Solid-Phase Extraction and Spectrophotometric Determination of Molybdenum(VI) in Soil and Plant Samples as a Mo(V)-Thiocyanate Complex

A method for the preconcentration and determination of molybdenum(VI) in soil and plant samples using Amberlite XAD-7 resin and spectrophotometry is proposed. Molybdenum was preconcentrated as its Mo(V)-thiocyanate complex using a column containing Amberlite XAD-7 resin and determined spectrophotometrically at 461.0nm in acetone after elution. We investigated several parameters that affect the recovery of molybdenum, such as acidity, amount of reducing and complexing agents, flow rates, volume of sample solution, type and amount of eluent, and the presence of diverse ions. The limit of detection of the proposed method was 38µgL^–1 of molybdenum. The recovery of molybdenum was 98.25±0.05 at 95% confidence level. The highest preconcentration factor was 100 for 250mL of sample volume. The proposed method was applied to soil and plant samples, and molybdenum was determined with a relative error of <3.5%.     

Sensitized multiphoton dissociation of UF6 IN SF6-UF6 mixtures by a tea CO2 laser

UF₆ undergoes decomposition in the presence of SF₆ when mixtures of both are irradiated with a TEA CO₂ laser. The mechanism for UF₆ decomposition may involve vibrational energy transfer from excited SF₆ and laser absorption from the same laser pulse by excited UF₆ in its vibrational quasi-continuum     

Speciation of Cr(III) and Cr(VI) in water after preconcentration of its 1,5-diphenylcarbazone complex on amberlite XAD-16 resin and determination by FAAS

A simple and sensitive method for the speciation, separation and preconcentration of Cr(VI) and Cr(III) in tap water was developed. Cr(VI) has been separated from Cr(III) and preconcentrated as its 1,5-diphenylcarbazone complex by using a column containing Amberlite XAD-16 resin and determined by FAAS. Total chromium has also been determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with KMnO₄. Then, Cr(III) has been calculated by subtracting Cr(VI) from the total. The effect of acidity, amount of adsorbent, eluent type and flow rate of the sample solution on to the preconcentration procedure has been investigated. The retained Cr(VI) complex was eluated with 10 ml of 0.05 mol l⁻¹ H₂SO₄ solution in methanol. The recovery of Cr(VI) was 99.7±0.7 at 95% confidence level. The highest preconcentration factor was 25 for a 250 ml sample volume. The detection limit of Cr(VI) was found as 45 μg l⁻¹. The adsorption capacity of the resin was found as 0.4 mg g⁻¹ for Cr (VI). The effect of interfering ions has also been studied. The proposed method was applied to tap water samples and chromium species have been determined with the relative error <3%.     

Amberlite XAD-4 functionalized with succinic acid for the solid phase extractive preconcentration and separation of uranium(VI)

Amberlite XAD-4 resin has been functionalized with succinic acid by coupling it with dibromosuccinic acid after acetylation. The resulting resin has been characterized by FT-IR, elemental analysis and TGA and has been used for preconcentrative separation of uranium(VI) from host of other inorganic species prior to its determination by spectrophotometry. The optimum pH value for quantitative sorption of uranium(VI) in both batch and column modes is 4.5-8.0 and desorption can be achieved by using 5.0 ml of 1.0 mol l⁻¹ HCl. The sorption capacity of functionalized resin is 12.3 mg g⁻¹. Calibration graphs were rectilinear over the uranium(VI) concentrations in the range 5-200 μg l⁻¹. Five replicate determinations of 50 μg of uranium(VI) present in 1000 ml of solution gave a mean absorbance of 0.10 with a relative standard deviation of 2.56%. The detection limit corresponding to three times the standard deviation of the blank was found to be 2 μg l⁻¹. Various cationic and anionic species at 200-fold amounts do not interfere during the preconcentration of 5.0 μg of uranium(VI) present in 1000 ml (batch) or 100 ml (column) of sample solution. Further, adsorption kinetic and isotherm studies were also carried out by a batch method to understand the nature of sorption of uranium(VI) with the succinic acid functionalized resin. The accuracy of the developed solid phase extractive preconcentration method in conjunction with Arsenazo III procedure was tested by analyzing marine sediment (MESS-3) and soil (IAEA soil-7) reference material. Further, the above procedure has been successfully employed for the analysis of soil and sediment samples.     

