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Copyright of Acta Scientiarum Naturalium Universitatis Pekinensis is the property of Editorial Office of Acta Scientiarum Naturalium Universitatis Pekinensis and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

"Tobacco-free" or synthetic nicotine products have been favored by the majority of young people, which undoubtedly increase the potential health risks and regulatory challenges. Currently, there are few reliable methods for the determination of authenticity of natural nicotine and synthetic nicotine. The analytical techniques based on mass spectrometry have broad application prospects in component sequence analysis. structure analysis, molecular weight determination and component content determination. The synthesis processes of natural nicotine and synthetic nicotine are different, and their isotopic fractionations are also different. Here, a method of tandem mass spectrometry based on isotope model peak was developed using this feature. The source or naturalness of nicotine is verified by comparing the abundance and area ratio of [M + H]+ and [M+H+1]+ peaks of nicotine, and the abundance ratio of [M+H]+ and [M+H+1]+ peaks as fragments of parent ions. A total of 47 experimental results showed that the m/z 164. 1. 163. 1 peak abundance ratios and the area ratios of natural nicotine and synthetic nicotine in MS spectra were significantly different. In addition, in MS/MS spectra, the abundance ratios of fragment ions of m/z 163. 1. 164. 1 also had significant differences. Among the variables with significant differences. the overall abundance ratio of synthetic nicotine was higher than that of natural nicotine. The evaluation model for the identification of natural nicotine and synthetic nicotine was further constructed by combining chemometric methods. Using OPLS-DA modeling, the discriminant accuracy was 97. 87%. Moreover, rankings of importance of variables differed depending on the model of the evaluation. 164. 1-85. 1/84. 1, 164. 1-85. 1/(84. 1+85. 1), 163. 1-131. 1/131. 1. 163. 1-131. 1/(130.1+131. 1) were the key discriminant variables. This method has the advantages of simple operation, rapid operation and no need for quantitative analysis, which will help to accurately identify, label and supervise tobacco products from different nicotine sources on the market. [ABSTRACT FROM AUTHOR]

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND With mining activities taking place on a global scale, the concern for environmental issues within and around mines continues to increase. The advent of multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) has promoted the geochemical study of isotopes and has led to the widespread use of isotope tracing techniques to investigate various issues in the mining environment. OBJECTIVES To systematically summarize the various types of studies currently conducted on the application of isotope tracing technology in mining environments, with the aim of highlighting the importance of the application of isotope tracing technology in complex mining environments and the diversity of scientific problems it can solve. METHODS Data published by scholars at home and abroad by July 2022 has been collected and compiled on testing and analyzing the supply source/connection of mine water body, sulfate/carbonate source and the cause of acid mine wastewater (AMD), migration and transformation of mining elements, different sources and contribution rates of heavy metal pollution with the help of isotope tracer technology. The study area covers more than 40 regions in 20 countries. RESULTS It is found that hydrogen and oxygen isotope tracing techniques in water bodies are effective tools for mine water source analysis, hydraulic linkage studies and AMD source identification. Sulfate sulfur and oxygen isotope tracing techniques provide important support for the study of sulfate sources in mine environments, AMD acidification processes and pollution, bacterial sulfate reduction and elemental migration transformation. Heavy metal isotope (Pb, Cd, Zn, Hg isotopes) tracing technology is an effective way to investigate the sources of metal pollution in mines and nearby environments and the contribution of different sources. CONCLUSIONS Although isotope techniques play an important role in resolving the sources of environmental pollutants in mines and the mechanisms of migration and transformation of characteristic pollutants and revealing the hydrogeochemical processes in mines, most of the current studies are limited to the application of single/few isotopes for short time tracing studies of environmental media in mines. Therefore, further development of multi-isotope tracing technology is needed in the future, as well as long-term and continuous monitoring and investigation of various problems in the mine environment. New and effective methods for pollution prevention and control are also proposed.

Southwest China is the largest concentrated karst landscape distribution area in the world, with dense river networks and abundant hydroelectric resources in the area, which is an important area for the development of hydroelectric power generation in China. To elucidate the impact of karst reservoirs on the carbon cycle of the river system, this work summarizes the research progress of damming in karst watersheds on different forms of carbon transport transformation and the environment in recent years. Through the study of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate inorganic carbon (PIC) and particulate organic carbon (POC) transport and transformation and their control mechanisms in the river-reservoir system in the karst region by spectroscopy, stability and radioisotopes, this work found that the carbon cycle in karst reservoirs exhibits obvious seasonal distribution characteristics, as well as cascade reservoirs, which may further amplify a single reservoir's environmental influence. These results not only contribute to the understanding of the reservoir carbon cycle but also help to explore the "missing" carbon sinks in the river carbon cycle and to more accurately assess the role of karst reservoirs in the global river carbon cycle. In general, karst reservoirs are likely to be more responsive to increased anthropogenic activities than nonkarst reservoirs, which implies that the role of karst reservoirs in the global warming trend needs to be more accurately assessed, and in future research, a systematic characterization of the carbon transport and transformation of different forms from microscopic to macroscopic levels by different analytical tools will more accurately answer this question.

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The coexistence of ammonium, arsenic and dissolved iron in groundwater is a common phenomenon in aquifer systems. They have a strong interaction and affect the nitrogen cycling and the migration and transformation of arsenic in groundwater systems. Based on the systematic survey of international and national literature on the process and influencing factors of groundwater nitrogen cycling, the functional microorganisms and their characteristics related to groundwater nitrogen cycling, and the hydrogeochemical process of arsenic enrichment in groundwater, this paper deciphers effects of nitrogen cycling (including nitrification, denitrification, Feammox, Anammox, and dissimilatory nitrate reduction to ammonium) on the migration and transformation of arsenic in groundwater. We proposed that the dynamic transformation of iron oxides and dissolved Fe (II) in aquifers is an important bridge for nitrogen cycling and the migration and transformation of arsenic in groundwater. The processes of nitrogen cycling in aquifers with different redox environments, the coupling mechanism between nitrogen cycling and arsenic migration and transformation, the interactions among Fe(III) - Fe(II) cycling, nitrogen cycling, and arsenic migration and transformation, nitrogen-iron-arsenic cycling in the surface water-groundwater interaction zone and its response to human activities are important scientific issues and research trend that need to be paid attention to in this field in the future. The solution of these scientific problems is not only conducive to identifying the source, migration and transformation of nitrogen in groundwater, but also beneficial to improving the systematical understanding of enrichment mechanism of groundwater arsenic.

