Determination of Pentachlorophenol in Seafood Samples from Zhejiang Province Using Pass-Through SPE-UPLC-MS/MS: Occurrence and Human Dietary Exposure Risk.

Pentachlorophenol (PCP) has attracted wide attention due to its high toxicity, persistence, and bioaccumulation. In this study, a sensitive UPLC-MS/MS method for the determination of PCP in seafood samples was developed and validated. The samples were ultrasonic extracted with acetonitrile containing 1% acetic acid-acetonitrile and followed by using a pass-through solid-phase extraction (SPE) cleanup on Captiva EMR-Lipid cartridges. The linearity of this method ranged from 1 to 1000 µg/L, with regression coefficients of >0.99. The detection limit and quantitation limit were 0.5 µg/kg and 1.0 µg/kg, respectively. The recoveries in different types of seafood samples ranged from 86.4% to 102.5%, and the intra-day and inter-day relative standard deviations (RSDs) were 3.7% to 11.2% and 2.9% to 12.1%, respectively (n = 6). Finally, the method has been successfully utilized for the screening of PCP in 760 seafood samples from Zhejiang Province. PCP was detected in 5.8% of all seafood samples, with the largest portion of detections found in shellfish, accounting for approximately 60% of the total. The average concentrations detected ranged from 1.08 to 21.49 µg/kg. The non-carcinogenic risk indices for adults and children who consume PCP ranged from 10-4 to 10-3 magnitudes. All of these indices stayed significantly below 1, implying that the health risk from PCP in marine organisms to humans is minimal.

Investigation of the conversion mechanism of endogenous semicarbazide in shrimp on the amino acid level.

Semicarbazide (SEM), the metabolite of antibiotic nitrofurazone, is often used as the biomarker to determine the use of nitrofurazone. Frequent false-positive events of SEM have brought great trouble to the aquatic industry in international trade. In this paper, the situation of endogenous SEM in aquatic products was investigated, and the possible mechanism of amino acid conversion into SEM was studied by establishing a simulated oxidation system and a urea system. The results revealed the presence of endogenous SEM in the muscle tissue of shrimps, and the content of SEM ranged from 0.56 to 5.28 ng/g, which presented as Macrobrachium nipponense>Macrobrachium rosenbergii>Procambarus clarkii. The increase in SEM production of control lysine under natural oxidation conditions suggests that oxidation has an effect on the conversion of SEM. Under the action of the simulated oxidation system, the SEM of Arginine, Lysine, Citrulline and Glutamine among the 21 amino acids were increased, and the polymer azine was formed. In combination with the structure of four amino acids, it was presumed that the group of amide is a key intermediate structure for the formation of endogenous SEM. In addition, under the urea system, the content of SEM produced by amino acids increased after the addition of urea, and the concentration of urea had a significant correlation with the content of SEM. Taken together, the production of endogenous SEM in shrimps is related to amino acids and urea, and the urea cycle and other substances containing amide structures should also be considered in future explorations.

[Purification and structural elucidation of exoploysaccharide from a new marine bacterium Lentibacter algarum ZXM100T].

Exopolysaccharide La0.1-1 was extracted from the broth of a marine bacterium Lentibacter algarum ZXM100T isolated from the seawater in the coastal region of Qingdao and purified by Q Sepharose Fast Flow ion-exchange chromatography and Superdex 75 gel-permeation chromatography. Its physiochemical properties and primary structural characters were investigated by chemical analysis together with high performance liquid chromatography (HPLC), high performance gel permeation chromatography (HPGPC) and gas chromatography and mass spectrometry (GC-MS). The results show that the total sugar content of the exoploysaccharide La0.1-1 was about 66% with an average molecular weight at 12.0 kDa. La0.1-1 is mainly composed of Gal, Man, GlcN at the ratio of 1.35:1.1:1.0. Results of GC-MS and NMR demonstrate that the exopolysaccharide La0.1-1 mainly exists with the beta configuration. The primary linkage styles are --> 2)-Manp(1 --> and --> 3)-Galp(1 --> with a small amount of --> 4)-Galp(--> 1 and --> 4)-Manp(1 --> linkages. The linkage mode of GlcN is --> 4)GlcN(1 --> and terminal linkage. The exopolysaccharide has mainly a linear sructure with a few branches linked to 0-6 of --> 2)-Manp(1 --> and 0-4 or 0-6 of --> 3)-Galp(1 -->. 1D-NMR data also revealed that La0.1-1 is substituted by certain acetyl; the acetyl is mainly linked to N-2 of GlcN. The exopolysaccharides of the bacterium of Lentibacter genus is reported for the first time, and an exopolysaccharide with novel structure was obtained, which enriched marine polysaccharide resources.

Determination of chlorobenzenes in water samples by solid-phase disk extraction and gas chromatography-electron capture detection.

