-1 , which were at lower pollution level, and 1.2-212 ng.L-1 in the samples from its three major input rivers. The spatial distribution of OCPs in the water of lake was varying, and Xin'an River, the mainstream of the lake, was the main input source of OCPs. Also, different contamination patterns among sampling seasons were found, the concentrations of OCPs in surface water collected in wet period were higher than those in dry season, which display the characteristics of nonpoint source pollution. According to the ratio of feature components, the OCPs in surface water from the Lake Qiandao originated largely from long distance transmission or degradation of technical HCHs, while additional sources of DDTs existed in the region. In addition, human health risk assessment of ingestion through the drinking water and skin contact absorption was performed using EPA recommends methods, the carcinogenic and non-carcinogenic risks caused by OCPs were 0. 06 x 10(-7)-23. 2 x 10(-7) and 3.43 x 10(-5) -6.01 x 10(-3), respectively. According to the acceptable risk level, the carcinogenic and non-carcinogenic risks of the chemicals investigated can be considered negligible in water body of Lake Qiandao.

[Characteristics and evaluation of volatile organic compounds discharge in typical enterprise wastewater in Hangzhou City].

Totally 77 kinds of volatile organic compounds (VOCs) in inlet/outlet wastewater of 10 typical enterprises in Hangzhou City were determined by headspace-gas chromatography-mass spectrometry, then the discharge characteristics of VOCs were analyzed, and the monitoring results were evaluated. The results indicated that 22 kinds of VOCs were detected in inlet wastewater, the range of VOCs concentrations was 7-3.39 x 10(6) microg x L(-1), while 14 kinds of VOCs were detected in outlet wastewater, the range of VOCs concentrations was 16- 6.82 x 10(4) microg x L(-1). The concentrations of VOCs in inlet/outlet wastewater of flavors and fragrances manufacturing enterprises were much higher than those of other industries. When using the third class discharge standard of "integrated wastewater discharge standard" (GB 8978-1996) as the evaluation criteria, the toluene concentration detected in outlet wastewater of enterprise 1 was 2.45 x 10(3), microg x L(-1), which exceeded the standard limit. In addition. When the discharge multimedia environmental goals (DMEG(WH)) of VOCs in water was used as the evaluation criteria, the concentrations of n-butyl alcohol, isopropyl alcohol, acetone in outlet wastewater of enterprise 3 exceeded their respective discharge multimedia environmental goals.

[Simultaneous determination of nine microcystins in surface water by solid phase extraction and ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry].

A method has been developed for the simultaneous determination of nine microcystins (MCs) in surface water by solid phase extraction-ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (SPE-UPLC-ESI-MS/MS). The samples were enriched and purified by an HLB solid phase extraction column. The separation was performed on an ACQUITY UPLC system with a BEH C18 column with the gradient elution of acidified acetonitrile and water (both containing 0.1% (v/v) formic acid). The nine MCs were determined in the modes of electrospray positive ionization (ESI+) and multiple reaction monitoring (MRM). Good linearities were observed in the ranges of 0.1-50 microg/L for MC-RR and 0.5-100 microg/L for the others with correlation coefficients over 0. 999 0 and the limits of detection for the nine MCs were in the range of 0.1-0.5 ng/L. The recoveries were in the range of 75.8%-109% in the three spiked levels of 1.0, 10 and 50 microg/L with the relative standard deviations of 0.49%-10.0%. The method is characterized by high sensitivity and precision, extensive analytical range and quick analytical rate. This method was used in the analysis of water samples from two reservoirs situated in Hangzhou, and the 3 and 8 microcystins were detected individually.