Kanev Igor L, Mikheev Andrei Y, Shlyapnikov Yuri M, Shlyapnikova Elena A, Morozova Tamara Y, Morozov Victor N
Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences , Pushchino, Moscow region 142290, Russia.
Anal Chem. 2014 Feb 4;86(3):1511-7. doi: 10.1021/ac403129f. Epub 2014 Jan 24.
It was demonstrated that electrospraying (ES) of solvents from a glass capillary proceeds without emission of light provided that the current is kept below a certain critical level (<100 nA at positive potential and <25 nA at negative potential for 96% ethanol; < 40 nA at positive potential for water). Though the onset of corona, as detected by the appearance of light, was always accompanied by a break in the current-voltage slope, such breaks also happened before the onset of corona, so they cannot be used as an adequate indicator of corona ignition. Of four ROS studied (hydrogen peroxide, ozone, hydroxyl radicals, and superoxide anions), only H2O2 and ozone were found to be generated at a current of 150-200 nA in detectable quantities: with a yield of 0.5-1 H2O2 molecules per electron at positive potential and 1.5-3 at negative potential. Despite the low yield of the ROS, jack bean urease was shown to be inactivated when the enzyme solution with a concentration below 20 μg/mL was electrosprayed at a current of 200 nA. Addition of 0.1 mM EDTA totally protected the activity of the electrosprayed urease.
结果表明，只要电流保持在一定临界水平以下（96%乙醇在正电位时<100 nA，负电位时<25 nA；水在正电位时<40 nA），从玻璃毛细管进行溶剂的电喷雾（ES）过程中就不会发光。尽管通过光的出现检测到的电晕起始总是伴随着电流-电压斜率的中断，但这种中断在电晕起始之前也会发生，因此它们不能用作电晕点火的充分指标。在所研究的四种活性氧（过氧化氢、臭氧、羟基自由基和超氧阴离子）中，仅发现过氧化氢和臭氧在150 - 200 nA的电流下能以可检测的量生成：在正电位时每电子产生0.5 - 1个过氧化氢分子，在负电位时为1.5 - 3个。尽管活性氧的产率较低，但当浓度低于20 μg/mL的酶溶液在200 nA的电流下进行电喷雾时，刀豆脲酶被证明会失活。添加0.1 mM的乙二胺四乙酸（EDTA）可完全保护电喷雾脲酶的活性。
