Spectrophotometric flow injection determination of dissolved titanium in seawater exploiting in-line nitrilotriacetic acid resin preconcentration and a long path length liquid waveguide capillary cell

• Published in: Analytica chimica acta 2019-04, Vol.1053, p.54-61
• Main Authors: Feng, Sichao, Wu, Jingfeng, Yuan, Dongxing, Huang, Yongming, Lin, Kunning, Chen, Yaojin
• Format: Article
• Language: English
• Subjects: Acetic acid; Acids; Aluminum; Ammonium; Ammonium acetate; Ascorbic acid; Cadmium; Chemical analysis; Chromium; Copper; Dissolved titanium in seawater; Elution; Estuaries; Estuarine environments; Flow analysis; Iron; Lead; Liquid waveguide capillary cell; Manganese; Nickel; Nitrilotriacetic acid; Nitrilotriacetic acid resin; pH effects; Resins; Seawater; Spectrophotometry; Tiron; Titanium; Water analysis; Water sampling; Zinc
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2018.11.034

A sensitive spectrophotometric method for the determination of dissolved titanium (Ti) in seawater is developed. It involves in-line preconcentration and a long path length liquid waveguide capillary cell (LWCC). Nitrilotriacetic acid (NTA) resin is used to preconcentrate Ti from ∼25 mL seawater sample at pH 1.7, and elution is accomplished with 0.8 mol L−1 hydrochloride acid. The eluted Ti solution is buffered to pH 6.0 with 1.0 mol L−1 ammonium acetate and mixed with 1.5 mmol L−1 Tiron solution. The mixture is then injected into LWCC and measured by spectrophotometry at 420 nm. Before the preconcentration step, the sample is treated with 7 mmol L−1 ascorbic acid to reduce Fe(III) to Fe(II), in order to eliminate the Fe interference. The method is not interfered by Fe(III) and Cu(II) present in seawater samples at concentrations 50-fold higher in relation to Ti, and by Cd(II), Pb(II), Cr(VI), Mn(II), Al(III), Zn(II), and Ni(II) at concentrations 100-fold higher in relation to Ti. It is time efficient (7.5 minutes per sample), sensitive (0.10 nmol L−1 detection limit), precise (1.40% measurement RSD at 1.00 nmol L−1 Ti) and is characterized by a linear range of 0.50–5.00 nmol L−1 Ti. The method was applied to analysis of natural water samples collected from the Jiulongjiang Estuary, Fujian, China. [Display omitted] •Sensitive spectrophotometric detection of dissolved Ti in seawater is developed.•NTA resin is used to preconcentrate dissolved Ti in seawater at pH 1.7.•Fe(III) is reduced to Fe(II) before resin to avoid Fe retention and interference.•In-line preconcentration and detection is realized with flow analysis and LWCC.•Estuarine dissolved Ti is analyzed and reported.