自动电位滴定法测定热镀锌助镀剂中氯化铵的含量

Determination of ammonium chloride in plating aid of hot-dip galvanizing by automatic potentiometric titration method

建立了自动电位滴定法准确测定热镀锌助镀剂中氯化铵含量的方法,探讨了自动电位滴定法测定热镀锌助镀剂中氯化铵含量的复合掩蔽剂A用量、复合掩蔽剂加入的介质条件和滴定起始pH对滴定突跃的影响。进行了相应的方法学验证。结果显示,对于氯化铵含量为10 g/L的助镀剂在体系介质pH为5~6时加入复合掩蔽剂A溶液15 mL、体积比为1∶1的甲醛水溶液5 mL,用0.1 mol/L氢氧化钠溶液自动电位滴定仪滴定。方法学验证显示,线性回归方程为y=0.934 9x-0.043 25,r^(2)=1,氯化铵在5~40 g/L范围内与氢氧化钠消耗量呈良好的线性关系;重复测定6次,样品加标回收率范围在100.1%~100.8%,表明该方法的准确度高。不同人员和仪器7次测定消耗0.1 mol/L氢氧化钠的RSD值(n=7)为0.28%,氯化铵含量的RSD值(n=7)为1.28%,实验结果符合国家标准要求(RSD<5%),测定结果没有显著性差异(t=1.329,P>0.05)。

An automatic potentiometric titration method is developed to determine the concentration of ammonium chloride in plating aid for hot dip galvanizing.The study also examines the impact of various factors,such as the dosage of compound masking agent A,the medium conditions for adding compound masking agent,and the initial pH of titration,on the titration jump.Furthermore,a comprehensive validation of the methodology is conducted.Experimental findings indicate that a solution containing 15 mL of composite masking agent A and 5 mL of 1∶1 formaldehyde solution are added into the plating aid that contains 10 g·L^(-1) of ammonium chloride at a pH of 5-6.The solution is then titrated using a 0.1 mol·L^(-1) sodium hydroxide solution and an automatic potentiometer.Methodological validation demonstrates that the linear regression equation is y=0.9349x-0.04325,with an r^(2) value of 1,indicating a strong linear relationship between sodium hydroxide consumption and ammonium chloride concentration in the range of 5 g·L^(-1) to 40 g·L^(-1).The method is repeated six times,and the recovery rate of spiked samples ranges from 100.1%to 100.8%,indicating a high accuracy.RSD value(n=7)is 0.28%for the consumption of 0.1 mol·L^(-1) sodium hydroxide by various personnel and instruments over seven trials.Similarly,RSD value(n=7)for the content of ammonium chloride is found to be 1.28%.Experimental findings accord with China's national standard requirement of RSD<5%,and statistical analysis reveal no significant difference in determination results(t=1.329,P>0.05).