Solid Sampling Pyrolysis Adsorption-Desorption Thermal Conductivity Method for Rapid and Simultaneous Detection of N and S in Seafood.

In this work, a rapid method for the simultaneous determination of N and S in seafood was established based on a solid sampling absorption-desorption system coupled with a thermal conductivity detector. This setup mainly includes a solid sampling system, a gas line unit for controlling high-purity oxygen and helium, a combustion and reduction furnace, a purification column system for moisture, halogen, SO2, and CO2, and a thermal conductivity detector. After two stages of purging with 20 s of He sweeping (250 mL/min), N2 residue in the sample-containing chamber can be reduced to <0.01% to improve the device's analytical sensitivity and precision. Herein, 100 s of heating at 900 °C was chosen as the optimized decomposition condition. After the generated SO2, H2O, and CO2 were absorbed by the adsorption column in turn, the purification process executed the vaporization of the N-containing analyte, and then N2 was detected by the thermal conductivity cell for the quantification of N. Subsequently, the adsorbed SO2 was released after heating the SO2 adsorption column and then transported to the thermal conductivity cell for the detection and quantification of S. After the instrumental optimization, the linear range was 2.0−100 mg and the correlation coefficient (R) was more than 0.999. The limit of detection (LOD) for N was 0.66 µg and the R was less than 4.0%, while the recovery rate ranged from 95.33 to 102.8%. At the same time, the LOD for S was 2.29 µg and the R was less than 6.0%, while the recovery rate ranged from 92.26 to 105.5%. The method was validated using certified reference materials (CRMs) and the measured N and S concentrations agreed with the certified values. The method indicated good accuracy and precision for the simultaneous detection of N and S in seafood samples. The total time of analysis was less than 6 min without the sample preparation process, fulfilling the fast detection of N and S in seafood. The establishment of this method filled the blank space in the area of the simultaneous and rapid determination of N and S in aquatic product solids. Thus, it provided technical support effectively to the requirements of risk assessment and detection in cases where supervision inspection was time-dependent.

Effects of single and combined exposure to BDE-47 and PFOA on distribution, bioaccumulation, and toxicity in blue mussel (Mytilus galloprovincialis).

The contamination of 2,2',4,4'-Tetrabrmodiphenyl ether (BDE-47) and perfluorooctanoic acid (PFOA) has drawn a worldwide attention over the risks in ecological and food safety. In this work, blue mussel (Mytilus galloprpvincialis) was employed to investigate the combined effects of BDE-47 (10 ng mL-1) and PFOA (100 ng mL-1) on tissue distribution, accumulation, elimination, and toxicity. Results suggested that BDE-47 and PFOA accumulated mostly in digestive gland, followed by gills and gonad, and M. galloprovincialis displayed higher accumulation capacity to BDE-47 than PFOA. Co-exposure treatment reduced the accumulation of BDE-47, and enhanced the accumulation of PFOA. Furthermore, biochemical and histopathological tests revealed that the aggravated toxicity in co-exposure groups was mainly attributed to the oxidative stress and damage of tissue structure. This work could be helpful to get a better understanding of the combined behaviors and cumulative risks of BDE-47 and PFOA in marine ecosystem.

Uptake, Tissue Distribution, and Elimination of 8:2 Polyfluoroalkyl Phosphate Diesters in Mytilus galloprovincialis.

Although the distribution of 8:2 polyfluoroalkyl phosphate diester (8:2 diPAP) in aquatic environments has been reported, details on its uptake, tissue specificity, and elimination in bivalve mollusks remain to be clarified. The present study is the first report on the accumulation and elimination of 8:2 diPAP in mussels (Mytilus galloprovincialis). The tissue-specific accumulation and depuration of 8:2 diPAP and its metabolites were investigated via semistatic seawater exposure (8:2 diPAP at a nominal concentration of 10 µg/L), through water-borne exposure with static daily renewal over a 72-h exposure period and a 360-h depuration period. The digestive gland was found to be the target organ where accumulation and biotransformation primarily occur. The bioaccumulation factor values (mL/g dry wt) in different organs were in the following order: digestive gland (1249) > adductor muscle (315) > gills (289) > gonad (82.9) > mantle (33.0). Moreover, the distribution of 8:2 diPAP among tissues may be related to the total protein content. The 8:2 diPAP tended to be excreted in feces. The compounds 8:2 fluorotelomer carboxylic acid, 8:2 fluorotelomer unsaturated carboxylic acid, 7:3 fluorotelomer carboxylic acid, perfluorooctanoic acid, and perfluoroheptanoic acid were detected and quantified as phase I metabolites, and the concentration of all phase I metabolites relative to the 8:2 diPAP concentration (72 h) was 0.304 mol%. A phase II metabolite, 8:2 fluorotelomer alcohol conjugated with sulfate, was detected but not quantitated in the digestive gland. A biotransformation pathway of 8:2 diPAP in M. galloprovincialis was proposed on the basis of the results obtained in the present study and previous studies. These findings improve our understanding of the accumulation of perfluorocarboxylic acids in bivalve mollusks. Environ Toxicol Chem 2021;40:1992-2004. © 2021 SETAC.

