Development of Simplified Analytical methods for In-situ Detection of Ammonia and Urea in Aqueous Solutions
Date
2021-06-09
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Abstract
In-field analysis of nitrogen-containing compounds such as ammonia and urea remains challenging due to the limitations of conventional methods such as non-portability, the toxicity of reactants, and the need for a trained operator. This study presents a colorimetric pH detection paper-based sensing as a promising technology which has the potential to replace conventional methods such as spectrophotometry and electrochemical methods for in-field screening of nitrogen-containing compounds. The application of filter paper and smart-handy devices (e.g., the smartphone camera and RGB app.) makes these sensing devices convenient, inexpensive, and suitable for instant field application. Moreover, the use of non-toxic reagents further stimulates the exclusivity of this technique. Besides, the pervaporation and headspace gas diffusion eliminate the interferences and sample pre-treatment requirement, which reduce the analysis time and cost.Cost-effective, highly sensitive, and convenient anthocyanin-based paper sensors for in-field determination of ammonia and urea were fabricated in this project. Sensors were fabricated by immobilization of anthocyanin extracted from natural sources such as red cabbage (Red-C), blueberry (Blue-B) and blackberry (Black-B) in deionized water (Aq100) and 80% ethanol-water mixture (Aq20Et80) by simple immersion. Ammonium ion and urea were converted to ammonia by alkalinization and thermo-catalytic urea hydrolysis, respectively. The generated ammonia is detected by the anthocyanin-based sensor. The sensor reaction zone imaged by a smartphone (or flatbed scanner) and processed for RGB quantification by ImageJ software to correlate the analyte concentration with red intensity absorbance. The anthocyanin-based ammonia sensor offered a dynamic linear working range (1-10 mg NH3-N/L) with 0.2911 mg NH3-N/L limit of detection (LOD). Similarly, the anthocyanin-based urea sensor presented a dynamic linear working range (5-30 mg urea-N/L) with 0.2911 mg urea-N/L limit of detection (LOD). The accuracy of the proposed paper-based sensors was validated by the standard spectrophotometry method, which makes the fabricated sensors suitable for in-field analysis.
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Haq, S. (2020). Development of Simplified Analytical methods for In-situ Detection of Ammonia and Urea in Aqueous Solutions (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.