Background contamination is a major problem in the analysis of organophosphate esters (OPEs). In this study, the possible sources of OPEs pollution were screened and several different ways were applied to minimize the blank contamination. Under the strict quality control measures, the cleanup efficiency of different solid phase extraction (SPE) was investigated for OPEs in different environmental matrices. A method was developed for the detection of 7 OPEs in dust, soil and sediment samples by gas chromatograph coupled with mass spectrometry ( GC / MS). Target compounds were extracted by hexane:dichloromethane (1 : 1, V/ V) followed by aminopropyl silica gel SPE column cleanup for dust, and target compounds in soil and sediment were Soxhlet extracted and cleanuped by two-step SPE. The results showed that the aminopropyl silica gel SPE column displayed the best purification performance among the three employed columns. Instrumental detection limits among the 7 OPEs ranged from 2. 5 to 25. 8 μg / L, and the method limits of quantification (MLOQs) in dust and soil sample ranged from 1. 4 to 15. 7 ng / g and 0. 3 to 2. 9 ng / g, respectively. The average recoveries of 7 OPEs in different matrices ( dust and soil) at two spiked concentration levels ranged from 67. 9% to 117. 4% . The proposed method was successfully applied to detect OPEs in different environmental matrices collected in Shanghai.

In order to learn the enzymatic hydrolysis characteristics of steam-explosion pretreated corn straw by cellulase, the effects of substrate concentration, cellulase concentration and temperature were determined. The kinetics of the hydrolysis reaction could be described with the Michealis-Menten equation, and the hydrolysis reaction obeyed the classical first-order reaction rate in the first three hours. In the condition of 45 degrees C and pH 5.0 and the stirring rate 120 r/min, the Michealis constant (Km) and maximum rate (Vm) for 1.2 FPU/mL of cellulase were 11.71 g/L and 1.5 g/(L x h). The kinetic model, including the parameters such as substrate concentration, enzymatic concentration and temperature, was suit for the hydrolysis reaction under the temperature range from 30 degrees C-50 degrees C.
Catalysis ; Cellulase ; chemistry ; Hydrolysis ; Kinetics ; Plant Stems ; Steam ; Zea mays