In this paper, uricase, catalase, and electron mediator were coimmobilized on the surface of the tin oxide (SnO2)/indium tin oxide (ITO) glass, to develop a disposable potentiometric uric acid biosensor. The SnO2/ITO glass was employed as a pH sensor, fabricated by sputtering SnO2 thin films on the ITO glass. 3-Glycidyloxypropyltrimethoxysilane (GPTS) was utilized to immobilize uricase, catalase and the electron mediator (ferrocenecarboxylic acid, FcA) on the sensing window. The experimental results reveal that the optimal weight ratio of uricase, FcA to catalase (CAT) is 4:1:2. The sensor responds linearly between 2 mg/dl and 7 mg/dl at pH 7.5, in 20 mM of test solution, with a correlation coefficient of 0.99213. Accordingly, no significant interference was observed when interfering substances, glucose, urea and ascorbic acid, were added to the uric acid solution. Moreover, the recorded voltage was relatively constant during the first 28 days of measurement. Consequently, a potentiometric uric acid biosensor was realized with the advantages of low cost and simple fabrication.
This paper introduces a novel “direct reaction - hot extrusion” technique for producing high effective, fast modification and high Sr content Al-Sr20 master alloy. It mainly contains four processes: 1) Alloying by a medium-frequency induction furnace with complementary mechanical and electromagnetic stirring; 2) Degassing and deslagging by a rotary degassing method; 3) Casting coarse alloy bars; 4) Producing Al-20Sr master alloy wire by using a hot-extrusion process of large cross-section deformation. Microstructural characterizations revealed that the intermetallic Al4Sr phase in the Al-Sr20 alloy was homogeneously distributed in Al matrix with small size and roundish shapes, which ensured the master alloy wire exhibit advantages including high recovery, good reproducibility, no delitescence of modification, no corrosion on equipments, and good workability with smooth surface, no bubbles, no peeling and no cracking. This Al-Sr20 master alloy has been industrially applied in Al-Si alloys casting in automobiles and motorcycle wheels, etc.
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