新型液-液微萃取--气相色谱法测定海水中的有机氯农药

本文采用了一种新型的液---液两相微萃取技术作为海水样品前处理方法,对海水中的八种有机氯农药(α-BHC,β-BHC,γ-BHC,δ-BHC,p,p,-DDE,o,p,-DDT,p,p,-DDD,p,p,-DDT)进行萃取、富集和分离,采用配微池电子捕获检测器气相色谱法分析测定。对影响萃取效率的因素进行了优化。结果表明,在优化条件下,六六六、滴滴涕在1.0-100.0μg/L范围内有良好的线性关系,R≥0.9963,检测限为0.004~0.016μg/L。     

Boundary element analysis of the droplet dynamics induced by spark-generated bubble

Spark bubble droplet generation (SBDG) method is the most recently developed drop-on-demand droplet generation technique where the oscillation of a spark-generated bubble near a circular aperture causes a single droplet quite smaller than the aperture to form and break off. This paper investigates the fluid dynamics of the droplet generated through a flat plate aperture as well as through the nozzle of an axisymmetric chamber using boundary element method and high-speed photography. The results revealed that the bottom wall of the chamber would strongly influence the behavior of the bubble oscillating inside. In addition, it was found that with the same normalized nozzle size and bubble distance from air–liquid interface, a relatively smaller and faster droplet is generated from the chamber nozzle as compared with that formed through the flat plate aperture. Furthermore, although the droplet size decreases, its pinch-off time was found to increase by increasing the size of chamber feeder canal.     

Simultaneous separation/preconcentration of ultra trace heavy metals in industrial wastewaters by dispersive liquid-liquid microextraction based on solidification of floating organic drop prior to determination by graphite furnace atomic absorption spectrometry

In the present work, an efficient microextraction method was applied to separation and preconcentration of Ni(II), Co(II), Pb(II) and Cr(III). This method is dispersive liquid-liquid microextraction based on solidification of floating organic drop, which overcomes the most important problems of each aforementioned technique. The influences of analytical parameters, including pH, extraction solvent volume, disperser solvent type and its volume, concentration of chelating agent, salt effect and extraction time on the quantitative recoveries of nickel, cobalt, lead and chromium ions were investigated. Under the optimized conditions, the limits of detection were 0.2 ng L(-1) for Cr and 1.3 ng L(-1) for Co, Ni and Pb, with a preconcentration factor of 800 times. The relative standard deviations of 6.2% at 6.0 ng L(-1) of Cr and 7.2% at 10 ng L(-1) of Co, Ni and Pb were obtained (n=7). The proposed method was successfully applied for the analysis of ultra trace metals in water and wastewater samples.     

Hollow fiber-protected liquid-phase microextraction of triazine herbicides

A new microextraction technique termed hollow fiber-protected liquid-phase microextraction (LPME) was developed. Triazines were employed as model compounds to assess the extraction procedure and were determined by gas chromatography/mass spectrometry. Toluene functioned as both the extraction solvent and the impregnation solvent. Some important extraction parameters, such as effect of salt, agitation, pH, and exposure time were optimized. The new method provided good average enrichment factors of > 150 for eight analytes, good repeatability (RSDs <3.50%, n = 7), and good linearity (r2 > or = 0.9995) for spiked deionized water samples. The limits of detection (LODs) were in the range of 0.007-0.063 microg/L (S/N = 3) under selected ion monitoring mode. In addition to enrichment, hollow fiber-protected LPME also served as a technique for sample cleanup because of the selectivity of the membrane, which prevented large molecules and extraneous materials, such as humic acids in solution, from being extracted. The utilization of this procedure in the extraction of a slurry sample (mixture of soil and water) also gave good precision (RSDs <5.00%, n = 3) and LODs (0.04-0.18 microg/L, S/N = 3). Finally, the comparison of the new method with the static solvent drop LPME and solid-phase microextraction was performed. The results demonstrated that hollow fiber-protected LPME was a fast, accurate, and stable sample pretreatment method that gave very good enrichment factors for the extraction of triazine herbicides from aqueous or slurry samples.     

Impact of beta-cypermethrin on soil microbial community associated with its bioavailability: a combined study by isothermal microcalorimetry and enzyme assay techniques

In this study, an isothermal microcalorimetric technique has been used to show that beta-cypermethrin (CYP) had no significant effect (p > 0.05) on soil microbial activity at 80 μg g(-1) soil. Our soil enzyme data indicated that beta-CYP ranging 10-80 μg g(-1) soil had no significant effect (p > 0.05) on soil enzyme activities such as β-glucosidase, urease, acid-phosphatase, and dehydrogenase. Therefore, our results infer that beta-CYP would not pose severe toxicity to soil microbial community, but its toxic level may vary greatly with environment that associates with its increase in bioavailability: the level in soil (at μg g(-1)) < the level in sediment (varying from μg g(-1) to μg L(-1)) 0.05). These results suggest that the heavy application of beta-CYP may not cause damage to soil microbial community which is very different from its high toxicity to the aquatic organism.     

