Flow Rate Of Sample Solution Research Articles

Application of modified multiwalled carbon nanotubes as solid sorbent for separation and preconcentration of trace amounts of manganese ions

In this work, the potential of modified multiwalled carbon nanotubes for separation and preconcentration of trace amounts of manganese ion is studied. Multiwalled carbon nanotubes were oxidized with concentrated HNO3 and then modified with loading 1-(2-pyridylazo)-2-naphtol. Mn(II) ions could be quantitatively retained by modified multiwalled carbon nanotubes in the pH range of 8–9.5. Elution of the adsorbed manganese was carried out with 5.0mL of 0.1molL−1 HNO3. Detection limit is 0.058ngmL−1 and analytical curve is linear in the range of 0.1ngmL−1–5.0μgmL−1 in the initial solution with a correlation coefficient 0.9977 and the preconcentration factor is 100. Relative standard deviation for eight replicate determination of 0.5μgmL−1 of manganese in the final solution is 0.41%. The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type, breakthrough volume and interference ions, were studied for preconcentration of Mn(II) ions in detail to optimize the conditions. The method was successfully applied for separation, preconcentration and determination of manganese in different samples.

Hybrid cell sorters for on-chip cell separation by hydrodynamics and magnetophoresis

The classification of cells is important for medical diagnosis and medicine research. A micro-scale analysis system for blood allows immediate diagnosis, regardless of time or location. Rapid handling of biological cells is required for the development of lab-on-a-chip and point-of-care technologies. In previous papers, the reported sample solution flow rates for hydrodynamic cell separation ranged from 0.1 to tens of μl min−1. This paper proposes a hybrid cell sorter that combines hydrodynamics and magnetophoresis. This cell sorter is proposed for improving the classification efficiency of a virtual impactor-based cell sorter and for permitting the hydrodynamic cell separation with high throughput. In addition, its performance has been evaluated in the classification of Jurkat cells and blood cells. In the Jurkat cell experiment, the classification efficiency of Jurkat cells at the major outlet decreased from 70 to 50.8% with the proposed hybrid scheme. The flow rate for cell separation was 1 ml min−1. The classification efficiency of red blood cells (RBCs) increased from 75.2 to 86.8% with the application of a magnetic field. Also, the classification efficiency of white blood cells (WBCs) decreased from 83.8 to 70.9% with an applied magnetic field. Experimental results demonstrated that the classification efficiency of blood cells can be modulated and enhanced by magnetophoresis and that the hybrid cell sorter has potential for lab-on-a-chip applications.

Ionspray microchip

AbstractAn ionspray microchip is introduced. The chip is based on the earlier presented nebulizer microchip that consists of glass and silicon plates bonded together. A liquid inlet channel, nebulizer gas inlet, and nozzle are etched on the silicon plate and a platinum heater is integrated on the glass plate. The nebulizer microchip has been previously used in atmospheric pressure chemical ionization, atmospheric pressure photoionization, sonic spray ionization, and thermospray ionization modes. In this work we show that the microchip can be operated also in ionspray mode by introducing high voltage to the silicon plate of the microchip. The effects of operation parameters (voltage, nebulizer gas pressure, sample solution flow rate, solvent composition, and analyte concentration) on the performance of the ion spray microchip were studied. Under optimized conditions the microchip provides efficient ionization of small and large compounds and good quantitative performance. The feasibility of the ion spray microchip in liquid chromatography/mass spectrometry (LC/MS) was demonstrated by the analysis of tryptic peptides of bovine serum albumin. Copyright © 2010 John Wiley & Sons, Ltd.

