Determination of trace mercury in environmental and foods samples by online coupling of flow injection displacement sorption preconcentration to electrothermal atomic absorption spectrometry

The toxic effects of mercury are well-known. To establish sources of mercury contamination and to evaluate levels of mercury pollution, sensitive, selective, and accurate analytical methods with excellent reproducibility are required. We have developed a novel methodology for the determination of trace mercury in environmental and foods samples by online coupling of flow injection (FI) displacement sorption preconcentration in a knotted reactor (KR) to electrothermal atomic absorption spectrometry (ETAAS). The developed methodology involved the online formation of copper pyrrolidine dithiocarbamate (Cu-PDC), presorption of the resulting Cu-PDC onto the inner walls of the KR, and selective retention of the analyte Hg(ll) onto the inner walls of the KR through online displacement reaction between Hg(ll) and the presorbed Cu-PDC. The retained analyte was subsequently eluted by 50 microL of ethanol and online detected by ETAAS. Interferences from coexisting heavy metal ions with lower stability of their APDC complexes relative to Cu- PDC were minimized without the need of any masking reagents. The tolerable concentrations of Cu(II), Cd(II), Fe(III), Ni(III), and Zn(II) were up to 12, 20, 16, 20, and 60 mg L(-1), respectively. No additional chemical modifiers for the stabilization of mercury were required in the present system owing to the stability of Hg-PDC at the drying stage, and no pyrolysis stage was necessary due to the effective removal of the matrices. With consumption of 2.5 mL of sample solution, an enhancement factor of 91 was obtained in comparison with direct injection of 50 microL of aqueous solution. The relative detection limit (3s) was 6.2 ng L(-1), corresponding to an absolute detection limit of 15.5 pg. The precision (RSD, n = 13) was 1.1% at the 2 microg L(-1) level. The method was successfully applied to the determination of mercury in several certified environmental and foods reference materials and locally collected water samples.     

Determination of arsenic and mercury in sunflower oil by electrothermal atomic absorption

A simple and fast method for the determination of arsenic (As) in sunflower oil by electrothermal atomic absorption (ETAAS) is described. The optimal instrumental parameters for ETAAS measurement of As species in stable and homogeneous soap emulsions prepared from oil samples with tetramethylammonium hydroxide (TMAH) have been established. The limit of determination is 5 ng g^-1 total As in sunflower oil. A second approach involving extraction of As and mercury from sunflower oil and consequent ETAAS measurement is also described. Simultaneous quantitative extraction of As(III), As(V), monomethylarsonate (MMA) and dimethylarsinate (DMA) as well as Hg(II), monomethylmercury(II)chloride (MMC), dimethylmercury (DMM), diethylmercury (DEM) and diphenylmercury (DPM) is achieved by using an extraction mixture comprising of 0.1^M NH₃/0.01^M EDTA. Pre-reduced palladium is applied as an effective modifier for the next ETAAS measurement of all extracted species. The method of standard addition is employed for calibration. The accuracy and reproducibly of the methods was established by spike and recovery experiments and parallel analysis of sunflower oils from the marketplace. Limits of determination of 2 ng g^-1 for As and 3 ng g^-1 for mercury were obtained.     

Application of Polypropylene Amine Dendrimers (POPAM)-Grafted MWCNTs Hybrid Materials as a New Sorbent for Solid-Phase Extraction and Trace Determination of Gold(III) and Palladium(II) in Food and Environmental Samples

A new method which utilizes a polypropylene amine dendrimers (POPAM)-grafted multi-walled carbon nanotubes (MWCNTs) hybrid materials as an effective sorbent in solid-phase extraction has been developed for separation and preconcentration of Au(III) and Pd(II) trace levels in food, water and soil samples. The optimum experimental conditions such as pH, flow rates, type, concentration, and volume of the eluent for elution of gold and palladium ions, breakthrough volume, and effect of potentially interfering ions on separation and determination of these noble metals were investigated. The extraction recoveries for the mentioned noble metals were greater than 98 % and the limits of detection were 0.08 and 0.12 ng mL^?1 for gold and palladium, respectively. The relative standard deviations of the method were less than 4 % for eight separate column experiments for determination of 5.0 μg of gold and palladium ions. The adsorption capacity of the modified MWCNT was 92 mg g^?1 for gold and 74 mg g^?1 for palladium on POPAM-grafted MWCNTs. Validation of the suggested method was performed by analyzing certified reference materials. Finally, the proposed method was applied for determination of gold(III) and palladium(II) in real samples, including fish, shrimp, water, and soil.     

Arsenic speciation analysis in mono-varietal wines by on-line ionic liquid-based dispersive liquid–liquid microextraction

A highly efficient separation and pre-concentration method for arsenic species determination, based on ionic liquid (IL) dispersive microextraction technique implemented in a flow analysis system, is proposed. Highly selective separation of arsenite species [As(III)] was achieved by chelation with sodium diethyldithiocarbamate (DDTC) followed by dispersion with 40 mg of 1-octyl-3-methylimidazolium hexafluorophosphate ([C₈mim][PF₆]) IL. Analyte extraction, retention and separation of IL phase were achieved with a packed microcolumn and As(III) was determined in eluent solution by electrothermal atomic absorption spectrometry (ETAAS). Concentration of As(V) was deduced by the difference between total inorganic arsenic and As(III). Thus, determination of total arsenic was performed by previous degradation of organo-arsenic species, followed by a reduction. Under optimal conditions, As(III) extraction efficiency was 100% and a sensitivity enhancement factor of 46 was obtained with only 4.0 ml of sample The method was successfully applied for arsenic speciation studies in mono-varietal wines.     

Determination of Trichothecenes in Cereal Matrices Using Subcritical Water Extraction Followed by Solid-Phase Extraction and Liquid Chromatography-Tandem Mass Spectrometry

Subcritical water extraction followed by solid-phase extraction and ultra-high performance liquid chromatography coupled with tandem mass spectrometry detection is reported for the first time for the determination of 6 trichothecenes (deoxynivalenol, deoxynivalenol-3-glucoside, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, HT-2 toxin, and T-2 toxin) from different cereals. Water with 1% formic acid was used as the extraction solvent followed by a solid-phase extraction clean-up, achieving good performance with acceptable extraction recoveries, method detection limits between 0.05 μg kg^?1 and 4.0 μg kg^?1, and method quantification limits between 0.4 μg kg^?1 and 20 μg kg^?1. The use of water as the extraction solvent allowed a selective extraction affording low matrix effect levels and the detection and quantification of natural target trichothecenes at very low concentration levels. This extraction method was applied to different cereals, a pseudocereal and an oilseed sample, of which maize, millet, and oat were contaminated by at least one trichothecene.     

Fractionation of platinum group elements in aqueous systems: comparative kinetics of palladium and platinum removal from seawater by Ulva lactuca L

A marine macroalga, Ulva lactuca L., was used as a substrate to compare the kinetics of palladium (Pd) and platinum (Pt) removal from seawater. This work indicates that, while the equilibrium behaviors of Pd and Pt are in many respects similar, their kinetic behaviors are quite distinct. The removal of both Pt(II) and Pt(IV) from seawater by U. lactuca is slower than the removal of Pd(II) by approximately an order of magnitude. Relative Pd and Pt removal rates are strongly influenced by system hydrodynamics. Under quiescent conditions, lambda(Pd)/lambda(Pt), the ratio of Pd and Pt removal rates, is 7 +/- 2, whereas under turbulent conditions lambda(Pd)/lambda(Pt) can be as large as 27. These observations suggest that the disparate kinetic behaviors of Pd and Pt may produce considerable differences in the environmental dispersion of these elements.     