BACKGROUND: With mining activities taking place on a global scale, the concern for environmental issues within and around mines continues to increase. The advent of multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) has promoted the geochemical study of isotopes and has led to the widespread use of isotope tracing techniques to investigate various issues in the mining environment. OBJECTIVES: To systematically summarize the various types of studies currently conducted on the application of isotope tracing technology in mining environments, with the aim of highlighting the importance of the application of isotope tracing technology in complex mining environments and the diversity of scientific problems it can solve. METHODS: Data published by scholars at home and abroad by July 2022 has been collected and compiled on testing and analyzing the supply source/ connection of mine water body, sulfate/ carbonate source and the cause of acid mine wastewater (AMD), migration and transformation of mining elements, different sources and contribution rates of heavy metal pollution with the help of isotope tracer technology. The study area covers more than 40 regions in 20 countries. RESULTS: It is found that hydrogen and oxygen isotope tracing techniques in water bodies are effective tools for mine water source analysis, hydraulic linkage studies and AMD source identification. Sulfate sulfur and oxygen isotope tracing techniques provide important support for the study of sulfate sources in mine environments, AMD acidification processes and pollution, bacterial sulfate reduction and elemental migration transformation. Heavy metal isotope (Pb, Cd, Zn, Hg isotopes) tracing technology is an effective way to investigate the sources of metal pollution in mines and nearby environments and the contribution of different sources. CONCLUSIONS: Although isotope techniques play an important role in resolving the sources of environmental pollutants in mines and the mechanisms of migration and transformation of characteristic pollutants and revealing the hydrogeochemical processes in mines, most of the current studies are limited to the application of single/ few isotopes for short time tracing studies of environmental media in mines. Therefore, further development of multiisotope tracing technology is needed in the future, as well as long-term and continuous monitoring and investigation of various problems in the mine environment. New and effective methods for pollution prevention and control are also proposed. [ABSTRACT FROM AUTHOR]

BACKGROUND: Multi - collector inductively coupled plasma - mass spectrometry ( MC - ICP - MS) has been widely applied to accurate and precise measurements of isotope ratios due to its high sample throughput, strong ionization ability of ICP sources and high mass resolution. For decades, the standard - sample bracketing (SSB) method has been used to correct for instrumental mass bias during the measurement to achieve accurate results. When the content of the target isotope in samples is low, the measurement results are easily influenced by the background signals. “On Peak Zero” correction deducts the background signal from the total signal, which is an effective method to eliminate the background interference and has been widely used, but no research has been conducted to systematically explore the mathematical principles behind this correction. OBJECTIVES: To establish a mathematical model for the “On Peak Zero” correction, and verify its confidence by applying it to isotope measurements of different concentrations of Li, S, Fe, Sr, Nd and Pb standard solutions. METHODS: In this study, a mathematical model of the influence by the background signal on isotopic composition was established by mathematical reasoning and approximate substitution. Standard solutions of different concentrations of Li, S, Fe, Sr, Nd and Pb were prepared for the application of the “On Peak Zero” method through experimental analysis. Two types of blank signals were subtracted separately from the aggregate signals to simulate isotope measurements without and with “On Peak Zero” correction. RESULTS: The results indicate that the lower the concentration of the target element, the greater is the blank solution signal influence on the accuracy of the sample to be tested, and the “On Peak Zero” method can better eliminate the influence of the blank solution on the sample measurements. The simulation results based on this model were consistent with the real experimental results in this study. CONCLUSIONS: The mathematical model and the data explain well the effect of background concentration on the experimental isotope values, and are useful for understanding the application of the “On Peak Zero” method in MC-ICP-MS isotope analysis. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Stable isotope ratios of carbon, nitrogen, hydrogen and oxygen act as "nature's recorder". A s a carrier for individual human information, human hair can be measured by isotope ratio mass spectrometry ORMS) to translate into information about people's dietary habits, health condition and life track. The basic principle behind establishing dietary lifestyle using isotopic profiles of human hair is the fact that the body's only source of C, N is a person's staple diet. It may have significant differences in carbon, nitrogen isotopic compositions of human hair that are living at different regions. The aim of the study was to analyze the discrepancy of 15N and 13C stable isotope ratios in human hair collected from different cities, and explore the relationship between carbon and nitrogen isotope ratios and human groups, such as gender and age. The carbon and nitrogen isotope ratios in the human hair of 247 local residents from 8 different cities were investigated by IRMS. The results showed that there were significant difference in carbon and nitrogen stable isotope ratios of human hair from different cities. The value of δ13 C was negatively correlated with vegetable consumption per capita. The value of δ15N was positively correlated with meat consumption per capita, and might be increased by high intake of fish. The relationship between δ13C, δ15N and the factors of gender and age demonstrated that there were no significant difference between males and females, but the age of females showed a weakly negative correlation with δ13 C. By comparing the data of this paper and other literatures, the carbon and nitrogen stable isotopes in the hair of residents in China were different from other countries, which implied that there were various dietary habits in different countries. [ABSTRACT FROM AUTHOR]

Inductively coupled plasma sector field mass spectrometers(ICP-SFMS) mainly include high-resolution ICP-MS (HR-ICP-MS), multi collector ICP-MS (MC-ICP-MS) and full spectrum ICP-MS. The HR-ICP-MS generally adopts the revise Nier-Johnson magnetic-electrostatic sectors double focusing geometry, the MC-ICP-MS generally adopts the forward Nier Johnson electrostatic-magnetic sectors double focusing geometry, and the full spectrum ICP-MS with detector array adopts the Mattauch-Herzog geometry. The performance improvement of ICP-SFMS is mainly reflected in the frequency turning ICP design, which improves the tolerance and reliability to the matrix, the J-type sampler cone and X-type skimmer cone are used to improve the sensitivity, the large pumping speed interface pump can reduce the vacuum in the interface area and improve the sensitivity of the instrument, and the improved ion transfer lens system can improve the abundance sensitivity of actinide isotopes. High resolution isotope ratio can be obtained by changing the slit width in front of the detectors. The use of multiple Daly detectors can improve the detection ability of low abundance isotopes. The signal output of low abundance isotope measurement can be improved by automatically switching the high resistance of Faraday cup amplifier through software. The improvement of the performance of ICP-SFMS makes it more widely used in nuclear geological analysis. In situ U-Pb dating of pitchblende micro area can be carried out by LA-HR-ICP-MS, uranium isotope fractionation can be determined with high precision by MC-ICP-MS, and refractory elements such as U, Th, Nb, Ta, Zr and Hf can be determined by LA-HR-ICP-MS. [ABSTRACT FROM AUTHOR]