Sorbent extraction of 4-(2-thiazolylazo) resorcinol (TAR)–metal chelates on Diaion SP-850 adsorption resin in order to preconcentration/separation

A sensitive and simple separation-enrichment technique for the determination of trace amounts of some metal ions was described. By the passage of aqueous samples including Fe(III), Cu(II), Ni(II) and Co(II) ions–4-(2-thiazolylazo) resorcinol (TAR) chelates through Diaion SP-850 column, metal chelates adsorb quantitatively and almost all matrix elements were passed through the column to drain. Quantitative recoveries for analyte ions were obtained at pH 6 at 3 ml/min flow rate of sample solution in 0.5 g Diaion SP-850 filled glass column. The investigations were also carried out on the interferences from other concomitant ions in the sorption process. After optimization, a preconcentration factor of 60 and a recovery values as % higher than 95 were achieved. The detection limit ( N = 10, 3 sigma) for Fe(III), Cu(II), Ni(II) and Co(II) were found as 3.6, 1.1, 2.8 and 2.3 μg l −1, respectively. The applications to the determination of iron, copper, nickel and cobalt in real samples and the validation of the analytical methodology employing NIST SRM 1549 milk powder, NIST RM 8433 Corn Bran and BCR 144R Sewage sludge of domestic origin as certified reference materials were performed.

Salicylaldoxime이 내포된 p-Dichlorobenzene 미세결정을 이용한 Cu(II)의 예비농축 및 정량

Salicylaldoxime (SA)이 내포되어 있는 미세결정 p-dichlorobenzene 흡착제(p-dichlorobenzene-SA)를 이용하여 시료에 흔적량으로 들어있는 Cu(II)를 예비농축시킨 후 불꽃 원자흡수분광법으로 정량하는 방법을 개발하였다. 시료 용액의 pH, 킬레이트제 salicylaldoxime의 양, 흡착제 p-dichlorobenzene-SA의 양 그리고 시료 용액의 흐름속도 등 여러 실험조건을 최적화하였다. 여러 공존이온에 대한 방해효과를 조사한 결과, <TEX>$CN^1$</TEX>가 다른 이온들보다 비교적 심하게 방해하였다. <TEX>$1\;{\mu}g\;mL^{-1}\;CN^-$</TEX>에 의한 방해효과는 Ni(II)를<TEX>$20\;{\mu}g\;mL^{-1}$</TEX> 되도록 조절한 결과, 완전히 제거할 수 있었다. 본 방법으로 얻은 직선 감응범위, 상관계수(<TEX>$R^2$</TEX>) 및 검출한계는 각각 <TEX>$3.0\sim100\;ng\;mL^{-1}$</TEX>, 0.9901, 및 <TEX>$3.1\;ng\;mL^{-1}$</TEX> 이었다. 본 방법을 실제 시료에 적용가능 여부를 확인하기 위해 수용액 시료(폐수, 저수지물 및 시냇물)와 식품시료(오렌지 쥬스, 생계란 및 탈지분유)에 응용하였다. 회수율은 93~104% 범위이었으며, ICP-MS를 이용하여 직접 측정한 값과 본 방법으로 측정한 값을 비교한 결과, 95% 신뢰수준에서 잘 일치하였다. 본 방법을 쌀가루 인증표준물질(certified reference material, CRM) 시료에 응용해 보았으며 좋은 결과를 얻었다. 실험 결과들로부터 본 방법은 여러 실제 시료에 들어있는 Cu(II)를 농축 및 정량하는데 응용할 수 있음을 확인하였다. A technique for the determination of trace Cu(II) in various real samples by FAAS after the column preconcentration onto p-dichlorobenzene-SA adsorbent, which is microcrystalline p-dichlorobenzene loaded with salicylaldoxime (SA) has been developed. Several experimental conditions such as pH of the sample solution, the amount of chelating agent salicylaldoxime, the amount of adsorbent p-dichlorobenzene-SA, and flow rate of sample solution were optimized. The interfering effects of various concomitant ions were investigated. <TEX>$CN^-$</TEX> interfered more seriously than any other ions. However, the interference by <TEX>$1\;{\mu}g\;mL^{-1}\;CN^-$</TEX> could be overcome completely by controlling the concentration of Ni(II) to <TEX>$20\;{\mu}g\;mL^{-1}$</TEX>. The linear range, correlation coefficient (<TEX>$R^2$</TEX>) and detection limit obtained by this technique were <TEX>$3.0\sim100\;ng\;mL^{-1}$</TEX>, 0.9901, and <TEX>$3.1\;ng\;mL^{-1}$</TEX>, respectively. For validating this technique, the aqueous samples (wastewater, reservoir water and stream water) and the food samples (orange juice, fresh egg and skim milk) were used. Recovery yields of 93~104% were obtained. These measured mean values were not differents from ICP-MS data at 95% confidence level. The good results were obtained from the experiments using the rice flour certified reference material (CRM) sample. Based on the experimental results, it was found that this technique could be applied to the preconcentration and determination of Cu(II) for various real samples.

