A novel capillary microextraction on ordered mesoporous titania coating combined with electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of V, Cr and Cu in environmental and biological samples

In this work, an ordered mesoporous titania film was introduced to coat a capillary by means of sol-gel technique. Sol-gel titania coating was developed for the preconcentration/separation of trace V, Cr and Cu by capillary microextraction (CME), and the adsorbed analytes were eluted for electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) detection. By immobilizing sol-gel titania on the inner surface of a fused-silica microextraction capillary, the sol-gel titania coating was prepared easily. Its adsorption properties, stability and the factors affecting the adsorption behaviors of V, Cr and Cu were investigated in detail. At pH range of 7 to 9, the titania-coated capillary (50 cm x 0.25 mm) is selective towards V, Cr and Cu, and the target analytes could be desorbed quantitatively with 50 microl of 1.0 mol l(-1) HNO3 at the rate of 0.05 ml min(-1). With a consumption of 2 ml sample solution, an enrichment factor of 33.3, and a detection limit (3 s) of 1.1 pg ml(-1) (10.5 fg) for V; 3.3 pg ml(-1) (33.0 fg) for Cr and 6.3 pg ml(-1) (63.1 fg) for Cu respectively were obtained. The precisions Relative Standard Deviations (RSDs) for nine replicate measurements of 1 ng ml(-1) V, Cr and Cu were 3.4, 5.1 and 6.4%, respectively. The proposed method has been applied to the determination of V, Cr and Cu in human urine and lake water, and the recoveries for these elements were 89.2 approximately 105%. The developed method was also applied to the determination of the target elements in NIES No. 10-a (rice flour-unpolished) and NIES No. 9 (sargasso) certified reference materials, and the results found are in good agreement with the certified values.     

Chromium(III)-imprinted silica gel for speciation analysis of chromium in environmental water samples with ICP-MS detection

A new chromium(III)-imprinted 3-(2-aminoethylamino) propyltrimethoxysilane (AAPTS)-functionalized silica gel sorbent was synthesized by a surface imprinting technique and was employed as a selective solid-phase extraction material for speciation analysis of chromium in environmental water samples prior to its determination by inductively coupled plasma mass spectrometry (ICP-MS). The prepared Cr(III)-imprinted silica gel shows the selectivity coefficient of more than 700 for Cr(III) in the presence of Mn(II). The static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Cr(III) were 30.5 mg g(-1) and 13.4 mg g(-1). It was also found that Cr(VI) could be adsorbed at low pH by the prepared imprinted silica gel, and this finding makes it feasible to enrich and determine Cr(VI) at low pH without adding reducing reagents. The imprinted silica gel sorbent offered a fast kinetics for the adsorption and desorption of both chromium species. Under the optimized conditions, the detection limits of 4.43 pg mL(-1) and 8.30 pg mL(-1) with the relative standard deviations (R.S.D.s) of 4.44% and 4.41% (C=0.5 ng mL(-1), n=7) for Cr(III) and Cr(VI) were obtained, respectively. The proposed method was successfully applied to the speciation of trace chromium in environmental water samples. To validate the proposed method, two certified reference materials were analyzed and the determined values were in a good agreement with the certified values. The developed method is rapid, selective, sensitive and applicable for the speciation of trace chromium in environmental water samples.     

Ultrasensitive determination of cadmium in seawater by hollow fiber supported liquid membrane extraction coupled with graphite furnace atomic absorption spectrometry

A new procedure, based on hollow fiber supported liquid membrane preconcentration coupled with graphite furnace atomic absorption spectrometry (GFAAS) detection, was developed for the determination of trace Cd in seawater samples. With 1-octanol that contained a mixture of dithizone (carrier) and oleic acid immobilized in the pores of the polypropylene hollow fiber as a liquid membrane, Cd was selectively extracted from water samples into 0.05 M HNO₃ that filled the lumen of the hollow fiber as a stripping solution. The main extraction related parameters were optimized, and the effects of salinity and some coexisting interferants were also evaluated. Under the optimum extraction conditions, an enrichment factor of 387 was obtained for a 100-mL sample solution. In combination with graphite furnace atomic absorption spectrometry, a very low detection limit (0.8 ng L^− 1) and a relative standard deviation (2.5% at 50 ng L^− 1 level) were achieved. Five seawater samples were analyzed by the proposed method without dilution, with detected Cd concentration in the range of 56.4–264.8 ng L^− 1 and the relative spiked recoveries over 89%. For comparison, these samples were also analyzed by the Inductively Coupled Plasma Mass Spectrometry (ICP-MS) method after a 10-fold dilution for matrix effect elimination. Statistical analysis with a one-way ANOVA shows no significant differences (at 0.05 level) between the results obtained by the proposed and ICP-MS methods. Additionally, analysis of certified reference materials (GBW (E) 080040) shows good agreement with the certified value. These results indicate that this present method is very sensitive and reliable, and can effectively eliminate complex matrix interferences in seawater samples.     

