Stable isotope ratio analysis of carbon to distinguish sialic acid from freshly stewed bird's nest products

Abstract

Freshly stewed bird's nest products are easily adulterated with exogenous synthetic sialic acid to enhance the grade of the products and sell at high prices. This paper identifies the carbon stable isotope characteristics of sialic acid from natural and commercially synthetic sources using stable isotope ratio mass spectrometry (IRMS). Specifically, an off-line pretreatment technique combined with on-line LC-IRMS was developed to accurately determine δ¹³C values of sialic acid in a freshly stewed bird's nest. This method has no obvious isotope fractionation and good reproducibility. EA-IRMS was used to determine the δ¹³C values of commercial sialic acid. The results showed that the δ¹³C values of sialic acid from natural and synthetic sources were −29.90% ± 0.42% and −16.26% ± 3.91%, respectively, with distinct carbon stable isotope distribution characteristics. By defining a δ¹³C threshold value of −28.54% for natural SA, additional commercial SA from a minimum of 10% can be identified. Therefore, δ¹³C was proposed as a suitable tool for verifying the authenticity of fresh stewed bird's nests on the market.