Removal and Recovery of UO2(??) from Water Samples Using 2,2′‐Diamino‐4,4′‐bithiazole as a New Reagent for Solid Phase Extraction

AbstractA novel sensitive and simple method for rapid and selective extraction, preconcentration and determination of uranyl as its 2,2′‐diamino‐4,4′‐bithiazole (DABTZ) complex by using octadecylsilica columns and spectrophotometry is presented. Extraction efficiency and the influence of flow rates of sample solution and eluent, pH, amount of DABTZ, type and least amount of eluent for elution of uranyl complex from columns, break‐through volume and limit of detection were evaluated. Also the effects of various cationic and anionic interferences on percent recovery of uranyl were studied. Average extraction efficiency of ca. 90% was obtained by elution of the column with minimal amount of solvent in the presence of interferences. The average preconcentration factor, 136 and a detection limit 0.32 ng·mL−1 were obtained. The method was applied to the recovery and determination of uranyl in different water samples.

Solid phase extraction of copper(II) ions using C18-silica disks modified by oxime ligands

5-Tert-butyl-2-hydroxy-benzaldehyde oxime ( L 1 ) and 3,5- di-tert-butyl-2-hydroxy-benzaldehyde oxime ( L 2 ) are synthesized and characterized by conventional spectroscopic methods. These ligands are used as modifier of octadecyl silica membrane disks for separation and pre-concentration of trace amounts of copper(II) ions, followed by sulfuric or nitric acid elution and flame atomic absorption spectrometric (FAAS) determination. The effect of parameters influencing the extraction efficiency i.e. pH of sample solutions, amount of the oxime, type and volume of eluent, sample solution and eluent flow rates were evaluated. Under optimum experimental conditions, the maximum capacity of the membrane disks modified by 6 mg of L 1 or 4 mg of L 2 was found to be 284.7 (±2.8) μg of copper and 382.5 (±3.1) μg of copper, respectively. The detection limits of the presented methods are 0.29 ng ml −1 for L 1 and 0.25 ng ml −1 for L 2 . The enrichment factors are greater than 400 for both cases. These methods were successfully applied to the extraction, recovery and detection of copper in different water samples.

Spectrophotometric Determination of Malachite Green Residue in Water Samples After Preconcentration on Surfactant-Coated Alumina

ABSTRACT A new, simple, and reliable method for rapid preconcentration of trace levels of malachite green from water samples is developed using a sodium dodecyl sulfate coated alumina solid phase. The effects of pH, flow rate of sample solution, and foreign ions on the sorption of malachite green have been investigated. Two micrograms of malachite green from 250 mL of aqueous phase could be quantitatively extracted into a 500 mg of SDS coated alumina. The collected malachite green molecules were eluted with 2 mL of acetonitrile and determined spectrophotometrically at 617 nm. The detection limit corresponding to three times of the standard deviation of the blank was found to be 3.2 µg L−1. The proposed method was used for the separation and preconcentration of malachite green with high enrichment factor (about 250) from water samples.