Bioaccumulation and biotransformation of inorganic arsenic in zhikong scallop (Chlamys farreri) after waterborne exposure.

Arsenic (As) and As speciation in marine bivalves have been widely investigated. However, little is known about the bioaccumulation and biotransformation of inorganic As in different tissues of scallops. Therefore, the tissue-specific accumulation, biotransformation and subcellular partitioning of As were investigated in Chlamys farreri following 12 d inorganic As [arsenite (AsⅢ) and arsenate (AsⅤ)] exposure and 30 d depuration. Total As levels were highest in the kidneys and lowest in the adductor muscle after 12 d exposure for both As (Ⅲ) and As (Ⅴ) treatment groups, and the bioavailability of As (Ⅲ) was significantly higher than that of As (Ⅴ) for C. farreri. After 30 d elimination, total As levels were significantly decreased to the control levels. The subcellular fate of As in five different tissues was similar for different inorganic As treatment groups. The greatest proportion of As was found in the metallothionein-like protein fraction (MTLP) and the second was the cellular debris (CD). A little part of As (Ⅲ) could be oxidized to As (Ⅴ) in the gill and digestive gland for As (Ⅲ) treatment groups, and the reduction of As (Ⅴ) to As (Ⅲ) happened in the gill and kidney under As (Ⅴ) exposure. Although a high methylation activity was found in C. farreri, it varied in different tissues with different inorganic As species exposure. The present results indicated that exposure to As (Ⅲ) and As (Ⅴ) could induce different responses in bioaccumulation and biotransformation in five tissues of C. farreri.

Integrated analysis of physiological, transcriptomics and metabolomics provides insights into detoxication disruption of PFOA exposure in Mytilus edulis.

Perfluorooctanoic acid (PFOA), a persistent environmental contaminant, resists environmental degradation and bioaccumulates in food chains. Lots of literatures have proved that PFOA exposure could disrupt detoxifying function in a variety of organisms, however, it still remained poorly known about this in mollusk. Here, we examined physiological, transcriptomic, and metabolomic responses to PFOA in Mytilus edulis, a model organism frequently used in studies of aquatic pollution. We aimed to characterize PFOA-induced stress responses and detoxification mechanisms. PFOA exposure significantly altered antioxidant enzyme activity levels and the abundances of lipid peroxidation products. In addition, transcriptomic analysis indicated that several genes associated with oxidative stress and detoxication were differentially expressed after PFOA exposure. In combination, transcriptomic and metabolomic analyses showed that PFOA exposure disturbed several metabolic processes in M. edulis, including the lipid metabolism, amino acid metabolism, and carbohydrate metabolism etc. Molecular examination and enzymes assay of PFOA-exposed M. edulis after a 7-day depuration period still did not recover to control levels. The Pathway enrichment analysis proved that several pathways related to detoxification, such as c-Jun N-terminal kinase (JNK) and p38-dependent mitogen-activated protein kinase (MAPK) pathway, Peroxisome proliferator-activated receptor γ (PPARγ) pathway etc, were obviously affected. The present work verifies firstly PFOA disruption to molluscan detoxification and identifies the key pathways to understand the molecular mechanisms thereof. This study provides new insights into the detoxication disruption invoked in response to PFOA exposure in M. edulis.

Hyperaccumulation of cadmium by scallop Chlamys farreri revealed by comparative transcriptome analysis.

