Sodium trithiocyanurate(TMT) is a chelating agent,which could be used to precipitate metal ions from industrial waste waters and polluted natural waters.Recently,a non-edible substance TMT was detected in wheat flour,which had become a serious food safety hazard.It was urgent to establish a detection method suitable for total TMT in wheat flour and its additives.Wheat flour and different types of flour additives were extracted with acetonitrile-ammonium formate buffer for total TMT,then purified with a pass-through cleanup solid phase extraction column(SPE).In chromatographic analysis,the separation was carried out on a HSS T3 column using methonal-ammonium formate(pH 3.0) as mobile phase under gradient elution mode by ultra high performance liquid chromatography(UPLC),which exhibited an excellent chromatographic retention as well as a good anti-interference ability.The target compound was detected by MS/MS with electrospray ionization(ESI) under multiple reaction monitoring(MRM) mode.Acetonitrile-100 mmol/L formic acid/ammonium formate buffer solution(pH 2.5,8∶2) was selected as the best extraction solvent,of which the effect on total TMT extraction was optimized in detail.Firstly,the optimized extraction system of acetonitrile-ammonium formate not only has a high extraction efficiency,but also could overcome the problem of easy gluing of flour treatment agents 2(FTA2).The pH value of the extraction solvent had a significant influence on the extraction efficiency for TMT in three matrixes.With the decrease of pH,the extraction efficiency for TMT presented an increasing trend.As the increase of buffer salt concentration of ammonium formate,the extraction efficiency showed an upward trend,and reached to the highest percentage in three matrixes when the buffer salt concentration was set at 100 mmol/L.It was found that,with the increase of acetonitrile ratio from 40% to 90%,the recoveries for wheat flour and FTA1 merely changed a little,while the recovery for FTA2 increased significantly.Results showed that the buffer salt concentration,pH value,ion concentration,content of organic phase and the sample amount had great influence on the extraction efficiency for TMT in wheat flour and its additives.Thus,different factors should be considered comprehensively.The established method showed that TMT had a good linearity in the range of 0.5-250 ng/mL with correlation coefficients of 0.997 7.The average recoveries for TMT in wheat flour and flour additives at three spiked levels ranged from 95.0% to 110% with relative standard deviations(RSD) not more than 5.6%.The limits of detection(LOD,S/N=3) and the limits of quantitation(LOQ,S/N=10) were 0.02 mg/kg and 0.05 mg/kg,respectively.This method was successfully applied to the analysis for 76 batches of wheat flour,composite flour treating agent and single ingredient additive with the advantages of simplicity,preciseness,good feasibility and applicability.Results indicated that the optimized rapid detection method provided a technical support for ensuring the quality and safety of wheat flour.