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.

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.

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.

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.

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.

Tissue distribution and elimination features of florfenicol in hybrid sturgeon cultured in cool water.

In order to understand pharmacokinetics in vivo and tissue residues of florfenicol in Hybrid sturgeon cultured in cold water, changes in concentration of florfenicol in plasma, muscle, liver and kidney of sturgeon after administration were measured by high performance liquid chromatography mass spectrometry. The results show that after 15.0 mg/kg dose administration, the concentration change in plasma and liver, kidney and muscle of sturgeon are suitable for the one compartment open model. Florfenicol pharmacokinetic parameters in plasma, liver, kidney and sturgeon muscle showed that the peak concentration (Cmax ) were 549.7, 551.8, 958.2 and 405.4 µg/kg, respectively. The peak time (Tmax ) was 17.5, 14.2, 14.0 and 20.8 hr, respectively. The elimination half-life (T1/2 ) was 75.1, 99.8, 68.8 and 75.5 hr, respectively. Area under the curve were 70,048.9, 63,850.6, 109,579.9 and 53,437.3 µg/kg hr, respectively. Mean residence time was 100.6, 96.4, 96.5 and 104.6 hr, respectively. The absorption speed and elimination of florfenicol in cold water cultured sturgeon is slow, and the peak concentration is low, but the florfenicol was widely distributed in the body of sturgeon. The results provide a theoretical basis for formulation of medication and withdrawal period of florfenicol used in sturgeon cultured in cold water.

Direct Determination of Lead in Foods by Solid Sampling Electrothermal Vaporization Atomic Fluorescence Spectrometry.

A solid sampling method for the determination of lead in foods (including grains, vegetables and seafoods) using electrothermal vaporization atomic fluorescence spectrometry was established. The method introduced samples using electrothermal vaporization by quartz furnace and used on-line ashing and vaporization to remove matrix interferences for the specific trap of lead. It was proven by the certified reference material (CRM) and the recovery rate of the standards that the electrothermal vaporization was stable and there was no effect for sampling difference. The best operating program and parameters for the new method included ashing (850°C, 160 s), vaporization and trap (1050°C, 80 s; 800°C, 10 s), release (800°C, 10 s), and mixed Ar + H2 (85:15%, v/v) as carrier gas with flow rate of 500 mL/min. The relative standard deviations of repeated Pb measurements in CRMs were all below 5.0%, and the recovery rate ranged from 90.0 - 110.0%. The limit of detection (LOD) for the new method was 3.0 pg and the limit of quantification (LOQ) was 10.0 pg. The total time of analysis was less than 6 min. No significant differences existed between the results measured by the new method and microwave ICP-MS.

[Application of ICP-MS to Detect Rare Earth Elements in Three Economic Macroalgaes in China].

In order to investigate the content and distribution of rare earth elements (REE) in main economic macroalgaes in our country, fifteen rare earth elements in three economic macroalgaes (including 30 samples of kelp, 30 samples of laver and 15 samples of Enteromorpha) were detected using ICP-MS method. Results showed that the total content of REE in different species of macroalgaes was different. The highest total content of REE was in Enteromorpha (16,012.0 ng · g⁻¹), while in kelp and laver, the total REE was similar for two macroalgaes (3887.4 and 4318.1 ng · g⁻¹ respectively). The content of fifteen rare earth elements in kelp ranged from 7.9 to 1496.4 ng · g⁻¹; in laver, it ranged from 8.2 to 1836.6 ng · g⁻¹. For Enteromorpha, the concentration of 15 rare earth elements were between 19.2 and 6014.5 ng · g⁻¹. In addition, the content and distribution of different rare earth elements in different macroalgaes was also different. For kelp, the highest content of REE was Ce (1 496.4 ng · g⁻¹), and the second was La (689.1 ng · g⁻¹). For laver, the highest was Y (1836.6 ng · g⁻¹), and the second was Ce (682.2 ng · g⁻¹). For Enteromorpha, the highest was Ce (6014.5 ng · g⁻¹), and the second was La (2902.9 ng · g⁻¹). Present results also showed that three macroalgaes accumulated the light rare earth elements much more than the high rare earth elements. The light rare earth elements occupied 90.9%, 87.3% and 91.1% for kelp, laver and Enteromorpha respectively. The result that the Enteromorpha had high content of rare earth elements could provide important support for opening new research directions for the utilization of Enteromorpha.

Subcellular distribution and chemical forms of cadmium in the edible seaweed, Porphyra yezoensis.

The subcellular distribution and chemical forms of Cd were investigated in the edible seaweed, Porphyra yezoensis. The seaweed was exposed to different Cd concentrations (0.01, 0.05, 0.1, 0.5, 1.0 and 5.0mgl(-1)) for up to 96h. In both the controls (no Cd added) and treatment groups, 41.2-79.2% of Cd was localised in the cell wall, and the proportion of Cd in the cell wall increased with increasing concentrations of Cd and exposure time. In the control groups, 74.8% of Cd was extracted by 1M NaCl, followed by 2% acetic acid, HAC (18.9%). In the treatment groups, most Cd was extracted by 2% HAC. The proportion of Cd extracted by 2% HAC increased with exposure to increasing concentrations of Cd and over time. Cell wall deposition and forming of precipitates with phosphate may be a key strategy to reduce Cd toxicity in P. yezoensis.

Arsenic Species in Edible Seaweeds Using In Vitro Biomimetic Digestion Determined by High-Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry.

Arsenite [As (III)], arsenate [As (V)], methylarsonate (MMA), and dimethylarsinate (DMA) in five edible seaweeds (the brown algae Laminaria japonica, red algae Porphyra yezoensis, brown algae Undaria pinnatifida, brown algae Hizikia fusiformis, and green algae Enteromorpha prolifera) were analyzed using in vitro digestion method determined by high-performance liquid chromatography inductively coupled plasma mass spectrometry. The results showed that DMA was found in the water extracts of all samples; As (III) were detected in L. japonica and U. pinnatifida and about 23.0 and 0.15 mg/kg of As (V) were found in H. fusiformis and E. prolifera respectively. However, after the gastrointestinal digestion, As (V) was not detected in any of the five seaweeds. About 0.19 and 1.47 mg/kg of As (III) was detected in the gastric extracts of L. japonica and H. fusiformis, respectively, and about 0.31 and 0.10 mg/kg of As (III) were extracted from the intestinal extracts of Porphyra yezoensis and U. pinnatifida, respectively. The present results successfully reveal the differences of As species and levels in the water and biomimetic extracts of five edible seaweeds. The risk assessment of the inorganic arsenic in the five edible seaweeds based on present data showed almost no hazards to human health.