A study of the determination of several heavy metals in tobacco and a tobacco additive by Solid Phase Extraction and HPLC
A method for the determination of copper, nickel, tin, lead, cadmium and mercury in tobacco and a tobacco additive by solid phase extraction and high performance liquid chromatography (HPLC) has been studied. The samples were digested by microwave. The copper, nickel, tin, lead, cadmium and mercury ions in the digest were pre-column derived with tetra-(4-aminophenyl)-porphyrin (T4-APP). These chelates were then enriched using Waters Sep-Pak short-column solid phase extraction (1 cc/30 mg, 30 µm). This procedure enriches the extract by as much as 50 times. A 3.9´150 mm, 5 µm column (Waters XterraTM RP18) was used for HPLC determination of the above heavy metal chelates in a concentrated sample solution by gradient elution. The eluting solvents were methanol and acetone containing 0.05 mol/L pH10 pyrrolidine-acetic acid buffer. The flow rate of eluting solvent was 1.0 ml/min. The size of the injections was 20 µL. A Model 996 photodiode array detector (Waters Corporation) was employed throughout this study. The detection limits of nickel, copper, tin, lead, cadmium, and mercury were 42 ng/L, 38 ng/L, 82 ng/L, 60 ng/L, 50 ng/L and 25 ng/L, respectively. The determinations of the contents of the above heavy metal ions were performed by a calibration curve method. The relative standard deviation (RSD) of the analytical results and recoveries were 2.1~2.8% and 96~103%, respectively.