Halogenated polycyclic aromatic hydrocarbons (H-PAHs), including chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) and brominated polycyclic aromatic hydrocarbons (Br-PAHs), are compounds in which one or more hydrogen atoms replaced by chlorine or bromine atoms. These compounds are not only difficult to degrade but also highly fat soluble and toxic. They are a new type of high-risk organic pollutants with structures similar to those of dioxins, and their toxicity is even higher than that of the parent polycyclic aromatic hydrocarbons (PAHs). The bioaccumulation of H-PAHs can be predicted by their octanol-water partition coefficient ( K ow ); in general, higher bioaccumulation capacity and K ow values indicate greater fat solubility. Therefore, animal-derived foods with higher fat contents, such as animal meat, milk, aquatic products, and their processed forms, are more likely to be contaminated with higher contents of H-PAHs than those with lower fat contents. In this work, a gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) method coupled with stable isotope dilution was established to determine 15 H-PAHs in aquatic products. The instrument and pretreatment methods were systematically optimized. The GC-MS/MS used in this method can effectively eliminate matrix interferences and features high sensitivity and low analytical cost; thus, it has good application prospects. The samples were added with an isotope internal standard before extraction to calibrate the loss of the tested substance during the pretreatment process, extracted by accelerated solvent extraction, purified using gel permeation chromatography and PRiME HLB columns, and then analyzed by GC-MS/MS. The use of two DB-5MS chromatographic columns (30 m×0.25 mm×0.25 μm) and microplate fluidics technology to connect chromatographic columns 1 and 2 in series led to better separation effects, good peak shapes, and high target compound responses. The 15 H-PAHs demonstrated good linearities in the range of 1-50 μg/L, with correlation coefficients ( r ) greater than or equal to 0.993. The relative standard deviation (RSD) values of the relative response factor (RRF) of the H-PAHs were less than 9%, the method detection limit (MDL) was 0.009-0.072 μg/kg, and the method quantification limit (MQL) was 0.031-0.240 μg/kg. Three spiked levels of 0.25, 1.0, 2.5 μg/kg were added to the blank samples to determine the recovery and precision. The recoveries for these spiked levels were 74.6%-116.8%, 77.8%-123.2%, and 71.9%-124.8%, respectively, and the corresponding RSDs were 0.6%-8.2%, 0.6%-9.0%, and 0.4%-10.6%, respectively. The total actual content of H-PAHs in aquatic product samples was 0.60-3.54 μg/kg. Among the H-PAHs investigated, 9-chlorophenanthrene (9-ClPhe) showed the greatest detection rate (100%) and highest content (1.15 μg/kg), indicating that H-PAHs widely exist in aquatic products. Thus, further assessment of the dietary exposure risk of these compounds is necessary. The developed method simplifies the pretreatment step, and has the advantages of simplicity, rapid analysis, high recoveries, and good stability. It is suitable for the qualitative and quantitative analysis of H-PAHs in actual aquatic product samples and provides reliable technical support for the residue status and risk assessment of H-PAHs in aquatic products.

Polychlorinated naphthalenes (PCNs) have a structure similar to that of polychlorinated biphenyls (PCBs) and represent a new type of persistent organic pollutants (POPs) that are widely present in the environment and biological communities. PCNs can migrate and transform via different environmental media, which severely affects the health of humans and organisms. Researchers have devoted considerable focus on ambient air pollution. Although the current ambient air quality has not yet limited the concentration of PCNs, the Stockholm Convention has required parties to prohibit and eliminate their production and use. As one of the contracting parties, China is obligated to improve its environmental monitoring. In other words, the development of a method for monitoring PCNs in ambient air is important for understanding ambient air quality and safeguarding human health. PCNs are generally present at trace levels (pg/m 3 ) in ambient air. To achieve accurate quantification of PCNs, high demands are raised on the methods for extraction, purification, and instrumental analysis, which can directly affect the efficiency, accuracy, and sensitivity of a method. Considering the trace-level presence of PCNs in ambient air and the high efficiency and accuracy of the analytical method, accelerated solvent extraction (ASE), combined with column chromatography using a multilayer silica gel column and a neutral alumina column, was established for the extraction and purification of PCNs in ambient air. The important parameters involved in the aforementioned steps, such as the type of extraction and volume of elution solvent, were optimized. The results indicated that dichloromethane-hexane (1∶1, v/v) was the best extraction solvent for the recovery of PCNs. Hexane and dichloromethane-hexane (5∶95, v/v) were used as the elution solvents for the multi-silica gel column and neutral alumina column, respectively. Isotope dilution gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was used to quantify the target compounds. Gas chromatographic parameters, such as temperature program conditions and inlet temperature, were also optimized. The oven temperature program was as follows: 80 ℃ for 1 min, 80 ℃ to 160 ℃ at 15 ℃/min, 160 ℃ to 265 ℃ at 3 ℃/min, and 265 ℃ to 280 ℃ at 5 ℃/min, followed by holding the temperature at 280 ℃ for 10 min. The inlet temperature was set at 260 ℃. The optimal characteristics of ion pair, collision energy, and ion source temperature were determined by optimizing the key mass spectrometry parameters. The developed instrumental method, combined with suitable sample preparation techniques, was used to determine the concentrations of PCNs in ambient air samples. Quality control (QC) and quality assurance (QA) were performed by adding isotope internal standards before sampling, extraction, and injection analysis to monitor the entire analysis process. The relative standard deviations (RSDs) of the relative response factors (RRFs) for trichloronaphthalene to octachloronaphthalene were less than 16% in the concentration range of 2-100 ng/mL. The method detection limits (MDLs) for PCN homologues were in the range of 1-3 pg/m 3 (calculated using a sample volume of 288 m 3 ). The precision and accuracy of this method for determining PCNs in ambient air samples were evaluated using a spiked matrix. The average spiked recoveries of trichloronaphthalene to octachloronaphthalene were 89.0%-119.4%, 98.6%-122.5% and 93.7%-124.5% at low, medium, and high spiked concentrations (20, 50, and 90 ng/mL), respectively. The RSDs of the assay results were 1.9%-7.0%, 1.6%-6.6%, and 1.0%-4.8%, respectively. During the entire analysis process, the average recoveries of the sampling and extracted internal standards were 136.2%-146.0% and 42.4%-78.1%, respectively, and the corresponding RSDs were 5.6%-7.5% and 2.7%-17.5%. Thus, this method meets the requirements of trace analysis and exhibits good parallelism, high sensitivity, high accuracy, and good precision, and it is suitable for the accurate quantitative determination of trichloronaphthalene to octachloronaphthalene in ambient air.