Flame atomic absorption spectrometric determination of copper, zinc and manganese after solid-phase extraction using 2,6-dichlorophenyl-3,3-bis(indolyl)methane loaded on Amberlite XAD-16

A simple and selective method for the determination of Cu2+, Zn2+ and Mn2+ ions in real samples by FAAS after solid-phase extraction was developed. The method is based on the sorption of metal ions on Amberlite XAD-16 modified by 3-((2,6-dichlorophenyl)(1H-indol-3-yl)methyl)-1H-indole (DCPIMI) at a pH of 5.0. The metal ions retained on solid phase by complexation with ligand were then eluted with 6mL of 4molL−1 nitric acid in acetone. In order to obtain a reversible uptake and elution of metal ions, the influence of flow rates of eluent and sample solution, ligand concentration and amount of surfactant and condition of elution solution was also investigated. A preconcentration factor of 225 was achieved by passing 1350mL of sample through the solid phase, while the limit of detection (LOD) of Cu2+, Zn2+ and Mn2+ ions were found to be 1.9, 1.5 and 2.6ngmL−1, respectively, and the corresponding precision at 20μgL−1 was 2.1%, 2.3%, 3.0%.

Flame atomic absorption spectrometry for the determination of trace amount of rhodium after separation and preconcentration onto modified multiwalled carbon nanotubes as a new solid sorbent

The present article reports on the application of modified multiwalled carbon nanotubes (MMWCNTs) as a new, easily prepared and stable solid sorbent for the preconcentration of trace rhodium ion in aqueous solution. Rhodium ions were complexed with 1-(2-pyridylazo)-2-naphthol (PAN) in the pH range of 3.2–4.7 and then the formed Rh-PAN complex was adsorbed on the oxidized MWCNTs. The adsorbed complex was eluted from MWCNTs sorbent with 5.0 mL of N,N-dimethylformamide (DMF). The rhodium in eluted solution was determined by flame atomic absorption spectrometry (FAAS). Linear range for the determination of rhodium was maintained between 0.16 ng mL −1 and 25.0 μg mL −1 in initial solution. Relative standard deviation for the 10 replicated determination of 4.0 μg mL −1 of rhodium was ±0.97%. Detection limit was 0.010 ng mL −1 in initial solution (3S bl, n = 10) and preconcentration factor was 120. Sensitivity for 1% absorbance of rhodium (III) was 0.112 μg mL −1. The sorption capacity of oxidized MWCNTs for Rh (III) was 6.6 mg g −1. The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type, breakthrough volume and interference ions were studied for the preconcentration of Rh 3+. The proposed method was successfully applied to the extraction and determination of rhodium in different samples.

Preconcentration of beryllium via octadecyl silica gel microparticles doped with aluminon, and its determination by flame atomic absorption spectrometry

A simple and sensitive method is presented for solid phase extraction (SPE) and preconcentration of trace quantities of beryllium using octadecyl silica gel modifed with aurin tricarboxylic acid (aluminon). Beryllium is then determined by flame atomic absorption spectroscopy. Parameters affecting SPE such as pH, sample solution and eluent flow rate, type, concentration and volume of eluent, interfering ions and breakthrough volume, were investigated. Under optimal conditions, the beryllium ions were retained on the sorbent at pH 6–6.7, while 3.0 mL of 0.05 mol L−1 HNO3 is sufficient to elute the ions. The limit of detection (LOD) based on 3σ was 0.8 µg L−1 for 250 mL sample solution and 5 mL 0.05 mol L−1 HNO3 as eluent. The LOD can reach 0.1 µg L−1 for 1 L sample solution and 3 mL of 0.05 mol L−1 HNO3. The accuracy and precision (RSD %) of the method is >90% and <10%, respectively. The method was applied to the determination of beryllium in aqueous samples.

Simultaneous trace multielement determination by ICP-OES after solid phase extraction with modified octadecyl silica gel

Multielement simultaneous determination of 35 trace elements in environmental samples was carried out by inductively coupled plasma emission spectrometry (ICP-OES) after preconcentration with octadecyl silicagel, modified with aurin tricarboxylic acid (Aluminon). Optimal experimental conditions including pH of sample solution, sample volume, sample and eluent flow rate, type, concentration and volume of eluent and foreign ions effect were investigated and established. Trace element ions in aqueous solution were quantitatively adsorbed onto octadecyl silicagel modified with aurin tricarboxylic acid at pH 8.0 with a flow rate of 11.0 mL min −1. The adsorbed element ions were eluted with 3–5 mL of 0.5 mol L −1 HNO 3 at a flow rate of 10.0 mL min −1 and analyzed by ICP-OES simultaneously. The proposed method has at least preconcentration factor of 100 in water samples, which results high sensitive detection of ultra-trace and trace analysis. The present methodology gave recoveries better than 70% and RSD less than 16%.

