[Contamination status and the evaluation of dietary exposure of marine biotoxins in seafood in Ningbo City in 2017-2019].

OBJECTIVE: Ultra-fast liquid chromatography-tandem mass spectrometry method was developed for the analysis of contamination degree of biotoxins in seafood in Ningbo City from 2017 to 2019 and the assessment of dietary exposure was conducted. METHODS: Samples were extracted and purified with optimized pretreatment process and then injected for analysis. According to the result of the measurements, an international point estimate model was used to evaluate the dietary exposure of the population. RESULTS: For tetrodotoxin and 16 shellfish toxins monitored routinely, gonyautoxin5(GTX5), tetrodotoxin and homo-yessotoxin(hYTX) had higher detection rate, other toxins including okadaic acid(OA), dinophysistoxin1(DTX1), decarbamoyl gonyautoxin2(dcGTX2) and decarbamoyl gonyautoxin3(dcGTX3) were detected sporadically. The detection rates of TTX、GTX and hYTX were 27%, 52% and 12%, respectively. The concentration ranges of TTX, GTX and hYTX in polluted samples were 0. 003-0. 535, 0. 008-0. 189 and 0. 032-0. 110 mg/kg. The exposure risk indices(ERI) of TTX, GTX5, hYTX, dcGTX2 and dcGTX3 were 2. 5, 0. 026, 0. 0080, 0. 79 and 0. 32, respectively. CONCLUSION: Marine biotoxins have a lower dietary health risk to the population. It is must be given great attention that in the season of toxic red tide, the detection rates of higher toxic toxins, dcGTX2 and dcGTX3 increased significantly with high risks to human. Moreover, the dietary health risk of tetrodotoxin in routine surveillance in 2019 was higher.

[Improvement on flame atomic absorption spectrometry for determining Tin concentration in air of workplaces].

OBJECTIVE: To explore the influence factors on determining Tin concentration in air of workplaces with flame atomic absorption spectrometry and to establish an accurate, sensitive and high-efficient method. METHODS: The different reagents were used to digest the sampling filter membranes and the determining conditions of flame atomic absorption spectrometry were adjusted, then the determining results were compared. RESULTS: When 3 ml hydrochloric acid and 0.5 ml nitric acid served as the digesting reagents and the determining conditions of flame atomic absorption spectrometry were adjusted to the best conditions, there was the good linearity in the tested concentration range of Tin, the correlation coefficient was larger than 0.9990. The limit of quantification was 1.0 p.g/ml. The extraction recovery was between 99.6%-102.6%, and the RSD were all less than 5.0%. CONCLUSION: The proper kinds and quantity of digestive reagents in pretreatment of the samples should be chosen for the accuracy and precision of the determination according to the influence factors of determination.

Solid-phase extraction-based ultra-sensitive detection of four lipophilic marine biotoxins in bivalves by high-performance liquid chromatography-tandem mass spectrometry.

A solid-phase extraction (SPE) method for ultra-sensitive determination of four lipophilic marine biotoxins in bivalve samples by coupling high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) was developed. Azaspiracid-2 (AZA2), pectenotoxins-2, spirolide (SPX) and gymnodimine were simultaneously determined by HPLC-MS-MS in a positive multiple reaction monitoring mode. Separation was achieved on a reversed-phase C18 column with an acetonitrile-water gradient containing formic acid. During the analysis, solvent effects on the analytes were eliminated by using 1 : 1 water-methanol as dissolving solvent instead of pure methanol. Matrix effects in post-SPE extract and crude extract were seriously evaluated. Increased matrix effects in post-SPE extract countervailed the concentration purpose to some extent. The limits of detection of the SPE-HPLC-MS-MS method were determined to be in the range of 0.013-0.085 µg kg(-1), and the linear range of the method was in the range of 0.128-55.2 ng mL(-1) for the detected toxins. The proposed method was validated in terms of linearity (matrix-matched standard curves), precision, recovery, repeatability and limits of quantification. The recoveries of fortified samples at three different concentration levels were satisfactory, and the intra- and interday precisions were <7 and 10%, respectively.Several bivalve samples were analyzed to demonstrate the applicability of the proposed method. Different target toxins were detected in different kind of bivalves. Among them, AZA2 and SPX1 were first detected in Chinese shellfish. The levels of detected toxins were below the current European Union regulatory limits.

