Application of gas chromatography-stable isotope mass spectrometry to determine the oxygen isotope ratio of water in concentrated fruit juice

In this study, we developed a method to determine the authenticity of concentrated fruit juice using the delta O-18 ratio of water. We utilized the gas chromatography-isotope ratio mass spectrometry (GC-IRMS) technique along with the offline isotope exchange equilibrium method to pretreat and measure the oxygen isotopes in water in concentrated apple juice. This innovative approach uses anhydrous ethanol as a solvent to dissolve concentrated juices, thereby facilitating a more comprehensive reaction between the water in the sample and the CO2 standard gas. Additionally, the reaction vessel exhibits excellent air tightness, ensuring rapid equilibrium time and enabling accurate determination of delta O-18 in the water content of concentrated juice. The reaction vessel had excellent air tightness and rapid equilibration time, enabling accurate measurement of delta O-18 of water in concentrated fruit juice. The reaction vessel used had excellent air tightness and rapid equilibration time, ensuring accurate measurement of the delta O-18 of water in concentrated fruit juice. We analyzed 40 samples of concentrated apple juice and found that the range of delta O-18 values in the water of concentrated apple juice was between 1.29 parts per thousand and 7.59 parts per thousand. Additionally, we used prepared sucrose syrup as a simulated sample and found that the delta O-18 distribution range was between -10.43 parts per thousand and -10.53 parts per thousand. Furthermore, we conducted adulteration simulation experiments on randomly selected real samples and discovered a linear negative correlation between the adulteration ratio and the delta O-18 value of water in the samples.