Introduction of high carbon content solvents into inductively coupled plasma mass spectrometry by a direct injection high efficiency nebuliser

A preliminary investigation on the introduction of high carbon content solvents into inductively coupled plasma mass spectrometry (ICP-MS) by a direct injection high efficiency nebuliser (DIHEN) is presented. Ethanol, hexane, toluene and a natural gas condensate were introduced using a flow injection system. The performance for determinations of total concentrations of mercury present in organic solvents as different species was evaluated. The most critical operating parameters were the nebuliser gas flow rate and amount of oxygen added to the plasma. For the DIHEN a nebuliser gas flow rate of 0.3 L min(-1) and 50 mL min(-1) of oxygen added to the plasma auxiliary gas flow gave stable conditions and high analyte sensitivity. Species recoveries for HgCl2, CH3HgCl, (CH3)(2)Hg and Hg-0 in hexane were 99+/-4, 101+/-4, 95+/-4 and 104+/-7%, respectively. Detection limit for mercury in hexane was 85 pg mL(-1) based on 3sigma of a Hg-201-spiked blank. A gradual deposition was observed at the nebuliser tip, partly blocking the gas annulus. The rate of deposition seemed to be related to the amount of carbon introduced through the nebuliser. With the optimised conditions used in this work, the nebuliser could be used for approximately 50 hexane samples before cleaning was necessary.