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An electron source consisting of a heated filament has been added to the skimmer to suppress space charge effects in inductively coupled plasma mass spectrometry (ICPMS). Electrons from this source can reduce the space charge repulsion between the positive ions in the ion beam. As a result, ion transmission efficiency and analyte ion sensitivities are significantly improved across the full mass range. MO+/M+ abundance ratios are not affected, M2+/M+ abundance ratios increase only slightly, and no new background ions are created by this electron injection technique.

A novel lab-on-paper device combining electrochemical and colorimetric detection for the rapid screening of Au(III) in the presence of a common interference, Fe(III), in industrial waste solutions is presented here. With dilute aqua regia (0.1 M HCl + 0.05 M HNO(3)) as the supporting electrolyte, square wave voltammetry on paper provided a well-defined reduction peak for Au(III) at approximately 287 +/- 12 mV vs Ag/AgCl. Under the optimized working conditions, the calibration curve showed good linearity in the concentration range of 1-200 ppm of Au(III) with a correlation coefficient of 0.997. The limit of detection (LOD) of the proposed method is 1 ppm. Interferences from various cations were also studied. Fe(III) is the only metal that affects the electrochemical determination of Au(III) when present above a 2.5-fold excess concentration of that of the Au(III). To overcome this limitation, a colorimetric method was used to simultaneously detect Fe(III) as a screening tool. The procedure was then successfully applied to determine Au(III) in gold-refining waste solutions. The results are in agreement with those obtained from inductively coupled plasma-atomic emission spectrometry (ICP-AES).

Electrons from a heated tungsten filament are created inside the extraction lens and driven out toward the skimmer. These electrons move through the ion path and reduce space charge effects between positive ions in the beam. The ion transmission efficiency is improved by factors of two (for Pb+) to 27 (for Li+). The greater sensitivity improvement for low-mass ions leads to a substantial reduction in mass bias. With the additional electrons, MO+/M+ and M2+/M+ abundance ratios increase but can be minimized with a small reduction in aerosol gas flow rate. No new background ions are observed with this technique. Matrix effects can be significantly diminished when the electron source is operated under the high electron current mode. The mass dependence of matrix-induced suppression of analyte signals is essentially eliminated. Using flow injection analysis to minimize solid deposition, the technique can tolerate Na matrix up to 10000 ppm (1%) with only approximately 15% loss of analyte sensitivity.

Electrons are added from a heated filament at the base of the skimmer to reduce the space charge repulsion in the ion beam. This technique improves the analyte sensitivity moderately and also minimizes the matrix effects caused by other elements in the sample significantly. The suppression of signal for even the most troublesome combination of light analyte and heavy matrix elements can be attenuated from 90 to 99% to only 2-10% for 2 mM matrix solutions with an ultrasonic nebulizer. The supplemental electron current can be adjusted to "titrate" out the matrix effects as desired.