A design of thermal desorption unit for ultra-sensitive detection of compounds by ion mobility spectrometry.

A solvent-free, low-dead-volume design of a thermal desorption unit (TDU) was developed as an introduction system to significantly improve the performance of handheld ion mobility spectrometry (IMS). The TDU configuration eliminates solvent interference using solvent-free desorption, enhancing the sensitivity of IMS analysis and preventing signal overlap between the analyte and the solvents. Furthermore, the dead volume of the introduced TDU was decreased to diminish the peak broadening to a few seconds. The major advantage is the ability to maintain a uniform temperature within the TDU to avoid analyte condensation toward IMS. Furthermore, the designed platform was validated to analyze compounds with diverse physicochemical properties, including pesticides, drugs, and explosives. To demonstrate the potential of the TDU in real sample analysis, chlorothalonil (CTL) was chosen and determined as a test compound using the thin film microextraction method followed by IMS. Metal organic framework-808@5-nitroisophthalic acid (NIP) was synthesized by a solvothermal procedure, and electrospinning was applied to prepare the thin film. Several experimental factors influencing the extraction efficiency and signal of CTL were identified and optimized. The linearity, limit of detection, and limit of quantification were obtained to be 0.3-10 ng mL-1, 0.09 ng mL-1, and 0.3 ng mL-1, respectively. The intra- and inter-day repeatabilities were calculated as 2% and 6% for 0.5 ng mL-1, and as 3% and 7% for 5.0 ng mL-1. Several real samples, consisting of tomato, cucumber, and lake water, were chosen to assess the performance of the suggested approach. The spiking recovery values ranged from 98% to 107%. Additionally, the accuracy of the proposed approach was evaluated using the EPA 508 reference method.