顺序注射-化学发光法测定海水中皮摩尔级Fe(Ⅱ)浓度OA北大核心

Herein,an automatic and sensitive method for the determination of Fe(Ⅱ)at the picomolar level in sea-water is presented.This method employs a sequential injection technique and the chemiluminescence analysis of luminol catalyzed by Fe(Ⅱ)under alkaline conditions.The analysis system comprises an injection pump,a selector valve,a self-made three-channel reaction cell,a photon counter,a control module,and other components.Optimal conditions for the chemiluminescence reaction(including flow rates,pH,luminol reagent concentration,reagent and sample volumes,and reaction temperature)and protocol sequence were established.Under these optimal reaction conditions,the detection limit of the system for Fe(Ⅱ)concentration was as low as 4.1 pmol·L-1 when using a win-dow-detection strategy.Each analysis cycle consumed only 400 µL of the reagent and 80 µL of the sample.Chemi-luminescence intensity showed a linear response to the Fe(Ⅱ)concentration in the range of 0.01-8.0 nmol·L-1,with a relative standard deviation of 3.6％for 11 consecutive measurements of a 1.0 nmol·L-1 Fe(Ⅱ)standard solution.Interference studies indicated that free Cu(Ⅱ)significantly influenced the analysis of Fe(Ⅱ);however,in natural seawater,Cu(Ⅱ)mainly exists as organic complexes.Adding salicylaldoxime to complex residual Cu(Ⅱ)confirmed minimal interference from organic Cu(Ⅱ).In addition,tests with organic ligands(e.g.,ethylene diamine tetraacetic acid,diethylenetriamine pentaacetic acid,and ferrozine)showed that increasing organic ligand concentration de-creased the chemiluminescence intensity.However,when the concentrations of organic ligands were less than 50 times the Fe(Ⅱ)concentration,the decrease in the chemiluminescence intensity was no more than 9.5％.The accu-racy of the method was validated using reference seawaters(NASS-6 and NASS-7)and standard addition experi-ments with seawater samples.