Optical Determination of Low-Level Water Concentrations in Organic Solvents Using Fluorescent Acridinyl Dyes and Dye-Immobilized Polymer Membranes

• Published in: Analytical chemistry (Washington) 2001-11, Vol.73 (21), p.5339-5345
• Main Authors: Citterio, Daniel, Minamihashi, Katsuya, Kuniyoshi, Yuka, Hisamoto, Hideaki, Sasaki, Shin-ichi, Suzuki, Koji
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Dyes; Exact sciences and technology; Fluorescence; Polymers; Solvents; Spectrometric and optical methods; Water
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac010535q

The fluorescent acridinyl indicators 4-(9-acridinyl)-N-(5-hexenyl)-N-methylaniline (KD-F0011), 6-(9-acridinyl)-1,2,2,3-tetramethyl-2,3-dihydro-1H-perimidine (KD-F0021), and 6-(9-acridinyl)-2-(3-butenyl)-1,2,3-trimethyl-2,3-dihydro-1H-perimidine (KD-F0022) were designed, synthesized, and applied for highly sensitive optical determination of low-level water in organic solvents. All these dyes were found useful as fluorescence indicators for the detection of water below 1% (v/v) in different solvent media with a low detection limit of 0.002% (v/v) or 20 mg/L (22 ppm by weight) for KD-F0021 in THF solution. Sensing membranes made from poly(ethylene glycol) dimethacrylate by photocopolymerization with the indicator KD-F0011 were also prepared. Using the membrane sensor, the lowest detection limit of 0.001% (v/v) or 14 mg/L (20 ppm) water was achieved in diethyl ether samples. This system enables the continuous monitoring of the water content in a flow-through arrangement, where single-wavelength excitation (404 nm) and single-wavelength detection (532 nm) can be used for the fluorescence determination, allowing a simple measurement setup. In a continuous-flow experiment using THF samples, fully reversible and fast signal changes with t 95% = 1−2 min for water concentrations up to 0.50% (v/v) were observed. A detection limit of 0.004% (v/v) or 40 mg/L (45 ppm) water in THF was achieved. These characteristics make this type of sensor a useful tool for the on-line continuous monitoring of water present as an impurity in organic media, which is difficult to achieve using a Karl Fischer instrument.