Indirect speciation of Cr(III) and Cr(VI) in water samples by selective separation and preconcentration on a newly synthesized chelating resin

A new solid phase extraction method for the speciation, separation and preconcentration of Cr(III) and Cr(VI) was developed. As solid phase material, a new chelating resin, poly N-(4-bromophenyl)-2-methacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid-co-divinylbenzene was synthesized. Cr(III) was separated from Cr(VI) and preconcentrated by using a column containing chelating resin. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by hydroxylamine hydrochloride as a reducing agent. Then Cr(VI) was calculated by substracting Cr(III) concentration from the total chromium concentration. The parameters such as the effect of pH, eluent type, volume and concentration, flow rate of sample solution, sample volume and effect of interfering ions for the preconcentration of Cr(III) were investigated. The optimum pH was found to be 2. Eluent for quantitative elution was 10 mL of 1 mol L −1 HCl. The preconcentration factor of the method was 100. At the optimum conditions determined experimentally, the recovery for Cr(III) was found to be 95 ± 3%. The limit of detection (3 s/ b) of the method was 1.58 μg L −1. In order to determine the adsorption behaviour of chelating resin, the adsorption isotherm of Cr(III) was studied. Adsorption capacity and binding equilibrium constant were calculated to be 21.8 mg g −1 and 1.32 ×10 −2 L mg −1, respectively. The method was validated by analysing certified reference material (TMDA-54.4 a trace element fortified calibration standard). The proposed method was applied to the determination and speciation of chromium in tap water, lake water, spring water and wastewater samples with satisfactory results.

Pre-concentration of ultra trace amounts of copper, zinc, cobalt and nickel in environmental water samples using modified C18 extraction disks and determination by inductively coupled plasma–optical emission spectrometry

A highly sensitive and accurate method for pre-concentration and determination of ultra trace amounts of zinc, copper, cobalt and nickel ions in environmental water samples is proposed. The method is based on the solid phase extraction of these ions on C18-bonded silica extraction disks modified with a novel Schiff base 2,2′-[1,6-hexanediyl bis (nitriloethylidine)]bis-1-naphthol (HDN). The retained ions on the prepared solid phase was eluted with 10 mL 0.01 M nitric acid and measured by inductively coupled plasma–optical emission spectrometry. The extraction efficiency and the influence of the type and least amount of eluent for the stripping of ions from the disks, pH, flow rates of sample solution and eluent, amount of HDN, effect of other ions and breakthrough volume were evaluated. The limits of detection of the method were 0.2, 0.2, 0.8 and 0.6 µg L−1 for zinc, copper, cobalt and nickel, respectively and an enrichment factor of 100 was obtained. The proposed method was applied for determination of zinc, copper, cobalt and nickel ions in some natural and synthetic water samples with satisfactory results.