氧化石墨烯/壳聚糖微球吸附-电感耦合等离子体质谱法测定地质样品中痕量钽EI北大核心CSCD

建立了氧化石墨烯/壳聚糖微球吸附-电感耦合等离子体质谱法测定地质样品中痕量Ta的方法。合成了氧化石墨烯/壳聚糖微球,将其应用于地质样品中痕量Ta的分离富集,采用电感耦合等离子体质谱对富集后的试液进行测定。对氧化石墨烯含量、配体种类和浓度、pH、吸附时间、吸附剂用量等吸附条件和洗脱剂类型、体积、洗脱时间等洗脱条件进行了优化,在优化的条件下,对地质样品标准物质进行测定,Ta的方法检出限为2.0 ng/g,富集倍数为26.7倍。     

On‐Line Selective Solid‐Phase Extraction of Copper with a Surface Ion Imprinted Silica Gel Sorbent

Copper(II)‐ion imprinted silica gel (Cu‐IISG) sorbent was synthesized by surface imprinting technique and was employed as a selective solid‐phase extraction material for on‐line preconcentration and separation, then coupled with atomic absorption spectrometry (AAS) determination of Cu(II). The higher selectivity coefficient of Cu‐IISG for Cu(II) in the presence of competitive ions such as Fe(III), Ni(II) and Zn(II) was above 411, which was 35 times of NISG. The static adsorption capacity and dynamic adsorption capacity were 41.11 mg g^?1 and 16.20 mg g^?1, respectively. The Cu‐IISG offered a fast kinetics for the adsorption and desorption of Cu(II), which can be used for on‐line preconcentration and detection. Two certified reference materials of GBW07301a sediment and GBW07401 soil were analyzed and the determined values were in a good agreement with the certified values. The developed method was also successfully applied to the determination of trace copper in tea leaf with satisfactory results (recovery between 96.3% and 102.3%).     

Synthesis and Applications of Poly(Acrylphenylamidrazone-Phenyl-Hydrazide-Acylphenylhydrazine) Chelating Fiber for Preconcentration and Separation of Trae In(III), Zr(IV), Tl(I), V(V), Ga(III) and Ti(IV) from Solution Samples

 An ICP-OES method using a new poly (acrylphenylamidrazone-phenylhydrazide-acylphenylhydrazine) chelating fiber to preconcentrate and separate trace In(III), Zr(IV), Tl(I), V(V), Ga(III) and Ti(IV) ions from solution samples has been established. The new chelating fiber was synthesized using polyacrylonitrile fiber as a starting material and the structure of the chelating fiber was determined by FT infrared spectrometry. The acidity, adsorption rate, re-use, capacity and interference on the adsorption of ions on the chelating fiber as well as the conditions of desorption of these ions from the chelating fiber were investigated by means of inductively coupled plasma optical emission spectrometry (ICP-OES). The results show that the relative standard deviations for the determination of 10 ng/ml In, Tl, Ga and 1 ng/ml Zr, V, Ti were lower than 2.5%. The results obtained for these ions in real solution samples by this method were basically in agreement with the given values with average errors of less than 4%. Received November 29, 2000. Revision May 22, 2001.     