In China, the detection methods for polychlorinated biphenyls (PCBs) in aquatic products are mainly effective for 6 indicative PCBs and 12 coplanar dioxin-like PCBs, which only account for a limited proportion of PCBs in organisms. In this study, to obtain the detailed concentration levels of PCBs in organisms, elucidate the metabolism and enrichment characteristics of PCBs in organisms, and accurately evaluate the exposure level and risks of PCBs to humans, an improved method for the simultaneous determination of 82 PCBs in fish and shellfish samples was developed using isotope dilution-high resolution gas chromatography-high resolution mass spectrometry (ID-HRGC-HRMS). The recovery and reproducibility of two extraction methods, i. e., oscillatory extraction and accelerated solvent extraction (ASE), were compared. Finally, ASE was chosen for subsequent experiments. Specifically, after adding 1 ng 13 C-labeled extraction internal standards, the samples were extracted under pressure by ASE using a mixture of n -hexane-dichloromethane (1∶1, v/v). The experimental conditions employed for this were a pressure of 10.3 MPa, heating temperature of 100 ℃, heating time of 5 min, static time of 8 min, flush volume of 60%, purging time of 120 s, and 34 mL cells. Subsequently, the extracts were loaded on an 8 g acid silica gel (44%) column (inner diameter: 15 mm) and eluted with 90 mL of n -hexane. After purification and concentration, the analytes were determined by HRGC-HRMS with a fused-silica capillary column (DB-5MS, 60 m×0.25 mm×0.25 μm). The temperature program was optimized to separate the most target compounds at the baseline. Specifically, the initial oven temperature was 120 ℃, which was held for 1 min, following by heating to 180 ℃ at 30 ℃/min, heating to 210 ℃ at 2 ℃/min and holding for 1 min, and further heating to 310 ℃ at 2.5 ℃/min and holding for 1 min. The injector and ion source temperatures were 270 ℃ and 280 ℃, respectively. With a static resolution of 10000, the HRMS instrument was operated in the selected-ion monitoring mode at an electron energy of 35 eV. The 82 PCBs were qualified by their retention time and two characteristic ions, and thereafter quantified using the mean relative corresponding factor (RRF). The results showed that the relative standard deviation (RSD) of the RRF obtained from six-point calibration standard solutions was less than 20%. The linearity ranges were from 0.1 to 200 μg/L, and the correlation coefficients ( r 2 ) were greater than 0.99. Under optimum conditions, the method detection limits (MDLs) for the PCBs of biological samples were in the range of 0.02-3 pg/g. To validate the method, the fish and shellfish samples were spiked with a low level (0.4 ng) and high level (3.6 ng) of native PCB standards. The spiked recoveries using low-concentration native PCBs were 71.3%-139% in fish and 76.9%-143% in shellfish, and the RSDs ( n =7) were 2.1%-14% and 4.5%-14%, respectively. The spiked recoveries using high-concentration native PCBs were 77.6%-141% and 82.2%-131%, respectively, and the RSDs ( n =7) were 1.4%-9.4% and 1.7%-11%, respectively. An analysis of fresh fish and shellfish samples showed that the contents of a single PCB ranged from "not detected" to 54.1 pg/g, where 12 coplanar dioxin-like PCBs were detected in the range of 12.6 pg/g to 74.5 pg/g, six indicative PCBs in the range of 30.9 pg/g to 62.1 pg/g, and 82 PCBs in the range of 174 pg/g to 672 pg/g. It was concluded that this method could be successfully applied for the determination of PCBs in biological samples with good accuracy and precision. This comprehensive analytical method of PCBs in aquatic products provides effective technical support for biological monitoring; it will also aid in ecological and environmental management and the implementation of the Stockholm Convention policies.

A method for the determination of 14 polybrominated diphenyl ethers (PBDEs) in human serum using isotope internal standard-gas chromatography-high resolution dual-focus magnetic mass spectrometry (GC-HRMS) was developed. After thawed to room temperature, 0.5 mL serum samples were mixed with 13 C-labeled isotopic internal standard. Subsequently, methanol was added to precipitate the proteins in the samples. The effects of three kinds of acids on the removal of cellulite from the serum samples and the corresponding recoveries were compared, and the results revealed that sulfuric acid was the most optimal. The target compounds were extracted by liquid-liquid extraction (LLE), and the effects of different extraction solvents on recoveries were compared. The results indicated that n -hexane (6 mL)-methyl tert -butyl ether (6 mL) was the best extraction solvent. The extracts were cleaned and eluted using solid phase extraction cartridges. Furthermore, the factors that influenced the cleanup effects and recoveries, including the solid phase extraction columns and elution solvents, were investigated in detail. The results indicated that the optimal conditions were cleanup with a silica gel column and elution with hexane-dichloromethane (1∶1, v/v). The eluate was re-dissolved in hexane after being blown to near dryness using nitrogen. The detection of PBDEs was performed using GC-HRMS. The instrument conditions were optimized, and the capillary column used was an Rtx-1614 column (30 m×0.25 mm×0.1 μm). Helium was used as the carrier gas at a flow rate of 1.0 mL/min. The injector temperature was 290 ℃, and the oven temperature was programmed as follows: 150 ℃ for 2 min, 150 ℃ to 250 ℃ at 15 ℃/min, held for 1 min, 250 ℃ to 290 ℃ at 25 ℃/min, held for 3 min, and 290 ℃ to 320 ℃ at 25 ℃/min, held for 12.5 min. The injection volume was 1 μL in splitless mode. The samples were ionized in the positive electron ionization (EI) mode at 35 eV. Precursor ions and the production of each compound were identified using a voltage-selective ion detection (VSIR) program with a resolution of 10000. The ionization temperature was set at 280 ℃, and the transmission line temperature was set at 320 ℃. To ensure the integrity of the separation of low-brominated components, the column separation time was shortened, the response of high-boiling components was improved (BDE-190 and BDE-209), the decomposition of BDE-209 on the chromatographic column was effectively prevented, and the requirement of the simultaneous determination of multiple PBDEs was met. The method demonstrated good linearity in the range of 0.40 to 25 μg/L for BDE-209, and 0.08 to 5 μg/L for the other 13 PBDEs, with correlation coefficients greater than 0.995. The method detection limits (MDLs) were in the range of 0.01 to 0.51 μg/L, and the limits of quantification (LOQs) ranged from 0.04 to 1.70 μg/L. The recoveries of the 14 compounds ranged from 75.5% to 120.7%. The intra-day relative standard deviations (RSDs) were within 3.8%-10.9% ( n =6) and the inter-day RSDs were within 4.2% to 12.4% ( n =6). This method was successfully applied to the determination of 14 PBDEs in 15 serum samples from an adolescent population in an area. Notably, 1.86 to 4.66 ng/g lipid BDE-47 was detected in the serum samples with a detection frequency of 100%, and the other compounds were not detected. The results imply that the adolescent population in this region was exposed to some PBDE. Compared with the existing methods reported, this method has less sample demand and higher sensitivity and accuracy, can simultaneously determine 14 PBDEs, including BDE-209 in human serum, and effectively improve the efficiency of detection. This study offers a new method for studying the impact of polybrominated diphenyl ethers on population health in China.

