Determination of Heavy Metal Ions in Tobacco and Tobacco Additives

Abstract

This paper describes a new method for the simultaneous determination of heavy metal ions in tobacco and tobacco additives by microcolumn high-performance liquid chromatography. The samples were digested by microwave digestion. The lead, cadmium, mercury, nickel, cobalt and tin ions in the digested samples were pre-column derivatized with tetra-(o-aminophenyl)- porphyrin (To-APP) to form coloured chelates. The Hg-To-APP, Cd-To-APP, Pb-To-APP, Ni-To-APP, Co-To-APP and Sn-To-APP chelates were enriched by solid phase extraction with a C18 cartridge resulting in an enrichment factor of 50. The chelates were separated on aWaters Xterra™ RP18 microcolumn (50mm×1.0 mm, 2.5 μm) with a mixture of methanol-tetrahydrofuran (95:5, v/v, containing 0.05 mol L^–1 pyrrolidine-acetic acid buffer salt, pH=10.0) as mobile phase at a flow rate of 0.2 mL min^–1 and identified with a photodiode array detector at 350–600 nm. The metal chelates were fully separated in 2.0 min. The detection limits for lead, cadmium, mercury, nickel, cobalt and tin in the original digested samples were 4 ng L^–1, 3 ngL^–1, 6 ngL^–1, 5 ngL^–1, 5 ngL^–1 and 4 ng L^–1, respectively. The relative standard deviation for five replicate samples was 2.65~3.24%. The standard recoveries were 95.6~108%. The method was applied with good results to the determination of lead, cadmium, mercury, nickel, cobalt and tin in tobacco and tobacco additives.

KEYWORDS: Microcolumn high-performance liquid chromatography, tetra-(o-aminophenyl)-porphyrin, heavy metal ions.