A novel HPLC flow cell integrated UV light emitting diode induced fluorescence detector as alternative for sensitive...

A novel UV light emitting diode induced fluorescence detector (LED-IF) with HPLC flow cell was designed and evaluated for determination of aflatoxins. Ray tracing method was employed to optimize the design of the optical components (such as reshaping thin lens for light source and fluorescence collection), and optical structure, and the geometry of flow cell. An ordinary UV LED with wavelength of 370 nm and radiant power of 5 mW was used as excitation light source. A photoelectric amplifier AccuOpt2000 with light sensitivity of 10^-5∼10^-4lx was utilized for fluorescence detection, instead of a photo multiplier tube (PMT). The lowest detection limit (LOD) of the LED-IF was 0.077 ppb for aflatoxin B₁ by HPLC method without derivatization. The LED-IF was then coupled with a homemade iodine derivatization device, which was connected to the HPLC column outlet for determination of aflatoxins in edible oil and peanut samples. It was found that the edible oil sample contained aflatoxin B₁ and B₂ at average level of 7.14 (n = 3) and 0.30 ng/g (n = 3), respectively; while the peanut sample contained aflatoxin B₁ and B₂ at average level of 9.22 (n = 3) and 1.36 ng/g (n = 3), respectively. The overall power consumption of the LED-IF was 1 W/12 V. The sensitivity of the LED-IF was similar to commercial fluorescence detectors, which utilized a pulse Xe lamp as excitation light source and a PMT for detection, with power consumption of 150 W.