Applications of titania and zirconia hollow fibers in sorptive microextraction of N,N-dimethylacetamide from water sample

The convenient fabrications of titania and zirconia hollow fiber with three-dimensional porous structure using polypropylene hollow fibers as templates were developed. And an analytical method based on enrichment and extraction of analytes in the water sample, hollow fiber sorptive microextraction in combined with gas chromatography has been developed for the rapid analysis of N,N-dimethylacetamide (DMA) in the environmental samples. The results showed that zirconia hollow fiber gave higher extraction performance of DMA than that of titania hollow fiber. The method validations, including linearity, limit of detection, limit of qualification, precision, and repeatability were investigated. Linearity for six-point calibration curve was excellent with zirconia hollow fiber having r² value greater than 0.9993 at the linearity range of 0.001-1.0 mg mL⁻¹. In addition, it seems that hollow fiber sorptive extraction is a promising technique for the enrichment and purification of analytes extracted directly from liquid samples without any other pretreatment.     

Titania immobilized polypropylene hollow fiber as a disposable coating for stir bar sorptive extraction-high performance liquid chromatography-inductively coupled plasma mass spectrometry speciation of arsenic in chicken tissues

The bottleneck of applying stir bar sorptive extraction (SBSE) to elemental speciation analysis is lack of suitable extraction phases with good affinities to different elemental species. In this paper, a newly high polar extraction phase of titania immobilized polypropylene hollow fiber (TiO₂-PPHF) was prepared by sol–gel immersion and low temperature hydrothermal process and the obtained TiO₂-PPHF inherits the adsorption properties of TiO₂ and the toughness of PPHF. With a suitable size of stainless steel magnetic bar inserted into the prepared TiO₂-PPHF, a disposable TiO₂-PPHF coating stir bar was obtained. The prepared TiO₂-PPHF was characterized by X-ray diffraction spectrometry and scanning electron microscopy and the significant parameters affecting the extraction efficiency of different arsenic species were studied. Based on the above facts, a new method of SBSE combined with high performance liquid chromatography (HPLC)–inductively coupled plasma mass spectrometry (ICP-MS) was developed for the speciation of phenyl arsenic compounds and their possible transformation products in chicken tissues. Under the optimal conditions, limits of detection (LODs) of the developed method for eight target arsenic species were in the range of 11.4–64.6 ng L⁻¹ with enrichment factors of 8.5–22.3 (theory enrichment factor was 50), and the relative standard deviations (RSDs) were varying from 6.3 to 12.6% (c_AsIII/V = 5 μg L⁻¹, c_{MMA,DMA,p-ASA,4-OH,3-NHPAA,PA,4-NPAA} = 10 μg L⁻¹, n = 7). The proposed method was successfully applied to the speciation of arsenic in chicken meat/liver samples and the recoveries for the spiked samples were in the range of 78.5–120.4%. In order to validate the accuracy of the proposed method, a certified reference material of BCR-627 tuna fish tissue was analyzed and the determined values were in good agreement with the certified values. The TiO₂-PPHF was demonstrated to be a highly selective coating for the target arsenic species, and could be easily prepared in batches with low cost. In addition, with the disposable coating, the carry-over effect commonly encountered in conventional SBSE was avoided.     

Improved immobilization of 8-hydroxyquinoline on polyacrylonitrile fiber and application of the material to the determination of trace metals in seawater by inductively coupled plasma mass spectrometry

A modified synthetic method has been developed for immobilization of 8-hydroxyquinoline on polyacrylonitrile fiber. The synthetic conditions, e.g. reagent concentration, reaction temperature and time, were optimized. The features of the newly-modified fiber are higher exchange capacity compared with most other materials containing immobilized 8-hydroxyquinoline, better mechanic characteristics, high stability at both high and low pH, and ease of synthesis. This modified fiber can concentrate and separate trace metals from matrices with higher concentrations of alkali and alkaline earth elements. To validate the characteristics of the modified fiber, trace metals Ag, Be, Cd, Co, Cu, Mn, Ni, Pb, and Zn in the certified reference materials river water (SLRS-4) and seawater (CASS-4, NASS-5, SLEW-3) were preconcentrated before determination by inductively coupled plasma mass spectrometry. Good agreement was obtained between the data obtained by this method and the certified values.     

