LPAD: using network construction and label propagation to detect topologically associating domains from Hi-C data.

With the development of chromosome conformation capture technique, the study of spatial conformation of a genome based on Hi-C technique has made a quantum leap. Previous studies reveal that genomes are folded into hierarchy of three-dimensional (3D) structures associated with topologically associating domains (TADs), and detecting TAD boundaries is of great significance in the chromosome-level analysis of 3D genome architecture. In this paper, we propose a novel TAD identification method, LPAD, which first extracts node correlations from global interactions of chromosomes based on the random walk with restart and then builds an undirected graph from Hi-C contact matrix. Next, LPAD designs a label propagation-based approach to discover communities and generates TADs. Experimental results verify the effectiveness and quality of TAD detections compared with existing methods. Furthermore, experimental evaluation of chromatin immunoprecipitation sequencing data shows that LPAD performs high enrichment of histone modifications remarkably nearby the TAD boundaries, and these results demonstrate LPAD's advantages on TAD identification accuracy.

HiBrowser: an interactive and dynamic browser for synchronous Hi-C data visualization.

With the development of chromosome conformation capture technology, the genome-wide investigation of higher-order chromatin structure by using high-throughput chromatin conformation capture (Hi-C) technology is emerging as an important component for understanding the mechanism of gene regulation. Considering genetic and epigenetic differences are typically used to explore the pathological reasons on the chromosome and gene level, visualizing multi-omics data and performing an intuitive analysis by using an interactive browser become a powerful and welcomed way. In this paper, we develop an effective sequence and chromatin interaction data display browser called HiBrowser for visualizing and analyzing Hi-C data and their associated genetic and epigenetic annotations. The advantages of HiBrowser are flexible multi-omics navigation, novel multidimensional synchronization comparisons and dynamic interaction system. In particular, HiBrowser first provides an out of the box web service and allows flexible and dynamic reconstruction of custom annotation tracks on demand during running. In order to conveniently and intuitively analyze the similarities and differences among multiple samples, such as visual comparisons of normal and tumor tissue samples, and pan genomes of multiple (consanguineous) species, HiBrowser develops a clone mode to synchronously display the genome coordinate positions or the same regions of multiple samples on the same page of visualization. HiBrowser also supports a pluralistic and precise search on correlation data of distal cis-regulatory elements and navigation to any region on Hi-C heatmap of interest according to the searching results. HiBrowser is a no-build tool, and could be easily deployed in local server. The source code is available at https://github.com/lyotvincent/HiBrowser.

Multiplexing N-glycan analysis by DNA analyzer.

Analysis of N-glycan structures has been gaining attentions over the years due to their critical importance to biopharma-based applications and growing roles in biological research. Glycan profiling is also critical to the development of biosimilar drugs. The detailed characterization of N-glycosylation is mandatory because it is a nontemplate driven process and that significantly influences critical properties such as bio-safety and bio-activity. The ability to comprehensively characterize highly complex mixtures of N-glycans has been analytically challenging and stimulating because of the difficulties in both the structure complexity and time-consuming sample pretreatment procedures. CE-LIF is one of the typical techniques for N-glycan analysis due to its high separation efficiency. In this paper, a 16-capillary DNA analyzer was coupled with a magnetic bead glycan purification method to accelerate the sample preparation procedure and therefore increase N-glycan assay throughput. Routinely, the labeling dye used for CE-LIF is 8-aminopyrene-1,3,6-trisulfonic acid, while the typical identification method involves matching migration times with database entries. Two new fluorescent dyes were used to either cross-validate and increase the glycan identification precision or simplify sample preparation steps. Exoglycosidase studies were carried out using neuramididase, galactosidase, and fucosidase to confirm the results of three dye cross-validation. The optimized method combines the parallel separation capacity of multiple-capillary separation with three labeling dyes, magnetic bead assisted preparation, and exoglycosidase treatment to allow rapid and accurate analysis of N-glycans. These new methods provided enough useful structural information to permit N-glycan structure elucidation with only one sample injection.

Fluorescence-tagged amphiphilic brush copolymer encapsulated Gd2O3 core-shell nanostructures for enhanced T 1 contrast effect and fluorescent imaging.

