Simultaneous Determination of Tin, Nickel, Lead, Cadmium and Mercury in Tobacco and Tobacco Additives by Microwave Digestion and RP‐HPLC Followed by On‐Line Column Enrichment

Abstract

A new method for the simultaneous determination of five heavy metal ions, tin, nickel, lead, cadmium and mercury ions as metal-tetra-(2-aminophenyl)-porphyrin (T2APP) chelates was developed using reversed-phase high performance liquid chromatography (RP-HPLC) equipped with a photodiode array detector and combined with an on-line enrichment technique. The tin, nickel, lead, cadmium and mercury ions were pre-column derivatized with T 2APP to form color chelates. The Sn-T2APP, Ni-T2APP, Hg-T2APP, Cd-T2-APP and Pb-T2APP chelates can be absorbed onto the front of the enrichment column when they are injected into the injector and sent to the enrichment column [Waters Xterra TM RP18 (5m, 3.9´20 mm)] with a buffer solution of 0.05 mol/L pyrrolidine-acetic acid (pH = 10.0) as mobile phase. After the enrichment had finished, by switching the six-port switching valves, the retained chelates were back-flushed by mobile phase and traveling towards the analytical column. These chelates separation on the analytical column [Waters Xterra TM RP 18 (5m, 3.9´150 mm)] was satisfactory by gradient elution with methanol (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0) and acetone (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0) as mobile phase. The linearity range is 0.01~120 mg/L for each metal ion. The detection limits (S/N = 3) of tin, nickel, lead, cadmium and mercury are 4.0 ng/L, 3.5 ng/L, 2.5 ng/L, 3.0 ng/L and 3.0 ng/L, respectively. This method was applied to the determination of tin, nickel, lead, cadmium and mercury ions in tobacco and tobacco additives with good results.