Abstract: 【Objective】 DDGS, which is the byproduct in corn fermentation production, is always used as a protein substitute in animal production for its low starch, high protein, high fat, high digestible fiber and high effective phosphorus. With the expansion of DDGS industry, the residues of antibiotics caused by production process should be taken seriously. However, there is seldom reports about this. In this paper, some DDGS samples from the parts of the operation and use in China were collected, and then 70 kinds of antibiotics were analyzed, in order to know the current situation of antibiotics residues in feed of China. 【Method】 In this study, quadrupole time of flight mass (QTOF) was firstly used to establish a database based on drug mass, retention time and characteristic fragment, which contained macrolides, fluoroquinolones, sulfonamides, quinoxaline, β-lactam, lincosamides, tetracyclines and amphenicols, totally 70 kinds. A total of 74 samples from 9 provinces and autonomous regions were collected to detect the possible antibiotic residues. For pretreatment of the samples, a certain amount of a homogeneous sample was taken and a mixed solution of acetonitrile and water for extraction was added. After vortex, shock and centrifuged, the supernatant was passing over NH2 SPE column. The eluent was collected and concentrated by N2, and filtered by 0.22 μm. For analysis of samples, the antibiotic residues were initially screened to determine the type of residual antibiotics by the established database, and then the liquid chromatography-tandem mass spectrometry (LC-MS / MS) was used to determine the amount of the residual antibiotics. 【Result】The EU Directive 2002/657/EC regulations identify mass spectrometer of target compounds in application. A parent ion is 2 minutes while a product ion is 2.5. In this paper, all antibiotic results could meet the requirements, which was in accordance with the rule of corroboration target compounds. After qualitative analysis by QTOF qualitative analysis, only one DDGS sample contains antibiotic residues, which is typeoftrimethoprim. Parent ion peak, characteristics of secondary ion fragments, the peak time in samples was in accordance with the spiked completely, the same of all fragment ions and ion abundance. After quantitative analysis by LC-MS/MS, the residual amount of it was 107.7 ng•g-1. In added concentration range 10-1000 ng•mL-1 of Trimethoprim, the average recoveries were 75.2%-97.9%. The linear correlation coefficient was greater than 0.99, and the standard deviation within a between days was 2.8%-5%, and the standard deviation between days was 8%-10%. 【Conclusion】In this study, the antibiotics qualitative screening method of DDGS in QTOF can be used as a rapid screening method for antibiotic residues in corn DDGS. Typeoftrimethoprim may be added before the corn fermentation production of DDGS, in order to inhibit the growth of harmful microbes. Results indicated that the species of antibiotic residues in corn DDGS was less, and residual volume is low. But the potential risk can not be ignored. The relevant departments have not given the information which DDGS can be used in the fermentation process, and the range of species of antibiotics limited. The method of quantitative analysis QTOF should be studied directly as well as other antibiotics including virginiamycin QTOF analysis methods.

Key words: antibiotic , QTOF , LC-MS/MS , corn DDGS