To obtain suitable T 1 contrast agents for magnetic resonance imaging (MRI) application, aqueous Gd2O3 nanoparticles (NPs) with high longitudinal relativity (r 1) are demanded. High quality Gd2O3 NPs are usually synthesized through a non-hydrolytic route which requires post-synthetic modification to render the NPs water soluble. The current challenge is to obtain aqueous Gd2O3 NPs with high colloidal stability and enhanced r 1 relaxivity. To overcome this challenge, fluorescence-tagged amphiphilic brush copolymer (AFCP) encapsulated Gd2O3 NPs were proposed as suitable T 1 contrast agents. Such a coating layer provided (i) superior aqueous stability, (ii) biocompatibility, as well as (iii) multi-modality (conjugation with fluorescence dye). The polymeric coating layer thickness was simply adjusted by varying the phase-transfer parameters. By reducing the coating thickness, i.e. the distance between the paramagnetic centre and surrounding water protons, the r 1 relaxivity could be enhanced. In contrast, a thicker polymeric layer coating prevents Gd(3+) ions leakage, thus improving its biocompatibility. Therefore, it is important to strike a balance between the biocompatibility and the r 1 relaxivity behaviour. Lastly, by conjugating fluorescence moiety, an additional imaging modality was enabled, as demonstrated from the cell-labelling experiment.

Geographic and tissue-specific variations of the trace elements and trophic niches of three offshore cetaceans in Chinese waters.

Systematical investigation on trace elements' (TEs) distribution and trophic niches of cetaceans are essential to understand marine mammal ecology and environmental toxicology. Here, the concentrations of 10 TEs and isotopic values in six tissues of stranded Stenella attenuata (SA) and Kogia breviceps (KB) from the northern South China Sea (SCS) and Peponocephala electra (PE) from the East China Sea (ECS) were investigated. The TEs levels of the studied cetaceans were characterized by geo- and tissue-specific distributions. For SA and KB, most TEs levels were in the normal ranges, with low toxicological risk. For PE, several toxic TEs accumulated above the thresholds up to 892.80 µg/g of Hg and 335.24 µg/g of Cd, indicating that land-based anthropogenic pollution may be an ongoing threat to top predators in the ECS. The liver, spleen, and kidney are the main organs that accumulate toxic TEs, and there are strong positive, such as Se-Hg, correlations in several tissues. In particular, for PE with severe Hg and Cd exposure, tissue-specific distribution and correlations were more obvious. The results of stable carbon and nitrogen isotopes showed partly overlapped trophic niches of the three cetaceans, with similar calculated trophic levels in a narrow range of 4.29-4.43.

A case study on microplastics pollution characteristics in fouling organisms in typical aquaculture bay, China.

Microplastics (MPs) and fouling organisms are prevalent in oceans worldwide. The study aims to investigate the pollution characteristics of MPs in fouling organisms. The study found significant inter-specific differences in the MPs abundance, while the length of MPs is consistent. The average number of MPs in N. exigua is 0.00 ± 0.00. There is a correlation between MPs abundance and weight in sessile group, while gastropods don't. Direct observation has demonstrated that the radulae of N. radula can envelop MPs. Fiber and blue are the predominant forms and colors of MPs found in fouling organisms. It is noteworthy that all film and fragment MPs observed were of a blue hue and had a size limitation of 500 µm. The characteristics of MPs between sessile organisms are more similar than those between gastropods. This study has improved our understanding of the pollution characteristics of MPs in fouling organisms, specifically gastropods.

The occurrence of pollutants in organisms and water of inland mariculture systems: Shrimp aquaculture is a procession of Microplastics accumulation.

Microplastics (MPs) pollution in the ocean was widely concerned, but the current study on MPs pollution in the mariculture system is relatively lacking. This study researched the MPs pollution characteristics in water and shrimp at different stages of the pond and industrial aquaculture. The study shows that in the same aquaculture stage, MPs abundance in shrimp and water in pond aquaculture mode is higher than that in industrial aquaculture mode. The MPs pollution characteristics in shrimp and water show significant consistency. The hazard index of MPs in pond water and industrial models are 122 (Level Ⅲ) and 540 (Level Ⅲ), respectively, indicating that industrial aquaculture models may suffer from more severe MPs stress. The aquaculture period and mode significantly affected the MPs abundance of water and shrimp, but there was no interaction between the aquaculture period and mode. MPs abundance in shrimp show a significant relationship with the length of crustacean and weight. This study further enhanced the understanding of MPs pollution of water and organisms in different aquaculture modes at different stages, and warned MPs is widely spread in mariculture systems.