Cadmium (Cd) is a hazardous environmental contaminant, which has a serious effect on the ecosystem, food safety and human health. Scallop could accumulate high concentration of Cd from the environment and has been regarded as a Cd hyper-accumulator. In this work, we investigated the antioxidative defense, detoxification and transport of Cd in the kidneys of scallops by transcriptome analysis. A total of 598 differentially expressed genes including 387 up-regulated and 211 down-regulated ones were obtained during Cd exposure, and 46 up-regulated and 260 down-regulated ones were obtained during depuration. Cadmium exposure could cause oxidative stress in the kidneys, which was particularly shown in the pathways involved in proteasome and oxidative phosphorylation. The mRNA expression of 5 metallothionein (MT) genes were overexpressed under Cd exposure and significantly decreased during Cd depuration, which played a vital role in Cd chelation and detoxification. The expression of divalent metal transporter (DMT) genes were down-regulated insignificantly during accumulation and depuration of Cd, which suggested that the DMT played little roles in Cd transport in scallops. A positive relationship in the expression of the zinc transporter (ZIP6 and ZIP1) genes with Cd exposure and depuration was observed, which confirmed its important role for Cd uptake in the kidneys of scallops. 26S proteasome activities and MT expression were Cd-dependent. This study supplied the important reference on the hyperaccumulation of Cd by scallops and identified some effective bioindicators for the environmental risk assessment.

Nontarget Screening and Toxicity Evaluation of Diol Esters of Okadaic Acid and Dinophysistoxins Reveal Intraspecies Difference of Prorocentrum lima.

High-resolution mass spectrometry (HRMS) analysis with the assistance of molecular networking was used to investigate intracellular toxin profiles of five Prorocentrum lima (P. lima) strains sampled from the north Yellow Sea and South China Sea. Mice were used as a model species for testing the acute toxicity of intracellular okadaic acid (OA) and dinophysistoxins (DTXs) in free and esterified states. Results showed that OA and DTX1 esterified derivatives were detected in all P. lima samples, accounting for 55%-96% of total toxins in five strains. A total of 24 esters and 1 stereoisomer of DTX1 (35S DTX1) were identified based on molecular networking and MS data analysis, 15 esters of which have been reported first. All P. lima strains displayed specific toxin profiles, and preliminary analysis suggested that toxin profiles of the five P. lima strains might be region-related. Moreover, acute toxicity in mice suggested higher toxicity of esters compared with free toxins, which highlights the importance and urgency of attention to esterified toxins in P. lima.

Methodology and application of PCR-RFLP for species identification in tuna sashimi.

The Thunnini, or tuna, comprise many species with very different commercial values. The principal raw tuna product on the market is sashimi, for which the species used is difficult to identify through conventional morphological analysis. The present study amplified the cytochrome b gene (Cytb) of 4 major tuna species used for preparing sashimi-yellowfin tuna (Thunnus albacares), southern bluefin tuna (Thunnus maccoyii), bigeye tuna (Thunnus obesus), and Atlantic bluefin tuna (Thunnus thynnus)-and 4 species commonly mislabeled as components of tuna sashimi-albacore tuna (Thunnus alalunga), skipjack tuna (Katsuwonus pelamis), striped marlin (Tetrapturus audax), and swordfish (Xiphias gladius). Polymerase chain reaction (PCR) amplicons were digested with 5 restriction enzymes-Eco147 I, Hinf I, Mbo I, Xag I, and Hind II-to obtain characteristic restriction maps of the above-mentioned raw tuna species and the commonly mislabeled species. An identification method using PCR restriction fragment length polymorphism (PCR-RFLP) was established and validated using 39 commercial tuna sashimi samples, which verified that this method provides results consistent with those obtained by classical sequencing. PCR-RFLP has several advantages over classical sequencing, such as simplicity, speed and accuracy. This technique could support species identification for raw tuna and sashimi.

Integrated transcriptomic and proteomic analyses of the tissues from the digestive gland of Chlamys farreri following cadmium exposure.

