A micro mixed micelle-mediated preconcentration procedure for spectrophotometric determination of uranium in real and synthetic samples W. I. Mortada 1 • I. M. M. Kenawy 2 • G. G. El-Gamal 2 • S. M. N. Moalla 3 Received: 10 January 2017 Ó Akade ´miai Kiado ´, Budapest, Hungary 2017 Abstract A micro-cloud point extraction method was discussed for preconcentration and spectrophotometric quantification of U(VI). The method depends on complex formation between U(VI) and 2-(4-sulphophenyloazo)-1,8- dihydroxy-3,6-naphtalenedisulphonic acid (SPADNS) at pH 7.0 and subsequent extraction of the complex in a mixed surfactant medium (cethyltrimethyl ammonium bromide and Triton X-114). The separation was carried out in the presence of 1% Na 2 SO 4 at room temperature. The calibration curve was linear up to 3000 lgL -1 . The enrichment factor, detection limit and precision were 16.0, 1.05 lgL -1 , and 2.3%, respectively. The method was employed for the determination of U(VI) in real samples with different matrices. Keywords Micro cloud point extraction Á Preconcentration Á Uranium Á SPADNS Á Spectrophotometry Introduction Uranium (U) is a substantial element owing to its uses in nuclear energy production. It exists naturally in diverse minerals and rocks. Human exposure to U or its compounds can cause nephrotoxicity, lung cancer, and neuropathy [1]. In view of its applications and toxicity, the accurate detec- tion of trace U in real samples is a challenging task. Many technicalities have been applied for the quantita- tive measurement of U [2–8]. The efficiency of traditional spectrometric methods such as flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) is inadequate for trace determination of U [9, 10]. The other techniques are not available in most laboratories due to their high costs. Spectrometry remains a choice, and several procedures have been performed using this technique with different pre-concentration steps [11–13]. Examples of preconcen- tration procedures for U are solid-phase extraction [14], liquid–liquid extraction [15], ion exchange [16], flotation [17] and extraction chromatography [18]. An eco-friendly separation procedure is cloud point extraction (CPE) that utilizes a surfactant as extractant and it requires very small amount of organic solvents (such as methanol or ethanol) to dissolve the viscid phase. Classical CPE for preconcentration of metal ions involves four proceedings: formation of hydrophobic metal-complex, addition of surfactant, formation of micelles by heating, and phase separation [19–22]. The main disadvantages of the traditional CPE include relatively long time required to achieve the cloud point, the need of relatively large volume of sample (up to 50 mL) and the necessity to dilute the viscid phase with remarkable amount of organic solvent (e.g. 2 mL of acidified metha- nol). Recently, micro-cloud point extraction (MCPE) pro- cedure is developed to overcome these troubles [23, 24]. In this technique, heating step is discarded by using salting out effect [23, 25] and few tens microliter of the organic solvent, instead of milliliters in traditional CPE, is enough to dissolve the viscid phase [23]. & W. I. Mortada w.mortada@yahoo.com 1 Urology and Nephrology Center, Mansoura University, Mansoura, Egypt 2 Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt 3 Chemistry Department, Faculty of Science, Port Said University, Port Said, Egypt 123 J Radioanal Nucl Chem DOI 10.1007/s10967-017-5281-3