Complexing Membrane for Uranium Detection by Total Reflection X-Ray Fluorescence

Abstract

Uranium is well known for its use as a nuclear fuel. Its chemo toxic and radiotoxic properties may cause considerable hazards, even at environmental levels. 1 The earth crust contains about 2.4 mg/mL U and seawater contains 1 -3 ng/mL. Nowadays, uranium in environmental samples can be determined by several methods with different detection limits. In most cases, complicated pretreatment methods are needed, or especially high-cost instrumentation is required. [2][3][4][5][6][7][8] In the present study, a conventional method is presented for the detection of uranium in natural water samples by membrane separation followed by total reflection X-ray fluorescence (TXRF) analysis.In recent years, TXRF has become increasingly important in modern analysis and production control. 9 It is an economical method (low cost per sample) that provides reliable analytical results for trace elements in liquid or solid samples. 10 Hardly any other analytical technique is as universally suited for qualitative and quantitative determinations as TXRF, because of the presence of certain advantages, compared to other methods, which are mentioned below:(1) It has the ability to detect exceptionally small quantities of mass (ng or pg). (2) It simultaneously analyses (in one spectrum) most elements with atomic number higher than that of magnesium. (3) It can be used for the direct analyses of solid samples (e.g. membranes) or liquid deposits. (4) The analysis time for each sample is small, typically 100 -400 s. Most TXRF analyses are based on the deposition of small quantities of solutions (a few microliters) on the center of a quartz reflector. The liquid solution is left to dry, and then analyzed. The detection limits under these conditions are on the order of 10 -50 ng/mL. Other analytical techniques used for uranium detection are ICP-MS and ICP-AES with sub-ppb and 40 ppb detection limits, respectively.11 In general, the detection limits may differ depending on the specific analytical system, experimental conditions, etc.TXRF is a suitable method for determining uranium in liquid samples by using uranium L X-ray lines. On the other hand, the concentrations of uranium usually presented in water samples are in the low-ppb range. Zarkadas et al. 12 used a rather elaborate pretreatment step in urine samples, in order to achieve better detection limits. In the present study, novel membranes were prepared to analyze low uranium concentrations in water solutions (drinking water, distilled water). The membranes were deposited on the center of a quartz reflector. They contained different powerful complexing reagents as well as other auxiliary compounds.Seventeen complexing reagents were tested as well as many (35) of their combinations. The combination of dithizone and thiourea gave the best results, offering the best yields of uranium in water, compared to all of the other combinations tested. The compounds were chosen from a list of organic ligands that have shown great response to uranium complexation, according to the literature. These membr...

Trace determination of uranium preconcentrated using graphene oxide by total reflection X‐ray fluorescence spectrometry

“…The MDL increased with increasing ionic strength because the background intensity derived from scattered X‐rays caused by a small sodium salt spot on the fluorine resin‐coated slide glass increased with increasing ionic strength, which results in matrix effects . The MDL of the methodology was found to be comparable with previously reported TXRF‐based works using other preconcentration procedures . The MDL of these measurements have been 0.8, 0.067, and 0.02 μg L −1 , with preconcentration by using membrane‐containing complexing reagents with a 50‐ml sample, extractant of diethyl ether with a 50‐ml sample, and ionic liquid for cloud point extraction with a 7.5‐ml sample .…”

“…[41] The MDL of the methodology was found to be comparable with previously reported TXRF-based works using other preconcentration procedures. [18][19][20] The MDL of these measurements have been 0.8, 0.067, and 0.02 μg L −1 , with preconcentration by using membrane-containing complexing reagents with a 50-ml sample, [18] extractant of diethyl ether with a 50ml sample, [19] and ionic liquid for cloud point extraction with a 7.5-ml sample. [20] These previously reported TXRF analyses were performed using large-scaled instruments with high-power X-ray tubes (operated with 1,100 W for the membrane-based method or 1,200 W for the other method) and counting time of 400 s for the membranebased method or 1,000 s for the other method.…”

“…Because uranium has lower alpha-specific activity than the other actinides, a larger amount of samples or longer counting time are needed for adequate detection. [17] Uranium detection by means of total reflection X-ray fluorescence (TXRF) spectrometer has been applied to water samples preconcentrated by using membrane containing complexing reagents, [18] extractant of diethyl ether, [19] and ionic liquid for cloud point extraction. [20] These TXRF analyses were performed using large-scaled instruments with high-power X-ray tubes (operated with 1,100 or 1,200 W), demanding water-cooling systems and silicon drift detectors.…”

Selective Micellar Extraction of Ultratrace Levels of Uranium in Aqueous Samples by Task Specific Ionic Liquid Followed by Its Detection Employing Total Reflection X-ray Fluorescence Spectrometry

“…Detection of ultratrace levels of toxic heavy metals in contaminated environmental samples can prevent their damaging effects of pollution in very early stages. Precise determination of such low analyte concentration in complex environmental matrices by sophisticated analytical techniques such as atomic absorption spectroscopy (AAS), − atomic emission spectroscopy (AES), , mass spectrometry (MS), , and X-ray fluorescence spectroscopy (XRF), etc., require preconcentration of the analyte. Although a good number of preconcentration and separation techniques such as liquid–liquid extraction (LLE), , solid phase extraction (SPE), − , and ion-exchange chromatography (IEC) have been developed in the past but cloud point extraction (CPE) or micelle mediated extraction (MME) − ,− has emerged as the most simple and ecofriendly preconcentration procedure in the past 10 years.…”

Atomic spectrometry update—X-ray fluorescence spectrometry

“…TXRF continues to be used in a wide range of environmental and biological applications. Hatzistavros et al 143 applied a new method of sample preparation to the determination of U in water. Membranes containing a few micrograms of various complexing reagents in a polyvinyl chloride matrix were produced on quartz glass surfaces and immersed in water solutions.…”