OBJECTIVES: Cadmium causes the pollution of marine habitat and Chlamys farreri is an effective concentrator of heavy metals, the aim of this study was to study the response mechanism of C. farreri to cadmium stress at transcriptomic and proteomic levels. METHODS: Transcriptomic analysis based on RNA-sequencing and proteomic analysis based on isobaric tags for relative and absolute quantitation were performed to reveal the molecular response of C. farreri to different concentrations of cadmium (0.1, 0.3, and 1 mg/L). In addition, a protein-protein interaction (PPI) network was constructed based on the Cytoscape tool to identify hub proteins related to the response of C. farreri to cadmium stress. RESULTS: A total of 24 190 unigenes from 58 683 candidates were annotated in known databases. The numbers of the differentially expressed unigenes (DEGs) was different among the three cadmium-treated groups compared with the control group. DEGs were involved in many pathways such as ABC transporters, protein processing in endoplasmic reticulum and endocytosis. A total of 660 proteins were identified, and differentially expressed proteins (DEPs) among different groups were determined. The overlapping DEGs and DEPs were associated with cadmium response. The upregulated unigene0002618 and downregulated unigene0000904 may be more important for the response of C. farreri to cadmium stress. Unigene0009750 was the hub protein in the PPI network with the highest degree of 20. CONCLUSIONS: Our transcriptomic and proteomic analyses elucidated the molecular response of C. farreri to cadmium stress.

Study of Cd Content Distribution and Its Bioaccessibility in Edible Tissues of Crab Portunus trituberculatus from the Coastal Area of Shandong, China.

Bioaccessibility study is of great significance to the health risk assessment of trace elements in the seafood. In this work, the most consumed crab (Portunus trituberculatus) in coastal area of Shandong, China was analyzed to study the distribution and the bioaccessibility of cadmium (Cd) in the edible tissues of crab, and the dietary risk from consumption of crab was also evaluated. Results showed that the content of Cd in the whole edible tissues of 109 crab specimens ranged from 0.052 to 8.89 mg/kg ww (wet weight) with mean of 2.26 mg/kg ww. The Cd content in 85% of the crab samples was higher than the national food safety limits (0.5 mg/kg ww) of China. The gender study indicated that there was no significant difference in Cd content in total edible tissues between the males and females (p > 0.05). Cadmium was highly concentrated in the brown meat with mean value of 4.13 mg/kg ww, which was about 5 times higher than that in the white meat (0.75 mg/kg ww). The bioaccessibility of Cd ranged from 48.1 to 71.0% in the white and brown meat. The risk assessment based on the bioaccessibility of Cd revealed that the consumption of the edible crab brown and white meat for adults should be limited in 0.13 kg and 1.56 kg per week respectively.

[Pollution Characteristics of Perfluorinated Alkyl Substances (PFASs) in Seawater, Sediments, and Biological Samples from Jiaozhou Bay, China].

In order to explore the pollution levels and characteristics of perfluorinated alkyl substances (PFASs), seawater, sediment, and Ruditapes philippinarum samples were collected near the Jiaozhou Bay coast in April 2018. All samples were analyzed by using the high performance liquid chromatography-mass spectrometry method to determine the content of 35 types of PFASs. The results showed that 12 different PFASs were tested in the seawater with ∑PFASs concentrations of 21.1-38.0 ng·L-1; 10 types of PFASs were detected in sediments, with ∑PFASs content (dry weight) ranging from 0.459 to 1.20 µg·kg-1; 19 types of PFASs were measured in Ruditapes philippinarum, with ∑PFASs content (dry weight) of 15.5-27.5 µg·kg-1. Compared with other areas reported in the literature, the total pollution of Jiaozhou Bay was at medium or high levels. In addition, perfluorooctanoic acid (PFOA) was the dominant PFAS in the seawater, sediments, and Ruditapes philippinarum with a detection rate of 100%. 6:2 fluorotelomer phosphate diester (6:2 diPAP) was observed for the first time in seawater and sediments from Jiaozhou Bay and had the highest detection frequency and concentration of the precursor. Perfluorooctanesulfonamide (PFOSA) was the main precursor in Ruditapes philippinarum, of which the detection rate was 93.8%. Moreover, the organic carbon normalized sediment-water distribution coefficient (lg KOC) values were 5.24-6.37 and increased with an increase in carbon chain length. The bioaccumulation factors (lg BAF) and field-based biota-sediment accumulation factors (lg BSAF) were 2.53-4.32 and 1.30-2.50, respectively. The lg BAF values positively correlated with the carbon chain length, whereas the lg BSAF values decreased with an increase in the carbon chain length (C8-C13).

Development and Evaluation of a Novel Armored RNA Technology Using Bacteriophage Qß.

