Colorimetric sensor of schiff's reagent for formaldehyde gas detection

Abstract

Two gas sensing elements were developed for naked-eye detection of formaldehyde gas. Polyvinyl alcohol film and silica gel were doped with Schiff’s reagent as sensing reagent of different concentrations (0.8, 1.0 and 1.3 mM). The sensors were characterized by ATR-FTIR spectrophotometer, UV-Visible spectrophotometer and DR-UV-Vis spectrophotometer. The film sensor (size 0.7x0.8 cm, thickness 0.162 ±0.001 mm) was enclosed into a glass tube (4.5 mm i.d.) while the solid-phase sensor (0.01 g) was packed into a glass tube for easy usage. The formaldehyde generation system was developed in-house and their performance was tested. Formaldehyde gas with concentration of ca. 6 ppb and 62 ppb were used to test the performance of film and solid phase sensors. The gas mixture flow rate of 100 mL min-1 was used in this study. The both sensors showed color change from yellow to magenta or purple after exposure to formaldehyde gas and the intensity of the color depended on both Schiff’s reagent concentration and formaldehyde concentration. The solid sensor doped with 0.8 and 1.0 mM Schiff’s reagent could detect formaldehyde gas and gave different color tint with response time of 2 and 3 min, respectively. The film sensor doped with 1.3 mM could detect only ca. 62 ppb formaldehyde with response time of 11 min. The performance of the prepared sensors was evaluated by applying the sensors to detect a synthetic gas sample.