香菇中同时存在游离态甲醛和结合态甲醛，建立一种可以一次性快速测定这两种形态甲醛含量的方法。根据香菇中两种形态的甲醛析出条件，实验设计了2个步骤：第一步，先通过蒸馏提取香菇中游离态甲醛；第二步，加酸后再次蒸馏，提取香菇中结合态甲醛。实验设定条件为：蒸馏时间为4 min，加10%磷酸40 mL，水浴温度为60 ℃，水浴时间为60 min。结论为，当甲醛浓度为0.0~10.0 mg/L时，标准曲线线性关系良好，相关系数r为0.9995，游离态甲醛检测的加标回收率为87.8%~105.9%，相对标准偏差(RSD)在3.5%~7.0%；结合态甲醛检测的加标回收率为89.5%~105.8%，相对标准偏差（RSD）在2.5%~6.7%。香菇中结合态甲醛含量占总甲醛的62.6%~71.8%，游离态甲醛和结合态甲醛在伞部的含量均高于柄部的含量。全自动定氮仪可以一次性处理香菇中不同形态的甲醛，与高效液相色谱联用，能够自动、快速、高效地完成香菇中甲醛形态的检测与分析。

In order to one-time and rapidly determine the dissociative formaldehyde and conjugate formaldehyde in Letinous edodes, the method of combining full automatic nitrogen analyzer and high performance liquid chromatography (HPLC) was established. According to the precipitation conditions with different morphology of formaldehyde in Letinous edodes, the 2 steps were set to distill with the automatic nitrogen analyzer. The first step was distilled dissociative formaldehyde and the second step was adding-acid to distill the conjugate formaldehyde. The conditions of experiment were that distilling-time 4 min, 10% phosphoric acid 40 mL, water-bathing temperature 60 ℃, and water-bathing time 60 min. When formaldehyde concentration is 0.0~10.0 mg/L, the standard curve has good linear relationship, the correlation coefficient r is 0.9995. The recoveries of dissociative formaldehyde were 87.8%~105.9%, the relative standard deviation (RSD) was 3.5%~7.0%; the recovery of conjugate formaldehyde was 89.5%~105.8%, and RSD was 2.5%~6.7%. The automatic nitrogen analyzer could improve the extraction efficiency of different morphology of formaldehyde in Letinous edodes. The content of conjugate formaldehyde in Lentinus edodes accounted for 62.6%~71.8%. The contents of dissociative formaldehyde and conjugate formaldehyde in the umbrella part were higher than that in the stalk part. The method combined with high performance liquid chromatography and the automatic nitrogen analyzer was suitable for the batch detection of formaldehyde in Letinous edodes.

北京市农林科学院创新建设项目（KJCX20170419）；国家食品质量安全风险评估重大专项（GJFP201800601）