ZnO nanorod coating for solid phase microextraction and its applications for the analysis of aldehydes in instant noodle samples.

Zinc oxide (ZnO) nanorods based solid-phase microextraction (SPME) coating was directly prepared on stainless steel wires using in situ hydrothermal growth method. This coating has high surface-to-volume ratio with a diameter in the range of 300-500 nm and a thickness of about 3-5 μm. A guiding tube was introduced into the laboratory-made SPME fiber to protect the ZnO nanorods coating from shaving, which significantly improved the method repeatability and prolonged the service life of the coating. The extraction properties of the prepared fiber were investigated using headspace SPME (HS-SPME) coupled to gas chromatography (GC) for the determination of aldehydes in instant noodle samples. The extraction efficiency of the coating for the five aldehydes was comparable to that of a commercial 85 μm Carboxen/Polydimethylsiloxane fiber, which has been reported to have best affinity towards aldehydes among all commercial fibers. The linear ranges of the proposed HS-SPME-GC method were from 0.05 to 5 μg g⁻¹ (hexanal, nonanal and decanal) and 0.1-5 μg g⁻¹ (heptanal and octanal), with the correlation coefficients from 0.990 to 0.999. The method developed was successfully applied to the determination of five aldehydes in instant noodle samples, and the recoveries were found to be 70.5-129% at the spiking level of 2 μg g⁻¹.