Sol-gel zirconia coating capillary microextraction on-line hyphenated with inductively coupled plasma mass spectrometry for the determination of Cr, Cu, Cd and Pb in biological samples

A sol-gel zirconia coating was developed for the preconcentration/separation of trace Cr, Cu, Cd and Pb by capillary microextraction, and the adsorbed analytes were on-line eluted for detection using inductively coupled plasma mass spectrometry (ICP-MS). By immobilizing sol-gel zirconia on the inner surface of a fused-silica capillary, the sol-gel zirconia coating was simply prepared. Its adsorption properties, stability and the factors affecting the adsorption behaviors of Cr, Cu, Cd and Pb were investigated in detail. In the pH range from 7.8 to 10, the zirconia-coated capillary (35 cm x 0.15 mm) is selective towards Cr, Cu, Cd and Pb, and the analyzed ions could be desorbed quantitatively with 0.2 mL of 0.5 mol/L HNO(3) at a rate of 0.2 mL/min. With a consumption of 1.25 mL sample solution, an enrichment factor of 6.25, and detection limits (3sigma) of 9.9 pg/mL Cr, 17.9 pg/mL Cu, 4.5 pg/mL Cd and 3.7 pg/mL Pb were obtained. The precisions for nine replicate measurements of 1 ng/mL Cr, Cu, Cd and Pb were 4.9% Cr, 2.2% Cu, 2.0% Cd and 3.2% Pb (RSD), respectively. The proposed procedure has been applied to the determination of Cr, Cu, Cd and Pb in human urine, which was subjected to microwave-assisted digestion prior to analysis, and the recoveries for these elements were 89.2-101.8%. In order to validate the developed procedure, a NIES No.10-a Rice Flour-Unpolished certified reference material and a BCR No. 184 Bovine Muscle certified reference material were analyzed, and the results are in good agreement with the certified values.     

Synthesis of polypiperazine-amide thin-film membrane on PPESK hollow fiber UF membrane

A new interfacial polymerization (IP) procedure is developed in order to synthesize polypiperazine-amide thin-film membrane on the inner surface of poly(phthalazinone ether sulfone ketone) (PPESK) hollow fiber ultrafiltration (UF) membrane.A hollow fiber composite membrane with good performance was prepared and studied by FT-IR and scanning electron microscopy.     

Preconcentration using diethylenetriaminetetraacetic acid-functionalized polysiloxane (DETAP) for determination of molybdenum(VI) in seawater by ICP–OES

This paper reports a new method for preconcentration and separation of trace amounts of molybdenum in seawater samples prior to determination by inductively coupled plasma–atomic emission spectroscopy (ICP–OES). Diethylenetriaminetetraacetic acid-functionalized polysiloxane (DETAP) was synthesized by carboxymethylation of amino groups on triamine immobilized polymer, which was prepared by modification of 3-chloropropylpolysiloxane with diethylenetriamine. The resulting polysiloxane is highly selective and efficient in chelating Mo(VI) at trace levels. It can be used as a column packing material. The polysiloxane column can be reused over ten times without losing its original properties, so it is suitable for preconcentration of molybdenum species in seawater samples before determination. The parameters governing the characteristics of polysiloxane for adsorption of Mo(VI) were investigated. These include the effect of pH, amount of polysiloxane, equilibrium time, adsorption isotherm, maximum adsorption capacity, interfering ions, flow rate, capacity for reuse, and desorption. The precision of the preconcentration method, calculated as the relative standard deviation of seawater samples, was 3%. The preconcentration factor was 100. The detection limit, defined as 3 times the standard deviation of five replicate measurements of the blank sample at pH 3, was 0.17 g L^–1. Measurement results for standard reference materials were in good agreement with the certified values [(CRMs), NASS-2 Seawater (Open Ocean) and CASS-2 Seawater (Coastal)].     

模板法制备复合中空微球

本文报道以一种商品化的聚苯乙烯中空球为模板, 采用溶胀聚合技术合成了具有IPN(Inter-Penetrating Network)结构的复合中空球; 对其中的一种高分子网络进行化学改性引入所需官能团, 制得带有羧基的聚合物凝胶中空球; 利用凝胶诱导生长特性, 成功制得聚合物复合中空球. 此方法无需去除模板就可批量制备各种复合功能中空球.     

