Methodological variation in headspace analysis of liquid samples using electronic nose

Abstract

a b s t r a c tIn past years, numerous electronic nose (e-nose) developments have been published describing analyses of solid-, liquid-or gaseous media in microbiological-, environmental-, agricultural-or medical applications. However, little has been reported about complex methodological pitfalls that might be associated with commercially available e-nose technology. In this paper, some of these pitfalls such as temperature, the use of filters and mass flow using different sampling methods (static-and dynamic sampling) are described for two generations of conducting polymer e-noses (ST114/214, CPs, both Scensive Tech. Ltd.). A comparison with metal oxide semiconducting field effect transistor/metal oxide semiconductor (MOSFET/MOS) e-noses regarding stability across replicates and over time was made. Changes in temperature were found to give larger sensor responses, whereas the application of filters led to quantitative and qualitative changes in sensor responses due to a change in mass flow which was also affected by the sampling method. Static sampling provided more stable flows across replicates. Variation was investigated for CPs and MOSFET/MOS e-noses that gave different responses over time and across replicates. These methodological factors cause a lack of stability and reproducibility, demonstrating the pitfalls of e-nose technology and therefore limit their utility for discriminating between samples.

Electronic nose responses and acute phase proteins correlate in blood using a bovine model of respiratory infection☆

“…Ltd., Leeds, UK). Serum headspace was sampled using the static sampling method described previously [25]. Briefly, serum was defrosted and pipetted into Nalophan bags.…”

“…of replicates 3 to 5 were used for further analysis since they proved to be stable in flow [25]. All samples were blinded and analysed randomly.…”

“…These differences obtained with sensors 3, 6 and 7 allowed discrimination between infected and non-infected individuals. Discrimination based on individual samples was not possible because of large variation across all sensors due to methodological factors and inconsistencies of the sensor surface associated with them [25]. Discrimination was also made difficult by the temporal changes in divergences over the course of the infection.…”

Sample handling for electronic nose technology: State of the art and future trends

“…Such an approach makes it possible to estimate adsorption-desorption kinetics at the sensor surfaces just from the first seconds of measurement, because variation of sample concentration in the measuring cell occurs quickly and does not affect the character of sensor responses. This approach (called pressure balanced sample injection) can be used both for static and dynamic sample injection procedures [26,43,44].…”

Rapid lard identification with portable electronic nose

“…Receptors in an electronic nose are its sensors which can be selected to detect an odour of interest. In general, an electronic nose is a combination of an odour delivery system, sensor (array), data acquisition and data analysis unit [14]. Electronic noses have various applications in environmental and medical researches.…”