Lysine surface modified Fe₃O₄@SiO₂@TiO₂ microspheres-based preconcentration and photocatalysis for in situ selective determination of nanomolar dissolved organic and inorganic phosphorus in seawater

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• 作者：Shunxing Li^a ; ^b ; ^{shunxing_li@aliyun.com" class="auth_mail" title="E-mail the corresponding author}Author Vitae ; Wenjie Liang^bAuthor Vitae ; Fengying Zheng^a ; ^bAuthor Vitae ; Haifeng Zhou^bAuthor Vitae ; Xiaofeng Lin^bAuthor Vitae ; Jiabai Cai^bAuthor Vitae
• 关键词：Phosphorus speciation ; Sample pretreatment ; Preconcentration ; Photocatalysis ; Functional nanomaterials
• 刊名：Sensors & Actuators: B. Chemical
• 出版年：2016
• 出版时间：1 March 2016
• 年：2016
• 卷：224
• 期：Complete
• 页码：48-54
• 全文大小：1426 K

文摘

A new, sensitive, and rapid spectrophotometric method for selective determination of nanomolar levels of dissolved organic phosphorus (DOP) and inorganic phosphorus (DIP) in seawater was proposed. The microsphere of Fe₃O₄@SiO₂@TiO₂ (FST) was surface modified with lysine (FST-Lys) and used as solid phase adsorbent, photocatalyst, and sensor. After surface modification with lysine, the zeta potential vs pH curve for FST could be reversed and then 98.1% of DIP anions in the seawater could be specifically adsorbed by electric attraction onto FST-Lys (1.2 mg/mL) at the pH value of natural seawater (8.1–8.3) after only stirring for 30 min. The adsorbed DIP could be eluted with hydrochloric acid solution (pH 4.0) for electric repulsion. Therefore, acid hydrolysis of DOP could be inhibited and its influence on the determination of DIP could be avoided. DIP could be determined spectrophotometrically and selectively by phosphomolybdenum blue method. After UV irradiation, DOP was photodegraded by FST-Lys into DIP, the total concentration of dissolved phosphorus (i.e., DIP and DOP) could be determined, and then the concentration of DOP could be calculated. FST-Lys could be easily recycled by applying an external magnetic field while maintaining the adsorption and catalytic activity without significant decrease even after running 10 times. The proposed method with high sensitivity (detection limit of 1.42 nmol/L), wide linear range (3.0–1200 nmol/L), and selective determination was successfully applied for in situ measure of DIP and DOP in South China Sea and the Taiwan Channel.