"Why would you need to detect and measure the ethanol in the environment?" -One might ask.
Well, as a matter of fact, the measurement of ethanol concentrations in the environment is of considerable significance for a surprisingly variety of purposes, which may include: ethanol production, industrial chemical processing, fuel processing and use, societal applications, and physiological research. In order to detect and analyze the ethanol present in the environment, numerous tools and methods are used diversely.
Well, as a matter of fact, the measurement of ethanol concentrations in the environment is of considerable significance for a surprisingly variety of purposes, which may include: ethanol production, industrial chemical processing, fuel processing and use, societal applications, and physiological research. In order to detect and analyze the ethanol present in the environment, numerous tools and methods are used diversely.
Ethanol sensors today
Most ethanol sensors today rely upon the use of metal oxides and powders that catalyse the oxidation of ethanol and use electrochemical or electrical conductivity. The problem for these common ethanol sensors include response times, power demands for metal oxide, conducting polymer based sensors or even the need for oxygen in many sensors. As a matter of fact, power demand is a key problem particularly when sensor heating is required. Fiberoptic and luminescence-based sensors also consume high power levels or are physically large.
Ethanol detection in aqueous environments using micro-capacitors and dielectric polymers
Using micro-capacitors and dielectric polymers is one method of detecting and analysing any ambient ethanol in an aqueous environment. This is a better apparatus than a large number of commercial ethanol measurement systems that are commonly available, but in general, these systems are designed exclusively for measurements in vapour form, operate at relatively high power levels, are bulky, and possess limited functionality that is not sufficient for a number of applications.
This unique technique is one that can also measure ethanol concentrations in aqueous mixtures. This detector was actually part of a project whose major goal was to develop an ethanol micro-sensor of reduced size with low-power requirements and without the need for oxygen, while providing accurate measurement of significant ethanol levels in aqueous solutions. It consists of using a permeable membrane to transport ethanol vapours to a chemi-capacitor array. The fixed plate micro-capacitors inside were already filled with a polymeric dielectric material, siloxanefluoro alcohol, whose dielectric constant increases when ethanol vapour is absorbed. Measurements of ethanol's liquid concentration are then made in its vapour-phase by sampling the saturated vapours through a vapour permeable nano-pore filter. The performance of these sensors was then analysed over a range of ethanol/water mixture concentrations and flow cell temperatures. The limit of detection for ethanol in water using the capacitive micro-sensors in the present arrangement was found to be 40 ppm, which is in fact extremely precise.
This unique technique is one that can also measure ethanol concentrations in aqueous mixtures. This detector was actually part of a project whose major goal was to develop an ethanol micro-sensor of reduced size with low-power requirements and without the need for oxygen, while providing accurate measurement of significant ethanol levels in aqueous solutions. It consists of using a permeable membrane to transport ethanol vapours to a chemi-capacitor array. The fixed plate micro-capacitors inside were already filled with a polymeric dielectric material, siloxanefluoro alcohol, whose dielectric constant increases when ethanol vapour is absorbed. Measurements of ethanol's liquid concentration are then made in its vapour-phase by sampling the saturated vapours through a vapour permeable nano-pore filter. The performance of these sensors was then analysed over a range of ethanol/water mixture concentrations and flow cell temperatures. The limit of detection for ethanol in water using the capacitive micro-sensors in the present arrangement was found to be 40 ppm, which is in fact extremely precise.
Ethanol detection in air and water using the znose instrument
The zNose instrument is another innovative way of detecting and measuring ethanol in air or water. The zNose is a very sensitive ultra-fast gas chromatograph designed to detect vapours covering a specific range. It simulates an almost unlimited number of virtual chemical sensors, which can produce high-resolution images based upon aroma chemistry. The zNose is able to perform analytical measurements of volatile organic vapours and odours in near real time with part-per-trillion sensitivity. Separation and quantification of the individual chemicals within an odour is also performed in the following seconds.
To detect ethanol in ambient air, the instrument first has to be calibrated by injecting known amounts of ethanol into a known volume of air in a Tedlar bag. For instance, injecting 1 µL of pure ethanol into 1000 mL of air will produce 415.3- ppmv of ethanol vapour.
To detect ethanol in water, headspace vapours from water were sampled directly using a sample needle filter attached to the inlet of the zNose. The concentration of ethanol in detected this way from water at room temperature is very low because ethanol is very soluble in water. Heating the water sample using a vial heater can greatly increase the accuracy of results. For example, a 300-ppm water standard at 40°C had a precise response of 104 ppmv.
By using the zNose instrument, even though ethanol is at the lower limit of detectable compounds, concentrations well into the low part-per-million range can be quantified with good precision and accuracy. Because ethanol is very soluble in water, measurements are best performed with water samples elevated to at least 40°C. Nevertheless, precisions up to <5ppm of ethanol present in air or water can be measured precisely using the instrument.
To detect ethanol in ambient air, the instrument first has to be calibrated by injecting known amounts of ethanol into a known volume of air in a Tedlar bag. For instance, injecting 1 µL of pure ethanol into 1000 mL of air will produce 415.3- ppmv of ethanol vapour.
To detect ethanol in water, headspace vapours from water were sampled directly using a sample needle filter attached to the inlet of the zNose. The concentration of ethanol in detected this way from water at room temperature is very low because ethanol is very soluble in water. Heating the water sample using a vial heater can greatly increase the accuracy of results. For example, a 300-ppm water standard at 40°C had a precise response of 104 ppmv.
By using the zNose instrument, even though ethanol is at the lower limit of detectable compounds, concentrations well into the low part-per-million range can be quantified with good precision and accuracy. Because ethanol is very soluble in water, measurements are best performed with water samples elevated to at least 40°C. Nevertheless, precisions up to <5ppm of ethanol present in air or water can be measured precisely using the instrument.