A solventless method for detecting trace level phosphate and arsenate in water using a transparent membrane and visible spectroscopy

• Published in: Talanta (Oxford) 2021-04, Vol.225, p.122023-122023, Article 122023
• Main Authors: Ibnul, Nayeem K., Tripp, Carl P.
• Format: Article
• Language: English
• Subjects: Arsenate; Molybdenum blue method; Phosphate; Solid particles; Transparent membrane; Visible spectroscopy
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2020.122023

The molybdenum blue method is the American Public Health Association (APHA) approved method for the detection and quantification of phosphate in water. The standard molybdenum blue method, APHA 4500 PE has a detection limit of 30 μgL−1 phosphate (10 μgL−1 phosphorus) in freshwater with a 5 cm cuvette. To further lower the detection limit to sub μgL−1 levels, we have developed a simple, fast, and solventless method for conversion of phosphate present in solution to a solid for quantification by Visible spectroscopy. The process converts the anionic heteropolymolybdate ions into a solid colloidal precipitate by charge neutralization with the cationic surfactant cetyltrimethylammonium bromide (CTAB), and the precipitate is then captured on a Visible transparent membrane. A Visible spectrum is then recorded in transmission mode through the membrane and the concentration of the phosphate is determined from the intensity of a band cantered at 700 nm. Using this method, the detection limit for phosphate in water is lowered to 0.64 μgL−1. The approach has also been extended to detect arsenate in water with a detection limit of 4.8 μgL−1 arsenate. . The method is also used to investigate real matrices with accuracy that matches the standard APHA method for detection of phosphate in water. [Display omitted] •Detection of phosphate and arsenate in real water matrices using a transparent membrane and visible spectroscopy .•Attained a detection limit of 0.64 μgL−1 phosphate and 4.8 μgL−1 arsenate in water.•Linearity over the range of 0.5 μgL−1 to 100 μgL−1 and accuracy with the standard APHA approved method for phosphate detection was obtained.