Simultaneous determination of small amounts of Cu(II), Zn(II), Co(II) and Mn(II) with α, β, γ, δtetrakis(4-carboxyphenyl) porphine (TCPP) by HPLC was developed. The metal-TCPP complexes were quantitatively formed within 20min at room temperature in the presence of Hg(II) and pyridine([Hg
2+]Total≥10
-6mol dm
-3 and [Pyridine]
Total≥10
-2mol dm
-3) over the following pH ranges of 7.0?11.2(Cu), 7.0?10.9(Zn), 8.2?10.2(Co) and 7.8?10.7(Mn). Pyridine not only acted as an accelerator for complexation, but also as a selective modifier, as seen by the retention behavior of the Co complex in the chromatogram. Recommended procedure: Prepare a sample solution containing up to 1.6μg of Cu(II), Zn(II), Mn(II) and Co(II) in a 25cm
3 amber-colored-volumetric flask, to which add 2cm
3 of 1×10
-4mol dm
-3 TCPP, 0.25cm
3 of 1mol dm
-3 pyridine solution, 0.5cm
3 of 0.1mol dm
-3 sodium tetraborate pH buffer solution(pH 9.3), and 1cm
3 of 1×10
-4mol dm
-3 mercury(II) solution. Leave to stand at room temperature for 30min and dilute to 25cm
3 with water. Inject 0.1cm
3 of the mixture into the HPLC system [mobile phase: 50w/w% mixture of acetonitrile and aqueous acetic acid-sodium acetate solution(pH 3.5), flow rate 0.5cm
3/min, column: Merck CGC glass cartridge LiChrosorb RP-18 (5μm: 3.2 mm i.d.×150 mm)], and measure the absorbance at 420nm. The molar absorptivities (ε/cm
-1mol
-1 dm
3) of Cu-, Zn-, Mn- and Co-complexes at 420nm were 2.35×10
5, 5.81×10
5, 5.25×10
4 and 6.46×10
-4, respectively. The peak height calibration curves of these metal ions were linear over the range of 4×10
-8 to 1×10
-6mol dm
-3, and the relative standard deviation (5 determinations) at the center of the calibration range were 3.6%(Cu), 3.3%(Zn), 1.6%(Co) and 4.3%(Mn). Up to 100μg of alkali metal ions (Na
+, K
+), alkali earth metal ions (Mg
2+, Ca
2+, Ba
2+, Sr
2+), and anions (Cl
-, Br
-, NO
3-, SO
42-, ClO
4-. CH3COO
-) did not interfere with the determination.
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