Molecularly imprinted solid-phase extraction coupled to liquid chromatography for determination of Sudan dyes in preserved beancurds

New molecularly imprinted microspheres synthesized by suspension polymerisation using phenylamine and naphthol as mimic template were successfully applied as selective sorbents for the solid-phase extraction used for the simultaneous determination of four Sudan dyes from preserved beancurd products. The obtained imprinted microspheres showed good recognition and selectivity to the four Sudan dyes in aqueous solution and the affinity could be easily controlled by adjusting the property of the solution. Under the selected experimental condition, the recoveries of the Sudan dyes in preserved beancurds at three spiked levels were ranged between 90.2-104.5% with the relative standard deviation of less than 6.8%. The limit of detection (LOD) and limit of quantification (LOQ) based on a signal-to-noise of 3 and 10 were in the range of 0.005-0.009 μg g⁻¹ and 0.015-0.030 μg g⁻¹, respectively. Comparing with alumina and C₁₈-based extraction, the selectivity and repeatability of molecularly imprinted solid-phase extraction (MISPE) were obviously improved. This method could be potentially applied for the determination of Sudan dyes in complicated food samples.     

微柱高效液相色谱法测定茶多酚的研究

研究了用固相萃取预分离,微柱高效液相色谱法测定茶叶中多酚的方法。茶叶中的多酚用80%乙醇超声震荡萃取,提取液用C18固相萃取小柱预分离,以WatersXterraTMRP18(1.0×50mm,2.5μm)色谱为固定相,1%的醋酸和甲醇梯度洗脱为流动相,在该条件下茶叶中主要的多酚在3.0min内可达到基线分离;用紫外二极管矩阵检测器检测,方法标准回收率为95%～103%,相对标准偏差为1.2%～1.6%。用该方法测定了几种茶叶样品中的多酚,结果令人满意。     

Platinum and palladium emissions from on-road vehicles in the Kaisermühlen Tunnel (Vienna, Austria)

Total and size-segregated Pt and Pd emission factors from on-road vehicles were measured in the Kaisermühlen Tunnel in Vienna, Austria. Aerosol sampling was performed simultaneously inside and outside the tunnel during April and May 2005. Analysis of the acid-digested aerosol samples was performed using a preconcentration procedure with subsequent on-line detection by electro-thermal atomic absorption spectrometry (ETAAS). Inside the tunnel distinctly increased Pt and Pd concentrations were found with highest levels in total suspended particulate matter samples and reduced concentrations in the size-segregated PM10 and PM2.5 samples. Emission factors were calculated from concentration differences between tunnel inside and tunnel outside samples, the distance between tunnel entrance and sampling location, the ventilation rate, and the number of vehicles passing through the tunnel. Emission rates observed for Pt ranged from 38 +/- 5.9 to 146 +/- 13 ng veh(-1) km(-1), whereas the emission factors of Pd varied between 13 +/- 2.1 and 42 +/- 4.1 ng veh(-1) km(-1). Variations in the emission rates were assumed to originate from alterations in traffic conditions. Size-segregated investigations revealed that the major part of Pt and Pd emissions were released in the coarse aerosol mode (size fraction > PM10), nevertheless a considerable fraction (approximately 12% and approximately 22% respectively) was emitted in the inhalable PM2.5 fraction.     

响应面法优化固相微萃取-气质联用法检测鸭肉中挥发性风味物质

为优化鸭肉中挥发性风味物质的萃取条件,在单因素试验基础上,根据Box-Behnken 试验设计原理,以鸭肉挥发性风味物质的色谱图总峰面积为响应值进行响应面分析。结果表明,最佳萃取条件为鸭肉萃取量为2.4g、萃取时间42min、萃取温度49℃。在此条件下检测到鸭肉中含有烯烃类、醛类、酮类、含氮含硫含氧类及杂环化合物等挥发性风味物质27 种。     