Cross-identification of N-Glycans by CE-LIF using two capillary coatings and three labeling dyes.

Recombinant protein biopharmaceuticals comprise a significant portion of the current drug development landscape. The glycosylation profile of these proteins is a key quality parameter as it can affect their safety, efficacy, and stability. However, glycan analysis is challenging because of the complexity of their structures. To overcome this challenge in achieving accurate glycan identification, cross-identification of N-Glycans by CE-LIF method using two capillary coatings and three labeling dyes was developed in this work. This work explored whether complementary separation capabilities can be achieved using homemade polyvinyl alcohol (PVA) coating and commercial Guarant™ (Guarant) coating in the analysis of N-glycans. Similar separation profiles were observed using the two capillary coatings, and hence the N-glycan GU databases generated by these coatings were comparable and complementary. The performance of cross-validation by labeling with three fluorescent dyes indicated that low covariance of APTS and Turquoise™ labeling can be obtained, and hence these two labeling mechanisms provided better accuracy for the identification of glycans. Superior reproducibility with RSDs less than 1% for all target glycan standards was achieved by the internal standards (IS) method using maltodextrin ladders as additives in the separation buffer. The developed CE-LIF analysis method was applied to the identification of N-glycans in IgG samples.

Combination Treatment with Methylene Blue and Hypothermia in Global Cerebral Ischemia.

Therapeutic hypothermia (TH) is the most potent therapeutic strategy for global cerebral ischemia (GCI), usually induced by cardiac arrest. TH has been shown both to suppress the delayed neuronal cell death in the vulnerable hippocampal CA1 subregion and to improve neurological outcomes in experimental animals after GCI. However, given the multiple adverse effects resulting from TH, application of such a therapy is typically limited. In recent years, methylene blue (MB) has emerged as a potential therapeutic drug for the treatment of neurodegenerative diseases. In this study, we investigated the beneficial effects of mild TH combined with MB treatment after GCI. We report that both the neuronal survival in the hippocampal CA1 region and the hippocampus-dependent spatial learning and memory in the combined treatment animals were enhanced compared to those in the single treatment animals. Mechanistic studies revealed that combined TH and MB treatment significantly attenuated mitochondrial dysfunction induced by GCI in the hippocampus CA1 region. The combined treatment also markedly suppressed GCI-induced reactive gliosis and inflammation and reduced oxidative stress while enhancing the antioxidant capacity of hippocampal CA1 neurons. Finally, combining TH and MB synergistically attenuated the intrinsic cytochrome c/caspase-3 apoptotic pathway induced by GCI. Our results suggest that TH and MB act synergistically to protect the ischemic brain and suppress cognitive impairment caused by GCI.

An efficient "off-on" carbon nanoparticle-based fluorescent sensor for recognition of chromium(vi) and ascorbic acid based on the inner filter effect.

A simple approach based on calcination treatment of diethylenetriaminepentaacetic acid (DTPA) was developed to prepare water-soluble nitrogen doped carbon nanoparticles (N-CNPs) with a high quantum yield of approximately 53.7%. The fluorescence of N-CNPs could be quickly and efficiently quenched by Cr(vi) rather than Cr(iii) based on an inner filter effect (IFE) process. The addition of ascorbic acid (AA) can recover the intensity of fluorescence of the N-CNP-Cr(vi) system through the reduction of Cr(vi) to Cr(iii) and inhibit the IFE process between N-CNPs and Cr(vi) (turn-on). Accordingly, an efficient N-CNP based fluorescent probe for sensitive and selective sensing of Cr(vi) ions and l-ascorbic acid (AA) has been established. The proposed fluorescence sensor displays excellent performance for Cr(vi) determination in the range from 0.5 to 160 µmol L-1 (R2 = 0.998) with a detection limit down to 0.15 µmol L-1. Moreover, the observed linear response concentration range was from 1 to 400 µmol L-1 for AA with a detection limit as low as 0.13 µmol L-1. The fluorescent probe was successfully applied to detect Cr(vi) concentration in different water samples and AA concentration in human serum samples.

