ABSTRACT
A valve-free continuous flow method and instrument were established,with only a multi-channel pump for delivering the sample and reagent,and without any injection or solenoid valves and sample loop for selecting and adding the sample or reagent.Nitrate was reduced to nitrite with Cu-Cd reductant column,and then detected with spectrophotometric detector.The proposed method was suitable for determination of nitrate at normal level in most of estuary and coastal seawaters.With the optimum parameters,the linear range and detection limit were 5-180 μmol/L and 0.27 μmol/L,respectively.The samples of 10 and 80 μmol/L nitrate were continually measured for 11 times,and the relative standard deviations were 1.4％ and 1.3％,respectively.The recovery of real samples at different salinity ranged between 99.4％ and 106.1％.There was no significant difference in the analytical results between the proposed method and the flow injection analysis (FIA).In comparison with FIA,the method and instrument were less cost and easy to operate,and was suitable to be applied in general laboratories and field for continuous monitoring.The method was successfully used to measure the nitrate in seawater samples in Xiamen's Western Harbor and monitor nitrate in Jiulongjiang estuary.
ABSTRACT
A magnetic extraction sorbent based on Fe3 O4@poly ( methacrylic acid-co-ethylene dimethacrylate) ( Fe3 O4@MAED ) was synthesized using methacrylic acid and ethylene dimethacrylate as monomer and cross-linker, respectively. The magnetic sorbent was characterized by FTIR spectroscopy, elemental analysis and transmission electron microscopy. At the same time, the Fe3 O4@MAED was used to extract four benzoylurea pesticides in water and juice samples under magnetic dispersive solid phase microextraction ( MDSPME ) format. To obtain the optimal extraction conditions, several parameters, including the amount of sorbent, desorption solvent, extraction and desorption time, pH value, and ionic strength in sample matrix were investigated. Based on this, a fast, simple and sensitive method for the determination of benzoylurea pesticides in water and juice samples was developed by the combination of MDSPME with HPLC equipped with diode array detector. Under the optimized experimental conditions, the developed method possessed expected linear dynamic ranges, coefficients of correlation ( R2>0. 99 ) and sensitivity. The limits of detection (S/N=3) for target analytes were 0. 10-0. 19 μg/L in water and 0. 12-0. 30 μg/L in juice, respectively. The RSDs for intra-day were less than 7% and inter-day RSDs were less than 11%. The developed method was successfully applied to the determination of benzoylurea pesticides residues in water and juice samples and the recoveries of spiked target compounds were in the range of 69. 4%-118. 0%. The results demonstrated that the Fe3 O4@ MAED could extract benzoylurea pesticides effectively through multi-interactions including hydrophobic, hydrogen-bond and ion-exchange interactions between sorbent and analytes.
ABSTRACT
Siderophores were produced and secreted with marine microorganisms as the highly specific iron chelators. A method of liquid chromatography-tandem mass spectrometric detection coupled with solid phase extraction pretreatment was developed for the determination of siderophores in seawater. The samples were filtered through a 0. 22 μm membrane, extracted with an ENVI-18 cartridge and then eluted with methanol. The separation of the analytes was performed on a reversed phase SB-C18 column with a gradient elution program by using 0. 1% ( V/V) formic acid and methanol as the mobile phases. Qualitative analysis was performed in multiple-reaction monitoring mode. Good linearity (R2>0. 99) was obtained for Pyoverdines-Fe, Ferrichrome, Ferrioxamine E at the concentrations of 0. 001-3. 00 μg/mL, 0. 005-15. 00 μg/mL, 0. 001-3. 00 μg/mL, respectively. The instrumental detection limits and limits of quantification for the three analytes were 0. 08, 1. 76 and 1. 36 ng/mL; 0. 27, 5. 87 and 4. 53 ng/mL, respectively. The relative standard deviations were lower than 12%, while the recoveries were 12. 1%-18. 6% for Pyoverdines-Fe, 82. 0%-97. 7% for Ferrichrome, and 70. 0%-98. 3% for Ferrioxamine E.
ABSTRACT
A method for the determination of bisphenol A, octyphenol, nonylphenol in water samples was developed using stir bar sorptive extraction (SBSE) based on poly (vinylimidazole-divinylbenzene) monolithic material (SBSEM) combined with high performance liquid chromatography with diode array detection.To achieve the optimum extraction performance, several main extraction parameters, including extraction and desorption time, pH value and contents of inorganic salt in the sample matrix, were investigated.Under the optimized experimental conditions, the method showed good linearity and repeatability, low detection limits (S/N = 3) and quantification limits (S/N = 10) of the proposed method for the target compounds were achieved within the range of 0.13-0.66 and 0.44-2.19 μg/L, respectively.The extraction performance of SBSEM to the target compounds was also compared with commercial SBSE which used polydimethylsiloxane as coating.The proposed method was successfully applied to the determination of the target compounds in water samples.The recoveries of spiked target compounds in real samples ranged from 37.8%-101.1%.The results indicated that the developed method possessed advantages such as sensitivity, simplicity, low cost and high feasibility.
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Objective To know the pollution level of phthalates in Jiulong River source water and the purification efficiency by conventional water treatment processes. Methods The samples of Jiulong River source water and treated water from two waterworks were collected and analyzed with GC-MS during Aug.-Sep.2006. Results Jiulong River had been polluted by phthalates. The prominent phthalates pollutants were dibutyl phthalate (DBP) and diethyl phthalate(DEP). The maximum concentrations reached 17.238 ?g/L and 11.701 ?g/L, respectively. PAEs content in tap-water was lower than the standard limits. Conclusion The conventional water treatment processes, preoxidation, coagulation, sedimentation, filtration and disinfection, could remove phthalates from the drinking water to a certain degree, but the risk of phthalates pollution in drinking water still exists.
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Objective To evaluate the efficiency of different wash methods for removing organophosphorus pesticide residues from cucumber. Methods The cucumber samples were soaked with tap water, washed rice water, salt solution and detergent solution respectively for 2 to 15 minutes then organophosphorus pesticide residues in the soak water samples were determined with ultrasonic extraction and gas chromatography. Results Soaked in tap water for 2 to 5 minutes was the most effective and convenient way to remove methamidophos and dimethoate with the highest removing rate (about 70%). Conclusion Soaked with tap water for 2 to 5 minutes is more efficient for removing organophosphorus pesticide residues from vegetable.
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Objective To analyze the residues of chrysanthemum ester pesticides and heavy metals in several typical Oolong tea samples for evaluating the drink safety. Methods The residues of chrysanthemum ester pesticides in the tea samples were extracted with ultrasonic method. Gas chromatography equipped with ECD was applied to determine the pesticide residues. The heavy metals in tea samples were analyzed with an inductively coupled plasma-mass spectrometer (ICP-Mass) and an atomic fluorescence spectrometer. Results The residues of chrysanthemum ester pesticides in the dry tea samples were 0.200-0.780 mg/kg, no residues was detected in the tea water. The content of heavy metals in the dry tea and tea water was very low, under the standard limits. Conclusion The Oolong tea samples chosen in the present investigation have not been polluted by chrysanthemum ester pesticides and heavy metals, according to the results, the Oolong tea made in the area is safe for drink.