Signal enhancement and reduction of interferences in inductively coupled plasma mass spectrometry with an argon–trifluoromethane mixed aerosol carrier gas

Publisher Website
Google Scholar
Abstract
The addition of trifluoromethane (CHF3) to the aerosol carrier gas in inductively coupled plasma mass spectrometry was assessed as a method of improving detection limits (DL) for elements such as As, Se, Cu and Zn in matrices containing interfering species. It was observed that in each case the analyte response was significantly increased with a coincident decrease in the blank signal. The improved DL for As in Cl– and Ca2+ matrices (interferences 40Ar35Cl+ and 43Ca16O+ 2 were 0.02 and 0.04 ng ml–1 compared with 0.65 and 0.28 ng ml–1, respectively, without CHF3; for 78Se (interference 40Ar38Ar+) 0.032 compared with 0.88 ng ml–1; for 63Cu in Na2SO4 or Na2HPO4 matrices (interferences 40Ar23Na+ and 31P16O2 +) 0.022 and 0.089 compared with 0.35 and 0.53 ng ml–1, respectively; and for 64Zn in an Na2HPO4 matrix (interferences H31P16O2 + and 31P16O17O+) 0.011 compared with 0.42 ng ml–1. The reduction of the interference is attributed to competitive reactions between the matrix species and the CHF3 or species derived from it in the plasma. The analyte enhancement effect is not yet clear. It has been suggested that this effect is related to elements with ionization potential (IP) in the 9–11 eV region and is affected by organic compounds added to the aerosol carrier gas stream. Copper (IP 7.73 eV), Al (5.99 eV), Br (11.30 eV) and l (10.44 eV) are exceptions to this assumption. Analytical curves of the studied elements at low ppb and sub-ppb levels (in the interfering matrices) further demonstrated the advantage of adding CHF3 in trace elemental analysis.

This publication has 22 references indexed in Scilit: