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Formaldehyde can have detrimental health effects on humans. To reduce exposure to formaldehyde, several methods have been reported for gas-phase formaldehyde determination including chromatography, capillary electrophoresis electrochemical and so on. Among these methods, colorimetric sensor is a promising technique for its high sensitivity, selectivity, low cost and compactness. However, it usually takes tens of minutes for one measurement. In this paper, a real-time continuous rapid formaldehyde determination system based on colorimetric sensor was presented. Through the study of the relationship between inlet diameter of gas and its bubble size and reaction speed, the reaction time is reduced to 1/3 with an ability to detect formaldehyde concentrations as low as 0.02 ppm. The system can also measure the formaldehyde concentration continuously and automatically, which is vital for locating pollution sources.

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In recent years, researchers have used various methods to study flexible sensors based on carbon nanomaterials, among which impedance analysis has unique advantages in studying the sensor mechanism. In this paper, we investigated the impedance characteristics of a flexible zero-dimensional carbon nanocomposite strain sensor, establishing a simple electrical model by electrochemical impedance spectroscopy (EIS). Based on the model, the sensing mechanism of the flexible strain sensor was analyzed. The noise analysis theory of the flexible strain sensor was established, and it is proved that the noise of the sensor can be reduced significantly when an AC signal is applied, which will improve the accuracy of the sensor.

Steam dryness detection is crucial in the field of oil exploitation. Steam dryness too high will be dangerous, whereas steam dryness too low will affect the efficiency of extraction. Therefore, real-time, high-precision detection of steam dryness is essential. The methods for detecting steam dryness include chemical, thermodynamic, radiometric, and microwave. The manual test method possesses the best detection accuracy. However, the real-time performance is not good, and the detection process is cumbersome. Here we propose using a silver nitrate solution to titrate chloride ions and combining them with the change in the absorbance of the solution to determine the endpoint of the titration. We report that the automatic chloride ion concentration measurement was a rep and that the detection of chloride ion concentration was 15 mg/L. The detection linearity reached 0.992. Therefore, our titration endpoint judgment method has better anti-interference.