Detection of lime juice adulteration by simultaneous determination of main organic acids using liquid chromatography-tandem mass spectrometry

In the present study, a novel liquid chromatography-tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of citric acid, iso-citric acid, and malic acid. Method validation was performed by studying accuracy, precision, linearity, limit of detection, and limit of quantification. Besides, the obtained results were compared to a validated HPLC-DAD method. The use of isotopically labeled citric acid as the internal standard allowed the accurate quantitation of organic acids without any significant matrix effects. Following quantification of main organic acids in the hand-squeezed lime juice samples, it was revealed that citric acid, iso-citric acid, and malic acid contents in the Persian lime juices ranged from 48.30 to 66.54 g/L, 0.24 to 0.61 g/L, and 1.73 to 10.49 g/L, respectively. Finally, among 30 industrial and 20 non-industrial lime juice samples collected from the market, 53 % of industrial and 60 % of non-industrial samples were detected as adulterated based on the citric acid to iso-citric acid ratio (over 300). The results of method validation demonstrated that LC–MS/MS could be used as a confirmatory method for the authenticity assessment of lime juice by regulatory bodies.