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A semicontinuous process for the synthesis of methyl carbamate from urea and methanol was investigated in the autoclave without the catalyst. Some significant parameters were determined in terms of the methyl carbamate yield. The optimal reaction conditions were found at an initial molar ratio of methanol/urea of 6:1, a reaction temperature of 423 K, a flow rate of fresh methanol at 4 mL/min, a stirring speed of 800 rpm and a reaction time of 6 hours, respectively. A MC yield of 98.7 % was obtained at the optimal reaction conditions. Furthermore, the kinetics of this reaction were researched and the reaction activation energy was obtained as 110.498 kJ/mol. It was demonstrated that removing methanol containing ammonia from the autoclave and replacing it with continuously feeding fresh methanol resulted in a higher reaction rate and a high MC yield.

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Abstract:A new atropine drug-FET sensor, which was made of an ISFET (ion sensitive field effect transistor) and a drug sensitive membrane prepared by adding electric active matter to a β-cyclodextrin solution, was developed. The pH influence, selectivity, response curve, reproducibility, stability, response time and life of this sensor were investigated. A preliminary application of the sensor was discussed as well. The experimental results indicated that the sensor showed a Nernst response to atropine with a slope of 58.0 mV/decade over the concentration range of 5.0×10 -3 -1.0×10 -6 mol/L and the pH range of 5.0-8.5. The sensor detection limit was 8.0×10 -7 mol/L. The performance of this sensor was very stable when it was used to determine atropine concentration in a medicinal injection. The obtained results agreed well with the pharmacopoeia method.