Application of Chemical Sensors and Sensor Matrixes to Air Quality Evaluation

The Influence of Hydrogen on the Indications of the Electrochemical Carbon Monoxide Sensors

This article examines electrochemical carbon monoxide (CO) sensors used as mobile devices by rescue and firefighting units in Poland. The conducted research indicates that the presence of chlorine (Cl2), ammonia (NH3), hydrogen sulfide (H2S), hydrogen chloride (HCl), hydrogen cyanide (HCN), nitrogen (IV) oxide (NO2), and sulfur (IV) oxide (SO2) in the atmosphere does not affect the functioning of the electrochemical CO sensor. In the case of this sensor, there was a significant cross effect in relation to hydrogen (H2). It was found that the time and manner of using the sensor affects the behavior in relation to H2. Such a relationship was not recorded for CO. Measurements in a mixture of CO and H2 confirm the effect of hydrogen on the changes taking place inside the sensor. Independently of the ratio of H2 to CO, readings of CO were flawed. All analyses showed a significant difference between the electrochemical CO sensor readings and the expected values. Only in experiments with a 1:3 mixture of CO and H2 was the relative error less than 15%. The relative error in the analyzed concentration range for a sensor with an additional compensation electrode ranged from 7% to 38%; for a sensor without this electrode, it ranged from 23% to 55%. It was ascertained that in the cases of measurements for tests carried out at higher concentrations of H2 in relation to CO, a sensor with an additional electrode is significantly better (more accurate) than a sensor without such an electrode. Differences at the significance level p = 0.01 for measurements made in the CO:H2 mixture at a ratio of 1:3 were ascertained.

Electronic noses: Powerful tools in meat quality assessment

Main factors that are considered by consumers when choosing meat products are colour and aroma, of which the latter is a more reliable indicator of quality. However, a simple sensory evaluation of hedonistic qualities is often not sufficient to determine whether protein is past its shelf life, and consumption of spoiled meat can lead to serious health hazards. Some volatile compounds can be used as spoilage indicators, and so a device equipped with a sensor sensitive to particular odorants would prove useful. Unfortunately, no such single compound has yet been identified, as the changes taking place in a sample of meat during storage are contingent on numerous factors. On the other hand, a combination of volatile compounds may form a unique 'fingerprint' which can be analysed pattern recognition algorithms with an electronic nose. It can supplement established techniques of meat quality assessment by providing results that correlate well with hedonic perception in a short time and at a low cost.