One-pot synthesis of magnetic iron oxide nanoparticle-multiwalled carbon nanotube composites for enhanced removal of Cr(VI) from aqueous solution.

Magnetic nanoparticle-multiwalled carbon nanotubes composites (MNP/MWCNTs) were prepared using 1,6-hexanediamine functionalized Fe3O4 nanoparticles (MNP) linked to carboxylic MWCNTs by facile one-pot solvothermal synthesis for highly efficient removal of Cr(VI) from aqueous solution. The easily obtained magnetic nanocomposites were systematically characterized, and several major factors affecting the adsorption-based removal were investigated, including solution pH, adsorbent dosage, temperature and contact time. The removal efficiency was highly dependent on solution pH; low pH facilitated removal with the maximum efficiency at pH 2.0. The adsorption isotherm was well fitted with the Langmuir isotherm model and the adsorption capacity increased with the temperature increasing. The adsorption kinetic data could be well described by the pseudo-second-order and the intraparticle diffusion models, indicating that the intraparticle diffusion was not the only rate-limiting step. The MNP/MWCNTs displayed excellent selectivity and high anti-interference ability toward Cr(VI) when confronted with commonly coexisting ions. By using an external magnetic field, the exhausted MNP/MWCNTs could be readily separated from the solution after adsorption of Cr(VI) and well regenerated, and could keep about 80% removal efficiency in the fifth adsorption-desorption cycle. The simple, rapid and reliable MNP/MWCNT-based method proved to be a cost-effective, convenient and potentially applicable way to targeted pollutant removal and wastewater treatment.

Multi-template imprinted polymers for simultaneous selective solid-phase extraction of six phenolic compounds in water samples followed by determination using capillary electrophoresis.

Novel multi-template molecularly imprinted polymers (mt-MIPs) with six phenolic compounds as the template, namely phenol, 4-chlorophenol (4-CP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,4-dichlorophenol (2,4-DCP), 2-chlorophenol (2-CP) and 2,6-dichlorophenol (2,6-DCP), were prepared by precipitation polymerization and used as the adsorbents of solid-phase extraction (SPE), and coupled with capillary electrophoresis (CE) for the simultaneous selective extraction, separation and determination of trace phenolic compounds in water samples. The resultant mt-MIPs exhibited uniform spherical morphology, large specific surface area and high thermal stability, and offered high selectivity towards the six template phenolic compounds. Various parameters affecting the molecularly imprinted SPE (MISPE) efficiency were investigated in detail, and excellent CE separation was realized within 7min. Good linearity was obtained in the range of 1-200µgL-1 for phenol and 4-CP, and 1-300µgL-1 for 2,4,6-TCP, 2,4-DCP, 2-CP and 2,6-DCP. High sensitivity was attained with low limits of detection and quantification ranging from 0.17 to 0.31µgL-1 and 0.57 to 1.03µgL-1, respectively. Satisfactory recoveries for spiked reservoir water, river water, tannery wastewater and tap water samples were achieved in the range of 82.13-105.63% with relative standard deviations within 1.68-6.96%. The developed MISPE-CE method proved practically feasible for simultaneous selective extraction/enrichment, separation and sensitive determination of multiple targets in complicated aqueous matrices.

Molecularly imprinted polymers for dispersive solid-phase extraction of phenolic compounds in aqueous samples coupled with capillary electrophoresis.