Foodborne viruses are a global threat to food safety. Real-time reverse transcription polymerase chain reaction (RT-PCR) is the most commonly used method to detect viral RNA in food. Armored RNA (AR) prepared using the MS2 phage system is a successful positive control for detecting foodborne viruses and is an important quality control process when using real-time RT-PCR. In this study, we report a novel technology for preparing AR using bacteriophage Qß and compare its stability with AR prepared using the MS2 phage system for packaging norovirus detection target RNA. AR could be successfully and efficiently produced using the developed bacteriophage Qß system. Two types of AR-AR-QNoV prepared using the Qß system and AR-MNoV prepared using the MS2 system-were stored at different temperatures for different durations. After incubating at - 20 °C for 360 days, the copy numbers of AR-QNoV and AR-MNoV decreased by 8.9% and 35.9%, respectively. After incubating at 4 °C for 60 days, the copy numbers of AR-QNoV and AR-MNoV decreased by 12.0% and 38.9%, respectively. After incubating at 45 °C, the copy numbers of AR-QNoV decreased by 71.8% after 5 days, whereas those of AR-MNoV decreased by 92.9% after only 4 days. After 5 days, AR-MNoV could not be detected using real-time RT-PCR. There was a significant difference in copy numbers decrease rate between AR-QNoV and AR-MNoV at three different temperatures (P < 0.05 ). Therefore, AR prepared using the new bacteriophage Qß system is more stable than the traditional AR, making the developed strategy a good candidate for AR preparation and quality control.

Subcellular distribution and chemical forms of lead in the red algae, Porphyra yezoensis.

The subcellular distribution and chemical forms of lead (Pb) were examined in the red algae, Porphyra yezoensis. The algae was exposed to three different Pb treatments (0.01, 0.1 and 1.0 mg L-1) for up to 144 h. In the control groups, about 45% of Pb was localized in the cell wall, and 27.5% in the organelle and soluble fractions respectively. The dominant chemical forms of Pb was extracted by 80% ethanol (52.9%), while the form extracted by NaCl (1 M) was lowest. In the treatment groups, the cell wall and the organelle fraction were the main subcellular fractions for the 0.10 mg L-1 and 1.0 mg L-1 groups; while for the 0.01 mg L-1 groups, Pb was approximately distributed in the cell wall, organelle and the soluble fractions. The dominant ethanol extractable form of Pb in the control and 0.01 mg L-1 groups were replaced by less active 2% acetic acid (HAc) extractable form in the 0.1 and 1.0 mg L-1 groups. Different from other terrestrial plants, the proportion of 1 M NaCl extractable form of the pectates and protein integrated Pb in P. yezoensis was lowest for both control and treatment groups. The strategy with deposition Pb in the cell wall and formation the precipitation of less active HAc extractable form maybe one of the mechanisms for accumulation, transportation and detoxification of Pb in P. yezoensis.

Selective enrichment and quantification of okadaic acid in shellfish using an immunomagnetic-bead-based liquid chromatography with tandem mass spectrometry assay.

Okadaic acid is a marine biotoxin that primarily occurs in shellfish and can cause diarrheic shellfish poisoning in humans. When analyzing biological samples using liquid chromatography with tandem mass spectrometry, the presence of complex matrices is a major issue. Thus, it is crucial to selectively and simply extract the target analyte from samples and minimize matrix effects simultaneously. To meet this need, an immunomagnetic-bead-based liquid chromatography with tandem mass spectrometry method was developed to detect okadaic acid in shellfish. Magnetic beads bound to monoclonal antibody against okadaic acid were used as affinity probes to specifically enrich okadaic acid in samples, which effectively eliminated matrix effects. A magnetic separator was used to aggregate and separate magnetic particles from sample matrices, and methanol was used to elute okadaic acid from the magnetic beads. Standard solution prepared with methanol was employed directly for quantitative analysis. Several experimental conditions were optimized to improve performance. The method is of interest as a rapid (10 min) sample clean-up and selective enrichment tool, and it showed good linearity and sensitivity, with reported limits of detection and quantitation of 3 and 10 µg/kg, respectively. Fifty-three shellfish samples from an aquatic products market were tested using this method, and four samples positive for okadaic acid were found.

Distribution of perfluorinated alkyl substances in marine shellfish along the Chinese Bohai Sea coast.

