Analytical Sciences

Membrane Solubilization Technique for Spectrophotometric Determination of Trace Formaldehyde in Rainwater

Keita MURAI,* Mayumi OKANO,* Hideki KURAMITZ,* Noriko HATA,* Takanori KAWAKAMI,** and Shigeru TAGUCHI*

*Graduate School of Science and Engineering (Science Div.), University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
**Water Quality Management Center, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan

A simple and sensitive spectrophotometry for formaldehyde in water by membrane solubilization technique was proposed. Formaldehyde was converted into a blue cationic dye with 3-methyl-2-benzothiazolinone hydrazone, and the dye was retained on a membrane filter as an ion-associate with tetraphenylborate anion. The filter retaining the blue dye was dissolved in 2-methoxyethanol containing sulfuric acid, and the absorbance of the solution was measured at 670 nm against the reagent blank. The formaldehyde from 0.007 to 0.2 mg L^-1 was determined with an RSD of less than 5%, and the detection limit was 0.002 mg L^-1. The proposed method was very simple and rapid. Twenty minutes was sufficient for the entire analytical procedure. When the method was applied to rainwater, the analytical results were in good agreement with those obtained by GC/MS.

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