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A new method for low mercury concentration analysis in drinking waters is presented. Membranes containing a few micrograms of various complexing reagents were produced on the surface of quartz glasses (reflectors). The reflectors were immersed in water solutions containing various concentrations of inorganic mercury salts at low concentrations (1-40 ng/mL). The membranes were left to equilibrate in 5-500 mL of solution for many hours; when the equilibration stage was finished they were cleaned with ultrapure water and left to dry. Analyses were performed by total reflection X-ray fluorescence (TXRF). The effects of various experimental parameters (complexing agent, equilibrium time, sample volume, etc.) as well as the selectivity of the membranes were studied. The complexing reagent dithizone with a PVC-based membrane gave the best results. The limit of quantitation was 0.8 ng/mL.

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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...