Peltier thermoelectric cooler improves both the signal-to-noise ratio and warm-up time of high-power LED induced fluorescence detector and application to aflatoxins

Abstract

High-power LED induced fluorescence detector (HP-LED-IF) suffers from problems of large noise and poor baseline stability. In this study, a Peltier thermoelectric cooler (PTC) was utilized to stabilize the HP-LED junction temperature of a HP-LED-IF to reduce the baseline noise for the first time. Compared with traditional fan cooling, the signal-to-noise ratio was improved to 3.8 times, and the warm-up time was shortened by 64.4%. For application, a 365/450 nm HP-LED-IF was constructed and coupled with HPLC for detection of aflatoxins. The limits of detections (LODs, 3 times peak-to-peak noise) for aflatoxin G₂ and B₂ were 1.2 and 1.0 pg/mL, respectively. In-situ photochemical derivatization reaction of G₁ and B₁ in 28 μL detection cell within 2.1 s flow time was found surprisingly for the first time, which enhanced the fluorescence signal by about 10 times. The LODs for aflatoxin G₁ and B₁ were 3.4 and 2.4 pg/mL, respectively. These LODs are among the lowest values that have been reported. This study provides a key technique to improve both the signal-to-noise ratio and warm-up time of HP-LED-IFs and a novel in-situ derivatization method for aflatoxins G₁ and B₁.

Keywords: High power LED; In-situ photochemical derivatization; LED induced fluorescence detector; Peltier thermoelectric cooler.