Abstract

In this study, formaldehyde (FA) in the air was collected and analyzed using metal-organic framework-5 (MOF-5) as the sorbent material (for both sorbent tube (ST) sampling and thermal desorption (TD) analysis) in gas chromatography-mass spectrometry (GC-MS) detection. A series of experiments was carried out to determine the optimal analytical conditions for maximum recovery of FA by TD-GC-MS. Optimal TD conditions for adsorption and desorption of MOF-5 were determined to be −25°C and 100°C, respectively. These conditions yielded good linearity (R2=0.9975), precision (mean 1.79±1.17%), and high sensitivity. The method detection limit (MDL) of 0.1ng was attained to determine 0.82ppb of FA in 100mL of air (limit of detection (LOD) of 8pg (0.06ppb)). The concentration of FA, when measured from ambient air samples using MOF-5, averaged 9.67ppb (n=3, RSE=2.39%). FA samples, when analyzed in parallel using the DNPH cartridge-HPLC-UV system recommended by the US EPA, yielded similar results (mean of 10.5ppb) to the MOF-5 dataset. In addition, trace quantities of FA (0.25ng) were also detected from samples of as little as 20mL of air. Our results suggest that MOF-5 is a suitable sorbent media for thermal desorption analysis and in fact surpasses the performance of commercial sorbents used for VOC analysis. As such, a GC-based detection method for FA comprising simple thermal desorption without complicated procedures, such as a derivatization step, was realized.

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