Simultaneous determination of aloin A and aloe emodin in products containing Aloe vera by ultra-performance liquid chromatography with tandem mass spectrometry
A novel method for the simultaneous determination of aloin A and aloe emodin in products labeled to contain Aloe vera has been developed and validated. This analytical procedure involved extracting a test portion of the product in acetonitrile : water (40 : 60, v/v), followed by centrifugation and filtration through a 0.2 μm PTFE filter. Quantitation was achieved using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with electrospray ionization (ESI) in the negative mode. The separation was carried out using a Waters Acquity UPLC BEH C18 column; 2.1 mm × 50 mm; 1.7 μm particle size. A five-minute gradient program was optimized at a flow rate of 0.5 mL min−1. Both water with 0.5% acetic acid and methanol with 0.5% acetic acid were used as mobile phases. The linear range was from 5.0 to 1000 ng mL−1 for aloin A and from 1.0 to 500 ng mL−1 for aloe emodin, with r ≥ 0.995 for both analytes. Since serious matrix effects (both ion suppression and ion enhancement) were eliminated by dilution for all samples, the recoveries for aloin A and aloe emodin ranged from 89–118%, and 74–108%, respectively, in the matrices tested. The method has been successfully applied to various products labeled to contain Aloe vera including liquids, capsules, soft gels and tabs. The amount of aloin A and aloe emodin in the samples ranged from none detected to 160.0 mg g−1 and from none detected to 3.8 mg g−1, respectively.