2-Mercaptobenzothiazole이 내포된 p-Dichlorobenzene 미세결정으로 예비농축시킨 후 Cd(II) 정량

실제 시료에 들어있는 흔적량 Cd(II)를 2-mercaptobenzothiazole이 내포되어 있는 미세결정 p-dichlorobenzene에 예비농축시킨 후 정량하는 감도좋은 방법을 개발하였다. 시료 용액의 pH, 킬레이트제 2-mercaptobenzothiazole의 양, 흡착제 p-dichlorobenzene-2-MBT의 양 그리고 시료 용액의 흐름속도 등 여러 실험조 건을 최적화하였다. 여러 공존이온에 대한 방해효과를 조사하였는데 다른 이온들보다 Cu(II)가 비교적 심하게 방해를 하였다. 그러나 Cu(II)에 의한 방해는 시료용액의 tartrate 이온의 농도를 0.01 M이 되게 하든지 또는 0.20 g의 p-dichlorobenzene에 내포된 2-mercaptobenzothiazole의 양을 0.08 g에서 0.12 g이 되게 하면 충분히 없앨 수 있었다. 이 방법에 의해 얻어진 직선 감응범위, 상관계수(<TEX>$R^2$</TEX>) 및 검출한계는 각각 0.5-30 ng <TEX>$mL^{-1}$</TEX>, 0.9962, 및 0.39 ng <TEX>$mL^{-1}$</TEX>로서, p-dichlorobenzene을 흡착제 매질로 이용하여 매우 좋은 결과를 얻었다. 이 방법을 실제 시료에 적용할 수 있을지를 확인하기 위해 수용액 시료(폐수, 시냇물, 그리고 저수지물)와 플라스틱 시료에 응용하였다. 회수율은 93-104% 정도였으며, ICP-MS를 이용하여 얻은 값과 이 방법으로 얻은 값은 F 시험법에 의하면 95% 신뢰수준에서 차이가 없는 것으로 나타났다. 실험 결과들로부터 이 방법은 여러 실제 시료에 들어있는 Cd(II)을 농축 정량하는데 응용할 수 있음을 알 수 있었다. A sensitive technique for the determination of trace Cd(II) in various real samples after preconcentration onto microcrystalline p-dichlorobenzene loaded with 2-mercaptobenzothiazole was developed. Several experimental conditions such as the pH of the sample solution, the amount of chelating agent 2-mercaptobenzothiazole, the amount of adsorbent p-dichlorobenzene-2-MBT, and the flow rate of sample solution were optimized. The interfering effects of various concomitant ions were investigated. Cu(II) interfered with more seriously than any other ions. However, the interference by Cu(II) could be overcome sufficiently by adjusting tartrate ion concentration to be 0.01M or by controlling the amount of 2-mercaptobenzothiazole contained in 0.20 g p-dichlorobenzene to be 0.12 g. The dynamic range, the correlation coefficient (<TEX>$R^2$</TEX>) and the detection limit obtained by this proposed technique were <TEX>$0.5{\sim}30$</TEX> ng <TEX>$mL^{-1}$</TEX>, 0.9962, and 0.39 ng <TEX>$mL^{-1}$</TEX>, respectively. Thus, good results were obtained by the use of p-dichlorobenze as adsorbent matrix. For validating this proposed technique, the aqueous samples(wastewater, stream water, and reservoir water) and the plastic sample were used. Recovery yields of <TEX>$93{\sim}104$</TEX> % were obtained. By F test, these measured data were not different from ICP-MS data at 95 % confidence level. Based on the results from the experiment, it was found that this proposed technique could be applied to the preconcentration and determination of Cd(II) in various real samples.

Solid phase extraction of Pd(II) on a newly synthesized chelating resin prior to determination by flame atomic absorption spectrometry

A new solid phase extraction method for the separation and preconcentration of Pd(II) was developed. As solid phase material, a new chelating polymer, poly [N-(4-bromophenyl)-2-methacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid - co-divinylbenzene] was synthesized. The parameters such as the effect of pH, eluent type, volume and concentration, flow rate of sample solution, sample volume and effect of interfering ions for the preconcentration of Pd(II) were investigated. The optimum pH was found to be 9. Eluent for quantitative elution was 10 mL of 1 mol L−1 HCl. The preconcentration factor of the method was 75. At optimum conditions, the recovery for Pd(II) was found to be 101 ± 4%. The limit of detection (3σ) was 1.1 µg L−1. The method was applied to the determination of palladium in tap water and converter samples with satisfactory results.