To ascertain the sources of the ground water in the Jiaozuo mine area, measured the conventional water chemical ions and environment isotopes (δ18O, δ²H, ³H) of various bodies of water (including spring water, surface water, Quaternary water, sandstone water, limestone water in Taiyuan formation outburst, Ordovician limestone water), obtained the component relationship of δD-δ18O in the shallow pore water and deep fissure water. By contrast with δ18O, δ²H,³H and CI-,TDS in the groundwater and surface water as well as spring water, the study came to a conclusion: the deep ground water in the mine area mainly receives the lateral recharge from the karst water in bare carbonate rock area at altitude of 400 ~ 800 m, while the shallow ground water mainly takes the local rainfall as its recharge source, and 70% of the ground water in the west mine district comes from the leakage of Dan River. The D drift feature of the ground water in the mine area is clearly obvious, which is the result of exchange interaction among the ground water, alkyl and H2S. [ABSTRACT FROM AUTHOR]

Rice is an important cereal that is consumed as both an energy and protein source by a large proportion of the population worldwide. However, clinical studies have found that rice grains are responsible for cases of severe asthma, eczema, and atopic dermatitis in some adult patients. Several allergenic proteins have been identified and biochemically and immunochemically characterized from rice grains. These include α -amylase/trypsin inhibitors, glyoxalase Ⅰ, and α -globulin. In this study, we proposed an approach for the simultaneous quantification of three allergenic proteins in rice and its products, based on a stable isotope-labeled signature peptide standard and liquid chromatography-tandem mass spectrometry. Samples of rice and products were extracted by a salt solution, hydrolyzed by Lys-C and Trypsin, and purified by C18-SD. The linear ion trap-high resolution mass spectrometry (LTQ-Orbitrap) and Protein Discovery software were used to acquire and identify allergenic proteins in rice samples. In present study, three proteins including seed allergenic protein RAG2, glyoxalase Ⅰ, and 19 kDa globulin were identified. To establish a stable quantitative detection method, the signature peptides selected from the identified enzymatic hydrolysis peptides must have greater abundance and higher specificity as characteristic peptides. Three corresponding signature peptides in rice were screened based on the principles of previous study, and were validated through comparisons of the basic local alignment search tool (BLAST) with the NCBI and UniProt databases. The three signature peptides were successively eluted by liquid chromatography and separated on a Poroshell column. They were then detected by positive electrospray ionization (ESI + ) in multiple reaction monitoring mode and quantified by an isotope dilution method. To achieve an improvement in the detection sensitivity and specificity, mass spectrometry parameters, such as the collision energy of three ion pairs of each peptide, were optimized. Three recombinant allergenic proteins and the winged stable isotope-labeled signature peptide standard were synthesized. These were then used to compare the effects of different enzymatic conditions, including hydrolysis solvents containing sodium dodecyl sulfate (SDS) with different contents, as well as the enzymes and their amounts, on the digestion efficiency. The data showed that the digestion efficiency of the three proteins could be improved to 65.7%-97.3% when 1 g/L of the SDS-containing hydrolysis solvent, and the combined digestion strategy of Lys-C and Trypsin, were adopted in the enzymatic process. These results indicate the following inferences: a small amount of SDS (1 g/L) in the enzymatic hydrolysis system is beneficial to complete protein denaturation, a Lys-C and Trypsin combined digestion strategy can complement the shortcomings of the two enzymes and improve the digestion efficiency, and the recoveries of the three proteins was not significantly increased by increasing the amount of enzyme when the ratio of protein to enzyme reached more than 20∶1. The method displayed good linearity in the range of 1-200 nmol/L with the correlation coefficients greater than 0.9972. The limits of detection and limits of quantification of the three proteins were 3 mg/kg and 10 mg/kg, respectively. The average recoveries of the three proteins spiked at three levels in different matrices ranging between 80.6%-103.7%, with the intra-day and inter-day precision less than 11.5%. Due to its high stability, excellent sensitivity, and simple operation, this method presents a wide range of application prospects in the analysis of the three allergenic proteins in different rice and rice food products.

As among the most widely used pesticides in agriculture, plant growth regulators (PGRs) have a positive influence on plants. However, the overuse of PGRs may induce toxicity in food and even be hazardous to human health. Numerous studies have investigated the presence and residues of PGRs on vegetables and fruits. Animal-derived foods are one of the most dominant food sources providing nutrients to fulfil the daily dietary intake, and could also be potentially contaminated by PGRs. However, there is little information on PGR residues in animal-derived foods. Standardization also lacks among the techniques for PGR determination in animal-derived foods, thereby restricting the further establishment of pesticide usage and food safety regulations. Therefore, in this study, a rapid and effective method for analyzing chlormequat chloride, thidiazuron, and paclobutrazol in animal-derived food samples was established. The method primarily involves high performance liquid chromatography-tandem mass spectrometry combined with the use of isotope-labeled internal standards. The extraction and clean-up procedures were based on the QuEChERS method. The analytes were extracted from pork, beef, chicken, pork liver, egg, and milk samples using acetonitrile, followed by 4 g anhydrous magnesium sulfate (MgSO 4 ), and 1 g sodium chloride (NaCl). The supernatant was removed using a mixture of 50 mg N -propyl ethylenediamine (PSA), 50 mg octadecyl silane (C18), and 150 mg MgSO 4 , and then passed through a 0.22 μm membrane filter before determination. The Agilent ZORBAX Eclipse Plus C18 column (150 mm×3.0 mm, 1.8 μm) was used to separate the analytes under a gradient elution program, with acetonitrile and 5 mmol/L ammonium acetate solution as mobile phases. The analytes were detected by mass spectrometry using the positive and negative electrospray ionization modes under the multiple reaction monitoring mode. Matrix-matched calibration combined with internal standards was used to quantify the PGRs. The linear regression correlation coefficients ( r 2 ) for the PGRs were all greater than 0.990 in the corresponding linear concentration ranges. Chlormequat chloride, thidiazuron, and paclobutrazol showed good linearities in the range of 0.1-100 μg/L for the egg and pork liver samples and 0.1-50 μg/L for the pork, beef, and chicken samples. For the milk samples, thidiazuron and paclobutrazol showed good linearities in the range of 0.05-10 μg/L, while chlormequat chloride showed linearity in the range of 0.05-5 μg/L. The limit of detection (LOD) and limit of quantification (LOQ) for each PGR were based on the signal-to-noise ( S/N ) ratios. Under optimal conditions, the LODs ranged from 0.01 μg/kg to 0.1 μg/kg, where the LOD was defined as the amount of the tested compound that generated an S/N ratio higher than 3. In addition, the LOQs were in the range of 0.5-5 μg/kg, with an S/N ratio higher than 10. The precision and accuracy were evaluated by recovery experiments. At the LOQ, twice the LOQ, and 10 times the LOQ, the mean recoveries were in the range of 70.0%-117.4%, and the relative standard deviations (RSDs) ranged from 0.8% to 16.1%. The results indicated that the proposed method is accurate and reliable. This method is a modification of the QuEChERS method, and is advantageous owing to its simplicity and high sensitivity. The use of matrix-matching calibration curves and internal standards can eliminate matrix interference, thereby increasing the accuracy of the method. This method satisfies the testing requirements for chlormequat chloride, thidiazuron, and paclobutrazol residues in animal-derived foods, and is promising for the determination of other PGRs or other types of pesticides in animal-derived foods.

