Analysis of vanilla extract by reversed phase liquid chromatography using water rich mobile phases

Abstract

Vanillin is the major constituent of vanilla extract, a flavoring ingredient used in food and beverages. Natural vanilla extract prepared from the bean of the tropical orchid, Vanilla planifolia, is expensive due to the limited supply of the vanilla bean. For this reason, synthetic vanilla extracts are widely used. Synthetic vanilla extracts are less complex and usually contain vanillin, ethyl vanillin, and other related compounds that are prepared from inexpensive starting materials. Several liquid chromatographic methods have been developed to quantitate coumarin, vanillin, and ethyl vanillin in vanilla extract. The use of water rich mobile phases in reversed phase liquid chromatography (RPLC), e.g., 1% butanol in water with 0.2% acetic acid with C18, C8, and cyanopropyl columns, has been investigated as a potential method to characterize the composition of synthetic vanilla extracts. Better resolution is achieved in the separation of vanillin compounds when hydrophobic alcohols are used as organic modifiers. This can be attributed to butanol partitioning into the bonded phase, which provides a more extended ordered surface increasing the contact surface area of the stationary phase and thereby increasing the selectivity of the separation. Using water rich mobile phases, constituents of vanilla extract in 36 commercial products obtained from stores in the local area were identified demonstrating the efficacy of the proposed RPLC method.