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《Analytical letters》2012,45(11):2321-2331
ABSTRACT ABSTRACTA new kinetic spectrophotometric method for the simultaneous determination of concentrations of micro bromide and iodide has been proposed. It is based on their catalytic effects on the reaction of m-cresol purple oxidized by potassium periodate in hydrochloride acid medium. The reaction rate was monitored by measuring the decrease in absorbance at 528nm and the increase in absorbance at 455nm. The total difference in absorbance of the sum of bromide and iodide is identical with determination of bromide was carried out after Cr(VI) oxidized I? to I2, and I2 was removed by extraction with CCI4, and the amount of iodide was measured by subtracting the absorbance change of bromide from the total absorbance change in the presence of bromine and iodide. The optimum conditions influencing the reaction rate were studied. The linear range of determination is 0~4.0μg/ml for Br? and 0~3.0 μg/ml for I?. The detection limits are 0.032μg/ml for Br? and 0.059 μ/ml for I?. The method was successfully applied to the determination of micro amounts of bromide and iodide in food and life samples. 相似文献
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We compared the photochemical reaction of m-cresol containing OH precursors such as H2O2, NO2- and NO3- in aqueous solution with those in ice. The results show that the conversion rate of m-cresol in aqueous solution was higher than that in ice. H2O2, NO2- and NO3- all accelerated the photoconversion of m-cresol in both aqueous solution and ice. The photochemical reactions of m-cresol obeys the first order kinetics equation. According to the photoproducts identified by GC-MS, we proposed that hydroxylation and nitration reactions occurred in both aqueous solution and ice. Coupling reaction was common in ice, however, in aqueous solution it was found only in UV system. Our results suggest that the photochemical reactions of m-cresol were different in aqueous solution and in ice. 相似文献
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柱前衍生高效液相色谱法分离分析甲酚异构体 总被引:1,自引:0,他引:1
提出了柱前衍生高效液相色谱法同时分离测定邻甲酚、间甲酚和对甲酚的方法。含甲酚异构体的样品与衍生化试剂按1比8(质量比)混合,加热回流衍生2 h。3种异构体的转化率依次为98.1%,99.0%,98.5%。选用Eclipse XDB-C_(18)色谱柱作为反相色谱柱,以甲醇和水以体积比为35比65的混合溶液为流动相,在260nm波长处进行测定,乙酸邻甲酚酯、乙酸间甲酚酯的峰面积与其浓度在(0.05~3.75)×10~(-5)mol·L~(-1)范围内呈线性关系,而乙酸对甲酚酯在(0.03~2.25)×10~(-5)mol·L~(-1)之间呈线性关系,检出限(3S/N)依次为1.88×10~(-5),1.88×10~(-5),1.13×10~(-5)mol·L~(-1)。此方法应用于实际样品的测定,回收率分别为104%,95%,100%,相对标准偏差(n=7)分别为0.22%,2.34%,0.90%。 相似文献
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《Analytical letters》2012,45(5):315-322
Abstract A survey of 14 substrates for the fluorometric determination of the oxidative enzyme-horseradish peroxidase was carried out. The compounds which seemed to act well as substrates are serotonin, guaiacol, o-cresol, p-cresol, m-cresol, homovanillic acid and m-tyrosine. L-Epinephrine, equilenin, equilin, β-estradiol, estriol, and estrone were studied and found not to be substrates of the system. The kinetics of the oxidation reactions were studied. They followed the Michaelis constant rate equation. The Michaelis constant, Km, was determined by a Lineweaver-Burk plot for each substrate. It would appear that the presence of a group in the ortho, para, or meta position of the phenolic ring decreases the binding of the subtrate to the enzyme's active site, as shown by the km values obtained. It may be concluded that m-tyrosine is the best substrate (lowest km value) when compared to all the substrates which have been studied to date by the authors. 相似文献
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动力学催化光度法测定痕量亚硝酸根 总被引:5,自引:2,他引:5
王瑜 《理化检验(化学分册)》2005,41(8):561-562,568
基于硫酸介质中亚硝酸根催化溴酸钾氧化间甲酚紫的褪色反应,建立了测定痕量亚硝酸根的新方法,并探讨了动力学条件,测定了反应的表观速率常数(k′=1.03×10-4s-1)和表观活化能(E′a=10.25kJ.mol-1)。方法的测定范围为8.0~150μg.L-1,检出限为0.9μg.L-1。方法已用于水样中亚硝酸根的测定。 相似文献
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