Desorption corona beam ionization coupled with a poly(dimethylsiloxane) substrate: broadening the application of ambient ionization for water samples

Current direct analysis methods in mass spectrometry (MS) are predominantly focused on desorbing and ionizing samples in the solid phase. Some sampling difficulties are associated with liquid (solution) or gas samples. The present study has expanded direct MS analysis to solution samples by using the desorption corona beam ionization (DCBI) technique in combination with poly(dimethylsiloxane) (PDMS) substrate sampling. Typically, the PDMS substrate is dipped in water for microextraction of pesticide compounds and then is transferred to an MS ion source for desorption and ionization. This approach improves the detection limit for DCBI and allows more organic compounds in complex mixtures to be identified within seconds. The practical application of this device is demonstrated by identifying five pesticides (acephate, isoprocarb, dimethoate, dichlorvos, and dicofol) in water. The obtained detection limits of pesticides are 1 μg/L, the measured dynamic ranges are 3 orders of magnitude, the calculated correlation coefficients are between 0.939 and 0.979 at concentration levels of 5-5000 μg/L, and the repeatabilities defined as a relative standard deviation of five successive injections are in the range of 13-17%. The results indicate that the DCBI technique coupled with PDMS sampling is an excellent method for the analysis of organic pesticides in solution, and it also opens up a new avenue for direct MS studies of solution samples with general importance.     

Combining drop-to-drop solvent microextraction with gas chromatography/mass spectrometry using electronic ionization and self-ion/molecule reaction method to determine methoxyacetophenone isomers in one drop of water

A novel analytical technique termed drop-to-drop solvent microextraction (DDSME) was developed to determine three methoxyacetophenone isomers in one drop of water, which were then detected by gas chromatography/mass spectrometry using electronic ionization mass spectrometry for quantification analysis and self-ion/molecule reaction/tandem mass spectrometry for isomer differentiation. The best optimum parameters for the DDSME technique were as follows: extraction time, 5 min; using toluene as the extraction solvent; volume of extraction solvent, 0.5 microL and no salt addition. The advantages of this method are rapidity, convenience, ease of operation, simplicity of the device, and extremely little solvent and sample consumption. The limit of detection (LOD) for this technique was 1 ng/mL. The relative standard deviation was less than 2.6% (n = 5). The linear range of the calibration curve of DDSME is from 0.01 to 5 microg/mL with correlation coefficient (r2) of >0.954. In the comparison of the LOD of DDSME with other sample pretreatment methods including liquid/liquid extraction (LLE), single-drop microextraction (SDME), solid-phase microextraction (SPME), and liquid-phase microextraction (LPME) using a dual gauge microsyringe with hollow fiber methods, this method shows much better in sensitivity than the LLE (25 ng/mL) and it is compatible with SDME (0.5 ng/mL), SPME (0.5 ng/mL), and LPME using a dual gauge microsyringe with a hollow fiber (1 ng/mL). However, DDSME was more convenient than the LPME using a dual gauge microsyringe with a hollow fiber method and much lower cost than the SPME technique.     

Mechanical properties of atmospheric ice

Mechanical properties of atmospheric ice obtained in a wind tunnel are measured. The ice is grown from supercooled droplets on a rotating aluminium cylinder of 31.5-mm diameter and 6.5-μm rugosity. Compressive strength is measured at two speeds of deformation (0.76 and 26 mm/min) for glaze and rime samples, as a function of air temperature for different atmospheric conditions (0.4 and 0.8 g/m³ liquid-water contents, 20 and 40 μm mean volume droplet diameters, and 4, 8, 15, and 20 m/s air velocities). These values of compressive strength are compared to the adhesive strength on aluminium, measured at a 26 mm/min speed of deformation. The ratio of compressive to adhesive strength has a maximum value of 135 for hard rime accreted at −10°C, with a wind velocity of 15 m/s, a liquid-water content of 0.8 g/m³ and a mean droplet diameter of 40 μm. The maximum compressive strength measured for the lower speed of deformation is 17395 kPa and 10745 kPa for the higher speed of deformation. The maximum adhesive strength measured is 181 kPa. On the other hand, compressive strengths measured at deformation speeds varying from 0.015 to 288 mm/min show that atmospheric ice has a ductile-brittle behaviour approaching that reported for snow ice and fine-grained lake ice.     

