Detection of volatile primary aliphatic amines: Highly selective and sensitive vapoluminescent sensing of n-butylamine

Detection of volatile amines is of great interest for environmental and industrial monitoring for the protection of human health from exposure to toxic substances. This contribution describes the vapochromic and vapoluminescent properties of a Lewis acidic Zn(salen)-type Schiff-base complex and its application as a chemosensor for detection of n-butylamine (BA) vapors. Annealed films of the complex were initially involved for vapochromic and vapoluminescence screening experiments to evaluate their response towards compounds representative of each of the different chemical classes of volatile organic compounds (VOCs). Then, a cost-effective, disposable paper-based vapoluminescent sensor, characterized by high optical uniformity and repeatability, was developed for the selective and sensitive direct in-situ detection of BA vapors. Under static exposure conditions, the sensor allows a sensitive vapoluminescent detection of BA, with a LOD down to 2.0 ppm, below the permissible exposure limit of 5 ppm established by OSHA for BA, and a linear dynamic range up to 50 ppm. The sensor response is not affected by the exposure temperature, only a different exposure time is required as the temperature varies, while average relative humidity levels lead to almost negligible changes in the sensor response. The sensor is highly selective for BA with respect to ammonia and the different chemical classes of VOCs, including relevant primary aliphatic amines, with the exception of propylamine and sec-butylamine, especially at low concentrations (tens of ppm). Selectivity for BA is also demonstrated by competitive experiments in the presence of a 10-fold ppm amount of all representative VOCs of each class as potential interferents.