Continuous flow analysis of mercury using a chalcogenide glass ion-selective electrode

A commercial Hg chalcogenide glass ion-selective electrode (ISE) has been c haracterized using scanning electron microscopy, X-ray diffraction, and X-r ay photoelectron spectroscopy, and the compositional data have been used in the fabrication of our own Hg ISE. It is shown that continuous flow analys is (CFA) is suitable for rapid determinations of ultratrace levels of mercu ry in saline media when used in conjunction with an extrapolation method th at predicts the steady-state potential of the Hg ISE by using the initial d ata following a stepwise change in aHg(2+). The CFA technique yields a near -Nernstian response of 28 mV per decade change in aHg(2+) in Hg buffers in the range 10(-18) to 10(-12) M Hg2+. It is shown that the repeatability of the CFA technique in seawater is +/- 0.03 pHg units, and a seawater matrix effect causes a significant offset and apparent error in the response of th e Hg ISE relative to Hg buffer standards. Standard addition CFA may be used to compensate for the seawater matrix interference. (C) 2000 John Wiley & Sons, Inc.