Necrostatin-1 protects hippocampal neurons against ischemia/reperfusion injury via the RIP3/DAXX signaling pathway in rats.

Global cerebral ischemia/reperfusion (I/R) induces selective neuronal injury in CA1 region of hippocampus, leading to severe impairment in behavior, learning and memory functions. However, the molecular mechanism underlying the processes was not elucidated clearly. RIP3 is a key molecular switch connecting apoptosis, necrosis and necroptosis. DAXX, as a novel substrate of RIP3, plays a vital role in ischemia-induced neuronal death. The aim of this study is to investigate the role and mechanism of RIP3/DAXX signaling pathway on neurons in CA1 region of the rat hippocampus after cerebral I/R. Global cerebral ischemia was induced by the method of four-vessel occlusion. RIP1 specific inhibitor Necrostatin-1 was administered by intracerebroventricular injection 1h before ischemia. Open-field, closed-field, and Morris water maze tests were performed respectively to examine the anxiety and cognitive behavior in each group. Hematoxylin and eosinstaining was used to examine the survival of hippocampal CA1 pyramidal neurons. Western blot or immunoprecipitation were carried to detect protein expression, phosphorylation, and interaction. We found that pre-treatment with Nec-1 protected locomotive ability, relieved anxiety behavior, and improved cognitive ability in the rats subjected to cerebral I/R. In addition Moreover, Nec-1 decreased significantly the dead rate of neurons in hippocampal CA1 region after cerebral I/R through suppressing RIP1-RIP3 interaction and RIP3 activation along with RIP3-DAXX interaction, and then blocked DAXX translocation from nucleaus to cytoplasm, which resulted in the inactiviation of DAXX. We concluded that pre-treatment with Nec-1 can protect neurons in the hippocampal CA1 region against ischemic damage through the RIP3-DAXX signaling pathway.

Parallel analysis and orthogonal identification of N-glycans with different capillary electrophoresis mechanisms.

The deep involvement of glycans or carbohydrate moieties in biological processes makes glycan patterns an important direction for the clinical and medicine researches. A multiplexing CE mapping method for glycan analysis was developed in this study. By applying different CE separation mechanisms, the potential of combined parallel applications of capillary zone electrophoresis (CZE), micellar electrokinetic chromatography (MEKC) and capillary gel electrophoresis (CGE) for rapid and accurate identification of glycan was investigated. The combination of CZE and MEKC demonstrated enhancing chromatography separation capacity without the compromises of sample pre-treatment and glycan concentration. The separation mechanisms for multiplexing platform were selected based on the orthogonalities of the separation of glycan standards. MEKC method exhibited promising ability for the analysis of small GU value glycans and thus complementing the unavailability of CZE. The method established required only small amount of samples, simple instrument and single fluorescent labelling for sensitive detection. This integrated method can be used to search important glycan patterns appearing in biopharmaceutical products and other glycoproteins with clinical importance.

Methylene blue improves streptozotocin-induced memory deficit by restoring mitochondrial function in rats.

The pathogenesis of Alzheimer's disease (AD) is well documented to involve mitochondrial dysfunction which causes subsequent oxidative stress and energy metabolic failure in hippocampus. Methylene blue (MB) has been implicated to be neuroprotective in a variety of neurodegenerative diseases by restoring mitochondrial function. The present work was to examine if MB was able to improve streptozotocin (STZ)-induced Alzheimer's type dementia in a rat model by attenuating mitochondrial dysfunction-derived oxidative stress and ATP synthesis decline. MB was administrated at a dose of 0.5mg/kg/day for consecutive 7days after bilateral STZ intracerebroventricular (ICV) injection (2.5mg/kg). We first demonstrated that MB treatment significantly ameliorated STZ-induced hippocampus-dependent memory loss in passive avoidance test. We also found that MB has the properties to preserve neuron survival and attenuate neuronal degeneration in hippocampus CA1 region after STZ injection. In addition, oxidative stress was subsequently evaluated by measuring the content of lipid peroxidation products malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Importantly, results from our study showed a remarkable suppression of MB treatment on both MDA production and 4-HNE immunoactivity. Finally, energy metabolism in CA1 region was examined by detecting mitochondrial cytochrome c oxidase (CCO) activity and the resultant ATP production. Of significant interest, our result displayed a robust facilitation of MB on CCO activity and the consequent ATP synthesis. The current study indicates that MB may be a promising therapeutic agent targeting oxidative damage and ATP synthesis failure during AD progression.