High-sensitivity capillary electrophoresis for speciation of organomercury in biological samples using hollow fiber-based liquid-liquid-liquid microextraction combined with on-line preconcentration by large-volume sample stacking

A hollow fiber-based liquid-liquid-liquid microextraction (HF-LLLME) combined with on-line large-volume sample stacking (LVSS) has been developed for the speciation of organomercury in biological samples by CE with UV detection. Separation was achieved in less than 11 min with an electrolyte consisting of 35 mM sodium tetraborate at pH 9.1. In LVSS, a reverse electrode polarity-stacking mode (REPSM) was applied as on-line preconcentration strategy. In HF-LLLME, the analytes were extracted from 12 mL volume of sample solution (pH adjusted to 3.0) into bromobenzene impregnated in the pores of the hollow fiber, and into an acceptor solution of L-cysteine (15 microL, 0.02% w/v) inside the hollow fiber. Under the optimized conditions, concentration factors of 2610-4580 were achieved and LODs in the range of 0.03-0.14 microg/L were feasible. The linearity was found to be over two orders of magnitude with correlation coefficient of 0.9991-0.9996. The developed method has been validated using a certified reference material (DORM-2, dogfish muscle), and the determined values coincided very well with the certified values. The method was also applied to the speciation of organomercury in three kinds of fish samples and human hair samples.     

Determination of pesticides in soil by liquid-phase microextraction and gas chromatography-mass spectrometry

Trace amounts of pesticides in soil were determined by liquid-phase microextraction (LPME) coupled to gas chromatography-mass spectrometry (GC-MS). The technique involved the use of a small amount (3 microl) of organic solvent impregnated in a hollow fiber membrane, which was attached to the needle of a conventional GC syringe. The organic solvent was repeatedly discharged into and withdrawn from the porous polypropylene hollow fiber by a syringe pump, with the pesticides being extracted from a 4 ml aqueous soil sample into the organic solvent within the hollow fiber. Aspects of the developed procedure such as organic solvent selection, extraction time, movement pattern of plunger, concentrations of humic acid and salt, and the proportion of organic solvent in the soil sample, were optimized. Limits of detection (LOD) were between 0.05 and 0.1 microg/g with GC-MS analysis under selected-ion monitoring (SIM). Also, this method provided good precision ranging from 6 to 13%; the relative standard deviations were lower than 10% for most target pesticides (at spiked levels of 0.5 microg/g in aqueous soil sample). Finally, the results were compared to those achieved using solid-phase microextraction (SPME). The results demonstrated that LPME was a fast (within 4 min) and accurate method to determine trace amounts of pesticides in soil.     

Minimization of sample volume with air-segmented sample injection and the simultaneous determination of trace elements by ICP-MS.

The application of inductively coupled plasma mass spectrometry (ICP-MS) to forensic chemistry was studied. The developed method, air-segmented sample injection (ASSI) coupled with ICP-MS, allowed the determination of about 25 elements at the sub-ppb level with only 0.2 ml of a sample solution. The optimum sample flow rate was found to be 0.4 ml min(-1), along with a sample suction time of 30 s. The proposed method was validated by determining trace elements in river-water certified reference material (SLRS-4) issued by National Research Council Canada. The analytical results of the proposed method were in good agreement with the certified values. This method was successfully applied to a human hair sample, the volume of which was 3 ml.     

ICP-AES determination of trace rare earth elements in environmental and food samples by on-line separation and preconcentration with acetylacetone-modified silica gel using microcolumn.

A novel method of online microcolumn separation and preconcentration coupled to inductively coupled plasma atomic emission spectrometry (ICP-AES) with the use of acetylacetone-modified silica gel as packing material was developed for the determination of trace rare earth elements (REEs) in environmental and food samples. The main parameters affecting online separation/preconcentration, including pH, sample flow rate, sample volume, elution and interfering ions, have been investigated in detail. Under the optimized operating conditions, the adsorption capacity values for Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu were 25.65, 23.23, 24.01, 19.40, 22.89, 23.77, 24.40, 23.96, 25.58, 25.15, 24.86, 22.75, 16.05, 24.13, 26.51 and 27.93 mg g(-1), respectively. Detection limits (3sigma) based on three times standard deviations of the blanks by 8 replicates were in the range from 48 pg mL(-1) for Lu to 1003 pg mL(-1) for Sm. With 90 s preconcentration time and 10 s elution time, the enrichment factor was 10 and the sample frequency was 28 h(-1). The precisions (RSDs) obtained by determination of a 250 ng mL(-1) (n = 8) REEs standard solution were in the range from 1.7% for Y to 4.4% for Sm. The proposed method was successfully applied to the determination of trace REEs in pig liver, agaric and mushroom. To validate the proposed method, we analyzed three certified reference materials (GBW07401 soil, GBW07301a sediment, and GBW07605 tea leaves). The determined values were in a good agreement with the certified values. The method is rapid, selective, sensitive and applicable to the determination of trace REEs in biological and environmental samples with complicated matrix effects.     