Molecular modeling assisted hapten design to produce broad selectivity antibodies for fluoroquinolone antibiotics

Antibodies with a wide recognition profile of fluoroquinolone antibiotics have been produced based on chemical criteria, theoretical studies, and molecular modeling assisted hapten design. The immunizing hapten preserves the most important and characteristic epitopes of this antibiotic family. The studies have taken into consideration the zwitterionic character of most of the fluoroquinolones and the relative concentration of the different species in equilibrium at physiologic pH. The hapten is prepared in the form of a stable prehapten through a 5 step synthetic pathway. Immediately before conjugation, the immunizing hapten is obtained by removing the diphenylmethane protecting group. The specificity of the antibodies obtained is directed toward the common area defined by the fluorine atom at position 6 and the β-ketoacid moiety. The ELISA developed is able to recognize with very good detectability important fluoroquinolones used in the veterinary field such as ciprofloxacin (CPFX, IC(50), 0.35 μg L(-1)), enrofloxacin (ERFX, IC(50), 0.65 μg L(-1)), danofloxacin (DNFX, IC(50), 7.31 μg L(-1)), difloxacin (DFX, IC(50), 0.91 μg L(-1)), sarafloxacin (SRFX, IC(50), 0.96 μg L(-1)), norfloxacin (NRFX, IC(50), 0.78 μg L(-1)), ofloxacin (OFX, IC(50), 1.84 μg L(-1)), flumequine (Flume, IC(50), 3.91 μ gL(-1)), marbofloxacin (MBFX, IC(50), 4.30 μ gL(-1)), and oxolinic acid (OXO, IC(50), 23.53 μg L(-1)). The results presented here demonstrate that the antibody affinity is strongly affected by the presence of divalent cations, owing to their complexation with the fluoroquinolone molecules. Moreover, the outcome from the effect of the pH on the immunochemical assays suggests that the selectivity could be modulated with the pH due to the zwitterionic character of the fluoroquinolones and as a function of their different pK(a) values.     

Ionic liquid ultrasound assisted dispersive liquid-liquid microextraction method for preconcentration of trace amounts of rhodium prior to flame atomic absorption spectrometry determination

In this article, we consider ionic liquid based ultrasound-assisted dispersive liquid-liquid microextraction of trace amounts of rhodium from aqueous samples and show that this is a fast and reliable sample pre-treatment for the determination of rhodium ions by flame atomic absorption spectrometry. The Rh(III) was transferred into its complex with 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol as a chelating agent, and an ultrasonic bath with the ionic liquid, 1-octyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide at room temperature was used to extract the analyte. The centrifuged rhodium complex was then enriched in the form of ionic liquid droplets and prior to its analysis by flame atomic absorption spectrometry, 300 μL ethanol was added to the ionic liquid-rich phase. Finally, the influence of various parameters on the recovery of Rh(III) was optimized. Under optimum conditions, the calibration graph was linear in the range of 4.0-500.0 ng mL(-1), the detection limit was 0.37 ng mL(-1) (3S(b)/m, n = 7) and the relative standard deviation was ±1.63% (n = 7, C = 200 ng mL(-1)). The results show that ionic liquid based ultrasound assisted dispersive liquid-liquid microextraction, combined with flame atomic absorption spectrometry, is a rapid, simple, sensitive and efficient analytical method for the separation and determination of trace amounts of Rh(III) ions with minimum organic solvent consumption.     

陶瓷微孔膜管制造微气泡的研究

气浮工艺中气泡的大小是衡量气泡制造技术的关键.研究了陶瓷微孔膜管产生微气泡的条件,并对两种不同材质的微孔膜管产生微气泡的结果进行了比较,从气泡形成机理上分析了影响气泡粒径分布的因素.实验采用静态显微摄像技术和图像分析系统时气泡粒径分布进行了表征.实验结果表明,利用陶瓷微孔膜管产生的气泡粒径主要集中在15～50 μm之间,平均粒径在25.7～44.2 μm之间.微孔膜管的孔径大小、表面性能,气体流量,剪切流流速,液体表面张力,黏度是影响气泡粒径分布的主要因素.     