Column Solid-Phase Extraction with 2-Acetylmercaptophenyldiazoaminoazobenzene (AMPDAA) Impregnated Amberlite XAD-4 and Determination of Trace Heavy Metals in Natural Waters by Flame Atomic Absorption Spectrometry

A column solid-phase extraction (SPE) preconcentration method was developed for the determination of Cd, Co, Cu, Ni and Zn ions in natural water samples by flame atomic absorption spectrometry. The procedure is based on the retention of analytes in the form of 2-acetylmercaptophenyldiazoaminoazobenzene (AMPDAA) complexes on a short column of AMPDAA-XAD-4 resin from buffered sample solution and subsequent elution with hydrochloric acid plus sodium chloride. Important SPE parameters were optimized using model solutions. The loading half-time, t_1/2, for Cd, Co, Cu and Zn was found to be less than 5min, and for Ni the value was 12min. The detection limit for Cd, Co, Cu, Ni and Zn was 0.028, 0.064, 0.042, 0.023 and 0.16µgL^–1, respectively, and the quantification limit was 0.043, 0.11, 0.099, 0.044 and 0.29µgL^–1, respectively. The AMPDAA-XAD-4 resin has good selectivity for Cd, Co, Cu, Ni and Zn over several electrolytes, especially over earth alkaline metals with tolerance limits of 0.05molL^–1. The method was validated by analysing a standard reference material (GBW 08301), and it was found that the results agree with those quoted by the manufactures. The developed method was applied to the determination of trace metal ions in tap water and river water samples with satisfactory results.     

Determination of trace heavy metals in waters by flame atomic absorption spectrometry after preconcentration with 2,4-dinitrophenyldiazoaminoazobenzene on Amberlite XAD-2

A new column, solid-phase extraction (SPE), preconcentration method was developed for determination of Cd, Co, and Cu ions in natural water samples by flame atomic absorption spectrometry. The procedure is based on the retention of analytes in the form of 2,4-dinitrophenyldiazoaminoazobenzene (DNDAA) complex on a mini column of DNDAA-XAD-2 resin. The effects of pH, eluent type, eluent concentration, eluent volume, resin quantity, sample volume, sample flow rate, and matrix ions (Na, Ca, and Mg) were investigated on the recovery of the metals using model solutions. The detection limit for Cd, Co, and Cu was 0.062, 0.084, and 0.057 μg L⁻¹ and the quantification limit was 0.17, 0.24, and 0.12 μg L⁻¹ respectively. The method was validated by the analysis of a certified reference material with the results being in agreement with those quoted by manufactures. The developed method was applied to the determination of trace metal ions in tap water, river water samples with satisfactory results.     

ADSORPTION OF CHLOROFORM AND TRICHLOROETHYLENE IN WATER WITH A NEW KIND OF HYPERCROSSLINKED RESINS

In this paper two newly developed hypercrosslinked resins were used to treat micropolluted drinking water and their static and kinetic adsorption were investigated at 293 K. The results show that these two adsorbents are superior to Amberlite XAD-4 for removing chloroform and trichloroethylene in aqueous solutions. The breakthrough capacity and the total capacities from mini-column adsorption studies for chloroform and trichloroethylene on XAD-4, ZH-01 and ZH-00 are calculated respectively under experimental conditions     

Facile one-step sonochemical synthesis of ultrafine and stable fluorescent C-dots

This work describes a one-step synthesis of carbon dots (C-dots), which is carried out by sonication of polyethylene glycol (PEG-400) for 0.5–3 h. The effect of the various experimental parameters, such as sonication time, amplitude and temperature on the size and the fluorescence of the C-dots was studied. It was found that the average diameter of the C-dots is between 2 and 9 nm, depending on the preparation conditions. The highest quantum yield of emission was ∼16%. These high fluorescence properties of the C-dots could be used for bioimaging and for solar cell applications.     

A rapid,mild, and efficient method for C-5 iodination/thiocyanation of 2-aminothiazoles

An efficient, green, rapid multitasking protocol for the selective C-5 substitution of 2-aminothiazole using iodic acid and aqueous PEG-400 was developed. The method found suitable for C-5 substitution i.e. iodination and thiocyanation of 2-amino thiazole using iodine and ammonium thiocyanate respectively. Iodic acid was found to be a good oxidant and aqueous PEG-400 as green reaction solvent.     

磷酸可待因在安伯来特IRP-69上的离子交换平衡特性研究

采用批式离子交换法研究了磷酸可待因在安伯来特IRP-69上的离子交换平衡特性、动力学及热力学特征.结果表明,在3个温度(298K、308K和318K)及研究的浓度范围内,离子交换吸附等温方程和Freundlich方程都能够对磷酸可待因在安伯来特IRP-69上的离子交换平衡等温线进行很好的拟合,其离子交换动力学特征基本符合二级动力学方程.磷酸可待因在安伯来特IRP-69上的离子交换行为的热力学参数(ΔH、ΔG、ΔS)都小于0.在3个温度(298K、308K和318K)下,同一初始浓度(350mmol/L)的磷酸可待因在安伯来特IRP-69上的平衡交换吸附量分别为1.1295mmol/g、1.1203 mmol/g和1.1129 mmol/g.