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Synthesis and Characterization of Controlled-Release Urea Fertilizer from Superabsorbent Hydrogels Salih Muharam; Afria Fitri; Lela Mukmilah Yuningsih; Yulia Mariana Tessa Ayudia Putri; Isnaini Rahmawati
Indonesian Journal of Chemistry Vol 20, No 3 (2020)
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (448.568 KB) | DOI: 10.22146/ijc.44230

Abstract

It is very important to develop controlled-release fertilizers to ensure efficiency and environmental protection. This study aims to make a superabsorbent hydrogel-based controlled-release urea fertilizer. Superabsorbent hydrogels were prepared from the cellulose of corn cobs cross-linking with epichlorohydrin, and then an amount of urea as a fertilizer was stored inside the hydrogels (GEL-A). The GEL-A functionalization with carboxy-methyl was also carried out in this study to improve the hydrophilicity of hydrogels (GEL-B). GEL-A and GEL-B were immersed in water at a certain pH and temperature range and the urea concentration released from the hydrogels was monitored by a spectrophotometer. The results showed that the urea released by GEL-A and GEL-B was not much different. Respectively, the urea efficiency of GEL-A and GEL-Bwas around 5.29% and 5.56% for 180 min. The urea released from both hydrogels was not significantly affected by changes in the temperature of the solution. Urea release was influenced by pH, and the rate of urea release of GEL-B was faster than GEL-A, so pH control was needed in the application of this slow-release fertilizer.
Electrogenerated Chemiluminescence for Immunoassay Applications Isnaini Rahmawati; Irkham Irkham; Rahmat Wibowo; Jarnuzi Gunlazuardi; Yasuaki Einaga; Tribidasari Anggraningrum Ivandini
Indonesian Journal of Chemistry Vol 21, No 6 (2021)
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/ijc.64596

Abstract

Electrogenerated chemiluminescence (ECL) has recently become one of the most prominent and well-established transducers for immunoassay techniques. ECL relates a luminophore concentration in solution with the emission of light triggered by an electrochemical stimulus. ECL immunoassay (ECLIA) performance depends on the parameters of its light generation, including the luminophore, the species that emit light called labels in ECLIA; co-reactants, which are added reagents that support the luminophore to undergo the excited state; electrodes, which are the place for the ECL reactions to take place; and the format of the immunoassay. This review discusses the behaviour of ECLIA parameters, the required instrumentations, and some important examples of detections based on ECLIA.
Carbon-coated nickel foam for hypochlorous acid sensor Afiten Rahmin Sanjaya; Hanzhola Gusman Riyanto; Isnaini Rahmawati; Yulia Mariana Tesa Ayudia Putri; Dede Nurhalimah; Endang Saepudin; Yudistira Tesla; Yuni Krisyuningsih Krisnandi
Environmental and Materials Vol. 1 No. 1: Juni (2023)
Publisher : Institute for Advanced Science, Social, and Sustainable Future

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.61511/eam.v1i1.2023.105

Abstract

The electrochemical detection method of hypochlorous acid (HOCl) using carbon foam electrodes have been successfully developed. The carbon foam was prepared from carbon-coated nickel foam which is synthesized using a hydrothermal-carbonization method. SEM characterization indicated that the optimum synthesis of carbon-coated nickel foam has been achieved on the 4th layer coating process with an expected spherical structure, while characterization using FTIR and Raman spectroscopy confirmed the formation of graphitic material with D band and G band characteristics. An electroactive surface area of ​​0.0236 cm2 was achieved. Cyclic voltammetry of HOCl in 0.1 M phosphate buffer solution pH 6.0 showed the best current response for HOCl reduction occurs at a potential of -0.3 V (vs. Ag/AgCl). Further detection of HOCl using amperometry technique in the concentration range of 2-200 μg/mL showed good linearity with sensitivity of 9.112 mA/µg/L and an estimated detection limit of 1.96 µg/mL. Good repetition is indicated by the RSD value of 2.499 % (n=5). This developed sensor also showed good selectivity in the presence of interference compounds, such as FeCl2 and CuSO4. Besides, the determination of HOCl in tap water has been successfully conducted and generated a comparable result with the UV-VIS method (3.30 µg/mL hypochlorite). The results indicated that the developed sensor is promising for the detection of HOCl in environmental applications.