[Determination of 11 triazole fungicides in fruits using solid phase extraction and gas chromatography-tandem mass spectrometry].

A method was developed and validated for the simultaneous determination of 11 triazole fungicides (tetraconazole, triflumizole, penconazole, hexaconazole, flutriafol, myclobutanil, etuconazole, propiconazole, tebuconazole, epoxiconazole and fluquinconazole) in fruits by gas chromatography-tandem mass spectrometry (GC-MS/MS). The triazole fungicides were extracted from the samples with acetonitrile, then enriched and cleaned-up with solid phase extraction (SPE) on a Carbon/NH2 cartridge (collecting 2 - 10 mL effluent). The detection was carried out by GC-MS/MS in the multiple reaction monitoring (MRM) mode, and the quantification analysis was performed by external standard method. The calibration curves showed good linearity in the range of 10 - 500 microg/L. The correlation coefficients were larger than 0. 994 0. The average recoveries of the 11 fungicides spiked in the fruits at the levels of 10, 50, 100 and 250 microg/kg were between 82.6% and 117.1%, and the relative standard deviations (RSD) were less than 10%. The limits of quantification (S/N = 10) were between 0.8 microg/kg and 3.4 microg/kg. The method possesses low background, high sensitivity, and quantification limits lower than that of the national standard and the values reported in the relevant literature. It can be applied to the routine analysis of the 11 triazole fungicides in fruits.

Use of tetraethylenepentamine-functional Fe3O4 magnetic polymers for matrix solid phase dispersion extraction and preconcentration of Cr(VI) in water samples at ultratrace levels.

A new method that utilizes tetraethylenepentamine-functional Fe(3)O(4) magnetic polymers (TEPA-NMPs) as a solid-phase extractant for matrix solid phase dispersion extraction (MSPD) has been developed for preconcentration of Cr(VI) at ultratrace levels prior to the measurement by flame atomic absorption spectroscopy (FAAS). The separation/preconcentration conditions of Cr(VI) was investigated, including the pH value, shaking time, adsorption temperature, sample volume, desorption conditions and interfering ions. The results showed the adsorption properties of the TEPA-NMPs were highly pH dependent. The data of adsorption kinetics obeyed pseudo-second-order rate mechanism well. Adsorption thermodynamic studies suggested that the adsorption processes of Cr(VI) onto the TEPA-NMPs was endothermic and entropy favored in nature. Under the best experimental conditions, the enhancement factor was 125 times, the detection limit of the method was 0.16 µg L(-1) and the relative standard deviation was 1.9% (n=7). Furthermore, the developed method was validated by comparing with Graphite Furnace atomic absorption spectrometry (GF-AAS) method, and has been applied for the determination of ultratrace Cr(VI) ions in the river and tap water samples with satisfactory results, which revealed the sensitivity of the proposed TEPA-NMPs MSPD-FAAS method was comparable with that of GF-AAS method.

[Determination of ciprofloxacin residue in fish/shellfish tissues using liquid chromatography-tandem mass spectrometry with isotope internal standard dilution technique].

Using isotope internal standard dilution technique, a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method has been developed for the identification and quantitative determination of ciprofloxacin residue in the tissues of various fishes/shellfishes. The homogenized tissue sample added with ciprofloxacin-D8 and phosphate buffer solution (pH 7.0) was extracted with acetonitrile under ultrasonication, and degreased with hexane. After solid-phase extraction (SPE) was performed on an Oasis MAX cartridge, the sample was separated on a Cloversil-C18 column (150 mm x 4.6 mm, 5 microm) by using the mobile phase consisting of CH3CN-0.05% CF3 COOH (25:75, v/v). The detection was carried out by LC-MS/MS using an electrospray ionization interface in multiple reaction monitoring (MRM) mode. The quantification using isotope-labelled internal standard was based on the peak area ratio of ciprofloxacin and deuterated internal standard in the MRM mode. The calibration curve was linear within the range of 0.1 - 50.0 microg/kg and the limit of quantification was 0.1 microg/kg (S/N > or = 10). The recovery was between 92.5% and 98.1%, and the relative standard deviation was less than 4.3%. The application of this method was further demonstrated by analyzing ten various real samples from local markets. The results show that this method is sensitive, accurate and suitable for the confirmative determination of ciprofloxacin residues.