Polycarboxylic microsphere polymer gel for solid phase extraction of trace elements

A simple and sensitive method has been developed for the determination of trace elements (Cd, Co, Cu, Ni, Fe and Pb) in sea water and natural waters by electrothermal atomic absorption spectrometry. The method is based on column solid phase extraction of trace elements on a newly synthesized polycarboxylic gel. The sorbent was prepared by dispersion copolymerization of methacrylic acid (as a monomer) and trimethylolpropane trimethacrylate (as a crosslinking agent) in the form of monodisperse microspheres. It exhibits high regeneration ability, chemical and mechanical resistivity. The influence of pH, flow rates and concentration of the eluent on the degree of sorption of trace elements have been evaluated. The maximum static adsorption capacities of the sorbent at the optimal conditions for lead, nickel, cobalt, iron, cadmium and copper are determined. Detection limits achieved for the elements studied for 100 mL water sample volume were between 0.005 and 0.05 μg L^?1. The relative standard deviation varied in the range 5–13% for all elements studied. The validity of the method was checked by an analysis of standard reference material SRLS-3 Riverine Water. Very good agreement between the analytical results and the certified values (t-test at 95% confidence level) was observed. The new polycarboxylic gel was applied to passive sampling procedures due to its high chemical and mechanical stability.     

纳米TiO2微柱分离富集测定环境样品中的微量碲

以处理过的纳米TiO2为微柱吸附材料,采用流动注射技术进行微量碲的分离富集,探讨了溶液的pH值、试样流速、试样体积、洗脱液浓度和用量以及干扰离子等因素的影响。 实验结果表明,pH值在8～9.5范围内,纳米TiO2对Te(Ⅳ)具有良好的吸附性能,吸附率接近99%,动态饱和吸附容量为37.02 mg/g;选用2 mL 0.5 mol/L NaOH溶液可将吸附的Te(Ⅳ)完全洗脱,富集倍数为30。 本法的检出限(3σ)为0.013 mg/L,相对标准偏差为RSD=1.99%。 将本法应用于水样的分析,碲的回收率在98%~103%之间,结果令人满意。     

Selective solid-phase extraction of lead(II) from biological and natural water samples using surface-grafted lead(II)-imprinted polymers

A new Pb(II)-imprinted amino-functionalized silica gel sorbent was synthesized by an easy one-step reaction by combining a surface imprinting technique for selective solid-phase extraction of trace Pb(II) prior to its determination by inductively coupled plasma optical emission spectrometry. The Pb(II)-imprinted amino-functionalized silica gel sorbent was characterized by Fourier transform infrared spectroscopy. Compared to non-imprinted polymer particles, the ion-imprinted polymers had higher selectivity and adsorption capacity for Pb(II). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Pb(II) was 19.66 and 6.20 mg g^?1, respectively. The largest selectivity coefficient of the Pb(II)-imprinted sorbent for Pb(II) in the presence of Cd(II) was over 450. The relative selectivity (α _r) values of Pb(II)/Cd(II) were 49.3 and 46.3, which were greater than 1. The distribution ratio (D) values of Pb(II)-imprinted polymers for Pb(II) were much larger than that for Cd(II). The detection limit (3σ) was 0.20 μg L^?1. The relative standard deviation was 2.0% for 11 replicate determinations. The method was validated for the analysis three certified reference materials (GBW 08301, GBW 08504, GBW 08511), and the results are in good agreement with standard values. The method was also successfully applied to the determination of trace lead in plants and water samples with satisfactory results.