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    A simple and green approach for colorimetric ammonia determination by combining pervaporation with paper impregnated anthocyanins extracted from red cabbage
    (2020-09-01)
    Jongprakobkit, Jurairat
    ;
    Wisaichon, Wannakan
    ;
    Praditweangkum, Wiboon
    This work reports on the development of a simple, green and inexpensive analytical method utilizing a microwell plate for ammonia determination by combining pervaporation with a paper-based colorimetric sensor. The method is based on the conversion of ammonium ions to ammonia gas by alkalinization of water samples using powdered calcium hydroxide. The generated ammonia gas diffuses freely across the headspace to a paper-based sensor impregnated with natural anthocyanins extracted from red cabbage using deionized water as a non-toxic solvent. The reaction causes the paper sensor to change color from pink to blue, and the sensor is then scanned on a flatbed scanner to quantify ammonia by correlation to the reflectance of the blue spot on the paper sensor. Under the optimal conditions, a working range of 1.00-25.0 mg N l<sup>-1</sup> was obtained. The limit of detection and the limit of quantification were found to be 0.29 and 0.98 mg N l<sup>-1</sup>, respectively. The method was successfully applied for determining total ammonia in water samples with recoveries in the range of 89.6-110.5%. No significant difference was observed between this method and the phenate spectrophotometric standard method.
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    Influence of milling time, NH3 additive and annealing temperature on physical properties of modified commercial TiO2 powders via ball milling process
    (2014-01-01)
    Techitdheera, Wicharn
    ;
    Rattanarak, Jiravat
    ;
    Mekprasart, Wanichaya
    ;
    Pecharapa, Wisanu
    N-doped TiO<inf>2</inf> were prepared via ball milling process with different operating times and annealing temperatures. Commercial TiO<inf>2</inf> anatase powders used as TiO<inf>2</inf> precursor were dispersed in ammonia solution for nitrogen source. Ball milled TiO<inf>2</inf> powders at various times were annealed in nitrogen atmosphere at different temperatures. Physical properties and surface morphologies after ball milling process were monitored by X-ray diffraction (XRD) and scanning electron microscope (SEM). The component of samples was characterized by energy-dispersive X-ray spectroscopy (EDX). The active surface area of the samples was investigated by Brunauer Emmet Teller method. SEM result indicated that large particle of TiO<inf>2</inf> precursor could be reduced via ball milling process leading to high active surface area by the increase of milling time. XRD result showed the crystalline structures of TiO<inf>2</inf> after milling process and nitrogen annealing were identical to TiO<inf>2</inf> precursor structure. Meanwhile, the appearance of impurity phase in TiO<inf>2</inf> precursor was also depreciated via ball milling process with ammonia solution and annealing under nitrogen atmosphere.
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    SiO2-Multiwalled carbon nanotube base gas sensor
    (2008-12-01)
    Jesen, S.
    ;
    Ruangphet, S.
    ;
    Cheirsirikul, S.
    The gas sensors are fabricated from multiwalled carbon nanotube-based. The electrode is constructed from platinum (Pt) and titanium (Ti). The gas sensors are used for detecting oxygen (O<inf>2</inf>), ethyl alcohol (C <inf>2</inf>H<inf>5</inf>OH) and ammonia (NH<inf>3</inf>) by measuring the charge of their electrical capacitance. In the ratio silicon dioxide (SiO <inf>2</inf>) : carbon nanotube (MWCNTs) = 100:1 by weight, the electrical capacitance of the film layer has changed at the highest rate. The response of oxygen with concentration of 10,000 ppm, 20% of ethyl alcohol and 20% of ammonia, it is found that the electrical capacitance of thin layer has change about 34%, 60% and 70%. © 2008 Trans Tech Publications, Switzerland.