QuEChERS-气相色谱-串联质谱法测定蔬菜中35 种多氯联苯

建立气相色谱-串联质谱（gas chromatography-tandem mass spectrometry,GC-MS/MS）法测定蔬菜中35 种多氯联苯的方法。样品用萃取柱、QuEChERS提取包两种方法进行提取比较其预处理效果,经无水硫酸镁脱水、乙二胺-N-丙基硅烷和石墨化炭黑净化,用GC-MS/MS在选择反应监测模式下进行测定,内标法定量。结果表明,35?种目标物在10～1?000?μg/L范围内呈良好线性,线性相关系数均大于0.999。方法检出限范围为0.65～18.12?ng/kg。在0.01、0.02、0.10?mg/kg?3?个加标水平下的平均回收率为72.3%～119.0%,相对标准偏差为0.4%～9.8%。该方法简单、快速、灵敏、准确,适用于蔬菜中多种多氯联苯残留量的快速测定。     

Solid-phase extraction for selective determination of bisphenol A in drinks and fruits by dummy surface molecularly imprinted polymer with direct synthetic method

A reliable and selective method was developed for the determination of bisphenol A (BPA) in drinks and fruit using dummy surface molecularly imprinted polymer (DSMIP) as a solid-phase extraction (SPE)-enrichment and separation sorbent coupled with high-performance liquid chromatography (HPLC). Tetrabromobisphenol A (TBBPA), whose structure is similar to BPA, was selected as a dummy template molecule. DSMIP has a higher selectivity for BPA than surface non-imprinted polymer (SNIP) when used as sorbents for SPE. Potential factors affecting the extraction efficiency, including conditioning, sample loading, washing and elution, and the breakthrough volume were optimised. Under the optimum experimental conditions, the recoveries of BPA in drinks and fruit were in the range from 98% to 105% with relative standard deviations (RSDs) below 7%, and a limit of detection (LOD) of 3 ng ml^?1. The developed extraction protocol eliminated the effect of template leakage on quantitative analysis and could be applied to the trace determination of BPA in complicated functional samples.     

HS-SPME结合GC-MS分析麻婆豆腐中挥发性风味成分

测定麻婆豆腐中挥发性风味成分,对中式菜肴风味稳定及工业化生产有重要贡献。采用顶空固相微萃取（HS-SPME）,结合气质联用技术（GC-MS）分析了实验室自制麻婆豆腐中挥发性风味成分,并对萃取头、预热时间、萃取时间、萃取温度进行了优化。确定了较佳的萃取条件:采用65μm PDMS/DVB的纤维萃取头,60℃预热30 min,萃取30 min。通过GC-MS检测,在麻婆豆腐中一共检测出挥发性风味物质共74种,主要包括烷烯烃类、醇类、醛类、脂类等化合物。含量较多的物质有:萜品油烯、左旋-beta-蒎烯、月桂烯、3-蒈烯、b-侧柏烯、（-）-柠檬烯等。研究表明,顶空固相微萃取技术及气质联用技术能很好的用来分析麻婆豆腐中的挥发性风味物质,且样品萃取条件的不同对麻婆豆腐风味成分的准确测定具有一定影响;不同种类的麻婆豆腐的在感官评鉴上也有所差异。      

Analysis of synthetic phenolic antioxidants in edible oils by micellar electrokinetic capillary chromatography

Synthetic antioxidants most used in oil-based food to avoid oxidation processes, butylated hydroxyanisole (BHA), butylated hydroxytolueno (BHT), and dodecyl gallate (DG), were analyzed in edible oils using micellar electrokinetic capillary chromatography (MECK) with bis-(2-ethylhexyl) sodium sulfosuccinate as the pseudostationary phase.

Studies involving solid-phase and liquid–liquid extraction were performed to find the best sample treatment before injection into the electrophoretic system. The best methodology for the isolation of antioxidants was extraction with acetonitrile from edible oil diluted with hexane. A method that allows the determination of the antioxidants present in these samples was proposed. With this method BHA, BHT and DG were evaluated at levels permitted in the European Union.     