High throughput human plasma N-glycan analysis using DNA analyzer and multivariate analysis for biomarker discovery.

Carbohydrates form the majority of organic compounds found in nature and their presence on proteins influences many important bioactivities. Therefore, glycan profiling shows potential in clinical applications. This work demonstrates the use of a high-throughput GlycanAssure™ sample preparation technology and multi-capillary DNA analyzer for the analysis of the major N-linked glycans (N-glycans) found in human plasma. The application involves two biomarker studies: (1) in profiling patients with chronic kidney disease and (2) in differentiating heart disease patients with normal controls in response to an antiplatelet drug from hypo-responders. Due to complexity of the study data, bio-statistical methods were applied to data processing. 37 N-glycan peaks were observed from separation results, with confirmed structure for most glycans. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to build models to differentiate the patient groups. The percentages of correct classification of the models reached 95.45% for the chronic kidney disease dataset and 85.42% for the anti-platelet drug response dataset. Given that blood N-glycan profiles had been shown to reflect certain disease states, this high-throughput platform could potentially be used for the simultaneous screening of multiple glycan biomarkers, with as little as one drop of blood sample.

Automated dynamic hollow fiber liquid-liquid-liquid microextraction combined with capillary electrophoresis for speciation of mercury in biological and environmental samples.

A simple home-made automatic dynamic hollow fiber based liquid-liquid-liquid microextraction (AD-HF-LLLME) device was designed and constructed for the simultaneous extraction of organomercury and inorganic mercury species with the assistant of a programmable flow injection analyzer. With 18-crown-6 as the complexing reagent, mercury species including methyl-, ethyl-, phenyl- and inorganic mercury were extracted into the organic phase (chlorobenzene), and then back-extracted into the acceptor phase of 0.1% (m/v) 3-mercapto-1-propanesulfonic acid (MPS) aqueous solution. Compared with automatic static (AS)-HF-LLLME system, the extraction equilibrium of target mercury species was obtained in shorter time with higher extraction efficiency in AD-HF-LLLME system. Based on it, a new method of AD-HF-LLLME coupled with large volume sample stacking (LVSS)-capillary electrophoresis (CE)/UV detection was developed for the simultaneous analysis of methyl-, phenyl- and inorganic mercury species in biological samples and environmental water. Under the optimized conditions, AD-HF-LLLME provided high enrichment factors (EFs) of 149-253-fold within relatively short extraction equilibrium time (25min) and good precision with RSD between 3.8 and 8.1%. By combining AD-HF-LLLME with LVSS-CE/UV, EFs were magnified up to 2195-fold and the limits of detection (at S/N=3) for target mercury species were improved to be sub ppb level.

Ion pair hollow fiber liquid-liquid-liquid microextraction combined with capillary electrophoresis-ultraviolet detection for the determination of thyroid hormones in human serum.

