钻井液用聚合物阳离子度测定方法的改进

四苯硼钠法是现有作为检测季铵盐阳离子度最为有效、广泛的方法之一，但该方法容易受到无机钾离子、铵离子等外界干扰和分子结构自身的影响，导致阳离子度测定结果的准确度较低。针对此问题，笔者对四苯硼钠返滴定法测定钻井液用聚合物阳离子度的方法进行改进，通过对样品采用90%～95%乙醇醇洗提纯，消除钾离子、铵离子和小阳离子单体的干扰；加入H₂O₂，通过进行热氧降解降低分子量，减弱分子结构的影响；优化出以下测定条件:样品加量为0.2 g、沉淀pH值3.0～4.0、沉淀温度为15～25℃和滴定pH值为7.0～8.0等，从而提高四苯硼钠测定方法的准确性。结果表明，四苯硼钠返滴定法的检出限量为0.1 g，加标回收率达到了分析测试要求的加标回收率指标，说明该方法具有良好的准确度。 

Improvement of Method for Measuring Degree of Cationic Substitution of Drilling Fluid Polymers

Testing the degree of cationic substitution of quaternary ammonium salts with sodium tetraphenylborate (STB) is one of the most effective methods that have been widely used. The drawbacks of this method are that the interference of inorganic potassium ions and ammonium ions, as well as the molecular structure of the samples make the test inaccurate to some extent. Studies have been conducted on the improvement of the accuracy of the STB method by eliminating ionic interferences to the STB method, optimizing the test conditions of the STB method and investigating the effects of the molecular structure of polymers on the measurement of cationic substitution. In laboratory tests, the polymer samples were purified with 90%-95% ethanol to eliminate interference from potassium ions, ammonium ions and low molecular weight (MW) cationic monomers from outside. The mass of sample was determined to be 0.2 g, pH value for the precipitation between 3.0 and 4.0, temperature for precipitation between 15℃ and 25℃, and pH value for titration between 7.0 and 8.0. H2O2 was used at a certain temperature to reduce the MW of polymers to minimize the effects of molecular structure on the test accuracy of test, thereby improving the accuracy of the STB method. The test results show that the modified STB method has good feasibility and accuracy; the identification limit of the test is 0.1 g, and recovery rate 92%-94%.