Simultaneous Determination of Silver, Nickel, Lead, Cadmium, and Mercury by On‐Line Column Enrichment, Followed by Reversed Phase High Performance Liquid Chromatography

Abstract

A new method for the simultaneous determination of five heavy metal ions, silver, nickel, lead, cadmium, and mercury ions as metal‐tetra‐(4‐aminophenyl)‐porphyrin (T₄APP) chelates was developed using reversed‐phase high performance liquid chromatography (RP‐HPLC), equipped with photodiode array detector and combined with on‐line enrichment technique. The silver, nickel, lead, cadmium, and mercury ions were pre‐column derivatized with T₄APP to form color chelates. The Ag‐T₄APP, Ni‐T₄APP, Hg‐T₄APP, Cd‐T₄APP, and Pb‐T₄APP chelates can be absorbed onto the front of an enrichment column when they were injected into the injector, and sent to the enrichment column [Waters Xterra^TM RP₁₈ (5 µ, 3.9 × 20)] with a buffer solution of 0.05 mol/L pyrrolidine‐acetic acid (pH = 10.0) as mobile phase. After the enrichment finished by switching the six ports switching valve, the retained chelates were back‐flushed by mobile phase and traveling towards the analytical column. The chelates separated on the analytical column [Waters Xterra^TM RP₁₈ (5 µ, 3.9 × 150)] 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, was satisfactory. The linearity range is 0.01 ∼ 120 µg/L for each metal ions. The detection limits (S/N = 3) of silver, nickel, lead, cadmium, and mercury are 3.0 ng/L, 2.5 ng/L, 2.0 ng/L, 1.5 ng/L, and 2.0 ng/L, respectively. This method was applied to the determination of silver, nickel, lead, cadmium, and mercury ions in water with good results.

Keywords:

• RP‐HPLC
• Tetra‐(4‐aminophenyl)‐porphyrin
• On‐line enrichment
• Heavy metal ions