Solid-Phase Extraction of Florfenicol from Meat Samples by a Newly Synthesized Surface Molecularly Imprinted Sol–Gel Polymer

A new molecularly imprinted polymer (MIP) as a solid-phase sorbent for selective extraction of florfenicol (FF) was prepared by combination of the surface molecular imprinting technique with the sol–gel process. The FF-imprinted silica sorbent was prepared using FF as template, 3-aminopropyltriethoxysilane as functional monomer and tetraethoxysilicate as cross-linker on the silica gel support. The non-imprinted silica (NIP) was synthesized in the same way without addition of FF. The MIP was evaluated as a sorbent in column extraction approach for extraction of FF from aqueous solutions followed by spectrofluorometric determination. The influence of certain variables including the sample pH, the sample volume, the sample flow rate, the type of eluent, and its flow rate on the extraction efficiency of FF was assessed. The prepared FF-MIP silica sorbent showed higher adsorption capacity (64.9 mg g^?1) and significant selectivity than the corresponding NIP (11.5 mg g^?1). The FF-MIP-based solid phase extraction method was successfully applied to the separation and determination of FF from fish and chiken meat samples under the optimized extraction conditions.     

Ionic Liquid-based Ultrasound-Assisted In Situ Solvent Formation Microextraction Combined with Electrothermal Atomic Absorption Spectrometry as a Practical Method for Preconcentration and Trace Determination of Vanadium in Water and Food Samples

A new and practical sample enrichment method termed ionic liquid-based ultrasound-assisted in situ solvent formation microextraction (IL-UA-ISFME) was combined with electrothermal atomic absorption spectrometry (ETAAS) for preconcentration and trace determination of vanadium in real samples. In this sample enrichment methodology, a hydrophilic ionic liquid (IL) ([Hmim][BF₄]) was added to the aqueous media containing an ion-exchange reagent (NaPF₆), in order to obtain a hydrophobic IL ([Hmim][PF₆]) as the microextraction solvent. The hydrophobic extraction solvent formed under these conditions was completely dispersed into the sample solution using ultrasonic radiation. Vanadium was complexed with N-benzoyl-N-phenylhydroxylamine (BPHA), and extracted into the IL phase during the dispersion of the hydrophobic IL. Main variables affecting the recommended method was studied in details and optimized. Under the optimum conditions, the combined methodology provided a linear dynamic range of 15–2,500 ng l^?1, a limit of detection (LOD) of 4.7 ng l^?1 and a relative standard deviation (RSD) of 4.0 %. The accuracy and validity of the method was checked by analyzing a certified standard reference material of water (SRM-1643e). Finally, the developed method was utilized for quantitation of vanadium in real water and milk samples.     

Automated online solid-phase extraction of albendazole and its metabolites in Chinese mitten crabs followed by stable isotope dilution UPLC–MS/MS analysis

The determination of albendazole (ABZ) and its metabolites, albendazole sulfoxide, albendazole sulfone, and albendazole 2-aminosulfone in crab tissue is a complex analysis involving the extraction of trace levels of potentially unstable analytes from a solid matrix. Here, we report on an online solid-phase extraction (SPE) for automated trapping of ABZ and its metabolites in Chinese mitten crab, Eriocheir sinensis H. Milne Edwards (E. sinensis), followed by stable isotope dilution UPLC–MS/MS analysis. The performance of online SPE was fully validated. Good linearity was obtained with correlation coefficients >0.99. In the analytical range, the intra-day and inter-day precision and accuracies (RSD %) were 1.44–4.62 and 3.28–6.93 %, respectively. The mean recoveries were in the range of 78.2–109.3 %. All these demonstrated that the online SPE is an excellent technique for trapping and purification of ABZ and its metabolites in crab tissue samples. Finally, this online SPE–UPLC–MS/MS strategy was successfully applied to analyze the crude extracts from several crab tissue samples.     