In this study, a comprehensive analytical method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed for the determination of nine N -nitrosamines in animal derived foods. There are many kinds of N -nitrosamines in foods that are harmful to human health. However, the national standard GB 5009.26-2016 pertains only to the detection of N -dimethylnitrosamine; there are many drawbacks of this method, such as complicated sample preparation, low recovery rate, and poor reproducibility. Hence, it is of practical significance to establish a method for the simultaneous determination of a variety of N -nitrosamines. The optimal extraction conditions for the developed method were as follows: 10.0 g aliquots of the sample were placed in a 50 mL centrifuge tube, followed by the addition of 10 mL acetonitrile and 200 μL internal working standard solutions. After 30 min of freezing treatment, 4 g magnesium sulfate and 1 g sodium chloride were added for dehydration, and the tube was centrifuged at 9000 r/min for 5 min. After vortex centrifugation, 5 mL of the clear supernatant was purified using 150 mg polystyrene divinylbenzene (PLS-A). The purified extracts were dewatered using 1.6 g MgSO 4 and 0.4 g NaCl, and then filtered through a 0.22 μm membrane filter unit prior to GC-MS/MS analysis. Temperature-programmed was applied at an initial temperature of 50 ℃. After 0.16 min, the temperature was raised to 220 ℃ at the rate of 900 ℃/min for 5 min. N -Nitrosamines were separated on an HP-Innowax column (30 m×0.25 mm×0.25 μm). Identification and quantification were achieved using an electron impact ion (EI) source in positive ion mode with multiple reaction monitoring (MRM). The internal standard method was used to quantify the N -nitrosamines. Under the optimal conditions, the correlation coefficients of the standard calibration curves were not less than 0.99 in the range of 0.1-50.0 μg/L. The limits of detection were 0.03-0.30 μg/kg ( S/N =3), and limits of quantification were 0.15-1.00 μg/kg ( S/N =10). At spiked levels of 0.5, 1.0, and 3.0 μg/kg, the average recoveries of N -nitrosamines in spiked samples ranged from 80.4% to 98.5%, with relative standard deviations between 2.41% and 12.50%. This method was used to determine animal derived food products, except N -itrosomethylethylamine and N -nitrosomorpholine, others were founded. The results showed that N -nitrosamines levels in salted aquatic products were generally higher than those of the other samples. The method established in this study is simple to operate, and it does not require any time-consuming distillation extraction. Furthermore, there is minimal consumption of samples and reagents; consequently, the experiment cost is reduced, and the method is environmentally friendly. This method has theoretical and practical significance for the control of N -nitrosamines residues in animal derived foods, establishment of detection standards, and corresponding management measures.

Gas chromatography (GC)-high-resolution mass spectrometry (HRMS) with accelerated solvent extraction (ASE)-purification simultaneously coupled to the isotope internal standard method is proposed for the determination of 32 polychlorinated biphenyls (PCBs) in aquatic products. Synchronous purification was achieved by adding 2 g of anhydrous sodium sulfate, 1 g of Cleanert Florisil, and 50 g of neutral alumina as the adsorbent to the ASE system. The PCBs were extracted from aquatic product samples using a dichloromethane- n -hexane (1:1, v/v) mixture at 100 ℃ with two extraction cycles. The extracting solution was purified twice with 0.5 mL concentrated sulfuric acid. After concentration to a constant volume, the target compounds were detected by GC-HRMS and quantified by the isotope internal standard method. Under the optimized conditions, the relative standard deviations (RSDs) of the mean relative response factor (RRF) for the 32 PCBs in the range of 0.1-20 μg/L were less than 15%. The limits of quantification were 0.3-1.9 ng/kg. At three spiked levels (5, 20, and 50 ng/kg) in grass carp and sea bass, the recoveries of the 32 PCBs were between 71.9% and 119.0%, with the RSDs varying from 3.5% to 19.6%. This method effectively reduces the matrix interference and shows high sensitivity, good reproducibility, and stable recovery, thus proving useful for the detection of PCBs in aquatic products.

A method for the preparation and certification of the reference material of tenuazonic acid (TeA) and tentoxin (TEN) in wheat flour was developed. This method provided methodological references to develop of standard material for analyzing alternaria toxins in grains. The wheat flour reference materials were based on wheat grains which were naturally contaminated with alternaria toxins. The certified values for TeA and TEN were determined by isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) and cooperated certification of multiple laboratories. The wheat flour reference materials were stored at room temperature, protected from light and characterized by low uncertainty. The wheat flour reference materials are currently the only wheat flour reference materials that naturally contaminate TeA and TEN, and it can be used in the evaluating related analytical methods involved in food safety risk monitoring, product quality testing and quality control measurements.

Analysis of neurotransmitters in brain tissue is useful for mechanistic studies of the central nervous system. Isotope dilution coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of glutamic acid, γ -amino butyric acid, acetylcholine, dopamine, and serotonin in the hippocampus tissue. A 2% (v/v) acetic acid in water-methanol (9:1, v/v) solution was used to prepare the standards and re-dissolute samples after nitrogen drying. An Ultimate AQ-C 18 column (150 mm×4.6 mm, 3 μm) was used as the analytical column and 0.1% (v/v) formic acid in water and methanol were used as the mobile phase. Gradient elution was performed and all target compounds were eluted over 3 min at 28℃. Vitamin C spiked during the sample pretreatment and storage periods significantly retarded the oxidation of dopamine and serotonin and improved the neurotransmitter stability. The developed method showed good linearities (correlation coefficient ( R 2 )>0.998), low detection limits (0.15-1.0 μg/L), good inter-and intra-day precisions (relative standard deviations:0.39%-13.6%), good accuracy (92.9%-119%), low carry-over, and excellent stability. Moreover, the method was successfully applied and validated in the determination of rat hippocampus exposed to bisphenol A.