A simple, rapid, sensitive and high throughput method is described, based on solid-phase disk extraction (SPDE) and gas chromatography-electron capture detection, for the determination of chlorobenzens (CBs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions were found to be as follows: 500 mL water sample (pH 2.5) extracted and enriched by an Empore 3-stn C18 (octadecyl) SPE disk at flow rate of 5 to 50 mL/min, eluted by 5 mL of acetone and 3 × 5 mL of methylene dichloride. The linearity of the method ranged from 0.02 to 0.4 µg/L for dichlorobenzene isomers, 0.0022-0.044 µg/L for trichlorobenzene isomers, 0.005-0.01 µg/L for tetrachlorobenzene isomers and 0.00025 to 0.005 µg/L for pentachlorobenzenes and hexachlorobenzenes, with correlation coefficients ranging between 0.9991 and 0.9999. The limits of detection were in the low ng/L level, ranging between 0.05 and 4 ng/L. The recoveries of spiked CBs with the external calibration method at different concentration levels in deionized/distilled water, tap water and sea water samples were 99-115, 91-106% and 96-110%, respectively, and with relative standard deviations of 4.5-7.6, 4.2-6.8 and 3.6-6.6% (n = 5), respectively. It is concluded that this method can successfully be applied for the determination of CBs in deionized/distilled water, tap water and sea water samples.

Determination of chlorobenzenes in pure, tap, and sea water by static headspace gas chromatography-electron capture detection.

A simple, efficient, solvent-free, and commercial readily available approach for determination of 11 chlorobenzenes (CBs) in water samples using the static headspace (HS) sampling and gas chromatography-electron capture detector has been described. The proposed static HS sampling method was initially optimized and the optimum experimental conditions found were 10 mL water sample containing 20% (w/v) sodium chloride placed in a 20 mL vial and stirred at 70°C for 30 min. The linearity of the method ranged from 0.16 to 8.0 µg/L for dichlorobenzene isomers, 0.0176~0.88 µg/L for trichlorobenzene isomers, 0.004~0.2 µg/L for tetrachlorobenzene isomers, and from 0.001 to 0.05 µg/L for pentachlorobenzene and hexachlorobenzene, with correlation coefficients ranging between 0.9992 and 0.9999. The limits of detection were in the low µg/L level, ranging between 0.0002 and 0.04 µg/L. The relative recoveries of spiked CBs with external calibration or standard addition method at different concentration levels in pure, tap, and sea water samples were 83~116%, 89~108%, and 93~112%, respectively, and with relative standard deviations of 1.9~6.3%, 1.6~5.4%, and 2.5~5.7% (n = 5), respectively. It is concluded that this method can be successfully applied for the determination of CBs in pure, tap, and sea water samples.

Simultaneous determination of albendazole and its metabolites in fish muscle tissue by stable isotope dilution ultra-performance liquid chromatography tandem mass spectrometry.

A rapid, specific, and sensitive method utilizing ultra-performance liquid chromatography tandem mass spectrometry was developed and validated to determine albendazole, albendazole sulfoxide, albendazole sulfone, and albendazole 2-aminosulfone in fish muscle tissue. The fish samples were extracted with ethyl acetate, then the organic phase was evaporated to dryness, and the residue was reconstituted in methanol-water solution and cleaned up by n-hexane. Reversed-phase separation of target compounds was achieved using a BEH C18 column and a gradient consisting of 0.2% (v/v) formic acid and methanol. Tandem mass spectrometry analyses were performed on a triple-quadrupole tandem mass spectrometer. In the whole procedure, the isotope-labeled internal standards were used to correct the matrix effect and variations associated with the analysis. The method was validated with respect to linearity, specificity, accuracy, and precision. The method exhibited a linear response from 0.1 to 20 ng mL(-1) (r(2) > 0.9985). The limit of quantitation for albendazole (ABZ), albendazole sulfoxide (ABZSO), albendazole sulfone (ABZSO(2)), and albendazole 2-aminosulfone (ABZ-2-NH(2)SO(2)) was 0.1, 0.1, 0.1, and 0.2 ng g(-1), respectively. The mean recoveries of ABZ, ABZSO, ABZSO(2), and ABZ-2-NH(2)SO(2) spiked at a level of 0.2-5.0 ng g(-1) were 95.3-113.7%, and the relative standard deviations of intra- and inter-day measurements were less than 6.38%. The method was later successfully applied to the determination of albendazole and its three metabolites in 60 fish samples collected from local markets.

Determination of marker residue of Olaquindox in fish tissue by ultra performance liquid chromatography-tandem mass spectrometry.

Methyl-3-quinoxaline-2-carboxylic acid (MQCA) is the last major remaining detectable metabolite of Olaquindox in animal tissue. A rapid, sensitive and specific ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the detection and quantification of MQCA in fish tissue using deuterated quinoxaline-2-carboxylic acid (d(4)-QCA) as internal standard. Various parameters affecting sample preparation, LC separation and MS/MS detection were investigated, and the optimal conditions concerned were determined. Fish tissue samples were subject to hydrochloric acid hydrolysis followed by Oasis MAX solid-phase extraction clean-up; analysis was performed using UPLC coupled to electrospray MS/MS. The chromatographic separation was achieved in less than 5 min. The limit of detection and the limit of quantification were 0.1 and 0.25 ng/g, respectively. The average recoveries of MQCA, spiked at levels of 0.25-50.0 ng/g, were from 92.7 to 104.3%. The relative standard deviation values were <6%. The validated method was successfully applied to analyze 60 batch samples collected from the local market.