同位素稀释-气相色谱-质谱法检测大鼠血浆中的内源性胍丁胺

建立了大鼠血浆中内源性胍丁胺的同位素稀释-气相色谱-负化学电离质谱定量分析方法。大鼠血浆样品经蛋白沉淀并蒸干后，用六氟乙酰丙酮衍生化，采用Florisil固相萃取柱净化，以稳定同位素标记的d₈-胍丁胺为内标，在气相色谱-质谱仪上采用负化学电离方式电离，选择离子模式检测。胍丁胺标准溶液的检出限为0.0057 ng/mL。血浆中添加的胍丁胺在1.14~57.0 ng/mL范围内呈良好的线性关系（r=0.997），方法回收率介于92.3%~109.8%之间，日内和日间精密度均小于15%。大鼠血浆中胍丁胺平均含量水平为（22±9）ng/mL，雌、雄大鼠血浆中的胍丁胺水平未见显著性差异（p>0.05）。该方法特异性好、灵敏度高，为生物体内胍丁胺的生理功能研究提供了高灵敏的分析方法。

Determination of endogenous agmatine in rat plasma by isotope dilution-gas chromatography-mass spectrometry

A method for the determination of endogenous agmatine in rat plasma was developed by isotope dilution-gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The plasma samples were analyzed after protein precipitation, evaporation, derivatization by hexafluoroacetone (HFAA), and clean-up on a Florisil SPE column. The GC-MS analysis utilized stable isotope d₈-agmatine as internal standard. The samples after treatment were tested by negative chemical ionization with selected ion monitoring (SIM) which was set at m/z 492 (molecular ion of agmatine) and m/z 500 (molecular ion of internal standard). The limit of detection (LOD) of agmatine standard solution was 0.0057 ng/mL. The calibration curve of the agmatine spiked in rat plasma showed a good linear relationship at the range of 1.14-57.0 ng/mL (r=0.997). The recoveries of agmatine spiked in rat plasma ranged from 92.3% to 109.8%. Inter-day and intra-day precisions were less than 15%. The average concentration level of agmatine in rat plasma was (22±9) ng/mL, and there was no significant difference between male and female SD rats (p>0.05). The method is high sensitive and specific, and can be used for the determination of endogenous agmatine in plasma. It provides a strong support for the subsequent research of agmatine.