A method was developed for the determination of monofluoroacetic acid (MFA) in plasma and urine by ion chromatography-triple quadrupole mass spectrometry (IC-MS/MS). A plasma sample was extracted with 3% (v/v) perchloric acid aqueous solution, and the extract was centrifuged to remove the protein and lipids. A urine sample was acidulated with 3% (v/v) perchloric acid aqueous solution. The target analyte was extracted with methyl tert -butyl ether (MTBE) at a pH between 0.5 and 1.0. After the MTBE was removed by blowing with nitrogen, the MFA in the residues was dissolved into 0.1% (v/v) ammonia solution. The separation of MFA was carried out on a Dionex Ionpac AS 19 analytical column (250 mm×2 mm, 7.5 μm) with gradient elution using KOH solution electrolytically generated from an on-line eluent generation cartridge. Before the eluent flow entered the mass spectrometer, an in-line suppressor was used to remove potassium ions. The MFA was detected with a negative electrospray ionization source in the multiple reaction monitoring (MRM) mode, and quantified with the stable isotope internal standard method. The correlation coefficient of the linear calibration curve of MFA was greater than 0.999 at the corresponding ranges of 0.1-1000 μg/L. The average recoveries were 96.2%-120% of MFA in plasma and urine samples with relative standard deviations of 1.1%-13.1% ( n =6). The limits of detection of MFA in plasma and urine samples were 0.03 μg/L and 0.1 μg/L, respectively. The method is simple, sensitive and accurate, and can be applied for the determination of MFA in plasma and urine samples.

An improved method based on the isotope dilution technique was developed for the determination of 20 polychlorinated biphenyls (PCBs) in fish samples, including seven indicator polychlorinated biphenyls. The analysis was performed by gas chromatography-triple-quadrupole mass spectrometry (GC-MS/MS) in the multiple reaction monitoring (MRM) mode. Two MRM transitions were monitored for each PCB congener for quantitation and qualification purposes. The edible parts of the fish samples were shattered, frozen, and dried. 13 C-PCB surrogate standards were spiked into the fish samples. The PCBs in fish samples and the surrogate standards were extracted by auto-Soxhlet extraction. The extract was cleaned-up by a disposable multi-layer column packed with acidic silica gel and basic alumina. 13 C-PCB recovery standards were spiked into the extract before injection. The separation was performed on a TG-5MS capillary column. Quantitation was performed by the internal standard method. Every group of PCBs used a same number chlorinated 13 C-isotope PCBs congener as the internal standard. The calibration curves of 20 PCB congeners were linear (correlation coefficient ( r )>0.99) within the range of 0.05-10 μg/L. For the recovery test, three levels were spiked in matrices. The average recoveries obtained by this method were 80.3%-117.6% and the relative standard deviations (RSDs, n =6) were 5.09%-18.5%. The limits of determination (LODs) were 0.01-0.02 μg/kg. Contents of the 20 PCBs in the fish samples were in the range 1.2-8.8 μg/kg (wet weight), while those of the seven indicator PCBs were in the range 0.68-6.4 μg/kg (wet weight). The method is suitable for determining polychlorinated biphenyls in fish samples.

A rapid method was established for the determination of zearalenone (ZON), nivalenol (NIV), deoxynivalenol (DON), 3-acetyl-deoxynivalenol (3-ACDON) and 15-acetyl-deoxynivalenol (15-ACDON) in various grains and their products by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted by acetonitrile-water (84:16, v/v), and cleaned-up by multifunctional column without any further step. The separation was carried out on an Acquity UPLC ® BEH C18 column (100 mm×2.1 mm, 1.7 μm) with gradient elution using acetonitrile-water as mobile phases. The analytes were quantified by isotope internal standard method. The correlation coefficients ( r 2 ) were all above 0.99. The limits of detection (LODs, S/N =3) ranged from 5 μg/kg to 20 μg/kg. The recoveries of the five mycotoxins spiked in blank grain and its product samples varied from 84.2% to 114.5%, with the relative standard deviations (RSDs) of 0.4%-9.9% ( n =6). The method is accurate, efficient, sensitive and practical.

The sensitive detection method of levodopa (L-DOPA) and dopamine (DA) in rat brain microdialysate of Parkinson's disease (PD) is an essential tool for the clinical study and attenuated synergistic drug screening for L-DOPA from traditional Chinese medicines. Using d0/d3-10-methyl-acridone-2-sulfonyl chloride (d0/d3-MASC) as stable isotope derivatization reagent, a novel ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for L-DOPA and DA by stable isotope- coded derivatization coupled with ultrasonic-assisted dispersive liquid-liquid microextraction (UA-DLLME). d3-MASC (light) and d3-MASC (heavy) were used as derivatization reagents for microdialysate samples and standards, respectively. Mixtures of the two solutions were prepared by UA-DLLME for UHPLC-MS/MS analysis with multiple reaction monitoring (MRM) mode. With d3-MASC heavy derivatives as internal standards for corresponding light derivatives from samples, the stable isotope internal standard quantification for L-DOPA and DA was carried out. The stable derivatives were obtained in aqueous acetonitrile (pH 10.8 sodium carbonate-sodium bicarbonate buffer) at 37 °C for 3.0 min, and then were separated within 2.0 min using gradient elution. Linear range was 0.20-1500.0 nmol/L (R > 0.994). LODs were 0.005 and 0.009 nmol/L for DA and L-DOPA (S/N = 3), respectively. This method was validated, and it showed obvious advantages in comparing with the reported methods in terms of sensitivity, analysis speed and anti-matrix interference. This method has been successfully applied to the study of effect of Shouwu Fang on L-DOPA and DA concentration fluctuations in PD rat brain microdialysate.

A method for the determination of endogenous agmatine in rat plasma was developed by isotope dilution-gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The plasma samples were analyzed after protein precipitation, evaporation, derivatization by hexafluoroacetone (HFAA), and clean-up on a Florisil SPE column. The GC-MS analysis utilized stable isotope d8-agmatine as internal standard. The samples after treatme were tested by negative chemical ionization with selected ion monitoring (SIM) which was set at m/z 492 (molecular ion of agmatine) and m/z 500 (molecular ion of internal standard). The limit of detection (LOD) of agmatine standard solution was 0.005 7 ng/mL. The calibration curve of the agmatine spiked in rat plasma showed a good linear relationship at the range of 1.14-57.0 ng/mL (r = 0.997). The recoveries of agmatine spiked in rat plasma ranged from 92.3% to 109.8%. Inter-day and intra-day precisions were less than 15%. The average concentration level of agmatine in rat plasma was (22 +/- 9) ng/mL, and there was no significant difference between male and female SD rats (p > 0.05). The method is high sensitive and specific, and can be used for the determination of endogenous agmatine in plasma. It provides a strong support for the subsequent research of agmatine.