In this study, a novel, inexpensive, sensitive and selective analytical method that combines ion pair hollow fiber liquid-liquid-liquid microextraction (IP-HF-LLLME) with capillary electrophoresis-ultraviolet detection (CE-UV) was developed for the simultaneous determination of six thyroid hormones (including diiodothyronine (T2), 3,3,5-triiodo-l-thyronine (T3), 3,5,3,5-tetraiodolthyronine (T4), 3,3,5-triiodothyronine (rT3), monoiodotyrosine (MIT) and diiodotyrosine (DIT)) in human serum samples. By the addition of a low concentration of sodium dodecyl sulfate (SDS) into the donor phase as an ion pair reagent, octanol as the organic extraction solvent and 30 mmol/L Na2CO3 as acceptor phase, six analytes with different polarity and water solubility were successfully extracted simultaneously using HF-LLLME. To the best of our knowledge, this is the first time that a liquid phase microextraction technique was proposed for the extraction of thyroid hormones in real samples. The CE separations were investigated in detail. When 20 kV of voltage was applied, the six compounds were separated within 13 min in 25 mmol/L phosphate buffer (pH 2.15) containing 10% (v/v) acetonitrile and 0.5% (m/v) polyethylene glycol (PEG). Under the optimized conditions, enrichment factors (EFs) ranging from 183- to 366-fold were obtained and the limits of detection (at a signal-to-noise ratio of 3) were at sub µg/L level. The established IP-HF-LLLME-CE-UV method was successfully applied to simultaneous determination of thyroid hormones and relative compounds in human serum samples with good recoveries for the spiked samples.

Zirconia coated stir bar sorptive extraction combined with large volume sample stacking capillary electrophoresis-indirect ultraviolet detection for the determination of chemical warfare agent degradation products in water samples.

In this study, a sensitive, selective and reliable analytical method by combining zirconia (ZrO2) coated stir bar sorptive extraction (SBSE) with large volume sample stacking capillary electrophoresis-indirect ultraviolet (LVSS-CE/indirect UV) was developed for the direct analysis of chemical warfare agent degradation products of alkyl alkylphosphonic acids (AAPAs) (including ethyl methylphosphonic acid (EMPA) and pinacolyl methylphosphonate (PMPA)) and methylphosphonic acid (MPA) in environmental waters. ZrO2 coated stir bar was prepared by adhering nanometer-sized ZrO2 particles onto the surface of stir bar with commercial PDMS sol as adhesion agent. Due to the high affinity of ZrO2 to the electronegative phosphonate group, ZrO2 coated stir bars could selectively extract the strongly polar AAPAs and MPA. After systematically optimizing the extraction conditions of ZrO2-SBSE, the analytical performance of ZrO2-SBSE-CE/indirect UV and ZrO2-SBSE-LVSS-CE/indirect UV was assessed. The limits of detection (LODs, at a signal-to-noise ratio of 3) obtained by ZrO2-SBSE-CE/indirect UV were 13.4-15.9 µg/L for PMPA, EMPA and MPA. The relative standard deviations (RSDs, n=7, c=200 µg/L) of the corrected peak area for the target analytes were in the range of 6.4-8.8%. Enhancement factors (EFs) in terms of LODs were found to be from 112- to 145-fold. By combining ZrO2 coating SBSE with LVSS as a dual preconcentration strategy, the EFs were magnified up to 1583-fold, and the LODs of ZrO2-SBSE-LVSS-CE/indirect UV were 1.4, 1.2 and 3.1 µg/L for PMPA, EMPA, and MPA, respectively. The RSDs (n=7, c=20 µg/L) were found to be in the range of 9.0-11.8%. The developed ZrO2-SBSE-LVSS-CE/indirect UV method has been successfully applied to the analysis of PMPA, EMPA, and MPA in different environmental water samples, and the recoveries for the spiked water samples were found to be in the range of 93.8-105.3%.

Sensitive determination of phenylarsenic compounds based on a dual preconcentration method with capillary electrophoresis/UV detection.

