## 5 Sensing Methods for Formaldehyde  
### Scopus Data-Base and Analytical Parameter Definition  
Research is currently aimed at developing increasingly low-cost systems with the aim of safeguarding the health of consumers. Given the ever-increasing attention being paid to these issues, it will be increasingly important to provide consumers with low energy consumption systems and sensors capable of detecting FA to allow for more careful monitoring. According to the WHO, for many of the diseases that arise with advancing age, we do not have efficient treatments available, nor, moreover, the specific symptoms of diseases that arise with aging could be delayed with the adoption of a healthy lifestyle. The studies for the monitoring of food conditions are placed in this context. With portable monitoring systems, it is possible to know the conditions of food in real-time, before it arrives on our tables and even, with the miniaturization of these systems, it will be possible to provide consumers when the food begins to deteriorate. In this contest, the sensing methods for determining FA play an important role in all the toxicological information above reported on this compound. The possibility to detect the FA level in any food matrix is relevant to the consumer human health protection. Following this statement, the authors performed a search on the Scopus database using different keywords, namely \"formaldehyde\" and \"food\" and \"sensor\" or \"electrochemical detection\": 96 documents including 52 in the last 5 years that document the growing interest and importance of this type of determination. The authors focused their attention on some papers investigating the main analytical parameters and also made a comparison with traditional procedures involving chromatographic techniques for understanding the goodness and efficiency or the limits of a proposed method. The papers were divided according to the matrix investigated. Before approaching the matrices, the authors would like to resume some important definitions and concepts as well: limit of detection (LOD) and limit of quantification (LOQ), defined as the quantities of analyte that produces a signal equal to three and ten times the standard deviation of the gross blank signal, respectively [44]; relative standard deviation (RSD), calculated from results generated under repeatability (or reproducibility) conditions [45]; recovery is the yield of a preconcentration or extraction stage of an analytical process for an analyte divided by the amount of analyte in the original sample [46]. Finally, it should be remembered that reaching good recoveries suggests that the proposed system is highly accurate: in some cases, this achievement allows to suggest to the authors to support the reliability and feasibility of the developed procedure in routine analysis or real-world applications. First, as it can be seen, over the sensing determinations [47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61], the two tables also show the main determinations carried out by traditional techniques (HPLC, GC, spectrophotometric techniques, etc.) for a comparison of the analytical parameters and for understanding the quality level reached by the electrochemical approach [51; 52; 53; 53; 62; 63; 64]. A clear difference between the papers regarding these two matrices can be drawn immediately: the fish matrix is more studied than the other one, diverse FA sensors are investigated for different kinds of fish, whereas, chicken is the preferred meat matrix considered. The first paper to be analyzed regards a FA rapid detection by means of a polydimethylsiloxane (PDMS) microfluidic chip [47]. [PERSON] et al. exploited the reaction between formaldehyde and acetylacetone in presence of ammonium acetate: the compound formed (i.e., 3,5-diacetyl-1,4-dihydrotidine) has an absorbance at 410 nm. A PDMS microfluidic chip was used for the measurements in the presence and absence of FA in the matrix.