Synthesis of nano B 2O 3/TiO 2 composite material as a new solid phase extractor and its application to preconcentration and separation of cadmium

A new solid phase extractor, nano-scale diboron trioxide/titanium dioxide composite material, was synthesized and used for separation and/or preconcentration of trace cadmium ion from various samples. The characterization of the synthesized material was performed by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffractometer methods (XRD). The specific surface area of the material was also determined and found as 3.4 m 2/g. Analytical parameters including pH of sample solution, sample volume, flow rate of sample solution, volume and concentration of eluent for the column solid phase extraction (SPE) procedure were examined. The effect of common matrix ions on the recovery of the cadmium has also been investigated and found that they did not interfere on cadmium preconcentration. Under the optimum experimental conditions, preconcentration factor and analytical detection limit were determined as 50 and 1.44 μg/L, respectively. The reusability (stabile up to 100 run) and adsorption capacity (49 mg/g) of the sorbent were excellent. The accuracy of the method was confirmed by analyzing certified reference materials (Tea leaves GBW-07605). The results demonstrated good agreement with the certified values (relative error <10%). The precision of the method was also satisfactory. The recovery of cadmium under the optimum conditions was found to be 96 ± 3% at 95% confidence level. The method was applied for the determination of cadmium in tap water and tea leaves.

Separation and preconcentration of uranium(VI) from aqueous samples using a surfactant-coated alumina modified with meloxicam

A new simple and reliable method for the separation, and preconcentration of trace levels of ions from water samples is developed using a modified sodium dodecyl sulphate (SDS) coated alumina solid phase. The effects of pH, flow rate of sample solution, and foreign ions on the sorption of uranium have been investigated. Twenty micrograms of ions from 1000 mL (pH 5) of aqueous phase could be quantitatively extracted into 1.5 g of meloxicam modified SDS coated alumina. The preconcentration could be made selective to ions by using EDTA as masking agent for transition metal ions and Th(IV). The collected ions were eluted out with 2 mL of HCl solution (1 M) and determined spectrophotometrically using arsenazo(III) as chromogenic reagent. The detection limit corresponding to three times the standard deviation of the blank was found to be 0.52 µg L−1. The relative standard deviation for recovery of 1.0 µg L−1 of ions from water sample (1000 mL) was 3.2% (n = 5). The proposed method was used for the separation of uranium ions from various water samples.

LC Determination of Phthalate Esters in Water Samples Using Continuous-Flow Microextraction

A novel method, continuous-flow microextraction (CFME) combined with liquid chromatography (LC) with variable-wavelength detector (VWD), has been developed for the determination of three phthalate esters (dimethyl phthalate (DMP), diethyl phthalate (DEP), and di-n-butyl phthalate (DnBP)) in water samples. Experimental parameters including extraction solvent, solvent drop volume, flow rate of sample solution, extraction time and ionic strength, which affected the extraction efficiency, were studied and optimized. Under the optimum extraction conditions, the method yields a linear calibration curve in the concentration range of 10–10,000 ng mL -1 for target analytes. The enrichment factors of this method for DMP, DEP and DnBP reached at 27, 44 and 20, respectively, and the detection limits were 2, 1 and 5n g mL -1 , respectively. Good repeatability of extraction was obtained with relative standard deviations below 8.6%. The results demonstrated that CFME followed by LC-VWD is a simple and reliable technique for the determination of phthalate esters in water samples.

Separation and preconcentration of cadmium ions using octadecyl silica membrane disks modified by methyltrioctylammonium chloride

A simple and selective method for the determination of cadmium in water samples by FAAS after solid phase extraction has been developed. The method is based on the sorption of cadmium as CdI 4 2− on octadecyl silica membrane disks modified by cationic surfactant of methyltrioctylammonium chloride in the pH range of 1–8. The sorbed cadmium is then eluted with 10 ml of 1 mol l −1 nitric acid in ethanol and is measured by flame atomic absorption spectrometry. The influence of flow rates of eluent and sample solution, iodide concentration and amount of surfactant in retention and elution of cadmium from disks was also investigated. A preconcentration factor of 100 was achieved by passing 1000 ml of sample through the membrane disk. The limit of detection (LOD) of cadmium was found to be 0.014 ng ml −1. Precision at 2.5 μg l −1 was 1.2% ( n = 8). The method was successfully applied to the determination of cadmium in some natural water samples. The accuracy was assessed through recovery experiment, independent analysis by graphite furnace atomic absorption spectrometry, and analysis of certified reference waters.