Identification of intermediates during the electrocatalysis oxidation of pretilachlor The degradation solution of electrocatalysis oxidation of preti lachlor was analyzed by GC MS, and the total ion current chromatograms of pretilachlor and its intermediates at different degradation time were shown in Fig. 4. A number of interme diates were formed during the 
degradation of pretilachlor. Nine intermediates were identified by comparing the obtained frag ments in mass spectra with the data in the other literatures. The mass spectral characterization of pretilachlor and interme diates and also the speculated structures were summarized in Table 1. By analyzing the fragments in mass spectra and compar ing with the data in literatures, it was found that compounds 2, 6 and 9 were in accordance with 2 chloro 2 _,6 _ diethyl N acetanilide, 2 chloro 2 _,6 _ diacetyl N acetanilide and 2 chloro 2 _ acetyl 6 _ ethyl N acetanilide.
Com pound 2 were detected during the direct oxidation of alachlor by O 3. And some intermediates similar to compound 6 and 9 MEK Inhibitors were also detected. The structures of compound 3 and 5 were in accordance with 2,6 diethyl N aniline and 2,6 diethyl N acetanilide. These compounds had similar structures with some intermediates in the bio degradation process of acetanilide herbicide. Until now, the intermediates similar to compound 1, 4 and 7 were undetected in degradation of acetanilide herbicide. According to the fragments in mass spectra, we speculated the struc tures of compound 1, 4 and 7 were 2,6 diethyl benzenediol, 2 hydroxy 2 _, 6 _ diacetyl N acetanilide, and 2 acetyl 6 ethyl N acetanilide.
The retention time of compound 8 was 24. 148 min and the MW is 311. It was consistent with the retention time of the standard pretilachlor solution. Therefore the chemical MEK Signaling Pathway formula of the com pound 8 must be the 2 chloro 2 _,6 _ diethyl N acetanilide. By analyzing the fragment of compound 10 in mass spec tra, compound 10 should be hydroxylalachlor, which was similar to the intermediate of photocatalysis degradation of alachlor. 3. 3. The degradation pathways of pretilachlor In the present, the common view of electrocatalysis oxidation mechanism for DSA electrode illustrated that two ways were partic ipated in the electrochemical oxidation of organic compounds: the direct electrochemical oxidation degradation at the electrode and the indirect oxidation of organic compounds by using the oxidative OH produced on the surface of electrode.
When OH as phys ical adsorbed oxygen was located on the surface of electrode, the electrochemical combustion would be happened and the organic compounds would be completely degraded, whereas, OH as chem ical adsorbed oxygen was located on the surface of electrode, the electrochemical conversion would be generated, resulting in incomplete degradation of organic compound. Neuronal Signaling Cyclic voltammogram was measured in order to examine the direct oxidation of organism on the Sb doped Ti/SnO2 electrode. Fig. 5 was the CV curves of Ti/SnO 2 electrode in 0. 25 mol L 1 sodium sulfate solution with and without pretilachlor.
No oxidized checkpoint kinase peak or deoxidized peak was observed in the CV curve of solution contain ing pretilachlor, which proved that direct oxidation of pretilachlor can not occur on the electrode surface. Taking terephthalic acid as OH capture agent, uorescence spectrum technique was employed to examine whether OH could be produced during the electrochemical degradation process or not in the previous experiment of our research group. The results proved that OH was produced on the surface of Ti/SnO 2 electrode during the electrolysis process, and OH caused the indirect oxida tion of organism. Based on the above discussion, we could speculate the degra dation process of electrocatalysis oxidation of pretilachlor, which mainly contains hydroxylation, oxidation, dechlorination, C O bond and C N bond cleavage, as shown in Fig. 6.
Oxidative OH generated on the anode surface or in the solution attacks the benzene ring of pretilachlor, leading to the formation of PARP compound 10. Then the electron density in the aromatic ring of compound 10 was increased and the electrophilic substitution of OH continuously occurred, resulting in the formation of compound 1. Meanwhile, the side chains would be oxidized into propionic acid, acetic acid, monochloroacetic acid and oxalic acid. In addition, OH also attacked on the side chain of benzene ring, resulting in the cleavage of C N bond and formation of compound 2 and 3, at the same time propionic acid, acetic acid and monochloroacetic acid were also generated. OH as chemical adsorbed oxygen on the surface of elec trode attacked on the ethyl side chain of pretilachlor, and formed compound 9 via oxidation reaction.
The continuous oxidation of compound 9 and the cleavage of C O induced the formation of com pound 6 and propionic acid. Then compound 4 could be formed via dechlorination and hydroxyl reaction of compound 6. Compound 5 was formed by dechlorination of pretilachlor on the cathode of electrolysis cell, where chloride atom in pretilachlor was substituted by hydrogen atom. Oxidation of the compound 5 then formed the compound 7.