标准里面的部分内容: Mobile phase :Dissolve triethylamine 5.6mL and acetic acid 1.14mL,dilute with water to 1000mL. Post column Reagent:Dissolve 0.65g of urea in a solution of 0.12g arsenazo acid in 400mL of water previously acidified with 6.3mL of nitric acid.Pass the solution through a filter ,wash the filter with 500mL of water,dilute with water to 1000mL. Flow rate of Post column Reagent:0.6mL/min 其中:Post column Reagent部分,好像是PAR柱后试剂,不知道有谁知道是什么意思?怎么使用?