Integrated sorption–energy-dispersive X-ray fluorescence detection for automatic determination of lead and cadmium in low-concentration solutions

Abstract

Sorbent material packed in a PTFE laboratory-made flow cell located in the specimen holder of an energy-dispersive X-ray fluorescence (EDXRF) detector has been used for in situ solid-phase extraction (SPE) preconcentration-detection of metals. The flow cell was connected to a single-channel flow-injection (FI) manifold (for full automation of the steps and proper development of the method) by two PTFE tubes of 0.5-mm inner diameter introduced into the spectrometer specimen holder by a small orifice without distortion or modification of the instrument. The optical window open in the PTFE flow cell was adjusted to the X-ray irradiation zone of the spectrometer and fixed to it. The approach was tested by using both Pb and Cd aqueous solutions and a Dowex 50 cation-exchange resin as a sorbent, and flushing the sample through the flow cell for EDXRF measurements after removal of the sample matrix. The limits of detection and the limits of quantification (LOQs) thus obtained were 0.15 and 0.5 microg for Pb and 0.3 and 0.8 microg for Cd, respectively, values that allow the approach to be used for the analysis of drinking water by injecting a 100-mL sample into the FI manifold, taking into account the EC drinking water directives. The linear dynamic ranges are between the LOQ and 600 microg for both analytes. The method was validated by the standard addition method using tap-water samples. In addition, the integrated SPE-EDXRF approach enables the study of the variables influencing the sorption step-namely the effects of the volume of sample flushed through the column, concentrations of the analytes in the sample, breakthrough volume of the resin, elution profiles, sample pH and retention and elution flow rates-in an automatic, cheap, fast and precise way.

Atomic spectrometry update. Environmental analysis

“…2.3.3 X-ray fluorescence spectrometry. The on-line coupling of FI and SPE to energy dispersive XRF has been reported for the determination of Cd and Pb in tap 146 and waste waters. 147 An FI manifold, incorporating an SPE column packed with Dowex 50 cation-exchange resin, was coupled directly to a lab-made 18 mL flow-cell of 10 mm path length, located in the X-ray spectrometer irradiation chamber.…”

Application of Small-Spot Energy Dispersive X-ray Fluorescence Instrumentation in Phytoremediation Activities around Metal Mines

“…1) and the low cost of the equipment have promoted the study of the suitability of this instrument for analytical purposes. 18,19 Typical of such instruments, the characteristic radiation emitted by the elements present in the sample is detected by a Si(Pin) diode detector with an energy resolution of 190 eV at 5.89 keV (Mn K a line). A hole mirror located in the path of the primary beam not only allows for a precise selection of the measurement spot using a color video camera, but also for viewing the area on a PC monitor during the measurement procedure.…”

Determination of copper, iron, nickel and zinc in ethanol fuel by energy dispersive X-ray fluorescence after pre-concentration on chromatography paper

“…This approach was previously used for water [14], environmental samples [15], engine oil [16], gasoline [1] and ethanol fuel analysis [17]. For this purpose, different solid supports have been used such as cellulose filter [14,17], C-18 or chelating solid phase [16,18], silica gel [19] and ion exchange resins [20,21].…”