Detection of hexanal in humid circumstances using hydrophobic molecularly imprinted polymers composite

Hexanal is a specific volatile organic compound (VOC) for monitoring the quality of various agricultural products and a biomarker for diagnosing lung cancer of human beings. However there is no existing hexanal gas sensor with high sensitivity and selectivity for hexanal detection in the presence of water vapor. Addressing this challenge, a quartz crystal microbalance (QCM) gas sensor modified with a hydrophobic molecularly imprinted polymers (MIPs) composite for hexanal detection was reported. Hexanal could selectively bind with the MIPs through hydrogen bonding while the hydrophobic silica nanoparticles could give the electrode resistant to water vapor. The QCM gas sensor showed the highest response to hexanal among the other tested vapors, and had little responses towards TMA, NH3, ethanol, acetone, acetic acid and diethyl ether. Octanal reached the second place followed by nonanal, but they two caused much less frequency shifts than that of hexanal. The QCM gas sensor was reliable for hexanal detection in the range of 1-80 ppm and able to detect hexanal amount from about 14.1 ppm-27.3 ppm in grass carp fillets with about 80% relative humidity in 7 days. The results displayed positive correlation with the solid phase micro extraction-gas chromatography mass spectrometer (SPME-GCMS) analysis of the same grass carp fillets samples, and the correlation coefficient was 0.98. It may offer some new ideas for gas sensors development with high sensitivity and selectivity in areas of quality evaluation of agricultural products and health evaluation of human beings.