Dechlorination of polychlorinated biphenyls using magnesium and acidified alcohols

Polychlorinated biphenyls (PCBs) were widely used in industry until their regulation in the 1970s. However, due to their inherent stability, they are still a widespread environmental contaminant. A novel method of degradation of PCBs (via hydrodehalogenation) has been observed using magnesium powder, a carboxylic acid, and alcohol solvents and is described in this paper. The rates of degradation were determined while varying the type of acid (formic, acetic, propionic, butyric, valeric, benzoic, ascorbic, and phosphoric), the amount of magnesium from 0.05 to 0.25 g, the amount of acetic acid from 0.5 to 50 μL and the concentration of PCB-151 from 0.1 to 50 μg/mL, as well as the alcohol solvent (methanol, ethanol, propanol, butanol, octanol, and decanol). The results of these studies indicate that the most rapid PCB dechlorination is achieved using a matrix consisting of at least 0.02 g Mg/mL ethanol, and 10 μL acetic acid/mL ethanol in which case 50 ng/μL of PCB-151 is dechlorinated in approximately 40 min.     

Synthesis of molecularly imprinted polymer as a sorbent for solid phase extraction of citalopram from human serum and urine

This paper describes a new method for the determination of citalopram in biological fluids using molecularly imprinted solid-phase extraction as the sample cleanup technique combined with high performance liquid chromatography. The molecularly imprinted polymers were prepared using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinker, chloroform as porogen and citalopram hydrobromide as the template molecule. The novel imprinted polymer was used as a solid-phase extraction sorbent for the extraction of citalopram from human serum and urine. Effective parameters on citalopram retention were studied. The optimal conditions for molecularly imprinted solid-phase extraction consisted of conditioning with 1 mL methanol and 1 mL of deionized water at neutral pH, loading of citalopram sample (50 μg L(-1)) at pH 9.0, washing using 1 mL acetone and elution with 3 × 1 mL of 10 % (v/v) acetic acid in methanol. The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of citalopram. Results from the HPLC analyses showed that the calibration curve of citalopram using MIP from human serum and urine is linear in the ranges of 1-100 and 2-120 μg L(-1) with good precisions (2.5 and 1.5 % for 10.0 μg L(-1)), and recoveries (between 82-86 and 83-85 %), respectively.     

On‐Site Formation of Emulsions by Controlled Air Plugs

Air plugs are usually undesirable in microfluidic systems because of their detrimental effect on the system's stability and integrity. By controlling the wetting properties as well as the topographical geometry of the microchannel, it is reported herein that air plugs can be generated in pre‐defined locations to function as a unique valve, allowing for the on‐site formation of various emulsions including single‐component droplets, composite droplets with droplet‐to‐droplet concentration gradient, blood droplets, paired droplets, as well as bubble arrays without the need for precious flow control, a difficult task with conventional droplet microfluidics. Moreover, the self‐generated air valve can be readily deactivated (turned off) by the introduction of an oil phase, allowing for the on‐demand release of as‐formed droplets for downstream applications. It is proposed that the simple, yet versatile nature of this technique can act as an important method for droplet microfluidics and, in particular, is ideal for the development of affordable lab‐on‐a‐chip systems without suffering from scalability and manufacturing challenges that typically confound the conventional droplet microfluidics.     

Continuous-flow microextraction exceeding 1000-fold concentration of dilute analytes

A novel liquid-liquid microextraction method, that we have termed continuous-flow microextraction (CFME), is described. In a 0.5-mL glass chamber, an organic drop (1-5 microL) is held at the outlet tip of a polyetheretherketone (PEEK) connecting tubing which is immersed in a continuously flowing sample solution and acts as the fluid delivery duct and as a solvent holder. Extraction takes place between the organic drop and the flowing sample solution that is continuously ejected out of the PEEK tubing. Concentration factors of between 260- to 1600-fold are achieved within 10 min of extraction. Aspects relevant to CFME were studied. In combination with gas chromatography-electron capture detection, CFME allows analytes to be detected at femtogram-per-milliliter levels. The performance of this technique was evaluated on the basis of the analysis of trace nitroaromatic compounds and chlorobenzenes in environmental samples.     

HS-LPME-GC法在烟用香精香料质量控制中的应用

采用顶空液相微萃取法(HS-LPME)对8个不同批次及掺兑不同比例其他烟用香精香料的1148#样品的挥发性成分进行提取并用气相色谱法分析,同时研究了不同萃取溶剂、萃取时间、萃取温度对分析结果的影响,确定了最佳条件:样品在70℃下平衡1.0h,搅拌速度300r/min,以4.0μL正十二烷作萃取剂,萃取时间为10min,并通过主成分分析(PCA)法对不同批次及掺兑样品进行模式识别。结果表明:此法能成功地将掺兑样品区分开来,可以成为烟用香精香料1148#质量控制的有效手段之一。     

Microcystin-LR induced oxidative stress and ultrastructural alterations in mesophyll cells of submerged macrophyte Vallisneria natans (Lour.) Hara

