oa South African Journal of Chemistry - Determination of Heavy Metal Ions in Tobacco and Tobacco Additives
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 a Waters Xterra RP18 microcolumn (50mm x 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 ng L-1, 6 ng L-1, 5 ng L-1, 5 ng L-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.
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