Utilization of cloud-point extraction for colorimetric determination of trace amounts of thorium(iv) in real samples

Abstract

A cloud point extraction process using mixed micelle of the cationic surfactant CTAB and non-ionic surfactant Triton X-100 to extract thorium(IV) from aqueous solutions was investigated. The method is based on the color reaction of thorium with 5-(2`,4`-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (DMPAHPD) in the presence of potassium iodide in hexamethylenetetramine buffer media and mixed micelle-mediated extraction of complex. The optimal extraction and reaction conditions (e.g. surfactant concentration, reagent concentration, effect of time) were studied and the analytical characteristics of the method (e.g. limit of detection, linear range, molar absorptivity, Sandell sensitivity, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 0.5-15 ng mL − 1 of thorium(IV) ion and the detection limit of the method is 0.16 ng mL − 1 . The interference effect of some anions and cations was also tested. The proposed method was successfully applied for the preconcentration of trace thorium in natural water samples as well as in plant material and soil samples prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES) with satisfactory results. A Perkin-Elmer Lambda 12 UV/Vis spectrometer was used for recording absorbance spectra with 1.0-mm quartz cell. A Perkin Elmer model 5300 DV; ICP-AES (Waltham, MA, USA) was used for all ICP-AES measurements. An Orion research model 601 A/digital ionalyzer pH meter was used for checking the pH of solutions. A water bath with good temperature control and a centrifuge with 10-mL calibrated centrifuge tubes (Superior, Germany) were used to accelerate the phase separation process. Tabletop Low Speed Large Capacity Centrifuge model L-550 was used Reagents Unless otherwise stated, reagents of analytical purity were used for all experiments and doubly distilled water (DDW) was used throughout. The surfactants, Triton X-100 and cethyltrimethylammonium bromide (CTAB) (obtained from Sigma company) were used without further purification. Stock solution of thorium at a concentration of 0.025 M thorium(IV) solution is prepared by dissolving 3.675 g of thorium nitrate [Th(NO 3 ) 4 .6H 2 O] in distilled water containing a few drops of nitric acid. The solution is made upto 250 mL and standardized gravimetrically by employing the iodide method. 0.1 M. working standard solutions were obtained by appropriate dilution of the stock. 5-(2`,4`-Dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (DMPAHPD) was prepared using conventional diazotization and coupling methods. 25 A solution of 1.0×10 − 3 M of DMPAHPD was prepared by dissolving appropriate amounts of this reagent in bidistilled water. The solution pH 7.8 ± 0.2 was adjusted with hexamethylenetetramine (HTM)/ hydrochloric acid buffer. N,N-dimethyl formamide (DMF) solvent and potassium iodide salt were purchased from Merck.

Simultaneous preconcentration of uranium and thorium in aqueous samples using cloud point extraction

“…In the present work, we have evaluated all the parameters and these are relatively higher than those reported by S. Shariati et al 3 These values are also found to be comparable and in some cases even better than the earlier reported CPE procedures for either U or Th. 18,[21][22][23][24][25][26][27][28][29][30] The minimum concentration level of U and Th which had been reported by S. Shariati et al 3 is lower than the present work and this is obviously because they used ICP-OES, which is more sensitive than UV-visible spectrophotometry. The proposed method, however, can be effectively used for the quantication of U and Th in drinking water.…”

“…20 Furthermore, CPE was recently demonstrated by Favre-Réguillon et al to have a higher EE than LLE. 21 A signicant number of literature reports are available on the CPE of U 18,21-27 and a few for Th [28][29][30] but only one report is available on the simultaneous preconcentration of U and Th along with zirconium and hafnium. 3 In the work of S. Shariati et al 3 the enrichment factors (EFs) obtained for U and Th upon preconcentration are 37.0 and 43.6, respectively.…”

Development of the Smartphone-Assisted Colorimetric Detection of Thorium by Using New Schiff’s Base and Its Applications to Real Time Samples

“…The interference study reveals there is no interference from UO 2 2+ , Zr 4+ , Ti 4+ , lanthanides and Al 3+ by this sensor L (Table S2). ,− Hence, L can be used as an excellent chromogenic sensor for Th 4+ detection in the presence of the competing metal ions and anions.…”

Mixed Micellar Cloud Point Extraction and Spectrophotometric Determination of Iron(II) Using 1,10-Phenanthroline: Effect of Sodium Nitroprusside on Extraction Efficiency

“…As a result, a substantial increase in the extraction efficiency of polar compounds may be noticed. These mixed surfactants have both hydrophobic and electrostatic interactions and that facilitates the extraction of compounds with different charges and the cloud point of the mixed micellar system has been decreased by salting out effect [9,10].…”