The study established a new method of identifying different ether vapors by detecting the cataluminescence (CTL) intensities of both ether vapors and its reaction residual gas (including undecomposed analytes and reaction products) on two catalytic materials. In our work, we designed a sensor system: two cylindrical ceramic heaters (inner diameter=4 mm, length=8 cm) sintered with nanosized MgO or ZrO₂ about 0.2 mm thick on the surface were placed into two quartz tubes (diameter=1 cm, length=10 cm) respectively (the catalytic materials could be the same or different on two ceramic heaters. Two quartz tubes were connected by a polytetrafluoroethylene (PTFE) tube (35 m×0.4 mm×0.3 mm) which ensured that the signal peaks of each ether vapor and its reaction residual gas could be separated. Four kinds of ether vapors (dimethyl ether, ethyl ether, isopropyl ether and n-butyl ether) were investigated in the sensor system. Firstly, CTL signal I₁ was generated when each ether vapor passed through nano-MgO or ZrO₂ (the first order reaction). Then residual gas from first reaction was regarded as a new reactant and continued to be oxidized on nano-MgO or ZrO₂, generating new CTL signal I₂ (the second order reaction). The CTL signals were measured using a photomultiplier in the BPCL Ultra Weak CTL Analyzer, and the data was processed by Origin 7.5. It was found that for each ether vapor the ratio of luminescent response signals (I₁/I₂) was constant despite different concentrations of ether vapor under the optimal conditions of wavelength of 425 nm, temperature of 240 ℃, and flow rate of 220 mL/min. Therefore the sensor could identify and distinguish different ether vapor. In the research, we obtained four groups of I₁/I₂ values for each ether vapor by changing the direction of gas flow passing through ZrO₂ or MgO (four groups: MgO-MgO, MgO-ZrO₂, ZrO₂-ZrO₂ and ZrO₂-MgO). According to different luminescent intensity ratios of ether vapor on different combinations of sensitive materials, we could enhance the sensor's capacity of distinguishing different kinds of ether vapor by collecting multidimensional data and information. The linear range of four ether vapors was 50～1000 ppm and the detection limits were below the allowable concentration of ether vapor in the air. Furthermore, some common pollutants in the air such as formaldehyde, benzene, toluene and ammonia would not affect the results of the analysis. This method could quickly and easily identify different ether vapors. Meanwhile, the residual gas of dimethyl ether from both first and second order reactions on MgO-MgO surface were analyzed by gas chromatograph to demonstrate the possible mechanism of the CTL reaction in this sensor.

Key words: cataluminescence, chemiluminiscence, ether vapor, identification, sensor