Comparative Metabolomic Profiling of Soil-Based and Hydroponic Lettuce Varieties Using Paper Spray Ionization Mass Spectrometry and Chemometric Approaches

Abstract

This study explores the application of paper spray ionization-mass spectrometry (PSI-MS/MS) in evaluating the metabolomic profiles of lettuce varieties cultivated under soil-based and hydroponic conditions. Compared to electrospray ionization tandem mass spectrometry (ESI-MS/MS), the PSI-MS/MS technique demonstrated improved sensitivity and robust ion signal intensity, allowing effective discrimination between the chemical constituents of the lettuce samples. Significant metabolic differences were identified between the cultivation methods, particularly in the negative ionization mode. PSI-MS/MS provided detailed insights into the chemical composition due to its high sensitivity and minimal sample preparation requirements. The study further analyzed three lettuce varieties (loose leaf, iceberg, and oak leaf) using PSI-MS/MS, revealing distinct ion profiles and variation in ion abundances. Chemometric techniques, including parallel factor analysis (PARAFAC) and partial least squares for discriminant analysis (PLS-DA) with variable selection were utilized to differentiate between lettuce varieties and cultivation methods. This approach highlighted the impact of growing conditions on the metabolic composition of lettuce, identifying key ions such as choline, mannose, and malic acid as significant markers. Overall, the integration of PSI-MS/MS with chemometric tools provides a comprehensive approach for metabolomic profiling, offering valuable insights into the effects of cultivation methods on the nutritional and chemical properties of lettuce. This study underscores the potential of PSI-MS/MS in agricultural and food science research, contributing to the optimization of cultivation practices and the enhancement of crop quality, while also adhering to the principles of green analytical chemistry.

Keywords:
paper spray ionization; PARAFAC; PLS-DA; lettuce hydroponic and soil-based agriculture; iceberg lettuce; loose leaf lettuce; oak leaf lettuce