Perfluorinated alkyl substances (PFASs) are emerging persistent organic pollutants, which pose a threat to human health primarily by dietary exposure, especially through seafood. Bohai Sea (a semi-closed sea located north of China) is an important shellfish aquaculture area that is possibly highly-polluted with PFASs. In this study, we first evaluated contamination by PFASs in a total of 230 samples of marine shellfish from the Bohai Sea. Samples included five important shellfish species, collected from important aquaculture spots distributed around the Bohai Sea. Samples were analyzed by an ultra-fast liquid chromatography-tandem mass spectrometry method, which could simultaneously detect 23 PFASs in shellfish. Our research verified that PFASs have become a threat to the safety of shellfish products in this area. Furthermore, contamination by PFASs in shellfish changed depending on the components of PFASs, the species of shellfish, and the sampling sites. Many of the 23 target compounds contributed to the high detection ratio (>50%) as follows: perfluorooctanoic acid (PFOA) > perfluorononanoic acid > perfluorodecanesulfonic acid > perfluorooctanesulfonic acid (PFOS). Compared with other dominant components, PFOA not only had the highest detection percentage in shellfish samples (98.3%), but its detection level contributed to 87.2% of total PFASs concentrations, indicating that PFOA is the major threat to the safety of shellfish products. The highest level of PFAS was found in clams (62.5 ng g-1 wet weight of PFOA). The concentration of total PFAS in different shellfish species showed the following trend: clams > mussels > scallops > whelks > oysters. The maximum concentration of total PFAS or PFOA was found in Shouguang. The total concentration of PFOS and its precursor were highest in Cangzhou, possibly due to local industrial activities. The results presented in this paper provide new data on the contamination of marine shellfish along the Bohai Sea coasts in China, and constitute a reference for future monitoring of contamination by emerging contaminants in Bohai coast.

Antimicrobial resistance, virulence and genetic relationship of Vibrio parahaemolyticus in seafood from coasts of Bohai Sea and Yellow Sea, China.

Vibrio parahaemolyticus is an important foodborne pathogen which commonly inhabits estuarine and marine environments and seafood. In the present study, 90 V. parahaemolyticus isolates from the main seafoods from three coastal provinces surrounding Bohai Sea and Yellow Sea, China were analyzed to elucidate their antimicrobial resistance, virulence and genetic relationship by multilocus sequence typing (MLST). The results showed that the virulence genes tdh and trh were detected in one isolate and five isolates respectively. Most of isolates showed resistance to ampicillin (86/90) and cephazolin (75/90). Some isolates were resistant to amikacin (27/90), cefuroxime sodium (18/90), tetracycline (16/90), sulphamethoxazole/trimethoprim (16/90) and streptomycin (13/90). Forty isolates (44.4%) possessed multiple antimicrobial resistance to at least three antimicrobials. The V. parahaemolyticus population was composed of 68 sequence types, of which 41 were novel to the pubMLST database, displaying a high level of genetic diversity. The phylogenetic relatedness of V. parahaemolyticus isolates was irrelevant to the collection sources. Moreover, there were no associations of antimicrobial resistance and trh positive virulence with genetic population of V. parahaemolyticus isolates. These results indicated that the diversity of antimicrobial-resistant or pathogenic V. parahaemolyticus isolates from coasts of Bohai Sea and Yellow Sea, China could pose a potential risk to human health.

Phycotoxins in scallops (Patinopecten yessoensis) in relation to source, composition and temporal variation of phytoplankton and cysts in North Yellow Sea, China.

The North Yellow Sea is a major aquaculture production area for the scallop Patinopecten yessoensis. In this study, the temporal and spatial variation of phycotoxins in scallops, phytoplankton, and their cysts were analyzed during a survey conducted from June 2011 to April 2012 around Zhangzi Island. The study area is a semi-enclosed epicontinental sea surrounded by the Shandong Peninsula, the Liaodong Peninsula and the Korean Peninsula. The three main results of the study were as follows: (1) The saxitoxin-group toxins, okadaic acid and analogues, and pectenotoxins were the major phycotoxin residues found in scallops; (2) Six kinds of toxic microalgae were identified, Protoperidinium spp., Gonyaulax spp., and Alexandrium spp. were the dominant taxa; Seven types of potential marine toxin-producing dinoflagellates, A. tamarense, A. catenella, Dinophysis fortii, G. catenatum, Gambierdiscus toxicus, Azadinium poporum, and Pseudo-nitzschia pungen were identified as the primary source of phycotoxins and were present at relatively high density from June to October; and (3) azaspiracids and domoic acid might be new potential sources of toxin pollution. This study represents the first assessment to phycotoxins around Zhangzi Island in the North Yellow Sea.

