有机元素微量分析标准物质——茴香酸的研制

茴香酸的分子式为C_8H_8O_3,碳含量63.15%、氢含量5.30%、氧含量31.55%、甲氧基含量20.40%。该标样与日本元素分析恳谈会委员会、英国化学协会微量化学委员会所公布的微量化学标样之一——香草醛一样,都具有相同的碳、氢、氧和甲氧基含量,美国国家标准局(NBS)发行SRM142茴香酸作为微量分析中甲氧基的分析标样。     

A new study of the enzymatic hydrolysis of carboxymethyl cellulose with a bulk acoustic wave sensor

A new bulk acoustic wave (BAW) cellulase sensing technique, which is based on the enzymatic hydrolysis process of sodium carboxymethylcellulose (CMC) by cellulase, was established. The frequency shift curves of BAW sensor indicated that the viscosity of the tested solutions decreased during the hydrolysis process. The hydrolysis rate of CMC by cellulase was calculated from the frequency shift curves. The hydrolysis rate of CMC under different pH conditions at 30°C showed that cellulase had high hydrolysis ability approximately at pH 5.0. Kinetic parameters (the Michaelis constant K_m and the maximum rate V_max) of the process were estimated by using a linear method of Lineweaver–Burk plot. K_m is 1.95±0.25 mg ml⁻¹ and V_max is −(4.25±0.58)×10⁻³ g^1/2 cm^−3/2 cP^1/2 min⁻¹. Also the activation energy (E_a) of the enzymatic hydrolysis, with a value of 51.99±1.26 kJ mol⁻¹, was estimated in this work.     

Rapid detection of Escherichia coliform with a bulk acoustic wave sensor based on the gelation of Tachypleus amebocyte lysate

A new sensing method (BAW-TAL technique), which combined the bulk acoustic wave (BAW) technique with the gelation reaction of Tachypleus amebocyte lysate (TAL), was used for viscosity and density measurement and applied to the detection of Escherichia coliform (E. coli). This method depended on the fact that the viscosity and density of the mixture increased, and as a result, the resonance frequency decreased correspondingly after TAL was mixed with the heated E. coli solution that contained endotoxin. Results showed that the frequency shift was linearly related to the logarithm of E. coli concentration in the range of 2.7x10(4)-2.7x10(8) cells/ml. The correlation coefficient was 0.996. This BAW-TAL method was compared with the standard pour plate counts (PPC) method. The proposed method was much more rapid and simpler for detection of E. coli than the traditional methods.     

高效液相色谱/安培检测法测定蜂蜜中苯酚残留量

研究了用高效液相色谱 /安培检测法测定蜂蜜中苯酚残留量。考察了试验参数对测定结果的影响。在所选试验条件下 ,苯酚保留时间约为 12min ,检出限为 2 .0ng·g- 1。三组不同水平的加样回收率为 91.6 10 1.9% ,相对标准偏差 2 .812 .8%。测定结果满意