A novel method based on off-line hollow fiber based liquid liquid liquid microextraction (HF-LLLME) combined with on-column anion selective exhaustive injection (ASEI)-capillary electrophoresis/ultraviolet (CE/UV) detection was proposed for the speciation of five phenylarsenic compounds including phenylarsonic acid (PAA), 4-aminophenylarsonic acid (4-APAA), 4-hydroxyphenylarsonic acid (4-HPAA), 4-nitrophenylarsonic acid (4-NPAA) and 3-nitro-4-hydroxyphenylarsonic acid (NHPAA) in this paper. In HF-LLLME, the target analytes were extracted from 5 mL aqueous samples (donor solution pH 2.15) through a thin phase of tributyl phosphate (TBP) inside the pores of a polypropylene hollow fiber and finally into an 18 µL 0.8 mmol/L Tris acceptor solution inside the lumen of the hollow fiber. Following HF-LLLME, the acceptor solutions were directly analyzed by ASEI-CE/UV. For ASEI, a large plug of water (91% length of total capillary) was introduced into the separation capillary before sample injection in order to prolong the sample injection time, and thus enhance the stacking efficiency. Under the optimized ASEI conditions, up to 236-fold of enrichment factor (EF) was obtained for the ASEI-CE/UV determination of target phenylarsenic compounds. By combining HF-LLLME with ASEI-CE/UV, EFs ranging from 155 to 1780-fold were achieved and the limits of detection (LODs) (at a signal-to-noise ratio of 3) were in the range of 0.68-6.90 µg/L for five phenylarsenic compounds; the relative standard deviations (RSDs) of corrected peak area were 5.6-11.8%. The proposed HF-LLLME-ASEI-CE/UV method was applied for the determination of five target phenylarsenic compounds in pig feed from a local pig farm, and storage pig litter, soil in agricultural field and lake water collected near this pig farm, the recoveries for the spiked samples were in the range of 85.7-104.5%, 66.7-96.2%, 28.9-46.9% and 86.9-107.8% for pig feed, pig litter, soil and lake water, respectively.

Phase transfer membrane supported liquid-liquid-liquid microextraction combined with large volume sample injection capillary electrophoresis-ultraviolet detection for the speciation of inorganic and organic mercury.

In this paper, a novel sample pretreatment technique termed phase transfer based liquid-liquid-liquid microextraction (PT-LLLME) was proposed for the simultaneous extraction of inorganic and organic mercury species. In PT-LLLME, an intermediate solvent (acetonitrile) was added into the donor phase to improve the contacting between target mercury species and complexing reagent. Meanwhile, a membrane supported (MS)-LLLME unit was designed to realize the PT-LLLME procedure. By using nylon membrane as supporting carrier, larger than 50 µL of acceptor solution could be hung up. Following PT/MS-LLLME, the acceptor solutions were directly analyzed by large volume sample stacking capillary electrophoresis/ultraviolet detection (LVSS-CE/UV). Accordingly, a new method of PT/MS-LLLME combined with LVSS-CE/UV was developed for the simultaneous speciation of inorganic and organic mercury species. Parameters affecting the extraction efficiency of PT/MS-LLLME were investigated in details. Under the optimized conditions, enrichment factors (EFs) ranging from 160- to 478-fold were obtained for the extraction of target mercury species by PT/MS-LLLME. By combining PT/MS-LLLME with LVSS-CE/UV, EFs were magnified up to 12,138-fold and the limits of detection (at a signal-to-noise ratio of 3) were at sub ppb level. The established approach of PT/MS-LLLME-LVSS-CE/UV was successfully applied to simultaneous determination of inorganic and organic mercury species in biological samples and environmental water samples.

High-sensitivity capillary electrophoresis for speciation of organomercury in biological samples using hollow fiber-based liquid-liquid-liquid microextraction combined with on-line preconcentration by large-volume sample stacking.

A hollow fiber-based liquid-liquid-liquid microextraction (HF-LLLME) combined with on-line large-volume sample stacking (LVSS) has been developed for the speciation of organomercury in biological samples by CE with UV detection. Separation was achieved in less than 11 min with an electrolyte consisting of 35 mM sodium tetraborate at pH 9.1. In LVSS, a reverse electrode polarity-stacking mode (REPSM) was applied as on-line preconcentration strategy. In HF-LLLME, the analytes were extracted from 12 mL volume of sample solution (pH adjusted to 3.0) into bromobenzene impregnated in the pores of the hollow fiber, and into an acceptor solution of L-cysteine (15 microL, 0.02% w/v) inside the hollow fiber. Under the optimized conditions, concentration factors of 2610-4580 were achieved and LODs in the range of 0.03-0.14 microg/L were feasible. The linearity was found to be over two orders of magnitude with correlation coefficient of 0.9991-0.9996. The developed method has been validated using a certified reference material (DORM-2, dogfish muscle), and the determined values coincided very well with the certified values. The method was also applied to the speciation of organomercury in three kinds of fish samples and human hair samples.