Detection of Polycyclic Aromatic Hydrocarbons in Water Samples by Annular Platform-Supported Ionic Liquid-Based Headspace Liquid-Phase Microextraction.

In this paper, a new method of annular platform-supported headspace liquid-phase microextraction (LPME) was designed using ionic liquid as an extraction solvent, wherein extraction stability and efficiency were improved by adding an annular platform inside the extraction bottle. The ionic liquid 1-silicyl-3-benzylimidazolehexafluorophosphate was first synthesized and proved to be an excellent extraction solvent. Coupled with liquid chromatography, the proposed method was employed to analysis of polycyclic aromatic hydrocarbons (PAHs) in water and optimized in aspects of extraction temperature, extraction solvent volume, extraction time, pH, stirring rate, and salt effect of solution. The results indicated that this method showed good linearity (R 2 > 0.995) within 0.5 µg·L-1 to 1000 µg·L-1 for PAHs. The method was more suitable for extraction of volatile PAHs, with recoveries from 65.0% to 102% and quantification limits from 0.01 to 0.05 µg·L-1. It has been successfully applied for detection of PAHs in seawater samples.

Determination of gentamicin C components in fish tissues through SPE-Hypercarb-HPLC-MS/MS.

In this work, an HPLC/MS/MS method for determination of gentamicin C components in fish tissues was developed based on strong cation exchange solid-phase extraction (SPE) purification coupled with Hypercarb chromatographic column in separation mode. Sample was extracted using trichloroacetic acid aqueous solution containing EDTA. Ion-pairing reagents were not needed because of the "graphite polarity retention effect" of the Hypercarb chromatographic column. HPLC-MS/MS was performed in multiple reaction monitoring (MRM) mode for simultaneous qualitative and quantitative analyses (using matrix external standard) of gentamicin C components in fish tissues. Good linearity was obtained for the target analytes within the concentration range from 0.0100 to 0.500 mg/L. The limits of quantification (LOQ) of this method were 10.0, 20.0, and 20.0 µg/kg for C1, C1a, and sum of C2 + C2a, respectively. The average recoveries of gentamicin C components were 80.0%-110% when spiked at three levels with the blank carp (Cyprinus carpio) matrix, and the relative standard deviations (RSD) were all less than 15% (n = 6). In addition, for the features of simple operation, high sensitivity and good reproducibility, the proposed method has been successfully applied for detection of gentamicin residues in fish tissues during actual breeding.

Biocontrol of Salmonella Typhimurium in Raw Salmon Fillets and Scallop Adductors by Using Bacteriophage SLMP1.

The aim of this study was to evaluate the effectiveness of bacteriophage (phage) SLMP1 to reduce Salmonella Typhimurium on contaminated raw salmon fillets and scallop adductors as a function of Salmonella inoculum level, phage dose, storage temperature, and storage time. Samples were inoculated with 102 and 104 CFU/g Salmonella and then treated with different concentrations of phage SLMP1, followed by incubation at 4, 15, and 25°C, respectively. The results showed that 108 PFU/g was the optimal concentration of phage for the control of Salmonella, which was applied in the following storage experiments over a 7-day period at 4°C, a 4-day period at 15°C, and a 2-day period at 25°C. For the salmon fillets samples, 102 CFU/g Salmonella could be reduced below the detection limit at all three temperatures, whereas 104 CFU/g Salmonella was first decreased and then increased at 15 and 25°C. For the scallop adductors samples, 102 CFU/g Salmonella could be reduced below the detection limit first and then increased after a certain period at 15 and 25°C. The variation trends of 104 CFU/g Salmonella in scallop adductors were similar to those in salmon fillets. The results also showed that the Salmonella counts of both inoculum levels on samples could be reduced below the detection limit or maintained at a low level by phage SLMP1 during storage at 4°C. Phage SLMP1 remained stable on raw salmon fillets and scallop adductors. This study indicated that phage SLMP1 has potential effectiveness as a biocontrol agent of Salmonella in seafood.