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Simultaneous Analysis of Five Areca Nut-Specific Nitrosamines by Isotope-Dilution Liquid Chromatography-Tandem Mass Spectrometry with On-Line Solid-Phase Extraction
Areca nut is widely consumed in Taiwan, India, and Southeast Asia. In 2004, the IARC has confirmed areca nut as human carcinogen. The alkaloid components of areca nut are responsible for potential carcinogenic effects, because they can further form areca nut-specific nitrosamines (ASNAs) through the endogenous nitrosation. Five ASNAs have been previously identified, namely 3-(methylnitrosamino) propionitrile (MNPN), 3-(methylnitrosamino) propanal (MNPA), N-nitrosoguvacine (NGCI), N-nitrosonipecotic acid (NNIP), and N-nitrosoguvacoline (NGCO).
In this study, we developed and validated an isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method to simultaneously determine five ASNAs in human saliva. The limits of detection are 0.34, 0.48, 0.45, 0.05, and 0.17 ng/mL for MNPN, MNPA, NGCI, NNIP, and NGCO, respectively. The intra- and inter-day precisions of five ASNAs are greater than 90%. The relative recoveries of five ASNAs in saliva at different concentrations were from 86 to 104 %.
This method was further applied to determine the five ASNAs in saliva of unripe areca nut chewers. Our results showed that only MNPN and NGCO were detected in chewers' saliva. This is the first study to successfully measure the ASNAs in saliva of unripe areca nut chewers in Taiwan.