An analytical method for the determination of urinary cotinine of children exposed to passive smoking was established based on stable isotope dilution by gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS). The samples were extracted and purified with chloroform. The extracts were determined by GC-MS/MS in multiple reaction monitoring (MRM) mode. The cotinine-d3 as an isotope internal standard was applied to quantify and confirm the urinary cotinine of children exposed to passive smoking. The method had a good linearity from 0.1 microg/L to 10 microg/L with the correlation coefficient (r) > 0.998. The recoveries of the cotinine in blank urine were from 79.2% to 112.8% at spiked levels of 0.1, 1.0 and 10 microg/ L, with relative standard deviations (RSDs) from 2.1% to 5. 8%. The limit of quantification ( LOQ) of the method was 0.1 microg/L. The developed method is accurate, sensitive, rapid and can be applied to detect urinary cotinine of children exposed to passive smoking at home.

Objective: To compare the accuracy of intaoperative methylene blue alone and in combination with (99m)Tc-sulfur colloid isotopic tracing for detection of sentinel lymph nodes (SLNs) in early-stage non-small cell lung cancer (NSCLC)., Methods: Sixty-one patients with operable NSCLC who did not receive previous radiotherapy or chemotherapy were enrolled. Methylene blue and (99m)Tc-sulfur colloid were injected into the subserosal layer adjacent to the tumor, and SLNs were defined as those with blue staining or those containing 3 times more radioactivity than the surrounding tissue detected with a gamma probe. The SLN were removed with systematic lymph node dissection. All the removed lymph nodes were examined histopathologically with HE staining and immunohistochemistry., Results: Methylene blue alone showed a low detection rate (60.0%) and sensitivity (58.33%) for SLNs compared with the combination of methylene blue and isotope tracing (96.15% and 92.86%, respectively)., Conclusion: The combination of methylene blue and (99m)Tc-sulfur colloid isotopic tracing allows accurate detection of the SLNs in early-stage NSCLC.

A method for the preparation and certification of the reference material of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in mussel tissue is described. The mussel tissue from Dalian Bay was frozen-dried, comminuted, sieved, homogenized, packaged, and sterilized by 60Co radiation sterilization in turn. The certified values for 18 OCPs and 16 PCBs were determined by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) using isotope dilution and internal standard quantitation techniques. The certified values were validated and given based on seven accredited laboratories, and these values are traceable to the SI (international system of units) through gravimetrically prepared standards of established purity and measurement intercomparisons. The certified values of PCBs and OCPs in mussel span 4 orders of magnitude with a relative uncertainty of about 10%. This material is a natural biological material with confirmed good homogeneity and stability, and it was approved as the grade "primary reference material" (GBW10069) in June 2012 in China. This reference material provided necessary quality control products for our country to implement the Stockholm Treaty on the monitoring of persistent organic pollutants (POPs). The material is intended to be used for the method validation and quality control in the determination of OCPs and PCBs in biota samples.

An approach for quantification of peptides by hydrolysis followed by reversed-phase liquid chromatography (RPLC)-stable isotope dilution mass spectrometry (MS) is presented. The purities of all the determined peptides were greater than 99% by using RPLC and over 90% detected by MS, indicating that the method was workable. The hydrolysis conditions optimized were 4-6 h with 6 mol/L HCl at 150 degrees C. Two or more amino acids were chosen to ensure the accuracy of the determined results. The content range of peptides was determined to be 62.07% - 88.18% with the relative standard deviations less than 8% and relative errors less than 5%. Besides Phe, Val and Ile which were commonly used for the analysis of peptide contents, Arg as another amino acid for peptide quantification can be chosen to enhance the popularity of the method. In a word, application of this method for direct determination of peptide content can avoid the side effects in the derivatization of amino acids and the tedious operation in liquid chromatography. This will improve the precision and accuracy of the method and provide an alternative for peptide quantification.

An accurate method was described for the determination of chloramphenicol (CAP) in pork. The analyte was quantified by isotope dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) operating in negative ion multiple reaction monitoring (MRM) mode. The sample was treated by liquid-liquid extraction with ethyl acetate followed by a clean-up step on an HLB solid-phase extraction cartridge. Chloramphenicol-D5 (CAP-D5) was added as an isotope internal standard. Under the optimized conditions, the calibration curve showed a good linearity in ranging from 0.01 to 0.5 ng/g CAP. The correlation coefficient r2 was 0.9998. The limit of detection and the limit of quantification were 0.004 and 0.02 ng/g, respectively. The average recoveries of CAP at 0.02 ng/g and 1.0 ng/g spiked levels ranged from 95.2%-109.1%, 99.7%-102.5%, respectively. The relative standard deviations (RSDs) of intra-day and inter-day were less than 2%. Meanwhile, matrix effect factors k of CAP and CAP-D5 were determined under different mobile phases and the sample solvent composition, the k was in the range of 0.950-1.015. The method can be used as a confirmed method for the determination of CAP in pork.

A method for the detection of the alpha, beta and gamma-diastereoisomers of hexabromocyclododecane (HBCDs) in foods of animal origin, such as fish, chick, milk, butter etc., was developed using ultra performance liquid chromatography-electrospray ionization mass spectrometry (UPLC-ESI-MS) and isotope dilution. The HBCDs with the spiked isotopic 13C-HBCDs, the internal standards, were extracted using Soxhiet extraction, and further purified using acidic silica treatment and solid phase extraction. The separation of HBCDs was performed on Waters ACQUITY UPLC system with the column of BEH C8 and the gradient elution solvent of methanol-acetonitrile and water at a flow rate of 0.2 mL/min. The HBCDs were identified on the basis of the retention times and precursor ions, and quantitatively determined under the selected ion recording mode, m/z 640.7 for the [M-H]-ion. The limits of detection (LODs) of HBCDs ranged from 0.1 to 0.4 ng/g; and the limits of quantification (LOQs) ranged from 0.4 to 1.2 ng/g. The average recoveries ranged from 92.9% to 99.3% for the spiked levels of 0.6, 2.0 and 6.0 ng/g. with the relative standard deviations (RSDs) between 3.1% and 8.0%.

A method for the determination of dioxin like polychlorinated biphenyl (DL-PCB) residues in milk has been developed using high resolution gas chromatography coupled with ion trap mass spectrometry (GC-MS/MS-IT). Analytical procedure consisted of accelerate solvent extraction (ASE), lipid removal with acidic silica and clean-up using anthropogenic isolation column packed with multilayer silica. The analytes were separated on a DB-5 capillary column, detected with multiple reaction monitor mode (MRM) and quantified using internal standard calibration curve of isotope dilution technique. The correlation coefficients of calibration standard solution were above 0. 999 9 for all the DL-PCBs. The recoveries and relative standard deviations of labeled compound solution were in the oranges from 39% to 129% and from 5% to 22%, respectively. The detection limits in the range from 3 to 11 pg/g (fat) were established for the 12 DL-PCBs.