Nickel foam-based preconcentrator for sensitive and accurate detection of low-concentration volatile organic compounds

Real-time sensing of volatile organic compounds (VOCs) at low concentrations is essential and promising for the detection of indoor environmental quality, which, however, still remains a major challenge. To address this issue, this study proposes an innovative preconcentrator that combines nickel foam with Tenax TA adsorbent to significantly improve the detection limits for VOC detectors. The device utilizes the inherent Joule heating characteristics of nickel foam to develop an in-situ heated preconcentration element. This design takes advantage of the multi-scale pore structure of Tenax TA-loaded nickel foam to reduce mass transfer resistance, and also utilizes the electrical heat generation capacity and high thermal conductivity of nickel foam to achieve rapid thermal VOC desorption. The maximum preconcentration factor was achieved up to 22. The minimum desorption time and temperature can be controlled at 1.1 min and 87 °C, respectively. Across thirty VOC-concentration-controlled repeated thermal cycling tests, the relative standard deviation of the toluene detection performances was less than 6 %. When combined with a portable photoionization detector (PID), the preconcentration detection system demonstrates a low limit of detection (LOD) of 4.8 ppb for toluene. The LOD of the system is approximately the lowest in the literature for toluene analysis at < 100 °C desorption temperature. Further reduction in the LOD is anticipated with the use of a more precise detector. These characteristics, including exceptional LOD, stability, and sensitivity, make this preconcentrator a promising candidate for air quality monitoring.