A simple and sensitive method for the simultaneous determination of seven phenolic compounds in aqueous samples was developed by dispersive solid-phase extraction (DSPE) coupled with capillary electrophoresis (CE), namely phenol, 4-chlorophenol (4-CP), pentachlorophenol (PCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,4-dichlorophenol (2,4-DCP), 2-chlorophenol (2-CP) and 2,6-dichlorophenol (2,6-DCP). Molecularly imprinted polymers (MIPs) prepared by precipitation polymerization with 2,4,6-trichlorophenol (2,4,6-TCP) as template were used as DSPE sorbents to selectively adsorb the phenols. Various parameters affecting the extraction efficiency were evaluated and excellent CE separation was achieved within 13.5 min by using 15 mmol/L borate buffer containing 15% (v/v) methanol at pH = 9.8. Under the optimized conditions, good linearity was obtained in the range of 2-200 µg/L for phenol, 2,4-DCP and 2,6-DCP, 2-300 µg/L for 4-CP and 2-CP, 1.5-150 µg/L for PCP, and 2-400 µg/L for 2,4,6-TCP, with the correlation coefficient (R2 ) higher than 0.9938. Limits of detection and limits of quantification were in the range of 0.18-0.44 µg/L and 0.59-1.45 µg/L, respectively. The developed MIPs-DSPE-CE method was also successfully applied to determine the seven phenolic compounds in lake, tap, seawater and tannery wastewater. The average recoveries at three different spiked levels ranged from 70.75 to 106.7% with the relative standard deviations of 1.15-6.28%.

Online spectrophotometric determination of Fe(II) and Fe(III) by flow injection combined with low pressure ion chromatography.

A simple and new low pressure ion chromatography combined with flow injection spectrophotometric procedure for determining Fe(II) and Fe(III) was established. It is based on the selective adsorption of low pressure ion chromatography column to Fe(II) and Fe(III), the online reduction reaction of Fe(III) and the reaction of Fe(II) in sodium acetate with phenanthroline, resulting in an intense orange complex with a suitable absorption at 515nm. Various chemical (such as the concentration of colour reagent, eluant and reductive agent) and instrumental parameters (reaction coil length, reductive coil length and wavelength) were studied and were optimized. Under the optimum conditions calibration graph of Fe(II)/Fe(III) was linear in the Fe(II)/Fe(III) range of 0.040-1.0mg/L. The detection limit of Fe(III) and Fe(II) was respectively 3.09 and 1.55µg/L, the relative standard deviation (n=10) of Fe(II) and Fe(III) 1.89% and 1.90% for 0.5mg/L of Fe(II) and Fe(III) respectively. About 2.5 samples in 1h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of water samples.

Multiresidue Determination of ß2-Agonists Including Phenylethanolamine A in Animal-Derived Food by Ultra-High Performance Liquid Chromatography/Tandem Mass Spectrometry.

A comprehensive ultra-high performance liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS) procedure for detection of nine ß-agonists in animal-derived food is described. The method was based on enzymatic hydrolysis with ß-glucuronidase from Helix pomatia, followed by a liquid-liquid extraction procedure with perchloric acid and a solid-phase extraction scheme using two kinds of cartridges, HLB and MCX. The influence of sample solution pH in the extraction recovery was studied, and pH 4.0 was found to give the best recovery. The analytes were eluted with methanol containing 4% ammonia. A validation procedure for quantitative analysis of ß-agonists in animal-derived food was performed. The three kinds of internal standards, d3-salbutamol, d6-ractopamine and d9-clenpenterol, were applied in the sample preparation and detection of UHPLC/MS/MS. The recoveries from spiked samples ranged between 74.9 and 106.9%. The relative standard deviations of detection were at 0.7-9.6%. The limits of detection and quantification were 0.01-0.05 and 0.03-0.20 µg/kg, respectively. The effect of sample matrix in the detection was discussed in detail.

Simultaneous determination of Cr(III) and Cr(VI) in tannery wastewater using low pressure ion chromatography combined with flow injection spectrophotometry.

