Determination of the rate constants and activation energy of acetaminophen hydrolysis by capillary electrophoresis.
A method based on capillary electrophoresis with electrochemical detection (CE-ED) was developed for the simultaneous determination of p-aminophenol and acetaminophen in the hydrolysates of acetaminophen. Effects of several important factors such as the acidity and concentration of running buffer, separation voltage, injection time, and working potential were investigated to acquire the optimum conditions. The detection electrode was a 300 microm carbon disc electrode at a working potential of +0.80 V (versus SCE). The two analytes can be well separated within 6 min in a 50 cm length fused silica capillary at a separation voltage of 18 kV in a 25 mM phosphate buffer (pH 6.5). The rate constants of acetaminophen hydrolysis in 0.5 M HCl at different temperatures were determined by monitoring the concentration changes of acetaminophen. At 70, 80, 90 and 100 degrees C, the measured rate constants of acetaminophen hydrolysis were 5.027 x 10(-3), 8.522 x 10(-3), 18.60 x 10(-3) and 32.76 x 10(-3) min(-1), respectively. The activation energy for acetaminophen hydrolysis was calculated to be 68.13 kJ mol(-1), which is in good agreement with the value in the literature.
Chen
Gang
G
Department of Chemistry, Fudan University, 200433, Shanghai, China. sgangchen@hotmail.com
Ye
Jiannong
J
Bao
Huimin
H
Yang
Pengyuan
P
D000082:Acetaminophen / Q000737:chemistry*; D018712:Analgesics, Non-Narcotic / Q000737:chemistry*; D002021:Buffers; D004566:Electrodes; D019075:Electrophoresis, Capillary / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D018712:Analgesics, Non-Narcotic; D002021:Buffers; D000082:Acetaminophen