Microcystins produced by cyanobacteria in the aquatic environment are a potential risk to aquatic plants. In the present study, the uptake of microcystin-LR (MC-LR) and related physiological and biochemical effects on Vallisneria natans (Lour.) Hara were investigated at concentrations of 0.1-25.0 μg L(-1). Results showed that O(2)(-) intensity was significantly induced at 1.0 μg L(-1) and reached a maximum level at 5.0 μg L(-1). Superoxide dismutase (SOD) and peroxidase (POD) were induced with increasing MC-LR concentrations as an antioxidant response. Catalase (CAT) was significantly induced while GSH/GSSG (reduced/oxidized glutathione) ratio was significantly reduced at 0.1 μg L(-1). The induction of glutathione S-transferase (GST) and inhibition of GSH revealed that GSH was involved in the detoxification of MC-LR in plants. Oxidative damage was evidenced by the significant increase of malondialdehyde content at 1.0 μg L(-1). A pigment pattern change and a series of significant ultrastructural alterations were also observed due to MC-LR exposure. The lowest non-effect concentration of MC-LR for V. natans at the subcellular and molecular level is around 0.5 μg L(-1). These results imply that even at relatively low MC-LR concentrations the aquatic plants may still suffer a negative ecological impact.     

Determination of Pentachlorophenol and Its Oil Solvent in Wood Pole Samples by SFE and GC with Postcolumn Flow Splitting for Simultaneous Detection of the Species

An alternative approach is described for the measurement of pentachlorophenol (PCP) and its oil solvent in wood samples by supercritical fluid extraction (SFE) and gas chromatography (GC). The determination is achieved over a single chromatographic run using postcolumn flow splitting for simultaneous ECD/FID detection of the SFE extracted species. First, PCP and oil components are quantitatively extracted from a 0.3-g wood sample using 10% MeOH/CO(2) supercritical fluid at 0.65 g/mL and 120 °C. An aliquot of the SFE solution is then mixed with 10 mL of a buffered aqueous phase at pH 9.4. After PCP is acetylated by the addition of 500 μL of acetic anhydride, it is followed by its extraction with 2.00 mL of hexane along with oil. Then, 0.5 μL of supernatant organic phase is injected into the GC for a selective and simultaneous determination of the species. The method has a linear response over 3 orders of magnitude for both species with a linear regression correlation coefficient higher than 0.98 (95% confidence limit) and an absolute detection limit of 60 ng of PCP and 80 μg of oil per 0.1-g wood sample. The precision (relative standard deviation) is 4% for PCP and 1% for oil as established for a typical average concentration sample. The accuracy of the SFE GC-ECD/FID combined technique for PCP and oil was assessed by analyzing wood samples collected from newly and in-service PCP/oil-impregnated red pine poles.     

燃烧裂解-离子色谱法测定工业废水中的可吸附有机卤素

可吸附有机卤素(AOX)是用来表征水体有机卤化物污染程度的有效指标.有机卤化物的广泛应用还会增加工业废水中AOX的残留水平,而有机卤化物往往具有高的毒性,因此需要重视工业废水中AOX的污染水平.AOX包括可吸附有机氯(AOCl)、可吸附有机溴(AOBr)和可吸附有机碘(AOI).该研究建立燃烧裂解-离子色谱法测定工业废...     

Increasing the sensitivity of liquid introduction mass spectrometry by combining electrospray ionization and solvent assisted inlet ionization

Combining electrospray ionization (ESI) and solvent assisted inlet ionization (SAII) provides higher ion abundances over a wide range of concentrations for peptides and proteins than either ESI or SAII. In this method, a voltage is applied to a union connector linking tubing from a solvent delivery device and the fused silica capillary, used with SAII, inserted into a heated inlet tube of an Orbitrap Exactive mass spectrometer (MS). The union can be metal or polymeric and the voltage can be applied directly or contactless. Solution flow rates from less than a 1 μL min(-1) to over 100 μL min(-1) can be accommodated. It appears that the voltage is only necessary to provide charge separation in solution, and the hot MS inlet tube and the high velocity of gas through the tube linking atmospheric pressure and vacuum provides droplet formation. As little as 100 V produces an increase in ion abundance for certain compounds using this method relative to no voltage. Interestingly, the total ion current observed with SAII and this electrosprayed inlet ionization (ESII) method are very similar for weak acid solutions, but with voltage on, the ion abundance for peptides and proteins increase as much as 100-fold relative to other compounds in the solution being analyzed. Thus, switching between SAII (voltage off) and ESII (voltage on) provides a more complete picture of the solution contents than either method alone.