Highly Sensitive and Rapid Flow-injection Fluorometric Determination of Lipid Hydroperoxide in Human Sebum

A highly sensitive and rapid flow-injection analysis (FIA) method for lipid hydroperoxide using diphenyl-1-pyrenylphosphine (DPPP) as a fluorescence reagent has been developed to investigate the relationship between lipid hydroperoxide contents in sebum and human skin conditions. The standard for lipid hydroperoxide, methyl linoleate hydroperoxide (MLHP), was prepared by irradiating black light to methyl linoleate, and purifying with solid-phase extraction. The purity of MLHP was determined by 1H NMR. The optimized FIA method exhibited the detection limit at 0.51 pmol, quantitation limits at 1.1 pmol, and analysis time for 10 minutes. A simple sebum collection protocol from a small area of human skin was also developed by using a piece of pre-cleaned filter paper. The quantitation limit with this sebum collection protocol was determined to be 3.8 pmol. The developed method was then applied for the analysis of lipid hydroperoxide in human sebum from 24 healthy individuals. The results demonstrated that the developed method was valid for the analysis of real-world samples. It was revealed that the inter-individual difference of lipid hydroperoxide contents in sebum was larger than expected.