目的  建立检测C群脑膜炎球菌多糖-破伤风类毒素结合疫苗（group C  meningococcal polysaccharide -tetanus toxoid conjugate vaccine, CPS-TT）中游离多糖的脱氧胆酸钠沉淀法。 方法  在不同pH条件下用脱氧胆酸钠（sodium deoxycholate，DOC）对CPS和TT进行沉淀，确定可有效分离游离多糖和结合多糖的最适沉淀条件，并对该法进行验证。 结果  DOC沉淀法的最适pH为3.5，在此pH条件下用DOC沉淀法检测3批CPS-TT显示，上清TT含量平均为2.3%。DOC沉淀法具有较好的准确度和精密度，3批CPS-TT的批内变异系数均小于5%。 结论  DOC沉淀法可用于C群脑膜炎球菌结合疫苗的质量控制。

 Objective  To establish a sodium deoxycholate (DOC) precipitation method for determination of  free polysaccharide in group C meningococcal polysaccharide-tetanus toxoid conjugate vaccine (CPS-TT).   Methods  CPS and TT were treated by acid precipitation with DOC, and the optimum precipitation conditions to separate unconjugated and conjugated CPS were determined. The DOC precipitation method was validated.  Results  The optimum pH condition of the DOC precipitation method was 3.5. The results of 3 batches of CPS-TT determined by the DOC precipitation method showed that average content of TT in supernatant was 2.3%. The established method had better accuracy and precision, and the variation cofficients of intra-assay for 3 batches of CPS-TT were all ＜5%.    Conclusion   The DOC precipitation method can apply to quality control of group C meningococcal conjugate vaccine.