Voltage program-based MEKC with LIF detection for rapid quantification of native capsaicin and dihydrocapsaicin in foods

Voltage program (VP)-based micellar electrokinetic chromatography (MEKC) with a laser-induced fluorescence (LIF) detector was developed for fast, high-sensitivity detection of native capsaicin (CAP) and dihydrocapsaicin (DHC) in various foods. The combination of mixed nonionic (Tween 20) and anionic (SDS) surfactants in a sodium borate running buffer showed excellent separation efficiency, selectivity, and speed without loss of resolving power (R-s > 2). Compared to conventional UV absorption, LIF showed enhanced detection sensitivity with detection limits at the pM level. In addition, the developed VP-based MEKC-LIF method was successfully applied for quantification of capsaicin in chili pepper, baechu, and kimchi at a 98% confidence level. CAP and DHC were also analyzed within a short time in extracts from real samples of gochujang, snacks (Swingchip (R)), black pepper, and ginger but were not detected in garlic.