Designing Pd-on-Au bimetallic nanoparticle catalysts for trichloroethene hydrodechlorination

Alumina-supported palladium (Pd) catalysts have previously been shown to hydrodechlorinate trichloroethene (TCE) and other chlorinated compounds in water, at room temperature, and in the presence of hydrogen. The feasibility of this catalytic technology to remediate groundwater of halogenated compounds can be improved by re-designing the Pd material in order to increase catalytic activity. We synthesized and characterized Pd supported on gold nanoparticles (Au NPs) of different Pd loadings. In all cases, we found that these catalysts were considerably more active than Pd NPs, alumina-supported Pd, ard Pd-black (62.0, 12.2, and 0.42 L x g(Pd)(-1) x min(-1), respectively). There is a synergistic effect of the Pd-on-Au bimetallic structure, with the material with the highest TCE hydrodechlorination activity (943 L x g(Pd)(-1) x min(-1)) comprised of Au NPs partially covered by Pd metal. The Pd-on-Au bimetallic catalyst structure provides a new synthesis approach in improving the catalytic properties of monometallic Pd materials. The resulting nanoparticle-based materials should be highly suitable as hydrodehalogenation and reduction catalysts for the remediation of various organic and inorganic groundwater contaminants.     

Development and Comparison of Sample Preparation Techniques for Chromatographic Analysis of Sulfonamide Residues in Bovine Milk

Most studies to determine sulfonamide residues in milk samples have used solid-phase extraction as the sample preparation technique. However, the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, introduced in 2003, has been used in the extraction of various compounds in food matrices. This study aimed to evaluate two sample preparation techniques: solid-phase extraction and QuEChERS, for chromatographic analysis of sulfonamides (sulfathiazole, sulfamethazine, and sulfadimethoxine) in bovine milk. The chromatographic parameters and the QuEChERS extraction procedure were developed by using different experimental designs, obtaining good peak resolution, recovery, precision, accuracy, linearity, selectivity, and limits of detection and quantification. In contrast, using solid-phase extraction, acceptable recoveries and selectivity were not achieved, despite the number of articles published that have applied this sample preparation technique for sulfonamide analysis. As a result of the experiments performed, probably sulfonamides are retained together with other components of the matrix in the sample pretreatment step (prior to its addition in the cartridge containing solid phase), which is an important part of solid-phase extraction with raw whole milk. Therefore, QuEChERS is a better method than solid-phase extraction for the analysis of sulfonamide residues in milk. Validation tests demonstrated that the method is appropriate, within the maximum residue limit (0.1 mg kg^?1). Moreover, it was possible to use a lower amount of solvent compared with previously published articles (6 mL against 10 or 15 mL).     

Determination of arsenic in chicken feed by hydride generation atomic absorption spectrometry after pre-concentration with polyurethane foam

A pre-concentration procedure with solid-phase extraction was developed for the determination of arsenic (As) in chicken feed using hydride generation atomic absorption spectrometry (HG-AAS). The procedure was based on the sorption of As(III) ions as complexes with ammonium pyrrolidine dithiocarbamate onto a mini-column packed with polyurethane foam. After pre-concentration, the As was removed from the mini-column by acid solution, and the analyte content in the eluate was measured by HG-AAS. The following main experimental conditions were established: adjustment of the As solution pH with 0.05?mol?l^?1 HCl, 2.88?×?10^?3?mol?l^?1 complexing agent concentration and 6.0?mol?l^?1 eluting hydrochloric acid concentration. The proposed method produced an enrichment factor of 67, with 0.050 and 0.165?µg?g^?1 limits of detection and quantification, respectively. The procedure was applied to the determination of As content in two types of chicken feed using the proposed procedure and atomic absorption spectrometry with electrothermal atomisation (ETAAS). The t-test indicated that the results were not significantly different at a confidence level of 95%.