Quantifying acetaldehyde in cider using a Mn(III)-substituted polyoxotungstate coated acoustic wave sensor

A new method for the quantification of acetaldehyde in a water matrix, namely commercial ciders, was developed using solid phase micro-extraction (SPME) followed by detection with a coated acoustic wave sensor. The sensitive coating was a polyoxometalate salt specially synthesised for this application, a compound tailored to be insoluble in water. Although the sample gaseous flow reaching the sensor needed to be dried, as the sensor itself responds to water, there was no sensitivity deterioration after contacting with water vapour, as frequency recover under dried nitrogen carrier was complete. Calibration lasted at least for two months. Comparing this sensor with the analogue previously coated with the soluble decamolybdodivanado phosphoric acid, the main advantage comes from the superior stability, and the possibility of keeping it in a wet environment without deterioration. The flow injection analysis (FIA) methodology here reported for the first time for acetaldehyde analysis in cider, allowed to obtain results not statistically different from the ones obtained with Gas Chromatography-Flame Ionization Detection (GC-FID) (alpha=0.05). Besides, the new methodology does not use expensive instrumentation and the analysis time is similar. Detection limit of this new method was 2.0 mg L-1, and quantification limit was 6.7 mg L-1, not much higher than the values of 1.4 mgL(-1) and 4.6 mg L-1, respectively, of the GC-FID. (C) 2017 Elsevier B.V. All rights reserved.