Introduction of alcohols in inductively coupled plasma mass spectrometry by a flow injection system

A flow injection system for the introduction of organic solvents in an instrument of inductively coupled plasma mass spectrometry, using the conventional pneumatic nebulization, is proposed. The instrumental parameters, such as radiofrequency power, nebulization gas flow rate, solution flow rate and time interval between consecutive injections, were optimized for injecting analytical solutions in methanol, ethanol, l-propanol and 1% (v/v) nitric acid in water. In comparison to the conditions for the aqueous solution, a higher power and lower nebulization gas flow rates were adopted for the alcohol solutions. The Ba2+/Ba+ signals ratios are lower in the alcohol solutions, while the CeO+/Ce+ signals ratios are similar in all solvents. The signal intensities for the studied isotopes are enhanced in the organic media, partially due to a criterium used in the optimization, that is, CeO+/Ce+ signal ratio below 3%. The enhancement is specially high for Se, As and Hg. The proposed FIA system, with an injection of a small volume, typically 100 mu l, of the organic solvent, on Line diluted 1+1 with water, and the continuous washing with an aqueous solution containing 1% (v/v) nitric acid, between the injections, allows the use of the instrument for more than 200 readings, without reoptimization of the plasma conditions and without visible carbon deposits on the cones. The addition of oxygen to the nebulization gas does not bring a real advantage. (C) 1999 Elsevier Science B.V. All rights reserved.