Trivalent and hexavalent chromium have been successfully separated and determined using low pressure ion chromatography combined with flow injection spectrophotometric analysis (LPIC-FIA). A column packed with crosslinking starch microspheres was used for on-line separation of Cr(III) from Cr(VI) in a flow-injection system because of its absorptive effect on Cr(III). To determine the concentration of Cr(III) and Cr(VI) in samples, we used 3.0 mmol/L nitric acid to elute adsorbed Cr(III) from the column and then used ceric sulfate-sulfuric acid as oxidant to convert all Cr(III) into Cr(VI). Then, Cr(VI) directly came from the samples and Cr(VI) came from Cr(III) successively formed a amaranthine complex with diphenycarbazide and the complex shows a maximum absorption at 530 nm. Analytical parameters including the concentration of eluent and oxidant solution, oxidizing temperature, length of oxidizing reaction coil, reaction coil and injection coil, interfering effects, etc., were optimized. The limit of detection was 1.25 µg/L for Cr(VI) and 3.76 µg/L for Cr(III). The linear relationship between absorption with the concentration of Cr(VI) and Cr(III) was 0.001-1.000 mg/L and 0.030-1.000 mg/L with correlation coefficients of 0.9995 and 0.9994, respectively. The relative standard deviation of Cr(VI) and Cr(III) was 1.21% and 1.66%, respectively (n=10). Major cations and anions did not show any interference. We validated this method through certified reference materials and through measuring the recovery in tannery wastewater.

The determination of trace lead in drinking water by flow injection spectrophotometry.

Lead is the non-essential trace element in the human body, and it has been confirmed that drinking water is one of the sources of lead in human body. In the research, based on the sensitive colour reaction of lead with I(-)-EV(+)-PVA, a simple, sensitive, accurate and portable method for the determination of trace lead in drinking waters was proposed. Chemicals and physicals had been optimized in detail. The apparent molar absorption coefficient was up to 7.4x10(5) mol L(-1) cm(-1). The developed method provided a linearity range over 5-80 microg L(-1). The regression deviation was between 0.71% and 2.33%. The 3sigma detection limit was 0.9 microg L(-1). Close to the quantitation limit for the analyte the relative standard deviation was 1.10% (n=10) at 40 microg L(-1). The method developed here for analysis of lead yielded results that were comparable with those of the GFAAS.

[Determination of aniline in water by flow injection spectrophotometry].

A new flow injection analysis spectrophotometric method for the determination of aniline in water sample was introduced. It is based on the chromogenic-reaction of diazotization-coupling with 1-naphthol in basic media, and coupled with the flow injection analysis for the determination of aniline. The absorbance intensity was registered in this reaction solution at 495 nm. The volume of the sample loop, the length of the reacting coil and chromogenic coil, the flow rate of reagent, the reagent concentrations of H2 SO4, NaNO2, NaOH and 1-naphthol, and the effect of coexistence ions were studied. The calibration graph is linear in the range of 0.005-2.0 mg x L(-1). The detection limit is 0.001 mg x L(-1), and the RSD was 0.7% (c = 0.25 mg x L(-1), n = 11). The proposed method is simple, accurate, sensitive and rapid, and was successfully applied to the determination of aniline in tannery wastewater with the recoveries in the range of 98.0%-103.0%.

Online preconcentration and determination of trace amounts of zinc in nature waters.

A simple, sensitive, reliable and flexible flow injection spectrophotometric method is proposed for on-line preconcentration and determination of trace amounts of zinc in water. At the presence of Tween-80 in pH 9.3 buffer solutions, the shade of color of Zn (II)-PAN complex is in a linear relation to the zinc amount at the point of the maximum absorption peak of 560 nm. The optimal experimental conditions, including reaction conditions and preconcentration conditions, had been obtained. The linear range of the proposed method was between 2.0 and 360 mug L(-1) and the detection limit was 0.42 mug L(-1). The relative standard deviation was 3.55% and 2.14% for 5.0 mug L(-1) and 50 mug L(-1) of zinc standard solution (n = 8). The method had been successfully applied to zinc determination in water samples and the analytical results were satisfactory.

[Study on a new method for determining trace amounts of manganese (II) in water by flow-injection catalytic kinetic spectrophotometry].

An on-line supported flow-injection catalytic kinetic spectrophotometry new method for the determination of trace amounts of manganese(II) in water was developed. The method is based on the significant catalytic action of trace manganese on the fading reaction of potassium periodate and magneson I in the presence of nitrilotriacetic acid. The chemical and flow injection variables were optimized. The absorbance intensity was registered in this reaction solution at 560 nm. Under the optimum conditions, a standard curve with good linearity and broad linear range can be obtained in the range of 20-200 microg x L(-1), the linear equation is H(mV) = 0.170 5c (microg x L(-1))+0.125 2 (r = 0.999 3), the detection limit is 1.3 microg x L(-1), the relative standard deviation is 3.57% (n = 8), and the sampling frequency is 15 samples per hour. The interference of foreign iron was studied. Satisfied results were achieved with the proposed method to analyze the Mn(II) in river water, waste water and pond water, and the range of recovery was 96%-102%. This method is simple, rapid, sensitive, accurate, highly selective and suitable for automatic and continuous analysis.

The determination of potassium concentration in vitreous humor by low pressure ion chromatography and its application in the estimation of postmortem interval.

An analytical method was developed for the determination of potassium in vitreous humor by low pressure ion chromatography (LPIC). Experimental conditions for LPIC analysis were optimized. High sensitivity and selectivity were obtained using this method. The LOD and LOQ were 1 and 2 mmol l(-1), respectively. The linearity was demonstrated from 2 to 20 mmol l(-1). The intra- and inter-day precision (CV) based on three concentrations was less than 5.0%. It was a simple and fast method to measure potassium and was suitable for evaluating the postmortem interval (PMI) in relatively well-preserved bodies. Sixty-two samples from medical-legal autopsies with known PMI were analyzed. A linear correlation equation for potassium concentration in the vitreous humor and PMI was established: [K(+)]=0.1702PMI+5.5678, r=0.8692.

[The effect of entrapment of CpG sequence with cationic PLG nanoparticles on the immune responses of mice to pig paratyphoid vaccine].

Cationic PLG nanoparticles and liposome were prepared and used as package molecules to pack up pUC18-CpG. The effects of the packed pUC18-CpG on the cellular and humoral immune responses were detected in the mice that were inoculated with pig paratyphoid vaccine. The results showed that compared with the control, the amount of IgG and the titre of specific antibody were significantly increased in the sera of mice immunized with the CpG plasmid entrapped by cationic PLG nanoparticles; the proliferation and induced IL-2 bioactivity of lymphocytes were significantly enhanced in the spleen of the immunized mice; the stimulatory effect of cationic PLG nanoparticles was similar to or stronger than that of cationic liposome. These indicated that cationic PLG nanoparticle could be employed as an effective package molecule to promote the immunostimulatory effect of pUC18-CpG.

[On-line determination of transitional metal ions by low-pressure ion chromatography with chemiluminescence detection].

The separation and determination of five transitional metal ions, Co2+, Cu2+, Mn2+, Fe2+ and Cr3+ by low-pressure ion chromatography with chemiluminescence detection were investigated for the first time. The separation was carried out on a C3 ion chromatographic column by using a step gradient elution with the mobile phase of oxalic acid-citric acid solution. The five transitional metal ions could be separated simultaneously. Luminol-H2O2-Mn+ system was used as the flow injection chemiluminescence analytical system. Under the optimum conditions with 0.5 mmol.L-1 luminol, 0.05 mol.L-1 H2O2 and 0.020 mol.L-1 NaOH, the linear ranges (mg.L-1) for Co2+, Cu2+, Mn2+, Fe2+ and Cr3+ were 0.001-0.1, 0.1-6, 0.06-4, 0.03-5 and 0.025-1 respectively; the detection limit (microgram.L-1) for Co2+, Cu2+, Mn2+, Fe2+ and Cr3+ were 0.85, 85, 42, 21 and 20. The present method is simple, rapid, accurate and has been successfully applied to detect Co2+ in vitamin B12 and Co2+, Cu2+, Mn2+, Fe2+ and Cr3+ in human hair sample with satisfactory results, which were in good agreement with those from atomic absorption spectrometry.