It is necessary to determine secondary amine to study the etiology of esophageal cancer. Anew method to determine secondary amine is presented in this article. The method is that methylbenzylamine can react with sodium nitroprusside in 20% acetaldehyde and NaHCO_3-Na_2CO_3buffer solution at 0℃ and form a stable and soluble blue compound. The maximum absorbingwavelength of the compound is 575 nm. When the concentration of methylbenzylamine is within1~2 5μg/ml, the relationship between the absorbance and the ...